Login

AgroMedicine Dictionary

Powered by East Carolina University NC State University NC Agricultural and Technical State University

A terms

A-weighted Network

Published
The three physical attributes of sound (noise) are intensity, frequency and duration. A-weighting is the use of a family of curves to simulate the loudness of sound as perceived by the human ear. This is necessary because the human ear is less sensitive to lower sound frequencies. This is particularly important in agromedicine, since deafness is associated with working in agriculture.

See also: sound

A-weighting

Published
A-weighting is the use of a family of curves to simulate the loudness of sound as perceived by the human ear.

abatement

Published
The reduction in degree or intensity of pollution

Abbreviated Injury Scale

Published
The Abbreviated Injury Scale (AIS) is an anatomical scoring system first introduced in 1969. Since that time it has been revised and updated against survival so that it now provides a reasonably accurate way of ranking the severity of injury. The latest incarnation of the AIS score is the 1990 revision. The AIS is monitored by a scaling committee of the Association for the Advancement of Automotive Medicine. Injuries are ranked on a scale of 1 to 6, with 1 being minor, 5 critical and 6 an unsurvivable injury.

ais_score

From: NORA, 2008.

Absolute Humidity

Published
Usually expressed in kilograms per cubic meter, absolute humidity is the amount of water present in a unit volume of air.

See also: relative humidity

Absorbed Dose

Published
The amount of a chemical that enters the body of an exposed organism.

Absorbent

Published
As an adjective absorbent  means capable of taking up liquids, as a noun it means a material that absorbs liquids. Liquids are taken up and distributed throughout the absorbent in contrast to adsorbent, which takes up liquids on to the surface.

Absorption

Published
The uptake of water or dissolved chemicals by cells or organisms.

See also: absorbent; adsorption

Absorption Factor

Published
The fraction of a chemical coming into contact with an organism that is absorbed and enters the body of the organism.

From: Dictionary of Toxicology, 2nd edition.

Absorption, of Toxicants

Published
The processes involved in the movement of the toxicant from the exterior environment or the lumen of the portal of entry (i.e., the skin, respiratory system or gastrointestinal tract) to the circulatory system (generally the blood, but can also include the lymphatic system). Absorption  of toxicant is generally a passive process, dependent upon the lipophilicity of the toxicant but, in some cases, it involves active or facilitated transport. Of importance in agromedicine in considerations of chemical hazards.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: entry mechanisms; penetration; penetration rate; penetration routes, dermal; penetration routes, gastrointestinal; penetration routes, pulmonary; percutaneous absorption

Acaricides

Published
Pesticides with specificity for mites, typically used for chemicals effective for control of phytophagous mites in contrast to those controlling parasitic mites.  A number of insecticides also display acaricidal activity. The acaricides include a diverse array of chemical structures. Common examples are dicofol and chlorobenzilate.

From: Adapted from the Dictionary of Toxicology, 2nd edition.

See also: dicofol

Accident

Published
An unplanned or unintended event or series of events that may result in death, injury, loss of or damage to a system or service; cause environmental damage or adversely affect an activity or function. [Note: Many public health injury prevention professionals prefer terms such as injury incident or unintentional injury].

From: NORA, 2008.

Accident Rate

Published
The number of accidents or accident-related events per stated unit time occurring in a larger defined category. Because of the many events and categories and the lack of formal rules in most accident rate reporting, both events and categories must be defined. For example, accident rates in agricultural could be reported as accidents per 100 farms per year or accident-related deaths per 100 farms per year. They could be further categorized as “per family farm’ or “per non-family farm”. The Occupational Safety and Health Administration has developed a formal process for calculating and reporting certain types of occupational accident rates.

Reference: https://www.osha.gov

Acclimatization

Published
Note: in countries outside the USA, acclimation, a synonym of acclimatization, may be preferred.



The functional adaptation of an organism to changes in their environment. Such changes occur in plants and animals (including humans) and may be periodic (seasonal) or episodic. In humans the changes are usually episodic and may be important in agromedicine, e.g., response to high or low temperature. Although this type of adaptation may also occur in farm animals, periodic adaptations such as having winter and summer coats are also important.

Accreditation

Published
Certification of the expertise of individuals in professions or defined specialties within professions. There is no formal or legally binding accreditation in for individuals or programs in agromedicine. In toxicology accreditation is done by several organizations that establish standards and accredit on the basis of education, experience, accomplishments and/or successful completion of a written examination.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: American Board of Toxicology; American Board of Veterinary Toxicology; American College of Toxicology

Accuracy

Published
Accuracy is widely used in everyday speech and may have many different meanings. While accuracy and precision are often considered to be synonymous they may be defined as separate and distinct terms. It has no special meaning with respect to agromedicine or agriculture. Some of the many characteristics held to be characteristic of accuracy are: being correct or precise; conforming to fact; ability of a measurement to match the actual value;

Acetaldehyde

Published
Ethanal; ethylaldehyde; acetic aldehyde, CH3CHO. CAS Number 75-07-0. An organic compound used in the manufacture of paraldehyde, acetic acid, butanol, aniline dyes, synthetic rubber, and in the silvering of mirrors. It is also used in trace quantities in artificial flavors. It is produced physiologically in significant quantities in individuals taking disulfiram who have subsequently ingested ethanol. The primary toxic action is irritancy. Acetaldehyde interferes with mitochondrial oxygen consumption and energy production in rat liver.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: alcohol dehydrogenase; aldehyde dehydrogenase; ethanol; disulfiram

Acetylcholine (ACh)

Published
CAS number of chloride 60-31-1, of bromide 66-23-9. The choline ester of acetic acid. ACh is released in vertebrates as the neurotransmitter for cholinergic neurons in the CNS, as well as at several peripheral locations: somatic neurons innervating skeletal muscle (neuromuscular junctions); preganglionic neurons in both divisions of the autonomic nervous system; parasympathetic postganglionic neurons; and a few sympathetic postganglionic neurons. ACh is important in agromedicine because of its role in organophosphorus and carbamate insecticide poisoning.  ACh is synthesized from choline and acetyl CoA by the mitochondrial enzyme choline acetyltransferase. Choline, but not ACh, is absorbed into nerve terminals by a specific, high-affinity, sodium- and energy-dependent process. This high-affinity uptake process is specific to cholinergic nerve terminals, is tightly coupled to ACh synthesis, is the rate-limiting step for ACh levels and is the target for some toxicants, such as hemicholinium-3. Cholinergic receptors (cholinoceptors), that mediate the effects of ACh, are generally classified as nicotinic or muscarinic, based on their binding preferences for nicotine and muscarine, respectively. Receptors can be blocked by such agents as d-tubocurarine, decamethonium, atropine and scopolamine. ACh is hydrolyzed to choline and acetate by acetylcholinesterase, that is an important target for a variety of toxic and therapeutic anticholinesterases, such as the nerve agents, carbamate, thiocarbamate and organophosphorus insecticides, and eserine.

acetylcholine

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: acetylcholine receptors, muscarinic and nicotinic; acetylcholinesterase; carbamate insecticides; organophosphorus insecticides

Acetylcholine Receptors, Muscarinic and Nicotinic (Cholinergic Receptors; Cholinoceptors)

Published
The receptors for the neurotransmitter acetylcholine (ACh) are classified into two major groups--muscarinic and nicotinic. The muscarinic receptors occur at autonomic effector cells and are stimulated by the alkaloid muscarine derived from certain mushrooms; these receptors mediate the effects of postganglionic parasympathetic neurons. Some muscarinic receptors also occur in autonomic ganglia and in cortical and subcortical neurons in the brain. Cholinergic agonists for muscarinic receptors include bethanechol and methacholine; the belladonna alkaloid atropine is an effective antagonist. Muscarinic receptors are subdivided into subtypes, such as M1 and M2 receptors, based on selective agonist/antagonist activities or binding affinities. The nicotinic receptors occur at autonomic ganglia and at the endplates of skeletal muscle and are stimulated by the alkaloid nicotine. Cholinergic agonists for nicotinic receptors include nicotine, and antagonists include d-tubocurarine, hexamethonium and some snake toxins. Acetylcholine receptors are important in Agromedicine because of their role in the mechanism of action of certain groups of insecticides, for example, the neonicotinoids bind to the nicotinic acetylcholine receptor. They may also be involved in the non-cholinergic effects of organophosphorus insecticides.

Adapted from: Dictionary of Toxicology, 2nd edition.

Acetylcholine Release

Published
Acetylcholine (ACh) is released from the nerve terminals of cholinergic neurons in response to an action potential in the neuron (excitation-secretion coupling). Agents that enhance ACh release cause hyperexcitability of cholinergic pathways. A toxin possessing this activity is black widow spider venom.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: black widow spider venom

Acetylcholinesterase

Published
AChE; Acetylcholine Acetylhydrolase; Cholinesterase; EC 3.1.1.7. An enzyme that hydrolyzes the neurotransmitter acetylcholine (ACh) to choline and acetate, and thus terminates the action of ACh. It is found extensively throughout the nervous system, as well as in many non-nervous tissues. The enzyme contains two binding sites for ACh: an anionic site and an esteratic site, containing a serine residue that is the target for numerous organophosphorus and carbamate inhibitors. The inhibition of AChE by these anticholinesterases leads to an accumulation of endogenous ACh, and thus results in hyperactivation of cholinergic receptors. Symptoms of acute poisoning can include irritability, tremors, convulsions and predominately parasympathetic effects, with death usually the result of respiratory failure. The acronym SLUD (salivation, lacrimation, urination, defecation) is used to describe the symptoms of acute poisoning. The recovery of enzyme activity varies within the groups of anticholinesterases: the carbamates are sometimes considered ''reversible” inhibitors because they are relatively transient, whereas the organophosphorus compounds are quite persistent, with some of these capable of aging and therefore causing permanent destruction of the enzyme. Since AChE is contained in erythrocytes, the assay of erythrocyte AChE activity can be used as a diagnostic tool to assess exposure to organophosphorus anticholinesterases.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: acetylcholinesterase, aging; anticholinesterases; acetylcholine receptors, muscarinic and nicotinic; carbamate insecticides; carbamate poisoning, symptoms and therapy; organophosphate poisoning, symptoms and therapy; organophosphorus insecticides

Acetylcholinesterase, Aging

Published
An event that occurs subsequent to the inhibition of acetylcholinesterase (AChE) by certain organophosphates and phosphonates, including numerous insecticides and their reactive metabolites (oxons). Although the precise mechanism involved has not been established, it is apparently a simple hydrolysis of an alkoxy group on the phosphorus atom. Cleavage of the P-O-alkyl, rather than the P-O-AChE, bond yields an inhibited enzyme with a spontaneous recovery rate near zero and that is refractory to reactivation by oximes. Fortunately, the methoxy and ethoxy groups prevalent in commercial insecticides age rather slowly. The isopropoxy group (e.g., DFP and sarin) ages within one to two hours, and the 1,2,2-trimethylpropoxy group (e.g., soman) ages within minutes.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: acetylcholinesterase

Acetylcholinesterase, Reactivation

Published
Acetylcholinesterase (AChE) that has been inhibited by a carbamate or organophosphorus (OP) anticholinesterase can be restored to normal functional capacity if hydrolysis removes the moiety carbamylating or phosphorylating the enzyme. This reactivation occurs spontaneously for both groups of anticholinesterases, with the reactivation of carbamates occurring much more rapidly than that of the OP compounds. The reactivation of OP-inhibited AChE can be enhanced by the use of oxime reactivators, such as N-methylpyridinium-2-aldoxime (2-PAM), provided that aging of the phosphorylated AChE has not occurred.

From: Dictionary of Toxicology, 2nd edition.

See also: acetylcholinesterase, aging; anticholinesterases; N-methylpyridinium-2-aldoxime

Acid/base Balance

Published
The ratio of acidic to basic ions in a solution. In vivo the acid/base balance is controlled physiologically, and disturbances, often resulting from the effect of toxicants, can have profound toxicological effects. Carbon dioxide is transported in the blood primarily as bicarbonate ions (HCO3-), the bicarbonate ion being formed in the red blood cell by carbonic anhydrase. The Henderson-Hasselbach equation illustrates the role of bicarbonate in maintaining blood pH at 7.4 acid-base_balance

Thus disturbances in acid/base balance affect blood pH, giving rise to acidosis or alkalosis.

From: Dictionary of Toxicology, 2nd edition.

See also: acidosis; acidosis, metabolic; acidosis, respiratory; alkalosis; alkalosis, metabolic; alkalosis, respiratory

acidity

Published
The quantitative capacity of aqueous solutions to react with hydroxyl ions. It is measured by titration with a standard solution of a base to a specified end point. Usually expressed as milligrams per liter of calcium carbonate.

From: Ensafe, Inc.

Acidosis

Published
A condition in which the pH of the blood is acidic beyond the normal range. Although acidosis can occur for reasons unrelated to toxic compounds, it may also result from the generation of an acidic metabolite (e.g., formic acid from methanol) by loss of base or by carbon dioxide retention. Therapeutically acidosis is treated by maintaining an adequate airway, artificial respiration to prevent carbon dioxide retention or by administering sodium bicarbonate, either i.v. or orally.

From: Dictionary of Toxicology, 2nd edition.

See also: acidosis, metabolic; acidosis, respiratory; alkalosis; alkalosis, metabolic; alkalosis, respiratory; maintenance therapy, respiration; maintenance therapy, water and electrolyte balance

Acidosis, Metabolic

Published
A form of acidosis resulting from the generation of excess acid and the resultant disturbance of the acid/base balance. It occurs not only in diabetes and renal disease, but also following acid salt poisoning, methanol poisoning, etc. Characteristic signs are a decrease in blood bicarbonate and increased respiratory rate.

From: Dictionary of Toxicology, 2nd edition.

See also: acidosis

Acidosis, Respiratory

Published
A form of acidosis resulting from failure to expire carbon dioxide. It can occur in pneumonia, emphysema and congestive heart failure, but also with poisons causing lung edema and with narcotic depressants. It involves an increase in blood bicarbonate concentration.

From: Dictionary of Toxicology, 2nd edition.

See also: acidosis

Acoustic Trauma

Published
Damage to the hearing mechanism of the inner ear by loud and/or persistent noise. Such noise exposure may be acute, perhaps as few as only a single excessively loud noise or chronic, less loud noise over an extended period of time.

See also: acoustics; deafness; sound

Acoustics

Published
This term is normally held to mean the science of the study of sound. More broadly, and more exactly, it deals with the propagation of mechanical waves in gasses, liquids and solids. Although this includes vibration, sound and ultrasound, undoubtedly the propagation of sound in air is most important. Important in agromedicine because of the association between deafness and the agricultural workplace.

See also: deafness

Acrolein

Published
Acraldehyde; acrylaldehyde; acrylic aldehyde; aqualin; 2-propenal; allyl aldehyde; NSC 8819. CAS number 107-42-8. A chemical intermediate in the manufacture of methionine, glycerine, acrylic acid esters, glutaraldehyde and cycloaliphatic epoxy resins. It is also a restricted use pesticide used as an aquatic herbicide. Apparently its only current use is in irrigation canals in the western USA.  Acrolein is formed during partial combustion of organic material (e.g., in forest fires, urban fires, exhaust emissions and tobacco smoke). The oral LD50 in rats is 46 mg/kg and in mice is 28 mg/kg. The irritation threshold is 0.1 ppm, the TLV-TWA 0.1 ppm, TLV-STEL 0.3 ppm and IDLH 5 ppm. Acrolein reacts with critical sulfhydryl groups in lungs, heart, eyes, skin and the respiratory tract, and causes disruption of intermediary metabolism, impairment of DNA replication, inhibition of protein synthesis and mitochondrial respiration, hepatic periportal necrosis, and destruction of NADPH-cytochrome c reductase. In humans, it causes intense irritation of eye and mucous membranes of the respiratory tract. Direct contact leads to skin or eye necrosis, pulmonary edema, bronchitis, tracheobronchitis, severe gastrointestinal distress and/or lachrymation. Inhalation can lead to pneumonia and nephritis, degeneration of the bronchial epithelium leading to emphysema and focal calcification of the renal tubular epithelium. After acute poisoning, the subject should be removed from the contaminated area and should be administered oxygen with subsequent corticosteroid treatment for pulmonary inflammation. If acrolein is ingested, gastric lavage, saline cathartics, and demulcents should be used.

acrolein

Adapted from: Dictionary of Toxicology, 2nd edition.

Reference: ATSDR Toxprofile, 05/2007.

Actinic Keratoses

Published
These are small, rough areas on skin that has been exposed to sunlight for extended periods. They may be precursors of certain types of cancer such as squamous cell skin cancers.

Action Level

Published
In the USA and in the context of agromedicine action level can refer to pesticide concentrations recommended by the Environmental Protection for action by the Food and Drug Administration and/or the Department of Agriculture when the food contamination in question occurs for reasons not associated with direct application.  Tolerances are set for concentrations resulting from direct application of the pesticide in question.

Activated Charcoal

Published
Charcoal that, after pyrolysis during manufacture, has been subjected to steam or air at high temperature, making it an effective absorber of many chemicals. It is used as an oral absorbent in treating oral intoxication from many toxicants.

Activation (bioactivation)

Published
In toxicology, any metabolic reaction of a xenobiotic in which the product is more toxic than the substrate. Such reactions are most commonly monooxygenations, the products of which are electrophiles that, if not detoxified by phase II (conjugation) reactions, may react with nucleophilic groups on cellular macromolecules such as protein and DNA. The activation of organophosphorus insecticides containing the P=S moiety to the P=O (oxon) derivative is important in agromedicine.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also:
reactive intermediates (reactive metabolites)

Active Sampling

Published
This term is usually used with reference to air sampling in which the sampling device may involve pulling air through a filter. This may be contrasted with passive sampling in which air is not pumped through a device but is subject to permeation and adsorption on a suitable surface. Similar distinctions and methods may be used for many other types of sampling.

See also: passive sampling

Active Transport

Published
active transport. The energy-dependent process of moving of chemicals across biological membranes. In toxicology, active transport is important as a mechanism for the absorption of chemicals in the gastrointestinal tract and for the excretion of toxicants and their metabolic products from the liver or the kidney or to restrict access to protected tissues such as brain and testes, active transport can mediate the uptake and/or efflux of chemicals. Although entry (uptake) of toxicants usually results from passive diffusion of lipophilic molecules some toxicants are absorbed by active transport because of their close similarity to either nutrients or endogenous metabolites (e.g., 5-fluorouracil is transported by the pyrimidine transport system, MPPT is transported by the dopamine transport system). Active transport systems have in common: requiring metabolic energy; inhibition by chemicals affecting energy metabolism; being saturable, acting against a concentration gradient and selectivity. The energy required can be obtained from the hydrolysis of ATP or coupling of carriers to ion channels.

Adapted from: Dictionary of Toxicology, 2nd edition.

Acute Toxicity

Published
Toxicity manifested within a relatively short time interval after toxicant exposure (i.e., as short as a few minutes to as long as several days). Such toxicity is usually caused by a single exposure to the toxicant.

From: Dictionary of Toxicology, 2nd edition.

See also: acute toxicity testing

Acute Toxicity Testing

Published
In the past, such tests were usually concerned with lethality estimated by the LD50 or LC50 tests. At present acute tests include those for eye and skin irritation and sensitization and changes in autonomic and cardiovascular function. More comprehensive acute toxicity tests also include gathering data on cause of death (where applicable), symptomatology, specific organ effects, metabolism and mode of toxic action, as well as forming the basis for subsequent subchronic studies.

From: Dictionary of Toxicology, 2nd edition.

See also: acute toxicity testing, factors affecting; dermal irritation tests; dermal sensitization tests; eye irritation tests; LC50; LD50; phototoxicity tests; testing variables, biological; testing variables, non-biological; toxicity testing; toxicity testing, factors affecting

Acute Toxicity Testing, Factors Affecting

Published
Biological variables including: species; strain; sex; stage of reproductive cycle; age; diet; disease and stress that can affect the results of acute toxicity tests. Non-biological variables include: environmental conditions (temperature, humidity, light cycle); housing (cage design, bedding, population density and composition); hygiene; statistical design and randomization. The two classes of variables are related since many of the non-biological variables directly affect such biological variables as stress and disease. These variables also affect subchronic and chronic tests and must be carefully controlled to ensure reproducibility. Important in agromedicine as acute toxicity testing is part of the basis for pesticide regulation and provides background for the treatment of poisoning by agrochemicals.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: acute toxicity testing; LD50; testing variables, biological; testing variables, non-biological

Acute Toxicity, Clinical Signs

Published
The signs of intoxication displayed by the person or animal that has been exposed to a toxicant. These signs will include levels of activity such as restlessness, irritability, hyperreflexia, confusion, delirium, mania, self-injury, convulsions, coma or circulatory collapse; they will also include autonomic signs such as diahrrea, altered pupil size, gooseflesh, hyperactive bowel sounds, hypertension or hypotension, tachycardia or bradycardia, and lacrimation. Other signs can include insomnia, muscle cramps and yawning. Important in agromedicine for acute poisoning by agrochemicals.

From: Dictionary of Toxicology, 2nd edition.

Adaptation

Published
In addition to adaptation to toxicants, organisms may adapt, physiologically, to extremes of temperature, low oxygen tension resulting from altitude, etc.

See also: adaptation to toxicants

Adaptation to Toxicants

Published
The ability of an organism to show either insensitivity, or decreased sensitivity, to a chemical that normally causes deleterious effects. The terms resistance and tolerance are closely related and have sometimes been used interchangeably. The present consensus is that resistance refers to the situation in which a change in the genetic constitution of a population in response to selection by the stressor chemical enables a greater number of individuals to resist the toxic action than were able to resist it in the unselected population. Thus, an essential feature of resistance is its inheritance by subsequent generations. In microorganisms this frequently involves mutations and induction of enzymes by the toxicant; in higher organisms it usually involves selection for genes already present in the population at low frequency. Tolerance is reserved for those situations in which individual organisms acquire the ability to resist the effect of a toxicant, usually as a result of prior exposure. Tolerance may also be used for populations that have the genes for resistance at a high frequency before exposure. More often, however, this is known as natural resistance, in contrast to acquired resistance, derived by selection as described above.

From: Dictionary of Toxicology, 2nd edition.

See also: cross-resistance

Adenocarcinoma

Published
A malignant tumor arising from epithelium and comprising malignant cells characteristic of the tissue from which it arises. Unlike an adenoma, these specific tissue characteristics are often unrecognizable in the cancer cells due to profound degeneration of morphology accompanying malignant transformation. Thus, the tissue of origin of a disseminated adenocarcinoma often cannot be determined.

From: Dictionary of Toxicology, 2nd edition.

See also: adenoma

Adenoma

Published
A benign (i.e., non-malignant) tumor arising from epithelium and containing cells characteristic of the tissue from which it arises. The term is most often applied to tumors of glands or of mucosal epithelium (e.g., the lining of the mouth, bronchial tree, intestines, etc.).

See also: adenocarcinoma

Administrative Controls

Published
In the general sense this term refers to exercise of authority over subordinate individuals and/or organizations, particularly with respect to administration. In agromedicine the Occupational Safety and Health Administration uses the term with respect to hazard control, particularly defining the administrative procedures involved.

Adolescents

Published
Individuals from the age of 13 through 17 years.

See also: age groups

Adrenergic Receptors

Published
There are two general types of a receptors: ß1 located in the heart; ß2 located in all other areas. ß-Blockers are classified as cardioselective or non-selective with regard to their ß1/ß2 activity, but these are not absolute terms.

Adsorption

Published
Process by which chemicals are bound to a surface. Usually used for binding to soil or other nonliving particles but also, less often, for binding to cell surfaces.

advanced air emission control devices

Published
Air pollution control equipment, such as electrostatic precipitators and high energy scrubbers, that are used to treat an air discharge which has been treated initially by equipment including knockout chambers and low energy scrubbers.

From: Ensafe, Inc.

advection

Published
Process of transport of an atmospheric property, or substance, within the atmosphere solely by the mass action of the atmosphere.

From: Ensafe, Inc.

Adverse Effect

Published
A pathological lesion, or a biochemical, metabolic or genetic change that affects the normal function of the organism, impairs the ability to adapt to environmental change, or causes a change in the genetic information transmitted to offspring.

From: Dictionary of Toxicology, 2nd edition.

Aerobic

Published
Although this terms means “requiring air”, in fact it is normally used to mean “requiring oxygen” as in the case of aerobic microoganisms. The alternative meaning as a type of exercise, is not discussed further.

Aerodynamic Diameter

Published
A standard for characterizing air-borne particles that are not spherical in shape. It includes both density and aerodynamic drag, and is expressed as the diameter of a unit density sphere with the same terminal settling velocity as the particle in question, whatever its shape, size or density. This value is of particular interest in respiratory toxicology since it reflects the ease of deposition of all particles except the very small, the deposition of which is determined by particle size alone. In agromedicine, of importance as a factor affecting exposure to particles in pountry houses, silos, etc., particles that may lead to respiratory distress.

Adapted from: Dictionary of Toxicology, 2nd edition.

Aeromonas Spp

Published
[fisheries] These bacteria may infect both cultured and non-cultured fish. Infections, including aeromonad gastroenteritis and wound infections, may occur in humans but are rare, the latter being more common in individuals with compromised immune systems. Aeromonas hydrophila is one of the better known species and is found in fresh and brackish water and can lead to gastroenteritis by ingestion or to wound infection by traumatic injury.

Aerosol

Published
A solid or liquid particle suspended in a gaseous medium and so small that its fall speed is small compared with the vertical components of air motion. Haze and cloud are the commonest atmospheric aerosols, with fall speeds much less than 10 mm/sec. Aerosols in the troposphere generally fall to the surface in a matter of hours or days; those in the stratosphere may remain there for months or years. Volcanoes are the major source of atmospheric aerosols, but human activities (e.g., cultivating dry soils, quarrying, industrial manufacturing, etc.) contribute about 30 percent of tropospheric aerosols. Tropospheric aerosols may act as condensation nuclei; some stratospheric aerosols, especially sulphate particles, have a climatic effect by increasing the Earth's albedo (whiteness or degree of reflection of incident light).

From: Dictionary of Toxicology, 2nd edition.

See also: air pollution

Aerosol Spray

Published
A container in which a propellant (e.g., ammonia, butane or chlorofluorocarbons) is mixed with a substance (e.g., paint, perfume, hairspray, polish or wound dressing) and held under pressure. When the pressure is released the substance is propelled through a nozzle as a mist of aerosols. A more primitive version of the aerosol spray is the liquid atomizer, in which the propulsion pressure is produced by a small hand-operated pump.

From: Dictionary of Toxicology, 2nd edition.

Aflatoxins

Published
A family of mycotoxins produced by the mold Aspergillus flavus and related fungi; included among them are carcinogens and hepatotoxicants. Aflatoxins affect male reproductive capacity and growth rate in birds. They are the causative agents in the Turkey X disease. Aflatoxin B1 is hepatotoxic and is one of the most potent carcinogens known, being active at dietary doses in the part per billion range. Aflatoxins are found as contaminants in both human foodstuffs and animal feed, particularly in corn and peanuts. The extent of aflatoxin contamination is a function of environmental conditions at the time of harvest and storage conditions. Although generally a liver carcinogen, there are species differences, mice being relatively insensitive and showing lung tumors on treatment. Aflatoxin B1(CAS number 1162-65-8)is oxidized by the cytochrome P450-dependent monooxygenase system to form a highly reactive epoxide. Carcinogenesis is believed to be initiated when this potent electrophile reacts with DNA, and hepatotoxicity when it reacts with proteins to cause either fatty liver or liver necrosis. Epidemiological studies in Africa and Asia indicate that it is a human liver carcinogen, although similar studies in North America where aflatoxin contamination is common are generally negative. More recent studies on the occurrence of hepatitis B virus indicate that the presence of this virus, endemic in many African and Asian populations, may potentiate aflatoxin carcinogenicity.

aflatoxin_B1

From: Dictionary of Toxicology, 2nd edition.

See also: activation, bioactivation; mycotoxins; reactive intermediates (reactive metabolites)

Age Groups

Published
Preferred presentation of research data involving age groups by groups of five years (e.g., <5 yrs, 5-9, 10-14 …… 55-59, 60-64, 65-69, etc.). If age group data focuses on youth ages 10-19, preferred presentation is by groups of 2 years (e.g., 10-11, 12-13, 14,15 …. 18-19). If an age group focuses on ages 65+ preferred presentation is by groups of 10 years (e. g., 65-74, 75-84 …. ).  When two or more age groups are collapsed use the same delineations, e. g., 5-14, 55-69. Other designations such as children, adolescents, adults or seniors while generally understood to be birth through 12, 13 through 17, 18 through 64 and 65+ respectively,  lack precise definition and, if used, must be defined in each study.

From: NORA, 2008.

Age-appropriate Work

Published
Work activities that are suitable based on physical and cognitive capabilities deemed to be typical by age demarcationss. Age-appropriate work standards are required for purposes of labor law enforcement.

From: NORA, 2008.

See also: age groups

Agency For Toxic Substance and Disease Registry (ATSDR)

Published
A division of the US Public Health Service charged, under the Superfund Amendments and Reauthorization Act (SARA) an act that amended the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, with the preparation and publication of toxicological profiles for hazardous substances most commonly found at facilities on the CERCLA National Priorities List and that pose the most significant potential threat to human health as determined by ATSDR and the US Environmental Protection Agency. Such profiles summarize the available adverse health effects and review the key peer reviewed literature. Each profile is first published as a draft for public comment then as a revised document with updated versions as appropriate. (www.atsdr.cdc.gov).

From: Dictionary of Toxicology, 2nd edition.

Agent

Published
In the context of agromedicine and/or toxicology an agent is a microorganism or chemical substance whose presence or excessive presence is necessary for the occurrence of a disease.

Aggregate Risk

Published
The sum of individual risks of adverse effects on an exposed population. It should be noted that the simple summation of risks, determined separately, into an aggregate may give an erroneous estimate. Risks may be additive, less than additive, or more than additive (synergistic).

From: Dictionary of Toxicology, 2nd edition.

Agricultural Accident Statistics

Published
There are numerous statistical analyses of agricultural accidents at both the state and national level. However, there is no single overarching source of these statistics or a single system for their classification. In general agricultural accidents fall into three categories, fatal traumatic injuries, non-fatal traumatic injuries and accidents with chronic sequelae. A useful summary of agricultural accident statistics covering cause, location, activity, characteristics of the injured., etc., is that of Purschwitz.

Reference: Purschwitz, M. A., Epidemiology of Agricultural Injuries and Illnesses, Chapter 14 in Safety and Health in Agriculture, Forestry and Fisheries (Langley, R. L., McLymore, R. L., Meggs, W. J.. and Roberson, G. T. editors). Government Institutes, Inc., Rockville MD (1997).

Agricultural Chemicals

Published
Those chemicals used in agriculture that are designed to increase yield of food and fiber either by direct action on crop plants or domestic animals (e.g., fertilizers, plant growth regulators, etc.) or by controlling their diseases, pests, predators or competitors (e.g., fungicides, insecticides, rodenticides, etc.). In the latter case selectivity (i.e., toxicity to the pest with lower toxicity to non-target species) is a desired quality, and the development of such specific toxicants is an important function of comparative toxicology. Other chemicals, although not directly involved in increased production, are used to improve cost effectiveness in agriculture by improving handling and storage qualities of the harvested crop. Agricultural chemicals have the potential of contaminating soil and also water (from surface run-off and leaching into the ground water). In addition, exposure to agrochemicals in both workers and the public can occur because of residues on crops, air contamination resulting from spraying and drift, exposure during manufacture and formulations, and contamination from waste disposal sites. The persistence and bioaccumulation of the older organochlorine insecticides has been well recognized. Newer insecticides, such as the organophosphates, carbamates, synthetic pyrethroids and neonicotinoids are more labile and less likely to cause ecological damage. Fertilizers can contribute to eutrophication and therefore alter ecological balance. Because of their actual or potential toxicity to non-target species, including humans, agricultural chemicals are regulated by law in many countries. Knowledge of agricultural chemicals is essential for all professionals active in Agromedicine.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: acaricides; fungicides; herbicides; insecticides; molluscides; nematocides; pesticides; pollution, agricultural chemicals; rodenticides

Agricultural Field Equipment

Published
Agricultural field equipment is, for all practical purposes, a synonym for agricultural implements, i.e., an implement that is designed to perform agricultural field operations.

The following are included under this term: Bulk carrier equipment (ABC); Mounted implement; Semi-mounted implement; Self-propelled machines (SPM); Towed implement (ATI); Tractors, agricultural

Adapted from: NORA, 2008.

See also: agricultural machinery

Agricultural Gases and Vapors

Published
There are numerous agricultural gases and vapors, some of which are serious health hazards. They include: ammonia; anhydrous ammonia; carbon dioxide; carbon monoxide; fumigants; hydrogen sulfide; methane. Most of these are indoor hazards, particularly in silos and containment facilities. When the chemical is normally used outdoors the principal danger probably lies in pre-use handling. Methane may be generated in manure pits.

See also: air pollution; ammonia; anhydrous ammonia; carbon dioxide; carbon monoxide; fumigants; hydrogen sulfide; manure pits; methane; silo gases.

See also: air pollution

Agricultural Hazardous Occupations Orders (AgHO)

Published
Part of the U. S. Department of Labor’s Fair Labor Standards Act (1938) as amended in 1968. The AgHO prohibit children under the age of 16 from being hired to perform specified hazardous jobs on the farm. An exemption is provided that allows 14 and 15 year olds to perform specified hazardous acts if they have successfully passed training in tractor safety and/or safe tractor and machinery operation.

From: NORA, 2008.

Agricultural Health Study (AHS)

Published
The AHS was initiated by the National Cancer Institute (NCI), the National Institute of Environmental Health Sciences (NIEHS), and the Environmental Protection Agency (EPA) in 1993 to evaluate the role of agricultural exposures, primarily to agrochemicals, in the incidence of cancer and other diseases in members of the farming community. Subsequently (2000), these agencies were joined by the National Institute for Occupational Safety and Health (NIOSH). The study is primarily epidemiological and the cohort consists of almost 90,000 farmers or the wives of farmers recruited in North Carolina or Iowa. The cohort also contains a small number (c. 5000) of "commercial pesticide applicators" from Iowa who work for pest control companies or for businesses that use pesticides regularly. This study has generated a large number of publications and provided important results. Considerable information is provided on-line.

References: http://www.cancer.gov/cancertopics/factsheet/Risk/ahs; http://aghealth.nci.nih.gov/results.html

Agricultural Industry

Published
The science, art and business of cultivating soil, producing crops, raising livestock  and also including transport, processing and sale of farm products. Farming, a slightly more restrictive term, is usually held to describe the production sectors of the agricultural industry, i.e., the science, art and business of cultivating soil, producing crops, and raising livestock. By extension and for convenience the term agricultural industry can also include forestry and fisheries from culture and/or harvesting to sale to the end-user. Agribusiness is a frequently used synonym.

See also: agricultural accident statistics; ANSI; ANSI standards; cumulative trauma disorders (CTDs); EPA pesticide standards; hygiene evaluation; systems standards; worker disabilities, disabled worker needs; worker disabilities, mobility aids; worker disabilities, prevention and safety; worker disabilities, resources for; worker disabilities, task difficulty rating

Agricultural Industry, and Cancer

Published
While overall cancer incidence in the USA is lower among farmers than in the population in general, some forms of cancer such as skin cancer are associated with farming. In recent studies, particularly in the Agricultural Health Study, some cancers are associated with exposure to agrochemicals, primarily pesticides.

Agricultural Industry, and Disease and Illness in

Published
While there is no disease or illness unique to the agricultural industry there are a number for which the incidence is higher in agriculture than in other occupations. Some examples include asthma and other respiratory diseases associated particularly with working in grain or closed animals facilities or skin cancer associated with UV light exposure.

See also: disease and illness

Agricultural Industry, and Mental Health Issues

Published
Although all of the various mental health problems that affect the population in general may be found among members of the agricultural workforce there are none that are restricted to this group of workers. However, mental health problems are frequently exacerbated by stress and the agriculture is, as a consequence of factors beyond the control of the participants, a particularly stressful occupation. Such stresses include economics, weather.

Agricultural Industry, and Safety and Health Regulations

Published
Safety and health regulations applicable to the agricultural industry may be promulgated by several federal and state agencies, including the USDA, the US EPA and OSHA. The aspect of agriculture most subject to regulations is that of pesticide use and the US EPA the agency most concerned with their promulgation. A detailed summary of such regulations up to 1997 may be found in Langley et al., 1997 and on the web sites of the agencies involved.

See also: agricultural industry, chemical hazards; agricultural machinery and equipment, design; cancer; crush point; pinch point

References: Tencer, GM., Chapter 13 in Langley, R. L., et al., (eds). Safety and Health in Agriculture, Forestry and Fisheries. Government Institutes, Rockville MD., 1997

http://www.osha.gov/dsg/topics/agriculturaloperations/

http://www.nclabor.com/osha/etta/indguide/ig10.pdf

http://www.epa.gov/oppfead1/safety/resource.htm

Agricultural Industry, Chemical Hazards in

Published
Any chemical entity or mixture of chemicals that is known to have an adverse effect(s) on human health, either acute or chronic.  Depending on the context it is correct to distinguish between chemical hazards and potential chemical hazards, The modern agricultural industry utilizes a large number of chemicals and chemical mixtures any of which, under the right exposure scenario, may be toxic to humans. The following is a list of chemicals and chemical classes, used in agriculture that may become toxicants to humans.

Pesticides

Insecticides

Fungicides

Herbicides

Nematocides

Rodenticides

Fumigants

Gases

Ammonia

Carbon monoxide

Carbon dioxide

Methane

Hydrogen sulfide

Nitrogen oxides

Welding fumes

Fuels, Solvents, Etc

Antifreeze

Diesel fuel

Gasoline

Hydraulic fluids

Kerosene

Motor oil

Mineral spirits

Paint thinner

Toluene

Transmission fluid

Biological agents

Endotoxins

Mycotoxins

Antimicrobial agents

Antibiotics

Fertilizers

Detergents

Reference: Meggs, W. J. and Langley, R. L., Chapter 16 inLangley, R. L., et al., (eds). Safety and Health in Agriculture, Forestry and Fisheries. Government Institutes, Rockville MD). 1997).

Agricultural Industry, Electrical Hazards

Published
Electrical hazards are associated with power tools and machinery as well as work places.

Agricultural Industry, Employee Responsibilities

Published
Agricultural employees are responsible for compliance with federal and state standards and regulations designed to maintain a safe and healthy workplace. A number of state Cooperative Extension Services have web sites that enumerate employee and employer responsibilities.

References: http://www.uvm.edu/~farmlabr/?Page=safety/responsibility.html&SM=safety/submenu_safety.html;

Langley, R. L., et al., (eds). Safety and Health in Agriculture, Forestry and Fisheries. Government Institutes, Rockville MD., 1997.

Agricultural Industry, Employer Responsibilities

Published
Employees have the responsibility to provide a safe and healthy workplace and to comply with all agricultural safety and health standards required by state and federal agencies. Furthermore, they are responsible for safety and health training and for keeping appropriate records of employee work-related injuries and illnesses. It is the responsibility of the employer to ensure employee compliance with health related rules and regulations. Regulations relevant to workplace safety and health may be promulgated by the US Department of Agriculture, OSHA and/or the US EPA. A number of state Cooperative Extension Services have web sites that enumerate employee and employer responsibilities.

References:

http://www.ers.usda.gov/publications/ah-agricultural-handbook/ah719.aspx

http://www.uvm.edu/~farmlabr/?Page=safety/responsibility.html&SM=safety/submenu_safety.html

http://www.osha.gov/dsg/topics/agriculturaloperations/standards.html

Langley, R. L., et al., (eds). Saftey and Health in Agriculture, Forestry and Fisheries. Government Institutes, Rockville MD., 1997.

Agricultural Industry, Machinery Hazards

Published
As agriculture becomes more mechanized, an increased proportion of agricultural injury becomes machinery-related. Roberson (1997) lists fourteen hazard categories related to farm machinery. They include:

Pinch point

Visibility

Speed

Entanglement

Thrown Objects

Work environment

Run over

Sharp edges

Energy release

Cumulative trauma

Roll over

Crush point

Falling

Chemicals

Reference: Hazard Categories (from Roberson, G. T., Chapter 15 in Langley, R. L., et al., (eds). Safety and Health in Agriculture, Forestry and Fisheries. Government Institutes, Rockville MD., 1997).

Agricultural Industry, Noise and Hearing Loss

Published
Excessive and/or continuous noise may result in damage to the inner ear and is a common cause of hearing loss.

Reference: Siebens, D., Chapter 4 in Langley, R. L., et al., (eds). Safety and Health in Agriculture, Forestry and Fisheries. Government Institutes, Rockville MD., 1997.

Agricultural Industry, Non-venomous Bites

Published
In addition to venomous bites, non-venomous bites, particularly by farm animals, may present a serious hazard.

Agricultural Industry, Vibration

Published
Machinery-induced vibration of the whole body has been associated with a variety of musculo-skeletal problems, including lower back pain. Machinery and/or power tool-induced arm vibration has been implicated in more localized musculo-skeletal problems.

Agricultural Industry, Zoonotics

Published
Infections transmitted from animals to humans. Transmission may be by arthropod bites or by direct contact with animal products. They include brucellosis and Lyme disease and can be serious health problems.

Agricultural Industry,Envenomization

Published
This term is used for snake and insect bites and stings as well as exposure to poisonous plants.

Agricultural Machinery

Published
See all entries following on various aspects of safety and operation of agricultural, including:
operating instructions;

operators at risk;

regulations;

safety concepts;

safety hierarchy;

warning signs of.

Agricultural Machinery and Equipment, Design

Published
Agricultural machinery and equipment includes both manual and powered devices used on the farm. Machinery used in forestry and fisheries are subject to the same design needs. In general, design needs include the following: to increase yield; to be more efficient, producing the same or better yields with less manpower; to be safer to operate.

Agricultural Machinery, and Operating Instructions

Published
The Occupational Safety and Health Act requires that employees operating machinery, including tractors, of safe operating practices when first assigned and at least annually thereafter.

Agricultural Machinery, and Operators at Risk

Published
Operators most at risk are those operating equipment alone and such individuals are advised to have cell phone contact available. Untrained operators are at significantly increased risk, whether operating alone or with other operators.

Agricultural Machinery, and Regulations

Published
Regulations for the safe operation of agricultural machinery are the responsibility of OSHA, the Occupational Safety and Health Administration and may be obtained from the OSHA web site. (www.OSHA.gov).

Agricultural Machinery, and Safety Concepts

Published
Safety concepts are discussed in detail by Roberson, 1997. Safety, hazard, risk, exposure, injury and illness are defined as they apply to agricultural machinery.

Reference: Roberson, G. T., Hazard Mangement and Safety with Agricultural Machinery. Chapter 15 in Safety and Health in Agriculture, Forestry and Fisheries (Langley et al., eds). Government Institutes, 1997.

Agricultural Machinery, and Safety Hierarchy

Published
Used by manufacturers to prioritize and deal with machinery related hazards: first – eliminate the hazard; second – apply latest safety technology; third – use warning signs; fourth – train and instruct; fifth – prescribe personnel protective equipment.

Reference: Roberson, G. T., Hazard Mangement and Safety with Agricultural Machinery. Chapter 15 in Safety and Health in Agriculture, Forestry and Fisheries (Langley et al., eds). Government Institutes, 1997.

Agricultural Sector Hazard

Published
An existing or potential condition on or off the agricultural sector work site, directly related to agricultural sector operations, that is associated with a high risk of physical or physiological harm.

From: NORA, 2008.

Agricultural Sector Injury

Published
Injury occurring in the agricultural sector work site directly related to agricultural sector operations, including injury to bystanders, or an injury occurring off agricultural sector property that involves agricultural sector work.

From: NORA, 2008.

See also: Farm and Agricultural Injury Classification Code

Agricultural Worker

Published
As defined in EPA Worker Protection Standards (WPS). While these emphasize pesticide handling and use they are too some extent more comprehensive. Many publications are available from the US EPA.

Reference: http://www.epa.gov/agriculture/awor.html

Agriculture

Published
Industry responsible for the production of food (crops and livestock), animal feed and fiber. While technically not including forestry, fisheries, hunting and trapping, it is often used as a collective term to include all of these activities.

From: NORA, 2008.

Agriculture, and Hazards in

Published
Hazards in any and all aspects of agriculture , forestry and fisheries are numerous and are frequently life-threatening. They may involve machinery and equipment or they may be result of aspects of the ambient environment, some of which may be extreme. Links to entries that treat hazards separately and in more detail are found in the following five entries. Most can be avoided by careful adherence to regulations either from OSHA or from the manufacturer

Agritourism

Published
Any attraction where the general public is invited to a farm, ranch or agricultural operation for the purpose of enjoyment, education or active involvement in farm activities.

From: NORA, 2008.

Agroecosystem

Published
A specialized ecosystem resulting from agricultural practices, with the specific introduction and culturing of crop plant or animal species and the elimination of pest plant or animal species. Agroecosystems are important in agromedicine and toxicology because of the widespread use of pesticides and other agricultural chemicals and their possible dissemination into air, ground water, surface water and the food chain.

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: ecosystems

Air

Published
Although used to define the earth’s atmosphere, air is used in many other contexts some of which have no relevance to the earth’s atmosphere.

Air Bone Gap

Published
In audiology a situation in which the air conduction tests are at variance with the bone conduction tests.

Air Conditioning

Published
Modifying the properties of indoor ambient air, notably temperature and humidity. Also used to indicate the equipment used to bring about such modification.

Air Emissions

Published
The release or discharge of a pollutant, from a stationary source, into the ambient air. This may involve release from a stack or as a dust, mist or vapor from manufacturing or formulation. Pollutants may also be discharged into the air from mobile sources or from area sources such as roads and fields.

Adapted from: Ensafe glossary of risk analysis terms.

Air Exchange Rate

Published
A measure of the extent of replacement of the air in an enclosed space. For shorter times it is expressed as a percentage of the air in the space per hour. For longer times it may be expressed as the number of total replacements per unit time. Different air exchange rates are recommended for different spaces, e. g., classrooms, operating rooms, parking garages. In agromedicine the air exchange rates for such structures as poultry houses is important, not only as it relates to the birds but also to worker health.

Air Filtration

Published
Removal of particulate matter (particulate air filter) or chemicals (chemical air filter) from the air. The air in indoor spaces of any kind including all types of buildings as well as airplanes, etc. They may also be used outdoors as, for example, to monitor air pollution. Particulate air filters are usually made from fibers and remove dust, bacteria, etc. Chemical air filters contain adsorbents and remove volatile organic chemicals.

Air Monitoring

Published
Continuous analysis for the presence of pollutants in the ambient air. This may be displayed in real time or after data analysis.

Air Pollution

Published
A serious problem in populated areas of industrialized nations and in other locations where, for example, excessive amounts of fossil fuels are burnt. Both the nature and source of air pollutants vary with the location: open country, remote from industry or heavy traffic, differs from the center of a large city or from an area downwind from a coal-fired power plant or other industry. In general, the principal air pollutants are carbon monoxide, oxides of nitrogen, oxides of sulfur, hydrocarbons and particulates. The principal sources are transportation, industrial processes, electric power generation, and the heating of homes and buildings. Of the organic constituents, hydrocarbons such as benzo[a]pyrene are produced by incomplete combustion and are associated primarily with the automobile. Hydrocarbons are usually not present at levels high enough to cause a direct toxic effect, but are important in the formation of photochemical air pollution. This is formed as a result of interactions between hydrocarbon and oxides of nitrogen in the presence of ultraviolet light, giving rise to lung irritants such as peroxyacetyl nitrate, acrolein and formaldehyde. Particulates are a heterogeneous group of particles, often seen as smoke, that are important as carriers of adsorbed hydrocarbons and as irritants to the respiratory system. The distribution of such particles in the atmosphere, as well as in the respiratory tract, is largely a function of their size. Respiratory system effects are the primary human health effects observed, with individuals possessing weak or immature respiratory and circulatory systems being at greatest risk. The known health effects of specific pollutants include: sulfur dioxide and sulfuric acid - bronchoconstriction and irritation of mucous membranes; nitrogen dioxide - pulmonary edema and hemorrhage; ozone - pulmonary edema and hemorrhage; carbon monoxide - headaches, dizziness and suffocation; lead - renal toxicity, impaired erythropoiesis, and nervous system damage (primarily in the fetus and young child); and dust and fibers - scarring or fibrosis in lungs. Environmental effects of air pollution include: injury to plants, including changes in color and growth, increased susceptibility to disease, death and ultimately replacement of species in ecosystems; chronic poisoning of domestic animals from ingestion of food contaminated with pollutants from air, primarily metals and fluoride (leading to fluorosis); damage to buildings, metal structures, rubber and other materials from acids and ozone; reduced visibility from particulates in smog; the ''greenhouse effect” from elevated carbon dioxide concentrations; the formation of acid deposition, primarily from the presence of sulfuric and nitric acids, that causes toxicity to fish and forests.

From: Dictionary of Toxicology, 2nd edition.

See also: acrolein; air quality index; air quality standards; carbon monoxide; particulates; pollution, effect on domestic animals; pollution, effect on plants

Air Purifying Respirator

Published
A modification of respirators designed to filter chemicals (without power assisted air flow) differing primarily that their effectiveness is improved by having battery-operated air flow. There are numerous designs, some filtering particles, others may be adapted for chemicals such as pesticides.

Air Quality Act, 1967

Published
U.S. Federal law that empowered the Department of Health, Education, and Welfare to designate areas within which air quality was to be controlled, to set ambient air standards, to specify technologies to be used in pollution control and to prosecute offenders if local agencies fail to do so. Subsequently replaced by the Clean Air Act, administered by the Environmental Protection Agency.

From: Dictionary of Toxicology, 2nd edition.

See also: Clean Air Act

Air Quality Criteria

Published
The levels and length of exposure above which adverse effects on human health may occur. Quantitative standards for air pollutants are defined by law.

See also: Air Quality Standards; Air Quality Index; Clean Air Act.

Air Quality Index

Published
A standardized system proposed by the Environmental Protection Agency (EPA) to give the public an indication of the degree of air pollution. The numbers of the index result from measurements of ozone, suspended particulates, sulfur dioxide and carbon dioxide. The descriptors associated with various index levels are: 0, no pollution; 100, standard; 200, alert; 300, warning; 400, emergency; 500, significant harm.

From: Dictionary of Toxicology, 2nd edition.

Air Quality Standards

Published
Legal standards of exposure to air pollutants that should not be exceeded in a given geographical area. The standard specifies both the concentration and the duration of exposure, and usually is below the threshold value.

From: Dictionary of Toxicology, 2nd edition.

Air Sampling Data Sheet

Published
Numerous forms have been developed for the reporting of indoor pollution; by government agencies, insurance companies and others. That developed by OSHA is one of the more comprehensive, requiring not only detailed results but also the identity, qualifications and work status of the individual doing the test as well as details of the equipment used.

See also: air pollution; air pollutants

Airline Respirator

Published
A breathing device consisting of a full face mask connected to a tank of compressed air. Also known as an air-supplied respirator.

See also: respirators

Airway

Published
Any segment, such as the bronchial tubes, conducting air between the mouth and the alveoli. Also used to describe the entire route for air flow between mouth and alveoli.

From: Dictionary of Toxicology, 2nd edition.

Airway Resistance

Published
The resistance to air flow caused by the airways between mouth and alveoli.

Alar

Published
Daminozide; butanedioic acid mono(2,2-dimethylhydrazide); N-(dimethylamino)succinamic acid; succinic acid 2,2-dimethylhydrazide. CAS number 1596-84-5. Plant growth regulator. Metabolized in mammals to 1,1-dimethylhydrazine. Banned for use in the USA on all food crops on the basis of chronic feeding tests in rodents in which the metabolite 1,1-dimethylhydrazine produced tumors at very high doses. Alar is still in use on non-food crops, primarily ornamentals.

alar

Adapted from: Dictionary of Toxicology, 2nd edition.

Alaska Marine Safety Education Association (AMSEA)

Published
A non-profit agency which conducts marine safety instructor-training and produces educational materials and training to commercial fishermen nationally.

From: NORA, 2008.

Alcohol

Published
A class of organic compounds containing one or more hydroxyl groups; the term alcohol is often used to refer specifically to ethanol (ethyl alcohol).

See also: ethanol

Alcohol Dehydrogenase (EC 1.1.1.1)

Published

An enzyme that catalyzes the conversion of alcohols to aldehydes or ketones.



RCH2OH + NAD+ → RCHO + NADH + H+



The reaction is reversible, and in vitro carbonyl compounds are reduced to alcohols. In vivo, however, the reaction proceeds in the direction of alcohol consumption, since aldehydes are further oxidized to acids. The enzyme is found in the soluble fraction of liver, kidney and lung, and is the most important enzyme involved in the metabolism of foreign alcohols. It is a dimer, the subunits of that can occur in several forms, thus giving rise to a large number of variants of the enzyme. It can use either NAD+ or NADP+ as a coenzyme, but the reaction proceeds more slowly with NADP+. Since aldehydes are toxic and, because of their lipophilicity, not readily excreted, alcohol oxidation may be considered an activation reaction, the further oxidation of the aldehyde being detoxication. Primary alcohols are oxidized to aldehydes, n-butanol having the highest oxidation rate. Secondary alcohols are oxidized to ketones, but the rate is less than that for primary alcohols, and tertiary alcohols are not readily oxidized. This reaction should not be confused with the monooxygenation of alcohols, a cytochrome P450-dependent reaction that occurs in the microsomes.



From: Dictionary of Toxicology, 2nd edition.

See also: acetaldehyde; ethanol

Aldehyde Dehydrogenase

Published
An enzyme that catalyzes the formation of acids from aliphatic and aromatic aldehydes; the acids are then available as substrates for phase II conjugating enzymes.



RCHO + NAD+ + O2 = RCOOH + NADH + H+



The enzyme from mammalian liver has been isolated, and a large number of aldehydes can serve as substrates. Aldehyde oxidase and xanthine oxidase are both flavoproteins that contain molybdenum. Their primary role, however, seems to be the oxidation of endogenous aldehydes formed as a result of deamination reactions. It should be noted that both the aldehydes and the acids may be toxic and this reaction, may not be a detoxication reaction. It is inhibited by disulfiram, used in the suppression of ethanol consumption in treatment of chronic alcoholism.

Adapted from: Dictionary of Toxicology, 2nd edition.

Aldicarb

Published
2-methyl-2-(methylthio)propanal O-[(methylamino)carbonyl]oxime; Temik. CAS number 116-06-3.  A systemic carbamate insecticide, acaricide and nematocide for soil use with an extremely high level of acute toxicity. It has also become a contaminant of ground water in some regions because of its relatively high water solubility. The acute oral LD50 in male rats is 0.93 mg/kg and acute dermal LD50 in male rabbits is 5.0 mg/kg. The 96-hour LC50 in rainbow trout is 8.8 mg/ l. It is a neurotoxicant by virtue of its ability to inhibit acetylcholinesterase. EPA put a phased ban in place in 2010, requiring an end to distribution by 2017, with a complete ban in place by 2018. aldicarb

Adapted from: Dictionary of Toxicology, 2nd edition.

See also: carbamate insecticides; carbamate poisoning, symptoms and therapy

Algae

Published
A very diverse group of simple eukaryotic plants. The group includes organisms that range from the unicellular to large multicellular organisms such as the giant seaweeds (kelp). The group is polyphyletic, i. e., lacking a common ancestor, almost certainly due to the fact that it represents an arbitrary combination of disparate groups each of which has, presumably, a common ancestor. They are referred to as “simple” because, regardless of size, they lack the internal anatomic structures characteristic of higher plants. Note that the cyanobacteria are often referred to as “blue green algae”. This is incorrect and should not be used. The cyanobacteria are prokaryotic and are, therefore, not algae. Most algae are important components of aquatic ecosystems and are not harmful to human health. Some algae, however, produce toxins and some forms of fish and/or shellfish poisoning are, in fact, due to the presence of accumulated algal toxins. For example, ciguatera fish poisoning is due to the presence in some food fish of ciguatoxins produced by the algal species Gambierdiscus toxicus. Other algae can be responsible for algae blooms such as red tide that can be a serious environmental problem.

See also: ciguatoxin; cyanobacteria; red tide

Reference: http://www.cdc.gov/nceh/hsb/hab/default.htm

Alkali

Published
Corrosive or caustic alkaline substance. When ingested cause chemical burns to the mouth, esophagus and stomach. Alkalis such as sodium and potassium hydroxide, ammonia, etc. are frequently found in the home as cleaning fluids, drain cleaners, etc.

From: Dictionary of Toxicology, 2nd edition.

Alkaline

Published
Having a pH higher than 7.0, i.e. between 7 and 14.

Alkaloids

Published
Organic nitrogenous bases produced (with the exception of ergot alkaloids) by dicotyledonous plants. They occur as salts with organic hydroxy acids such as hydroxybutanedioic, 2-hydroxy-1,2,3-propanetricarboxylic, tannic and quinic (1,3,4,5-tetrahydroxycyclohexanecarboxylic) acids. They have potent pharmacological activity and form the basis of many drugs. The majority are very toxic both by inhalation and ingestion. They vary considerably in their chemical properties and constitution depending on the parent base: aryl-substituted amines, indole, pyridine, quinoline and isoquinoline.  Most alkaloids are crystalline solids with a very bitter taste; they are sparingly soluble in water, but usually soluble in organic solvents such as ethanol, ether and trichloromethane. They are optically active, most being dextrorotatory; they have been used for the resolution of racemic acids into their enantiomorphs. They are basic, forming crystalline salts with acids; these are water-soluble. Drug preparations are usually based on the salts (e.g., hydrochloride, bromide, sulphate). Alkaloids give precipitates with such reagents as phosphomolybdic acid, potassium mercury (II) iodide and potassium triiodide. Commercially the alkaloids are extracted from powdered plant material with alcohol, water or dilute acid, and then precipitated out on the addition of base. The crude extract, often containing a range of alkaloids, is purified by physical methods of separation including fractional crystallization, countercurrent distribution, adsorption and partition chromatography. There are a very large number of plant alkaloids but few are important in agromedicine. ergot alkaloids are used in veterinary practice.

From: Dictionary of Toxicology, 2nd edition.

See also: ergot alkaloids

Alkalosis

Published
A condition in which the pH of the blood is alkaline beyond the normal range, usually above 7.8, due to a disturbance in the acid/base balance.

From:
Dictionary of Toxicology, 2nd edition.

See also: acid/base balance; acidosis; alkalosis, metabolic; alkalosis, respiratory

Alkalosis, Metabolic

Published
A form of alkalosis caused by severe vomiting and the resultant loss of hydrogen chloride or changes in potassium ion concentration, either of which may be due to a variety of poisons. It involves an increase in blood bicarbonate concentration.

From: Dictionary of Toxicology, 2nd edition.

See also: alkalosis

Alkalosis, Respiratory

Published
A form of alkalosis caused by excessive expiration of carbon dioxide. It involves little or no change in blood bicarbonate concentration, but rather an increase in carbonic acid. It may be due to hyperventilation or poisoning with toxicants such as salicylate.

From: Dictionary of Toxicology, 2nd edition.

See also: alkalosis

All-terrain Vehicle (ATV)

Published
A vehicle that: a) travels on low pressure tires; b) has a seat that is straddled by the operator; c) has a handlebar for steering control; and d) is meant for off-road use. An ATV can be either a 3-wheeler or a 4-wheeler.

From: NORA, 2008.

Allergen

Published
Any substance capable of eliciting an allergic response.

See also: allergenic reactions, allergic response; asthma

Allergenic Reactions, Allergic Response

Published
Allergic responses are of particular importance in agromedicine because of the high exposure to environmental allergens (e. g., ragweed and other pollens) as well as enclosed animal facilities. The term, allergic response, has been used in several different ways. The broadest definition, and the one upon which the Gell and Coombs classification of allergic response is based, is that it is any immune response detrimental to the host ( See Table). In this scheme, allergic responses are classified by the mechanism involved, rather than by the causative agent or symptoms produced. Consequently, many things not commonly thought of as allergic responses, such as systemic lupus erythematosis (SLE), serum sickness, tuberculosis and hemolytic anemia, are included. A narrower definition includes only those immediate hypersensitivity reactions, the local and systemic anaphylactic reactions that are produced by IgE antibodies. Although this definition includes common allergic responses such as the rhinitis and asthma produced by pollens and danders, it does not include the delayed-type hypersensitivity reactions such as contact dermatitis caused by poison ivy, drugs, cosmetics and certain metals, or the immediate hypersensitivity reactions not mediated by IgE (See: immediate hypersensitivity). Most environmental agents will produce either a type I or a type IV hypersensitivity reaction (See: hypersensitivity), the types most commonly referred to as allergic responses. For example, Bacillus subtilus, pesticides, food additives and drugs can produce both local and systemic anaphylactic reactions. Formaldehyde, antimicrobials used in cosmetics and poison ivy can all produce delayed-type hypersensitivity (See: delayed hypersensitivity). There are also a few notable environmental agents that produce type II and type III responses. The gold salts used in medicinal treatments and the mercury used in photography can cause type II and type III reactions, as can certain drugs (e.g., penicillin, quinidine, tetracycline). Many allergenic compounds can induce different types of responses depending on the conditions of exposure (e.g., concentration, route of exposure, genetic predisposition of the host, etc.). Many chemicals, drugs, metals and/or their metabolites are highly reactive and bind to or substantially alter native proteins. Often, these are low-molecular-weight compounds that are not allergenic in their native form, but as ''altered-self' proteins can induce a substantial allergic response. There is also an element of genetic predisposition in many allergic responses. For instance, family studies have shown that ragweed hay fever is more likely to occur in those individuals carrying various genetic markers.

Gell and Coombs classification scheme of allergy
Classification Mechanism Targets Examples
Type I- anaphylaxis IgE bound to mass cell/ basophil triggers the release of soluble mediators (e.g., leukotrienes and vasoactive amines such as histamine), after contact with antigen, to produce local or systemic effects. The effects occur within minutes of the secondary challenge Gastrointestinal tract (food allergies), skin (urticaria and atopic dermatitis), respiratory system (rhinitis and asthma) Local effects- asthma, urticaria(hives), rhinitis, atopic dermatitis. Systemic effects- vascular shock, asphyxia
Type II- cytolytic IgG and/or IgM directed against cells bind to the cells and result in the destruction of the cells via complement fixation, opsonization or antibody-dependent cellular cytotoxicity Tissues of circulatory system (e.g., red blood cells, white blood cells), their progenitors, and the spleen haemolytic anemia, leukopenia and thrombocytopenia, lungs and kidneys (Goodpasture’s disease)
Type III immune complex cytolytic Antigen/antibody complexes of a certain size deposit in various tissues and may then fix complement, resulting inflammation and destruction of nearby tissue Skin (systemic lupus erythematosis), joints(rheumatoid arthritis), kidneys (glomerular nephritis), lungs(hypersensitivity pneumonitis), circulatory system (serum sickness) Systemic lupus erythematosis (SLE), glomerular nephritis rheumatoid arthritis, serum sickness
Type IV- Delayed-type hyper- sensitivity Sensitized T cells induces a delayed-type hypersensitivity response. This response does not involve antibody. Effects generally appear 24-48 hr after exposure and peak 48-72 hr after exposure Any organ, but especially skin (contact dermatitis) Contact dermatitis, tuberculosis
Adapted from: Dictionary of Toxicology, 2nd edition.

See also: anaphylactic shock; antibody-dependent cytotoxicity; autoimmunity; complement; contact dermatitis; contact phytodermatitus; delayed hypersensitivity; immediate hypersensitivity; mast cells/basophils

Allergenicity

Published
The potential of a compound to provoke an allergic response.

See also: allergenicity testing; allergenic reactions, allergic response; asthma

Allergenicity Testing

Published
The most common methods for testing the allergenicity of a compound are the dermal sensitization tests. The radioallergosorbent test (RAST) can also be used to screen individuals for elevated levels of IgE specific for the tested allergen. A high level of IgE specific for that allergen would predict a type I, or anaphylactic, response to that compound.

From: Dictionary of Toxicology, 2nd edition.

See also: acute toxicity testing; allergenic reactions, allergic response; asthma; dermal sensitization tests; immunoassay; phototoxicity tests

Allergic Shellfish Poisoning

Published
Allergic reaction that can result in certain individuals after the ingestion of shellfish that contain powerful sensitizing agents. Such poisoning is rarely fatal.

From: Dictionary of Toxicology, 2nd edition.

Allergy

Published
Classically, an altered state of immune responsiveness to an antigen (protein, lipopolysaccharide, etc., of any substance capable of eliciting an immune response). Now common usage equates allergy and hypersensitivity, and refers to an enhanced immune reactivity. Thus, an allergic response is an unusually vigorous host reaction to an antigen. There are two fundamental types of allergic response. (1) Immediate -- unusual sensitivity to an antigen manifested by a tissue reaction occurring within minutes after an antigen combines with antibody. Anaphylaxis is an example. (2) Delayed--cell-mediated sensitivity manifested 24-48 hours after an antigen combines with antibody. Hypersensitivity to poison ivy is an example.

From: Dictionary of Toxicology, 2nd edition.

See also: allergenic reactions, allergic response

Alternative Communication System

Published
In forestry, a system by voice, hand or media other than horn or whistle which provides a safe and reliable method of communication between crew members.

From: NORA, 2008.

Alveoli

Published
In general, small hollows or cavities (e.g., tooth sockets or depressions in the gastric mucosa). The most important use of the term is for the terminal air sacs of the lung. The pulmonary alveoli are thin-walled hollow structures opening from an alveolar duct or sac. Each alveolus is approximately 250-350mm in diameter, and estimates of the total number in the adult human vary from 100 x106 - 500 x 106. The pulmonary capillaries pass between the alveoli with the blood air distance (capillary wall and alveolar wall) varying up to 2.5 mm. The large total alveolar surface area, up to 100 m2 at maximum inspiration, not only provides the surface for exchange of oxygen and carbon dioxide, but also makes the alveolar surface an important portal of entry for volatile toxicants and/or for the elimination of volatile toxicants or volatile products of toxicant metabolism.

From: Dictionary of Toxicology, 2nd edition.

Amanitin

Published
CAS Number 11030-71-0. A drug derived from the highly poisonous fungus Amanita phalloides (death cap). Alpha-amanitin, a cyclic octapeptide, is toxic because of its affinity for RNA polymerase II in eukaryotic cells. Since this enzyme is responsible for mRNA synthesis in the cell, the compound is a potent and selective inhibitor of mRNA synthesis. It is effective at concentrations below 1 mg/ml, and its specific action has made it useful in experimental biology. It is often used with actinomycin D to block RNA synthesis.

From: Dictionary of Toxicology, 2nd edition.

Ambient

Published
Environmental or surrounding conditions. In environmental toxicology, used to describe the concentration of a toxicant in the environment of a living organism. Conditions delineated may include noise as well as temperature, humidity and the concentration of toxicants or potential toxicants.

Ambient Air

Published
Environmental or surrounding conditions with specific reference to air rather than other media such as water.

Ambient Air Standard

Published
A quality standard for air in a particular place defined in terms of pollutants. Industries discharging pollutants are required to limit emissions to levels that will not reduce the quality of air below the standard. The principle is used widely in the USA.

From: Dictionary of Toxicology, 2nd edition.

American Association of Poison Control Centers (AAPCC)

Published
Establishes standards for poison control and information centers and procures information on the composition of commercial products that may cause accidental poisonings and on the acute toxicity of toxicants.

From: Adapted from Dictionary of Toxicology, 2nd edition.

American Board of Toxicology (ABT)

Published
A board in the United States that certifies diplomates in general toxicology following successful passage of a written examination. Recertification occurs at 5 year intervals. The Executive Office is in Raleigh, North Carolina, U.S.A.

From: Dictionary of Toxicology, 2nd edition.

American Board of Veterinary Toxicology (ABVT)

Published
Associated with the American Veterinary Medical Association and establishes standards for accreditation as a veterinary toxicologist. Accreditation is by examination.

From: Dictionary of Toxicology, 2nd edition.

American Chemistry Council

Published
The American Chemistry Council (ACC) is a trade association, representing companies engaged in the business of chemistry, currently estimated to be an $812 billion enterprise throughout the world. ACC's fulfills its mission through advocacy using member performance, political engagement, communications and scientific research.



American College of Occupational and Environmental Medicine (ACOEM)

Published
An international society of occupational physicians dedicated to providing leadership in the promotion of optimal health and safety of workers and workplaces. This is accomplished by: educating health professionals and the public; stimulating research; enhancing the quality of practice; influencing workplace and public policy; advancing occupational and environmental medicine.

Reference: http://www.acoem.org/vision.aspx#sthash.dEPI57b8.dpuf

American College of Occupational Medicine (ACOM)

Published
Former name of American College of Occupational and Environmental Medicine (ACOEM).

American College of Toxicology (ACT)

Published
A US professional society whose members are toxicologists from all specialties, although preponderantly those in or associated with regulatory toxicology. It organizes meetings, publishes a newsletter and journal and accredits toxicologists.

From: Dictionary of Toxicology, 2nd edition.

American Conference of Governmental and Industrial Hygienists (ACGIH)

Published
A non-governmental organization in the USA, important primarily for the development and publication of threshold limit values to air-borne toxicants in the workplace.

From: Dictionary of Toxicology, 2nd edition.

See also: threshold limit value, ceiling; threshold limit value, short-term exposure limit; threshold limit value, time-weighted average

American Dog Tick

Published
Dermacentor variabilis, is also known as the wood tick, is found predominantly east of the Rocky Mountains in the United States but also in some parts of Canada and Mexico as well as the Pacific Northwest Although the adults are most often found on dogs, the American dog tick will feed on other mammals, including humans. D. variabilis is a vector of the pathogens causing Rocky Mountain spotted fever and tularemia.

See also: ticks

American Industrial Hygiene Association (AIHA)

Published
Professional society of industrial hygienists devoted to the study of factors affecting the safety and health of industrial workers.

American National Standards Institute (ANSI)

Published
A non-profit organization that is involved in the development of voluntary standards for products, services and workplace personnel.

American Society of Agricultural and Biological Engineers (ASABE)

Published
A professional society of engineers that organizes meetings, promulgates standards and advances agricultural and biological engineering as a career profession.

American Society of Agricultural and Biological Engineers Standards

Published
Standards, engineering Practices, and data are generated by ASABE for one or more of the following reasons: providing interchangeability between similarly functional products and systems manufactured by two or more organizations; reducing the number and variety of components required to serve an industry; improving personal safety during operation of equipment; establishing performance criteria for products, materials, or systems; providing a common basis for testing, analyzing and describing the performance and characteristics of products, methods, materials, or systems; making available design data; developing a sound basis for codes, education, and legislation; providing a technical basis for international standardization; increasing efficiency in design, development and production.

American/Northern Lobster

Published
Crustaceans with large muscular claws such as the American/Northern lobster, Homarus americanus, can be dangerous since the claws can inflict serious crushing injuries.

Americans With Disabilities Act (ADA)

Published
The Americans with Disabilities Act of 1990 (ADA) is a law enacted by the U.S. Congress in 1990, in 2009. The ADA prohibits discrimination based on disability which is defined by the ADA as "a physical or mental impairment that substantially limits a major life activity." Definition of any particular “disability” is made on a case by case basis and certain specific conditions are excluded, including current substance abuse and visual impairment correctable by prescription lenses.

References: http://www.ada.gov/pubs/ada.htm; http://www.dol.gov/dol/topic/disability/ada.htm

Ammonia (NH3)

Published
CAS number 7664-41-7. A colorless gas with a pungent odor, detectable by humans down to concentrations of 53 ppm. Solutions in water, forming ammonium hydroxide (NH4OH), are alkaline and corrosive. It has numerous industrial uses, such as in the manufacture of nitric acid, fertilizers, explosives and synthetic fibers, and also in refrigeration. Ammonia is also used in household cleaners. Inhalation of concentrated vapors causes severe respiratory system distress, including spasm of the glottis, respiratory tract, edema and asphyxiation. Such exposure can be life-threatening, but if exposures are not acutely toxic, chronic residual effects do not result. It can cause alkali burns to the eye, with subsequent opacification, perforation of the cornea and iritis.

From: Dictionary of Toxicology, 2nd edition.

See also: air pollution

Reference: ATSDR Toxprofile, 09/2004.

Ammonia, Anhydrous

Published
Anhydrous (i. e., without water) ammonia is a widely used fertilizer. It can exist as either a liquid or a gas, commonly being transported and applied as a liquid. It is highly reactive with water (forming ammonium hydroxide) and with human tissues, causing burns (including corneal burns) and respiratory distress.  An extensive account of the dangers of anhydrous ammonia, its uses, storage, application, etc., has been prepared by the University of Minnesota Agricultural Extension Service (see reference below).

References:
Safe use: http://www.extension.umn.edu/distribution/cropsystems/dc2326.html Health information: http://www.ndhealth.gov/epr/resources/anhydrous.htm

Anaerobic

Published
Without oxygen. Anaerobic cells or organisms may be either facultative or obligate anarobes. A facultative anaerobe normally exists in aerobic conditions, but can live and metabolize in anaerobic conditions when necessary; examples would be oysters and vertebrate skeletal muscle fibers. An obligate anaerobe requires anaerobic conditions to grow and metabolize. From a toxicological standpoint, the bacterial genus Clostridium is an extremely important example, with C. botulinum, that produces botulium toxin, and C. tetani, that produces tetanus toxin, two extremely dangerous species.

From: Dictionary of Toxicology, 2nd edition.

See also: botulinum toxin; tetanus toxin

Analysis of Variance (ANOVA)

Published
A method for testing the significance of mean differences based on partitioning the total variation in a set of scores into additive parts; a parametric statistical procedure for evaluating hypotheses about mean differences. In the case of a single-factor experiment, the variation in the dependent measure can be explained by the variation resulting from the effects of the treatment or independent variable (i.e., differences between mean scores associated with groups receiving different treatments) plus that due to random error (i.e., the summed within group variation). The effect of the independent variable is tested by forming an F-ratio, that is an estimate of the variability (mean square) divided by the appropriate error term. In toxicology, the typical application of this method is to test for mean differences when more than two experimental conditions are being compared.

From: Dictionary of Toxicology, 2nd edition.

See also: F Test; statistics, function in toxicology; variance

Analytical Toxicology

Published
The application of qualitative and quantitative chemical and physical techniques to the field of toxicology. Analytical toxicology involves the separation of a substance into constituents and/or the identification and quantification of individual constituents. Analytical techniques include sample preparation, separation, detection and assay calibration. Because of the complex nature of many environmental and tissue samples, as well as the frequently low concentrations of toxicants and/or their derivatives present, many specialized and sophisticated techniques for separation, identification and quantitation are required. Important in agromedicine for the identification of contamination or poisoning  by agrochemicals.

From: Dictionary of Toxicology, 2nd edition.

See also: bioassay; chromatography; extraction; immunoassay; sampling; solvent partitioning; spectrometry

Anasakiasis

Published
An infestation, in humans, of the nematodes Anasakis simplex or Pseudoterranova decipiens brought about by ingestions of larvae in raw infected fish such as salmon, herring and Pacific cod. A recent increase in anasakiasis cases appears to be due to the increasing popularity of raw fish consumption in the form of sushi and sashimi.

Anemia

Published
A condition in which the blood hemoglobin concentration is below normal. Causes may include blood loss, increased intravascular destruction of blood cells or decreased production of blood cells. Injury to the gastrointestinal mucosa, with subsequent blood loss, is the most common cause of anemia. This may be drug-induced, stress-induced or congenital in origin. There are two types of drug-induced hemolysis: (1) drug-induced oxidation of hemoglobin in intrinsically defective red blood cells (i.e. pyruvate kinase or glucose-6-phosphate dehydrogenase defects); (2) drug-induced immune hemolysis. Marrow toxicity is manifest either by a direct toxicity on red cell mitosis or by interference with metabolism of essential red cell nutrients (i.e., folate or iron).

From: Dictionary of Toxicology, 2nd edition.

See also: hemolysis

Anesthesia

Published
A condition in which loss of consciousness, usually coupled with loss of response to pain and muscle contraction, permits medical or surgical procedures without response or discomfort to the patient. The four stages of general anesthesia with diethyl ether (no longer used) were outlined in 1920 by Guedel are still of general relevance, although newer anesthetics have different properties. Stage I (analgesia) begins with ether administration and lasts until consciousness is lost. Stage II (delirium) last from loss of consciousness until surgical anesthesia begins. Excitement and involuntary activity (laughing, shouting, thrashing, incontinence, irregular breathing, hypertension, etc) may occur, and the intensity and duration of this stage are minimized to prevent injury to patients. Stage III (surgical anesthesia) last from the end of the second stage until spontaneous respiration ceases and has been arbitrarily divided into four planes relating to changes in muscle tone, eye reflexes and respiration. This is the stage in which mostly surgery is done. The final stage (medullary depression) begins when spontaneous respiration ceases and ends when circulatory collapse and death occur. Anesthetics can be administered either by injection or inhalation. Sometimes an intravenous drug is used to induce, and a volatile drug to maintain, anesthesia. The uptake, distribution and elimination of the gaseous agents are greatly influenced by the physical laws of gases (e.g., Dalton’s or Henry’s laws). The mechanism of action of most anesthetics is still unknown. Some (like the barbiturates) act at specific sites on receptors, whereas others may have more generalized actions on cellular membranes. Anesthetics can be toxic due to direct effects on respiration and cardiovascular function, but also through mechanisms that affect temperature regulation (malignant hyperthermia) or as a consequence of anesthetic metabolism (halothane hepatitis).

From: Dictionary of Toxicology, 2nd edition.

See also: anesthetics; halothanes; malignant hyperthermia

Anesthetics

Published
Compounds that induce loss of sensation either in a specific part of the body (local anesthetics) or the body in general (general anesthetics), the latter generally involving loss of consciousness. Local anesthetics include compounds such as procaine and lidocaine, the actions of which involve neuronal sodium channels, and chlorethane, that acts by reducing the temperature of the skin and underlying tissue. General anesthetics include desflurane, enflurane, halothane, isoflurane, sevoflurane and propofol. Diethyl ether, formally used as an anesthetic, is no longer recommended.

From: Dictionary of Toxicology, 2nd edition.

See also: barbiturates

Animal and Plant Health Inspection Service (APHIS)

Published
A program of the US Department of Agriculture that deals in part with matters of toxicological interest, including residues of pesticides in foods.

Animal Bites

Published
Animal bites are a significant hazard in the agricultural workplace, not only from common domestic animal such as cattle hogs and horses or uncommon domestic animals such as large birds (e.g., ostriches) but also from reptiles, particularly snakes. Although less common in fishing, fish bites can be a significant hazard.

Animal Care

Published
Watchful and concerned attention, heed and caution for the biological (and psychological) needs of animals and for the concerns of people who work with or are aware of those animals. Specific components of animal care are described in the US government's Principles for the Utilization and Care of Vertebrate Animals Used in Testing, Research and Training. Topics of concern included in these principles are: transportation; ultimate benefit of animal use to humans and other animals; appropriateness of the species for a study and availability of alternatives; nature of the experimental procedures and steps to avoid discomfort, stress and pain; euthanasia; husbandry, including housing, food, environment and social interaction; veterinary care; qualifications of and safety precautions for animal care and research personnel.

From: Dictionary of Toxicology, 2nd edition.

See also: Guide for the Care and Use of Laboratory Animals

Animal Confinement

Published
A general term for any structure designed to limit the movement of animals ranging from the dedicated buildings associated with large scale poultry and hog production to corrals for cattle, horses, etc.

See also: animal housing

Animal Environment

Published
There are three levels: (1) the microenvironment or cage; (2) the macroenvironment or room; (3) the megaenvironment or building. Factors within these environments that may alter the animal, and therefore its responses, include: ambient temperature; humidity; ventilation; light (intensity, wave length and on/off cycle); sound (intensity, frequency and pattern); chemical contaminant (properties, interactions, exposure duration and frequency, and route of exposure); recent changes in environment; human interaction (routine or irregular, familiar or unfamiliar, proficient or stressful); vermin; water and food; bedding composition; olfactants; microbial contaminants; social interactions with the same or different species; cage or housing (composition, size, arrangement, comfort, security, ease of seeing into or out of, cleanliness and appropriateness for biological needs).

From: Dictionary of Toxicology, 2nd edition.

Animal Feed

Published
The convention that feed is fed to animals while food is eaten by humans is a useful, but not universally observed distinction.

Animal Feeding Operation (AFO)

Published
An animal feeding operation is defined by the United States Environmental Protection Agency as a lot or facility where animals are kept 45 days of the year or more and structures or animal traffic prevents vegetative growth.

From: NORA, 2008.

Animal Hazards

Published
There are numerous hazards associated with farm animals or feral animals found in the agroecosystem as well as with the structures used for housing production animals. Significant and serious hazards are also associated with fisheries, aquaculture and forestry.

See also: animal bites; animal housing

Animal Housing

Published
The term animal housing covers a broad range of structures, some designed simply as shelter for animals in adverse conditions such as high or low temperatures, high winds and excessive precipitation. Other structures are specifically designed for the purpose of maximizing production, such as chicken houses, pork production facilities, etc.  General design features of importance are those systems concerned with temperature control and ventilation together with the instruments necessary to monitor their performance. Hazards include those associated with building structures such as fire, electrical and mechanical hazards. Human health hazards include those associated with the animals including air pollution, respiratory disease, contact dermatitis and noise. Hazard controls for workers health include personal respiratory protection devices, worker training and regular scheduled maintenance.

See also: aerosols; air pollution; ammonia; dust; carbon dioxide; hydrogen sulfide; methane; odor

Animal Manure Pits

Published
Animal wastes from livestock confinement facilities are often stored as liquid waste in pits. These pits are frequently below the confinement facility in question. Many gases and organic chemicals are produced in manure pits and some of these may be a health risk if they rise above critical levels. This may occur due to improper handling. Such gases include ammonia, carbon dioxide, hydrogen sulfide and methane.

Animal Toxins

Published
All phyla of animals include organisms that produce toxins. Some are passively venomous (i.e., from chance ingestion) whereas others are actively venomous, injecting poisons through specially adapted stings or mouth parts. Many toxinologists consider it more appropriate to refer only to the latter group as venomous, the former being considered simply as poisonous. The components of animal toxins include enzymes, neurotoxic and cardiotoxic peptides, proteins and small molecules such as biogenic amines, alkaloids, glycosides and terpenes. The venoms may be complex mixtures including both proteins and small molecules and depend upon the interaction of the various components for the full expression of their toxic effect. For example, bee venom contains a biogenic amine, histamine, three peptides and two enzymes. Snake venoms frequently contain toxins that are peptides with 60-70 amino acids. The cardiotoxic or neurotoxic effects of these toxins are enhanced by enzymes such as phospholipases, peptidases or proteases that are often present.

From: Dictionary of Toxicology, 2nd edition.

See also: venom

Anion

Published
A negatively charged atom or molecule.

Anosmia

Published
Lack of the ability to perceive odor.

Anoxia

Published
A lack of oxygen. It also indicates a decrease in the oxygen content of tissues to below physiological levels and is therefore similar to hypoxia. Anoxia may result from low atmospheric oxygen pressure, anemia, interference with blood flow or the inability of tissues to utilize oxygen normally.

Anthelminthics

Published
Agents that kill worms. The worms of greatest concern are roundworms (nematodes) and flatworms (platyhelminthes) that are of agricultural and/or medical/veterinary importance, but not, generally, annelid worms.

From: Dictionary of Toxicology, 2nd edition.

Anthrax

Published
Anthrax is a serious bacterial disease, caused by the spore-forming Bacillus anthracis). While formerly responsible for considerable human and livestock mortality it is largely under control, although potential for use as a biological warfare agent exists. There are three types of anthrax: cutaneous, respiratory, and gastrointestinal. Humans can become infected by handling products from infected animals, by inhaling spores from infected animal products or by eating undercooked meat from infected animals.

Reference: http://www.bt.cdc.gov/agent/anthrax/needtoknow.asp

Anthropogenic

Published
Resulting from human activities.

Anthropometry

Published
The branch of anthropology concerned with comparative measurements of the human body and its parts. Important in agromedicine because of the use of anthropometric data in workplace and equipment design.

Anti-freeze

Published
A chemical that, when added to water-based mixtures, lowers their freezing point. Note that, since they are related properties, they also raise the boiling point. Anti-freezes commonly used in automotive engines include methanol, ethylene glycol and propylene glycol. All are used in agricultural settings and all are toxic.

See also: ethylene glycol; methanol; propylene glycol

Anti-pruritic

Published
Any medication for the prevention of itching.

Antibacterials

Published
Physical and chemical agents that either kill or inhibit the proliferation of bacteria. They may be considered bacteriocidal if a lethal effect is exerted or bacteriostatic if growth is inhibited in a non-lethal manner. In the latter case, inhibition is reversible in that growth is resumed upon removal of the agent from the growth medium. The most common antibacterial agents are classified as disinfectants, antiseptics, synthetic drugs or antibiotics. In order to be of value with regard to chemotherapeutic considerations, an antibacterial must exhibit selective toxicity.

From: Dictionary of Toxicology, 2nd edition.

See also: antibiotics; antimicrobials; bacteriostats

Antibiotics

Published
Biochemicals, originally of microbial origin, that are capable, at low concentrations, of inhibiting the growth of microorganisms. Modern usage of the term includes synthetic and semisynthetic compounds that exhibit antimicrobial activity. Their mechanisms of action result in either cidal or static effects, most often mediated by inhibition of cell wall biosynthesis (e.g., peptidoglycan in bacteria), protein biosynthesis, nucleic acid biosynthesis, intermediary metabolism, and/or cytoplasmic membrane physiology. Selective toxicity must be exhibited in order for a given antibiotic to be of value chemotherapeutically. Resistance to antibiotics may be due to one or more of the following: modification of the target in the cell or reduction of the physiological importance of the target; prevention of access to the target; production by the bacteria of inactivating enzymes (e.g., beta-lactamase). Many of the chemically modified antibiotics were produced in order to overcome, or bypass, resistance to the parent compound. The following are the most important classes of antibiotics.

Penicillins. Compounds produced by Penicillium chrysogenum that are bactericidal due to inhibition of cell wall biosynthesis. Chemical modifications have yielded compounds, such as benzylpenicillin, carbenicillin and methicillin, with improved properties. Resistance may be due to penicillinase (beta-lactamase) that opens the lactam ring given rise to penicilloic acid. Toxic side effects in humans include immune reactions, sometimes life threatening.

penicillin

Cephalosporins. Cephalosporins (e.g., cephalosporin C. CAS number 61-24-5) are produced by Cephalosporium sp. They are broad spectrum antibiotics that act by inhibition of cell wall biosynthesis and are active against penicillinase producing organisms. Principal toxic side effects are allergic hypersensitivity reactions, including anaphylactic shock, and nephrotoxicity. There is frequently cross-sensitivity with penicillin and penicillin-sensitive patients should not be given cephalosporins.

cephalosporin_c

Aminoglycosides. A class of antibiotics, all consisting of two or more amino sugars joined in a glycosidic linkage to a hexose nucleus, inositol. Streptomycin is a  representative member of this group, produced by soil actinomycetes. Semisynthetic aminoglycosides such as kanomycin also are produced. Aminoglycosides are active against many gram-negative and a few gram-positive bacteria due, apparently, to their ability to inhibit the first step of ribosomal protein synthesis and also, perhaps, from their ability to induce mistranslation of mRNA. Major toxic side effects are renal failure and hearing loss due to cochlear damage.

streptomycin

Tetracyclines. A family of antibiotics effective against gram-positive bacteria. Side effects from continued use in humans include photosensitivity, fatty liver and renal failure. Tetracyclines are deposited at sites of active calcification of teeth and bones and effects after birth on teeth exposed to tetracyclines in utero may be severe.

tetracycline

Macrolides. A group of compounds that possess a macrocyclic lactone ring with sugar substituents. Includes the erythromycins produced by Streptomyces erythreus. They are broad spectrum, acting by inhibition of protein synthesis.

erythomycin

Peptides. A large group of compounds, either cyclic and/or including one or more D-amino acids, for example bacitracin, the mode of action involving effects on the cytoplasmic membrane.

bacitracin_a

Polyenes. Cyclic compounds containing long chain polyunsaturated moieties. Includes antifungal agents such as nystatin, produced by Streptomyces noursei.

nystatin



Other miscellaneous antibiotics include chloramphemicol and griseofulvin. Chloramphenicol, an antibiotic produced by Streptmyces venezulae, is effective against gram-positive and gram-negative spirochaetes, psittacosis group, and rickettsiae that cause typhus. It blocks the ribosomal site for the attachment of the 3’-terminus of amino acyl-tRNA, thereby inhibiting protein synthesis. Toxic side effects include blood dyscrasias in humans, including aplastic anemia and granulocytopenia. High dosage in the neonate can be fatal. Griseofulvin is produced be Pennicillium griseofulvum concentrates in keratin and is effective against fungal infection of nails and hair.

chloramphenicol_and_griseofulvin

Adapted from: Dictionary of Toxicology, 2nd edition.

Antibody

Published
A large protein molecule expressed first on the surface of B cells. Stimulation of an immune response by a substance (antigen) that is complementary to, and binds with a particular antibody results in proliferation and differentiation of the B cells bearing that antibody. The end product of this response is one or more clones of plasma cells that secrete the antibody molecules into body fluids. Antibodies bind specifically with the substance that stimulated their production, but may cross-react with other substances. The natural function of antibodies is to bind foreign substances (e.g., microbes or microbial products) and eliminate them by a variety of subsequent mechanisms. Because of their specificity, antibodies are used in a variety of research, diagnostic and therapeutic procedures.

From: Dictionary of Toxicology, 2nd edition.

See also: immunoglobin

Antibody-dependent Cellular Cytotoxicity (ADCC)

Published
The non-specific lysis of antibody-coated cells by cells not sensitized to that antigen or antibody, such as cells from a non-immunized animal. This is accomplished by binding the constant, non-antigen-binding, portion of the antibody molecule, enabling attachment to and lysis of the target cell. It can occur in type II (cytolytic) allergic responses, as well as in tumor defense and foreign tissue graft rejection. It is believed to be mediated by killer (K) cells and, possibly, natural killer (NK) cells.

From: Dictionary of Toxicology, 2nd edition.

See also: allergenic reactions, allergic response

Anticholinesterases (acetylcholinesterase Inhibitors)

Published
A number of carbamate or organophosphorus (OP) esters can carbamylate or phosphorylate, respectively, the serine hydroxyl at the esteratic site of acetylcholinesterase (AChE), inhibiting the action of the enzyme. During the reaction, the original ester is cleaved; the leaving group refers to the portion of the toxicant not remaining bound to the enzyme. The carbamylated AChE is spontaneously hydrolyzed quite readily, leading to rapid recovery of enzyme activity; symptoms of poisoning persist for only a few hours. The phosphorylated AChE, however, is spontaneously hydrolyzed much more slowly, and the inhibitory action of OP anticholinesterases and the resultant symptomology are much more persistent, with inhibition by some compounds lasting several days or even weeks. “Aging” of the enzyme occurs with some compounds, after which spontaneous reactivation is impossible. A number of carbamate anticholinesterases are used as insecticides; others (e.g., neostigmine, eserine) are used therapeutically. A large number of OP insecticides, as well as the OP nerve gases, are anticholinesterases.

From: Dictionary of Toxicology, 2nd edition.

See also: acetylcholine; acetylcholinesterase; acetylcholinesterase, aging; carbamate insecticides; carbamate poisoning, symptoms and therapy; organophosphate poisoning, symptoms and therapy; organophosphorus insecticides

Antidote

Published
A compound that is administered in order to reverse the deleterious effects of a toxicant. Antidotes may be specific, exerting their effect through a mechanism related to the mechanism of action of the toxicant, or non-specific, counteracting the symptoms of toxicity in a manner not clearly related to the mechanism of action. An example of the former is 2-PAM (N-methylpyridinium-2-aldoxime), that reverses the effect of organophosphate acetylcholinesterase inhibition by dephosphorylating the phosphorylated enzyme. Syrup of ipecac is an example of a non-specific antidote since its mode of action is to eliminate toxicants from the stomach by induction of vomiting (emesis).

From: Dictionary of Toxicology, 2nd edition.

See also: therapy; therapy, non-specific; therapy, specific; therapy, specific: direct effect on toxicant; therapy, specific: effect on receptor site; therapy, specific: excretion; therapy, specific: metabolism of toxicant; therapy, specific: repair

Antiemetics

Published
Drugs that suppress vomiting. The chief antiemetics are the phenothiazines, such as chlorpromazine, perphenazine, prochlorperazine or promethazine. Induction of emesis by apomorphine or certain ergot alkaloids can be blocked by most neuroleptics due to their actions on dopamine receptors in the chemoreceptor trigger zone of the area postrema. Thioridazine is an exception, having no antiemetic effects in humans. Emesis induced by local effects on the gastrointestinal tract are not blocked by neuroleptics, although vestibular stimulation-induced nausea can be blocked by the more potent neuroleptics. In addition, phenothiazines such as chlorpromazine can be used to block the vomiting associated with radiation sickness, carcinomas, gastroenteritis, uremia or emesis induced by opioid analgesics, disulfiram, drugs used in the chemotherapy of carcinomas and tetracyclines. Although not recommended for this use, chlorpromazine will also suppress vomiting associated with pregnancy. Chlorpromazine is not useful in controlling motion sickness. Certain H1 histamine receptor blockers including dimenhydrinate (Dramamine), diphenhydramine, promethazine and other piperazine derivatives are useful in treating or preventing motion sickness. Many of the H1 receptor blockers have antimuscarinic properties, that may contribute to their antiemetic effect. The antimuscarinic agent scopolamine, for example, is a potent anti-motion sickness agent. Also, promethazine, that is one of the most effective anti-motion sickness drugs, also has potent antimuscarinic effects. Because morphine and its derivatives frequently result in nausea and vomiting, opiate antagonists, such as naloxone, will exert antiemetic effects like the neuroleptics.

From: Dictionary of Toxicology, 2nd edition.

See also: emesis; phenothiazines

Antigen

Published
A substance that elicits an immune response. In general a molecule must be foreign to the host, have a molecular mass in excess of 5000 daltons and have some degree of molecular complexity in order to be antigenic. Smaller molecules (haptens), including a number of xenobiotics, can be rendered antigenic by covalently coupling them to larger, more complex molecules (carriers). The antibodies elicited by the hapten-carrier conjugate will generally react with that conjugate and with the free hapten as well.

From: Dictionary of Toxicology, 2nd edition.

See also: antibody

Antihistamines

Published
Drugs, such as diphenhydramine or chlorpheniramine, that exert their pharmacodynamic effect by blocking H1 and/or H2 histamine receptors. Antihistamines are used to treat allergic symptoms (H1), motion sickness (H1) and stomach ulcers (H2). They are usually rapidly absorbed from the gastrointestinal tract, showing peak blood levels one to two hours after oral administration. Side effects of non-selective agents include sedation, nausea and vomiting, as well as atropine-like effects such as dry mouth, dysuria, hypotension and weakness. Selective H2 histamine antagonists (e.g., cimetidine, ranitidine, famotidine, nizatidine) have been widely used recently for treatment of stomach ulcers by suppressing gastric acid secretion. There are new H1 antagonists that do not cross BBB, such as terfenidine and its toxicity.

From: Dictionary of Toxicology, 2nd edition.

Antimicrobials

Published
Physical and chemical agents that kill or inhibit the proliferation of microorganisms. Antimicrobials that exert lethal effects are considered to function in a cidal manner, whereas those that merely inhibit growth in a reversible manner are considered to function in a static manner. They are referred to as germicides (e.g., bacteriocides, fungicides, etc.) and microstatic agents (e.g., bacteriostatic agents, fungistatic agents, etc.), respectively. Physical antimicrobial agents include temperature, radiation, ultrasonication and filtration. Chemical antimicrobial agents having non-selective toxicity that are used to kill or inhibit pathogenic (i.e., disease-causing) microorganisms are classified as disinfectants if employed for inanimate objects or antiseptics if they are applied topically to biological tissues. This latter group includes surface-active compounds, dyes, heavy metals, phenols, alcohols, aldehydes, acids, halogens, oxidants, etc. Chemical antimicrobial agents suitable for chemotherapeutic use (i.e. drugs) exhibit selective toxicity in that they inhibit the proliferation of microorganisms at concentrations that do not harm the host. This group includes certain antibiotics and synthetic drugs. In addition to the specific nature of the microorganism being inhibited, the efficacy of an antimicrobial is critically dependent upon concentration, time of exposure, temperature and pH.

From: Dictionary of Toxicology, 2nd edition.

See also: antibacterials; antibiotics; bacteriostats

Antitoxin

Published
Therapeutic antibodies that have been raised against a microbial, plant or animal toxin, and that can be used in the therapy of poisoned individuals to neutralize the toxin. The antitoxin can also be used prophylactically.

From: Dictionary of Toxicology, 2nd edition.

See also: antivenin

Antivenin

Published
A therapeutic agent produced against a venom, such as that from snakes or black widow spiders, by animals, frequently horses, that have been immunized against the venom. If delivered soon enough after envenomation, the antivenin can prevent or attenuate signs of poisoning and/or death. Such therapy may cause its own toxicological consequences due to immune responses to the foreign protein that constitutes the antivenin.

From: Dictionary of Toxicology, 2nd edition.

See also: antitoxin

Ants

Published
Ants are a large family (Formicidae) of the Order Insecta, with several thousand species worldwide. Although generally harmless to humans, some sting and are, consequently, considered pests.

Ants, Harvester

Published
Harvester ants are common in most areas of North America. Their bite can be painful but usually not dangerous.

Ants, Red Imported Fire

Published
This ant species (Solenopsis invicta) was introduced into Alabama around 1940 and is now present in all of the southeastern states as well as Oklahoma and Tennessee. These ants have a painful sting that results in a characteristic pustule. Allergic reactions, although uncommon, may be life-threatening. Symptomatic relief (ice packs, calamine lotion or antihistamines) may be useful and broken pustules should be treated to prevent infection.

Ants, Velvet

Published
These wingless wasps are widely distributed and possess a painful sting. Symptomatic relief (icepacks, calamine lotion or antihistamines) is generally the only treatment necessary.

Ants, Venom of

Published
Ant venoms, like those of other insects such as the honeybees, other bees, wasps and hornets are complex mixtures of allergic proteins (e. g., hyaluronidase, phosphatase), peptides and other large molecules (e. g., melittin) and small molecules (e. g. histamine). Apart from the relatively uncommon allergic reactions, these venoms have effects that are painful but not life threatening.

Aplastic Anemia

Published
Anemia resulting from the destruction of the ability of the bone marrow to generate all blood cells. This results in loss of erythrocyte concentrations in the blood and, consequently, reduced oxygen transport. This can result from bone marrow damage due to radiation or chemicals.

From: Dictionary of Toxicology, 2nd edition.

See also: chloramphenicol; clozapine

Apnea

Published
A condition characterized by lapses in breathing.

Approved Container

Published
A metal or polyethylene container that can be used to carry flammable liquids in quantities up to 5 gallons (18.93 liters). These containers must be accepted as satisfactory to contain flammable liquids by a nationally recognized testing laboratory, such as Underwriters Laboratory (UL) or Factory Mutual (FM).

From: NORA, 2008.

Aquaculture

Published
The farming of aquatic organisms, primarily for human food. Organisms so cultured include fish (e. g., catfish, salmon, striped bass), crustaceans (e. g., shrimp), mollusks (e. g., oysters) and others.

Aquatic Bioassay

Published
A procedure in which aquatic organisms are used to detect or measure biological responses to one or more substances, wastes or environmental factors, alone or in combination. Experimental procedures may vary considerably; therefore, it is important that biological, chemical and physical parameters be defined (e.g., test organism, type of exposure system, length of exposure, water quality). Common test organisms include bluegill sunfish (Lepomis macrochirus), fathead minnow (Pimephales promelas), rainbow trout (Oncorhychus mykiss), sheepshead minnow (Cyprinodon variegatus), daphnids (Daphnia species) and mysid shrimp (Mysidopsis species).

Aquatic Ecosystems

Published
An ecosystem involving strictly water, sediments and aquatic organisms, but not terrestrial elements. Model aquatic ecosystems have been developed to study the fate of chemicals in the environment.

From: Dictionary of Toxicology, 2nd edition.

Aquatic Toxicology

Published
A branch of toxicology that deals with adverse effects of toxicants on aquatic organisms (marine, estuarine or freshwater) and on aquatic ecosystems; largely a study of water pollution and its ecological effects.

From: Dictionary of Toxicology, 2nd edition.

See also: water pollution

Aquatic/aquaculture Hazards, Antibiotics

Published
Antibiotics are frequently used in fish culture and allergic sensitivity can be a problem for producers and feed formulators unless procedures are in place to reduce exposure.

Aquatic/aquaculture Hazards, Drowning

Published
Drowning can be a hazard particularly when fish (e. g., salmon) are cultured in open water enclosed by nets.

Aquatic/aquaculture Hazards, Electrical Hazards

Published
Electrical equipment is used extensively around, or even in, aquaculture ponds. Even though there are many safeguards for proper use the risk of electrocution is higher than in entirely land-based agriculture operations.

Aquatic/aquaculture Hazards, Feed Manufacture and Fish Processing

Published
These activities can be hazardous from the point of view of physical stress and, if automated as a result of mechanical or electrical problems.

Aquatic/aquaculture Hazards, Muscle Strains

Published
Both fishing and aquaculture (but particularly the former) frequently require considerable physical strength and as a result, muscle strains are an occupational hazard.

Aquatic/aquaculture Hazards, Non-Venomous Fish Bites and Spines

Published
Many fish are capable of inflicting moderate to severe injury from bites and penetrating spines even though neither may be venomous. Shark attacks, although statistically uncommon, are of particular concern and are the subject of a considerable literature, both technical and popular. Other examples of biting non-venomous fish include the barracuda (Sphyraena barracuda), and bluefish (Pomatomus saltatrix). Examples of fish with penetrating spines include croaker (Micropogonias unchulatus) and black sea bass (Centropristis striata) and puncture wounds may occur.

Aquatic/aquaculture Hazards, Venomous Fish Bites and Stings

Published
These effects are essentially all from stings that are supplied with venom by venom glands. Numerically, stingrays are the most important in this respect but other examples include catfish, toadfish and scorpionfish. Most venomous are stonefish, found in the southwest Pacific and Indian oceans.

Aramid

Published
The generic name for a high-strength, flame-resistant synthetic fabric used in the shirts and jeans of firefighters. Nomex, a brand name for aramid fabric, is the term commonly used by firefighters.

From: NORA, 2008.

Arch

Published
Any device attached to the back of a mobile vehicle and used for raising the leading end of trees or logs to facilitate movement.

Adapted from: NORA, 2008.

Arsenic (As)

Published
CAS Number 7440-38-2. A metalloid element that is used in metallurgy, glassmaking and agriculture, although agricultural uses are extremely limited. Human exposure occurs occupationally and via food, tobacco smoke, ambient air and water. Three major groups of arsenic compounds have been defined on the basis of biological considerations: inorganic arsenicals; organic arsenicals;and arsine (gas). Comparative toxicity of these groups is dependent on the route of exposure and their solubility; the more quickly absorbed compounds are more toxic, i. e., have lower LD50s. Arsenic is readily absorbed by the respiratory and gastrointestinal systems and is concentrated in the skin, hair and nails (Aldrich-Mee's lines). The toxicity of arsenic is related to reactions with SH-containing mitochondrial enzymes that result in impaired respiration. Arsenic may also compete with phosphate during oxidative phosphorylation. Detoxication is via reductive methylation and methylarsinic and dimethylarsinic acids are excreted into the urine. The acute signs of poisoning include fever, anorexia, hepatomegaly, cardiac arrythmia, transient encephalopathy and irritation of the gastrointestinal tract. Additional signs may include upper respiratory tract involvement and peripheral neuropathy. Chronic symptoms are exfoliation and pigmentation of skin, symmetrical distal neuropathy, altered hematopoiesis and liver and kidney degeneration. Epidemiological data indicate that arsenic is a human carcinogen. In humans, the fatal dose for arsenic has been reported to range from 1 to 2.5 mg/kg body weight. Biological indicators of poisoning are urine, blood and hair levels. 2,3-Dimercapto-1-propanol is the treatment for acute intoxication, but it is less effective in treating chronic exposures.

From: Dictionary of Toxicology, 2nd edition.

See also: arsenic, as arsenate; arsenic, as arsenite; 2,3-dimercapto-1-propanol; lead arsenate

Arsenic Reduction

Published
Organic arsenicals in which the arsenic is in pentavalent state may be reduced to trivalent arsenic compounds. In many cases (e.g., Tryparsamide), these compounds are antiparasitic or antiprotozoan compounds, and the reaction is an activation reaction since the reduced compounds are more effective.

From: Dictionary of Toxicology, 2nd edition.

Arsenic, As Arsenate

Published
Pentavalent arsenic; formerly used in insecticides, herbicides, fungicides and algicides, and is widely distributed in nature, being a contaminant of metal ores and coal. It is a carcinogen, but is less toxic than arsenite. Arsenate uncouples oxidative phosphorylation by substituting for inorganic phosphorus. The symptoms of acute poisoning are violent nausea and vomiting, abdominal pain, severe diarrhea and dehydration, as well as a sweet metallic garlic-type odor imparted to breath and feces. Therapy includes induction of emesis or gastric lavage, avoidance of aspiration of vomitus, correction of dehydration and electrolyte imbalance and chelation therapy with 3-5 mg/kg, i.m., 2,3-dimercapto-1-propanol.

From: Dictionary of Toxicology, 2nd edition.

See also: arsenic; arsenic, as arsenite

Arsenic, As Arsenite

Published
Trivalent arsenic; formerly used in insecticides, herbicides, fungicides and algicides, and is widely distributed in nature and as a contaminant of metal ores and coal. It is a carcinogen, but is also corrosive to epithelial cells and other tissues. Trivalent arsenic binds avidly to sulfhydryl groups of critical enzymes and impairs cellular metabolism. After acute poisoning, there is violent nausea and vomiting, abdominal pain, severe diarrhea and dehydration, with a sweet metallic garlic-type odor imparted to breath and feces. Therapy includes induction of emesis or gastric lavage, avoiding aspiration of vomitus, correction of dehydration and electrolyte imbalance. In severe cases, chelation therapy with 3-5 mg/kg, i.m., 2,3-dimercapto-1-propanol is used.

From: Dictionary of Toxicology, 2nd edition.

See also: arsenic, as arsenate; arsenic; 2,3-dimercapto-1-propanol

Arsenicals

Published
The general class of compounds containing arsenic in one of its valency forms. Organic arsenicals have been used as pesticides but such uses are rare, the decrease being by replacement or by regulation. The organic arsenical pesticides consisted of monosodium methane arsonate (MSMA), disodium methane arsonate (DSMA), calcium acid methane arsonate (CAMA), and cacodylic acid and its sodium salt.  They were used as herbicides on cotton and other agricultural crops, in forestry, on residential and other lawns and turf, and in non-crop areas such as rights of way, drainage ditch banks, fence rows, and storage yards. All uses have been cancelled by EPA.

From: Dictionary of Toxicology, 2nd edition.

See also: arsenic; arsenic, as arsenate; arsenic, as arsenite

Arthralgia

Published
A very general term meaning “pain in a joint” or more often “severe pain in a joint”. Such pains may have a variety of causes including, infection, arthritis, side effects of drugs or physical injury.

Arthropod

Published
The Arthropoda is the largest group of animals, variously estimated to include from 75 to 90% of all animal species. They are characterized by having a chitinous exoskeleton, segmented bodies and jointed appendages and an open blood system. Although different authorities describe the nature and  relationships within the phylum in different ways most would agree that there are five subphyla, one of which, the Trolobites, is extinct. The four extant subphyla are the Chelicerata, which includes the spiders and scorpions, the Myriapoda, which includes the centipedes and millipedes, the Crustacea, which includes the crabs and lobsters and finally, the Hexapoda, which includes the insects. As would be expected with such a large group of organisms, arthropods interact with humans in many ways and are of critical importance in agromedicine, primarily because some arthropods are hematophagous (blood feeding) and transmit diseases and while others have venomous stings and bites. Because of these harmful effects, particularly of insects, chemicals such as insecticides are frequently used to reduce population density. This introduces an addition factor of concern in agromedicine, the toxicity to non-target species, including humans, of control chemicals.  Despite these deleterious effects, many arthropods are beneficial in their relationship with humans, either as crop pollinators (e.g., bees) or as food sources (e. g., crabs, lobsters, honeybees).

See also: ants; assassin bugs; bed bugs; bees; beetles; blister beetles; blood feeding; brown recluse spider; bumblebees; butterflies; caterpillers; centipedes; chiggers; cicada killers; conenose bugs; deer flies; fire ants; fleas; flies; gnats; honey bees; hornets; horseflies; hymenoptera; lice; millipedes; mites; mosquitoes; moths; mud daubers; scorpions; spiders; sweat bees; ticks

Arthropod Control

Published
The phylum Arthopoda is by far the largest group of animals and includes many species (primarily insects) that transmit diseases, some of which are life-threatening. Given the very large number of species involved control procedures are also numerous, including both chemical and biological methods. Pest management systems have also been developed to control arthropods. However, some problems have proven intractable, the most important of which is the control of malaria-transmitting mosquitoes.

See also: Arthropod.

Arthropod, Disease Transmission

Published
Many human diseases of humans, livestock and companion animals are transmitted by arthropods, some of the most important being: canine/feline heartworms by mosquitoes; leishmaniasis by sand flies; Lyme disease by ticks; malaria by mosquitoes; Rocky Mountain spotted fever by ticks; West Nile virus by mosquitoes. Clearly an important term in Agromedicine. However, the number of diseases and the number of arthropods transmitting them do not lend themselves to a single dictionary entry. Each must be searched individually.

See also: Arthropod; Blood Feeding; Lyme Disease.

Arthropod, Growth and Development (metamorphosis)

Published
The egg, the initial stage in growth and and development for all arthropods, even the live births of scorpions resulting from eggs hatching in vivo. The immature stages (instars) range from small adult-like, although not fully differentiated, forms that undergo several molts before reaching the final adult form to grubs and caterpillars. The latter lack jointed legs and are usually very distinct morphologically from the adult form which they achieve through a complete metamorphosis via a pupal stage. Plant diseases and consumption are frequently due to caterpillars while human disease is usually transmitted by adult insects.

Asbestos

Published
CAS number 1332-21-4. Fibrous hydrated mineral silicates that are resistant to thermal and chemical degradation and have, therefore, been widely used as insulating materials. Asbestos has also been used in textiles, paints, plastics, paper, gaskets, brake linings, tile, cement and filters. The most widely used is chrysotile, a fibrous form of serpentine; other types include crocidolite, amosite and anthophyllite. Asbestos is poorly absorbed from the gastrointestinal tract and therefore displays low acute oral toxicity. Respiratory exposure, however, leads to a pulmonary fibrosis called asbestosis, whose signs include breathlessness, chest pain, cough, decreased lung function and cyanosis. Occupational exposures to asbestos have resulted in higher incidences of lung cancer (especially mesothelomias), especially in combination with cigarette smoking; the latent period is 15-30 years. This synergism may be the result of the inhibitory effect of trace elements in asbestosis, such as chromium, nickel or beryllium, on the detoxication of smoke carcinogens. Cancers can also occur in the pleurae, peritoneum, bronchi or oropharynx. Mesothelioma, a cancer of the thin membrane that surrounds the lung, invariably fatal, often within a few months of diagnosis. Although the mechanism of carcinogenesis is unknown, asbestos does not appear to be metabolized, and thus remains permanently within the body. An additional effect of asbestos exposure is the development of pleural or peritoneal mesotheliomas; the latent period is 3.5-30 years. Fibers can eventually become coated with mucopolysaccharides and hemosiderin to form “asbestos bodies.” No safe level of asbestos exposure to humans has been observed. Asbestos in the air occurs around asbestos mines and factories, but it also occurs in urban areas because of wear to brake linings and the flaking of insulation materials. Removal of asbestos from existing buildings during renovation or removal has become a major public health and toxicological concern.

From: Dictionary of Toxicology, 2nd edition.

See also: asbestosis

Asbestosis

Published
A respiratory disorder resulting from inhalation exposure to asbestos, characterized by fibrosis, calcification, bronchogenic carcinoma and mesothelial tumors. The asbestos fibers are not metabolized and are retained within the lungs for the life span of the animal. The mechanism of carcinogenesis is unknown, but resembles solid-state carcinogenesis. The latent period is long. Asbestosis is synergistic to the carcinogenesis caused by smoking. Asbestosis was recognized as long ago as 1907; however, the magnitude of the risk has become apparent only recently, primarily because of the increased incidence of lung cancer among asbestosis sufferers, especially those who are also cigarette smokers.

From: Dictionary of Toxicology, 2nd edition.

Aspergillus

Published
A large genus of fungi, some species of which are important medically and some of which have commercial importance. Aspergillus flavus produces aflatoxin, a known carcinogen, other species are known human pathogens. Commercially, aspergillus species are important in fermentation of rice to ethanol-containing beverages, such as sake and they are the principle organism is commercial citric acid production.

Asphyxiants

Published
Toxicants that exert their toxic effects by depriving the tissues of oxygen. They have been divided into the simple asphyxiants and the chemical asphyxiants. The simple asphyxiants act by diluting the oxygen in the inhaled air, thereby reducing its partial pressure in the alveoli and, consequently, its transfer into venous blood. As the partial pressure approaches that of the venous blood, the rate of transfer approaches zero. Such chemicals as nitrogen, nitrous oxide, hydrogen and helium are classified as simple asphyxiants. Chemical asphyxiants, on the other hand, act by chemical interactions, either to prevent oxygen transport to the tissues or to prevent oxygen utilization by the tissues. Carbon monoxide, for example, combines with hemoglobin to form carboxyhemoglobin and thus blocks oxygen transport, whereas cyanide reacts with the cytochrome oxidase complex to prevent oxygen utilization by mitochondria. Chemicals that inflame or irritate the respiratory tract, giving rise to pulmonary edema, may also cause death by asphyxiation, but are usually classified as primary lung irritants.

From: Dictionary of Toxicology, 2nd edition.

See also: carbon monoxide; cyanides; cyanide poisoning, therapy; irritants; nitrous oxide

Assessment

Published
A broadly used term meaning any type of evaluation.

Assigned Protection Factor (APF)

Published
The expected workplace level of respiratory protection that would be provided by a properly functioning respirator or a class of respirators to properly fitted and trained users.

Reference: Anna, DH (2011). The Occupational Environment: Its Evaluation, Control and Management, 3rd ed. Glossary, p. 1593.

Association of Official Agricultural Chemists International (AOAC)

Published
Formerly the Association of Official Agricultural Chemists. An association that publishes standard methods for chemical analysis of agricultural and related chemicals.

Asthma

Published
Asthma is a disorder that causes the airways of the lungs to swell and narrow, leading to wheezing, shortness of breath, chest tightness, and coughing. Affecting 5 – 10 percent of the population world-wide, asthma can be serious, even life-threatening. Asthma is caused by inflammation in the airways. When an asthma attack occurs, the muscles surrounding the airways become constricted and swelling of the lining of the air passages occurs, reducing air flow. Asthma attacks can last for minutes to days, becoming dangerous if airflow is severely restricted.

See also: agricultural health study; asthma, allergy testing; asthma, causative agents; asthma, clinical findings; asthma, epidemiology; asthma, pulmonary function testing; asthma, treatment

References: PubMed Health (http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001196/), Langley, R. L., et al., (eds). Safety and Health in Agriculture, Forestry and Fisheries. Government Institutes, Rockville MD., 1997.

Asthma, and Allergy Testing

Published
Allergy testing is frequently useful in identifying allergens that cause asthma attacks, since the identity of the allergen varies from one individual to another.

Asthma, Causative Agents

Published
In sensitive people, asthma symptoms may be triggered by inhaling allergens. Common asthma-causing allergens include: animals, including pet hair or dander, dust, respired chemicals (less commonly, ingested chemicals in food), mold, pollen, tobacco smoke. Non allergic causes include exercise, respiratory infections, cold weather and stress. Non-steroidal anti-inflammatory agents (NSAIDS), including aspirin may cause asthma attacks in some individuals. Although a personal or family history of allergies, such as hay fever (allergic rhinitis), may predispose to asthma this is not necessarily the case.

Asthma, Clinical Findings

Published
Most people with asthma have attacks separated by symptom-free periods. Symptoms include wheezing, which comes in episodes with symptom-free periods in between. Wheezing may cease spontaneously and usually improves with the use of bronchodilator drugs. Wheezing usually begins suddenly and, without treatment, may be worse at night or in early morning, when breathing in cold air or with exercise. Other symptoms include cough with or without sputum (phlegm) production, pulling in of the skin between the ribs when breathing (intercostal retractions) and shortness of breath that gets worse with exercise or other activity.

In severe attacks there may be a bluish color to the lips and face, decreased level of alertness, such as severe drowsiness or confusion, extreme difficulty breathing, rapid pulse, sweating and severe anxiety due to shortness of breath. Other severe asthmatic symptoms  include chest pain, tightness in the chest and abnormal breathing patterns, including temporary cessation.

Asthma, Epidemiology

Published
There are many published epidemiological studies of asthma (or the commonest symptom, wheezing) in farm populations and the overall incidence has been estimated at 6.5 to 13 percent, although it may be as high as 25 percent in grain or confined livestock workers.  More recently, wheezing as an effect of agrochemical exposure has been demonstrated in the Agricultural Health Study.

Asthma, Pulmonary Function Testing

Published
This may be helpful in diagnosis but many measures of pulmonary function may not be affected.

Asthma, Treatment

Published
Treatment involves prevention, i. e., avoidance of known allergens, control drugs to prevent attacks and rescue drugs for use during attacks.

Ataxia

Published
Inability to control motor coordination.

Atlantic Wolfish

Published
The Atlantic wolfish (Anarhichas lupus), also known as the wolf eel, can cause serious bite injuries to fisherman.

Atmospheric Half-life

Published
The time required for a 50% reduction of the concentration of an air pollutant present in the ambient atmosphere.

From: Dictionary of Toxicology, 2nd edition.

Atmospheric Residence Time

Published
The time required for reduction of the concentration of an air pollutant in the ambient atmosphere to a level equal to 1/e (c. 37%) of the original concentration.

Atrazine

Published
2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine; 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine. CAS number 1912-24-9. A selective pre- and post-emergence herbicide. The acute oral LD50 in rats ranges from 1,850 to about 3,000 mg/kg; the acute dermal LD50 in rabbits is 7,500 mg/kg. It is slightly toxic to fish. Experimentally it has been shown to act as a mutagen, carcinogen and teratogen.

atrazine

From: Dictionary of Toxicology, 2nd edition.

Reference: ATSDR Toxprofile, 09/2003.

Atrophy

Published
Reduction in size of a structure or organ. Atrophy can result from lack of nourishment or functional activity, cell death and subsequent reabsorption, diminished cell proliferation. These effects may result from ischemia, hormone changes or chemical toxicity.

Atropine

Published
dl-hyoscamine; tropine tropate; tropic acid ester with tropine; dl-tropyl tropate; α-(hydroxymethyl)benzeneacetic acid 8-methyl-8-azabicyclo[3,2,1-]oct-3-yl ester; 1αH,5αH-tropan-3αol (+)-tropate. CAS Number 51-55-8. One of the belladonna alkaloids (from Atropa belladonna) that crosses the blood-brain barrier. The oral LD50 in rats is 750 mg/kg. Atropine exerts its pharmacodynamic effects by competitively blocking muscarinic acetylcholine receptor sites. Atropine or atropinic drugs result in pupil dilation, dry mouth, inhibition of activity of sweat glands and, at toxic doses, tachycardia, palpitation, speech disturbance, blurred vision, restlessness, irritability, disorientation, hallucinations or delirium. A major cause of poisonings is the ingestion of drugs with atropinic properties, including antihistamines, phenothiazines and tricyclic antidepressants. Infants and young children are particularly susceptible to atropine intoxication, that may result from application of ophthamological treatments. Atropine has potent antispasmodic and antisecretory properties.

atropine

From: Dictionary of Toxicology, 2nd edition.

See also:
acetylcholine receptors, muscarinic and nicotinic

Attack Rate

Published
The proportion of a specific population affected during an outbreak.  The population is usually limited to those identifiably exposed. It is a special form of incidence rate used in outbreak investigation.

attack_rate

Attention Hyperactivity Deficient Disorder

Published
The defining attributes of this disorder are developmentally inappropriate lack of attention, impulsivity and hyperactivity. Distractability, failure to listen, inability to concentrate or pay attention to a task, excessive movement, constant fidgeting and excessive shifting from task to task are all common symptoms of this disorder. The etiology of this disorder is unknown; the diagnosis is most often made after the child starts school, and the treatment of choice appears to be stimulant medication. Exposure to chemicals or toxic agents may play an etiological role at least in some cases but this hypothesis remains both controversial and less commonly held.

See also: locomotor behavior; maintenance therapy; mental retardation; neurobehavioral teratology; neurobehavioral toxicology; postnatal behavioral tests.

Attributable Risk

Published
The rate of the occurrence of a toxic endpoint or disease that can be attributed to a specific exposure. Numerically it is derived by dividing the rate of occurrence in an unexposed population by that of an otherwise similar exposed population.

Audiogram

Published
A graph showing the audible threshold for standardized frequencies as measured by an audiometer.

Audiometry

Published
The testing of the ability to hear different sound frequencies. The test is performed using an  audiometer and is administered by a trained audiologist.  Audiometry testing is used to diagnose hearing loss and is important in agromedicine because of hearing loss from loud or continuous noise.

See also: agricultural industry, noise and hearing loss

Autoimmunity

Published
Any inappropriate immune system response to self components. The immune system, in order to protect the host normally distinguishes effectively between "self" and "non-self." Many different cell types must cooperate in any immune response and must therefore recognize each other as self. Additionally there must be tolerance to all normal host proteins. If normal autologous host proteins are not recognized as self (i. e., they are recognized as foreign or non-self), damage to the host frequently ensues. Autoimmune responses can be humoral (antibodies) or cell-mediated immunity (T cells). Autoimmunity can be a component of any of the four types of allergic response. There are a number of autoimmune diseases where such inappropriate responses are made against tissue antigens and/or antigens not normally accessible to the immune system, such as intracellular contents, brain tissue, sperm, etc. Antibodies to cell surface antigens can cause cell death by lysis or can interfere with cell function (See allergic response ; antibody-dependent cellular cytotoxicity; complement). If the antigens are inaccessible to the antibody, such as nuclear proteins, no harm is done to the intact cell, but soluble immune complexes form in the serum and can lodge in vessel walls, kidneys or lung tissue, producing an immune complex response (See allergic response table). These reactions are usually transitory unless the antigens are chronically presented to the immune system, for instance, by continuous cell damage from toxicants or drugs. Many environmental agents can induce an allergic autoimmune reaction. One of the most common ways for a compound to become allergenic is for it, or one of its metabolites, to become conjugated to a protein, either autologous or environmental (e.g. , in gastrointestinal contents or a manufacturing contaminant). This process is called haptenization, with the protein called the carrier and the smaller compound the hapten. The hapten-carrier combination is the actual immunogen and is recognized as ''altered-self” (i. e. foreign) by the immune system so that antibodies and/or cytotoxic T cells are generated against the entire molecule. It is unclear whether this breakdown of self-tolerance is due to the induction of new helper T cells or the inhibition of suppressor T cells (See T-cell ). The haptenization of these low-molecular-weight (500-1000) compounds accounts for the allergenicity of poison ivy, toluene diisocyanate and the ß-lactam antibiotics such as penicillin. Many drugs can produce autoimmune hemolytic anemia by adsorbing to erythrocytes. Alternatively, some compounds can substantially alter normal antigens without haptenization, so that they are seen as foreign. a-Methyldopa, a drug used in the treatment of essential hypertension, works in this way to modify erythrocyte surface antigens. Heavy metals are implicated in many autoimmune reactions although the mechanisms for this are not well understood.

From: Dictionary of Toxicology, 2nd edition.

See also: B cells

Auxiliary Generator

Published
Also called light plant or generator. Engine which provides additional electricity in fishing vessels.

From: NORA, 2008.

Avermectins

Published
Microbially derived insecticides and miticides of complex chemical structure that interact as agonists at the GABA receptor/chloride ionophore leading to sedation, anesthesia, coma and depression of vital centers. They may also act as agonists at the glycine receptor leading to paralysis. The avermectins display low acute mammalian toxicity.

From: Dictionary of Toxicology, 2nd edition.

Axon

Published
Long extension of a neuron, normally conducting impulses away from the nerve cell body (perikaryon). Axons vary greatly in length from less than 1 mm to more than 1 m. A steady movement of molecules from the neuron cell body along the axon towards the terminal branches and, to a lesser extent, a slower returning passage of molecules are termed anterograde and retrograde, axoplasmic transport, respectively. Axon transport is greatly facilitated by the cytoskeleton of neurofilaments and microtubules. From: Dictionary of Toxicology, 2nd edition.

See also: peripheral neuropathy; axonopathy

Axonopathy

Published
A form of axonal degeneration where the primary focus of injury is the axon itself. The axon is an extension of neuronal cytoplasm that may have a volume many times that of the neuronal cell body or perikaryon. Since the axon is dependent upon a continuous transport of substrate and macromolecules from the perikaryon, an axon will degenerate whenever the neuronal cell body dies, but this is not an axonopathy. Primary examples of toxicants that directly injure the axon are some organophosphorus compounds, such as tri-o-cresyl phosphate (TOCP), and the g-diketones. An alternative mechanism for axonal degeneration in toxic, nutritional or metabolic injury has been termed the ''dying back” phenomenon in which it is envisioned that the primary focus of injury is in the cell body, and the unsupported distal axon ''dies back.” This concept arose from the observation that in toxic neuropathies long axons are more vulnerable than short axons to degeneration, apparently reflecting the greater metabolic vulnerability of the cell body. The concept of axonopathy, on the other hand, would suggest that longer axons simply present more target for injury.

From: Dictionary of Toxicology, 2nd edition.

See also: peripheral neuropathy

Azinphosmethyl

Published
CAS number 86-50-0. An organophosphorus insecticide activated by cytochrome P450 to azinphosmethyl oxon, an acetylcholinesterase (AChE) inhibitor. Toxic to mammals, including humans. Inhibition of AChE is mode of toxic action in both target and non-target species.

azinophos-methyl

From: Dictionary of Toxicology, 2nd edition.

See also: organophosphorus insecticides
Return To Top