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IUPAC Glossary of Terms Used in Toxicology - Terms Starting with A

See abiotic

Not associated with living organisms.

abiotic degradation
Process in which a substance is converted to simpler products by physical or chemical mechanisms: examples include hydrolysis and photolysis.

abiotic transformation
Process in which a substance in the environment is modified by non-biological mechanisms.

Substance causes pregnancy to end prematurely and causes an abortion.

absolute lethal concentration (LC100)
Lowest concentration of a substance in an environmental medium which kills 100 % of test organisms or species under defined conditions.
Note: This value is dependent on the number of organisms used in its assessment.

absolute lethal dose (LD100)
Lowest amount of a substance which kills 100 % of test animals under defined conditions. Note: This value is dependent on the number of organisms used in its assessment.

absorbance, A
Logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects of sample cell walls). Depending on the base of the logarithm, a decadic and Napierian absorbance are used. Symbols: A, A10, Ae. This quantity is sometimes called extinction, although the term extinction, better called attenuance, is reserved for the quantity which takes into account the effects of luminescence and scattering as well.
Corrected from [3]
Note: When natural logarithms are used, the Napierian absorbance is the logarithm to the base e of the incident spectral radiant power, essentially monochromatic, divided by the transmitted spectral radiant power, Pλ.

absorbed dose (of a substance)
internal dose
Amount (of a substance) taken up by an organism or into organs or tissues of interest.
See absorption, systemic

absorbed dose (of radiation), D
Energy imparted by ionizing radiation to a specified volume of matter divided by the mass of that volume.

absorptance (in chemistry), α
Ratio of the absorbed to the incident radiant power. Also called absorption factor. When α ≤ 1, α ≈ Ae, where Ae is the Napierian absorbance.
See also absorbance

absorption (general)
  1. Process of one material (absorbate) being retained by another (absorbent). Note: The process may be the physical solution of a gas, liquid, or solid in a liquid, attachment of molecules of a gas, vapor, liquid, or dissolved substance to a solid surface by physical forces, etc.
  2. Transfer of some or all of the energy of radiation to matter which it traverses. Note: Absorption of light at bands of characteristic wavelengths is used as an analytical method in spectrophotometry to identify the chemical nature of molecules, atoms or ions and to measure the concentrations of these species.
    Corrected from [3]

absorption (in biology)
uptake Penetration of a substance into an organism and its cells by various processes, some specialized, some involving expenditure of energy (active transport), some involving a carrier system, and others involving passive movement down an electrochemical gradient.
Note: In mammals absorption is usually through the respiratory tract, gastrointestinal tract, or skin into the circulatory system and from the circulation into organs, tissues and cells.

absorption (of radiation)
Phenomenon in which radiation transfers some or all of its energy to matter which it traverses.

absorption, systemic
Uptake to the blood and transport via the blood of a substance to an organ or compartment in the body distant from the site of absorption.

absorption coefficient (in biology)
absorption factor
Ratio of the absorbed quantity (uptake) of a substance to the administered quantity (intake).
Note: For exposure by way of the respiratory tract, the absorption coefficient is the ratio of the absorbed amount to the amount of the substance (usually particles) deposited (adsorbed) in the lungs.

absorption factor
See absorptance (in chemistry), absorption coefficient (in biology)

abuse (of drugs, substances, solvents etc.)
Improper use of drugs or other substances.

Substance intended to kill mites, ticks or other Acaridae.

acceptable daily intake (ADI)
Estimate by JECFA of the amount of a food additive, expressed on a body weight basis, that can be ingested daily over a lifetime without appreciable health risk.
Note 1: For calculation of ADI, a standard body mass of 60 kg is used
Note 2: Tolerable Daily Intake (TDI) is the analogous term used for contaminants.

acceptable daily intake (ADI) not allocated
See no-acceptable-daily-intake-allocated

acceptable residue level of an antibiotic
Acceptable concentration of a residue which has been established for an antibiotic found in human or animal foods.

acceptable risk
Probability of suffering disease or injury which is considered to be sufficiently small to be “negligible”,
Note: Calculated risk of an increase of one case in a million people per year for cancer is usually considered to be negligible.

accepted risk
Probability of suffering disease or injury which is accepted by an individual.

accidental exposure
Unintended contact with a substance or change in the physical environment (including for example radiation) resulting from an accident.

acclimatization, biological
  1. Processes, including selection and adaptation, by which a population of micro-organisms develops the ability to degrade a substance, or develops a tolerance to it.
  2. In animal tests - allowing an animal to adjust to its environment prior to undertaking a study.

accumulation (in biology)
See bioaccumulation

Quantity referring to the differences between the mean of a set of results or an individual result and the value which is accepted as the true or correct value for the quantity measured.

acid dissociation constant, Ka
Equilibrium constant for the following reaction of an acid HB:

acid dissociation constant

where co = 1 mol dm-3 is the standard amount concentration and activity coefficients have been neglected.

Note 1: This constant, because activity coefficients are neglected, is valid at a specified ionic strength. The thermodynamic dissociation constant is found by suitable extrapolation of the conditional constant to zero ionic strength. Note that it is defined as a dimensionless quantity, but sometimes it is given dimensions by omitting the standard amount concentration.

Note 2: Because this constant differs for each acid and varies over many degrees of magnitude, the acidity constant is often represented by the additive inverse of its common logarithm, represented by the symbol pKa (using the same mathematical relationship as [H+] is to pH), viz.:

pKa = -log10Ka

In general, a larger value of Ka (or a smaller value of pKa) indicates a stronger acid, since the extent of dissociation is larger at the same concentration.

antonym alkalosis
Pathological condition in which the hydrogen(1+) (hydron) amount concentration of body fluids is above normal and hence the pH of blood falls below the reference interval.

action level
  1. Concentration of a substance in air, soil, water or other defined medium at which specified emergency counter-measures, such as the seizure and destruction of contaminated materials, evacuation of the local population or closing down the sources of pollution, are to be taken.
  2. Concentration of a pollutant in air, soil, water or other defined medium at which some kind of preventive action (not necessarily of an emergency nature) is to be taken.

activation (abiotic)
Conversion of a xenobiotic to a more toxic derivative by modification not involving biological catalysis.

activation (in biology)
See bio-activation

active ingredient
Component of a mixture responsible for the biological effects of the mixture.
Compare inert ingredient

active metabolite
Metabolite causing biological and (or) toxicological effects.
After [2]
See metabolite

active transport
Movement of a substance across a cell membrane against an electrochemical gradient, in the direction opposite to normal diffusion and requiring the expenditure of energy.

antonym chronic
  1. Of short duration, in relation to exposure or effect; the effect usually shows a rapid onset.
    Note: In regulatory toxicology, ‘acute’ refers to studies where dosing is either single or limited to one day although the total study duration may extend to two weeks to permit appearance of toxicity in susceptible organ systems.
  2. In clinical medicine, sudden and severe, having a rapid onset.
    After [2]

acute effect
Effect of finite duration occurring rapidly (usually in the first 24 h or up to 14 d) following a single dose or short exposure to a substance or radiation. Note: Acute effects may occur continuously following continuous dosing or repeatedly following repeated dosing.
After [2]

acute exposure
antonym chronic exposure
Exposure of short duration.
See acute, exposure

acute toxicity
antonym chronic toxicity
  1. Adverse effects of finite duration occurring within a short time (up to 14 d) after administration of a single dose (or exposure to a given concentration) of a test substance or after multiple doses (exposures), usually within 24 h of a starting point (which may be exposure to the toxicant, or loss of reserve capacity, or developmental change etc.).
  2. Ability of a substance to cause adverse effects within a short time of dosing or exposure.
  1. Change in an organism, in response to changing conditions of the environment (specifically chemical), which takes place without any irreversible disruptions of the given biological system and without exceeding normal (homeostatic) capacities of its response.
  2. Process by which an organism stabilizes its physiological condition after an environmental change.
    Note: If this process exceeds the homeostatic range, it becomes pathological and results in symptoms of disease (adverse effects).

added risk
Difference between the incidence of an adverse effect in a treated group (of organisms or a group of exposed humans) and a control group (of the same organisms or the spontaneous incidence in humans).

Surrender and devotion to the regular use of a medicinal or pleasurable substance for the sake of relief, comfort, stimulation, or exhilaration which it affords; often with craving when the drug is absent.

additive effect
Consequence which follows exposure to two or more physico-chemical agents which act jointly but do not interact: the total effect is the simple sum of the effects of separate exposures to the agents under the same conditions.

New chemical species AB, each molecular entity of which is formed by direct combination of two separate molecular entities A and B in such a way that there is change in connectivity, but no loss, of atoms within the moieties A and B.
Note 1: Stoichiometries other than 1:1 are also possible, e.g. a bis-adduct (2:1). An ‘intramolecular adduct’ can be formed when A and B are groups contained within the same molecular entity.
Note 2: This is a general term which, whenever appropriate, should be used in preference to the less explicit term complex. It is also used specifically for products of an addition reaction. [3]

Malignant tumor originating in glandular epithelium or forming recognizable glandular structures.

Benign tumor occurring in glandular epithelium or forming recognizable glandular structures.

  1. In pharmacology, a substance added to a drug to speed or increase the action of the main component.
  2. In immunology, a substance (such as aluminum hydroxide) or an organism (such as killed mycobacterium) which increases the response to an antigen.

administration (of a substance)
Application of a known amount of a substance to an organism in a reproducible manner and by a defined route.

Secreting adrenaline (epinephrine) and (or) related substances; in particular referring to sympathetic nerve fibers.
See sympathomimetic

Increase in the concentration of a substance at the interface of a condensed and a liquid or a gaseous layer owing to the operation of surface forces.
See also interfacial layer

adsorption factor
Ratio of the amount of substance adsorbed at the interface of a condensed and a liquid or gaseous phase to the total amount of the substance available for adsorption.

See astringent

advection (in environmental chemistry)
Process of transport of a substance in air or water solely by mass motion.

adverse effect
Change in biochemistry, physiology, growth, development morphology, behavior, or lifespan of an organism which results in impairment of functional capacity or impairment of capacity to compensate for additional stress or increase in susceptibility to other environmental influences.
After [2]

adverse event
Occurrence which causes an adverse effect.
Note: An adverse event in clinical studies is any untoward reaction in a human subject participating in a research project; such an adverse event, which may be a psychological reaction, must be reported to an institutional review board.

Organism which requires dioxygen for respiration and hence for growth and life.

Requiring dioxygen.

aerodynamic diameter (of a particle)
Diameter of a spherical particle with relative density equal to unity which has the same settling velocity in air as the particle in question.

Mixture of small particles (solid, liquid or a mixed variety) and a carrier gas (usually air).
Note 1: Owing to their size, these particles (usually less than 100 µm and greater than 0.01 µm in diameter) have a comparatively small sedimentation velocity and hence exhibit some degree of stability in the earth’s gravitational field.
Note 2: An aerosol may be characterized by its chemical composition, its radioactivity, the particle size distribution, the electrical charge and the optical properties.

See etiology

after-effect of a poison
Ability of a poison to produce a change in an organism after cessation of contact.

age sensitivity
Quantitative and qualitative age dependence of an effect.

antonym antagonist
Substance which binds to cell receptors normally responding to a naturally occurring substance and which produces an effect similar to that of the natural substance.
Note 1: A partial agonist activates a receptor but does not cause as much of a physiological change as does a full agonist.
Note 2: A co-agonist works together with other co-agonists to produce a desired effect.

air pollution
Presence of substances in the atmosphere resulting either from human activity or natural processes, in sufficient concentration, for a sufficient time and under circumstances such as to interfere with comfort, health or welfare of persons or to harm the environment.

air pollution control system
  1. Network of organizations which monitor air pollution.
  2. Group of measures or processes used to minimize or prevent air pollution.

Presence of albumin, derived from plasma, in the urine.

algicide algaecide
Substance intended to kill algae.

aliquot (in analytical chemistry)
Known amount of a homogeneous material, assumed to be taken with negligible sampling error.
Note 1: The term is usually applied to fluids.
Note 2: The term “aliquot” is usually used when the fractional part is an exact divisor of the whole; the term “aliquant” has been used when the fractional part is not an exact divisor of the whole (e.g., a 15 mL portion is an aliquant of 100 mL).
Note 3: When an aliquot is taken of a laboratory sample or test sample or the sample is otherwise subdivided, the samples have been called split samples.

antonym acidosis
Pathological condition in which the hydrogen(1+) (hydron) substance concentration of body fluids is below normal and hence the pH of blood rises above the reference interval.

alkylating agent
Substance which introduces an alkyl substituent into a compound.

One of several alternate forms of a gene which occur at the same relative position (locus) on homologous chromosomes and which become separated during meiosis and can be recombined following fusion of gametes.

Immunostimulant antigenic substance which may or may not cause a clinically significant effect but which is capable of producing immediate hypersensitivity.

Symptoms or signs occurring in sensitized individuals following exposure to a previously encountered substance (allergen) which would otherwise not cause such symptoms or signs in non-sensitized individuals. The most common forms of allergy are rhinitis, urticaria, asthma, and contact dermatitis.

  1. Pertaining to a systematic relationship between growth rates of different parts of an organism and its overall growth rate.
  2. Pertaining to a systematic relationship between size, shape, and metabolism in different species.

allometric growth
Regular and systematic pattern of growth such that the mass or size of any organ or part of a body can be expressed in relation to the total mass or size of the entire organism according to the allometric equation:
Y = bχα where
Y = mass of the organ, χ = mass of the organism, α = growth coefficient of the organ, and b = a constant.

allometric scaling
  1. Adjustment of data to allow for change in proportion between an organ or organs and other body parts during the growth of an organism.
  2. Adjustment of data to allow for differences and make comparisons between species having dissimilar characteristics, e.g., in size, shape, and metabolism.
    After [2]

allometry (in biology)
Measurement of the rate of growth of a part or parts of an organism relative to the growth of the whole organism.

Semiochemical that is produced by an organism inducing a response in an organism of another species that is favorable to the emitter.
See kairomone, synomone

all-or-none effect
See quantal effect

Baldness; absence or thinning of hair from areas of skin where it is usually present.

alveol/us (pulmonary), -i pl., -ar adj.
Terminal air sac of the lung where gas exchange occurs.

Surrounding (applied to environmental media such as air, water, sediment or soil).

ambient monitoring
Continuous or repeated measurement of agents in the environment to evaluate ambient exposure and health risk by comparison with appropriate reference values based on knowledge of the probable relationship between exposure and resultant adverse health effects.

ambient standard
See environmental quality standard

Ames test
In vitro test for mutagenicity using mutant strains of the bacterium Salmonella typhimurium which cannot grow in a given histidine-deficient medium: mutagens can cause reverse mutations which enable the bacterium to grow on the medium. The test can be carried out in the presence of a given microsomal fraction (S-9) from rat liver (see microsome) to allow metabolic transformation of mutagen precursors to active derivatives.

amnesic shellfish poisoning (ASP)
Serious illness which is a consequence of consumption of bivalve shellfish (mollusks) such as mussels, oysters and clams that have ingested, by filter feeding, large quantities of micro-algae containing domoic acid; acute symptoms include vomiting, diarrhea, and in some cases, confusion, loss of memory, disorientation and even coma.

amplification (of genes)
See gene amplification

antonym catabolism
Biochemical processes by which smaller molecules are joined to make larger molecules.

See anemia.

antonym aerobe
Organism which does not require dioxygen for life.
Note: Obligate (strict) anaerobes grow only in the absence of dioxygen. Facultative anaerobes can grow either in the presence or in the absence of dioxygen.

antonym aerobic
Not requiring dioxygen.

See anesthetic

Substance which relieves pain, without causing loss of consciousness.

analogue metabolism
Process by which a normally non-biodegradable compound is biodegraded in the presence of a structurally similar compound which can induce the necessary enzymes.

analytic study (in epidemiology)
Study designed to examine associations, commonly putative or hypothesized causal relationships.

Of or resembling anaphylaxis.

Life threatening type 1 hypersensitivity allergic reaction (see allergy) occurring in a person or animal exposed to an antigen or hapten to which they have previously been sensitized.
Note: Consequences of the reaction may include angio-edema, vascular collapse, shock, and respiratory distress.

Loss of normal cell differentiation, a feature characteristic of most malignancies.

Condition in which there is a reduction in the number of red blood cells or amount of hemoglobin per unit volume of blood below the reference interval for a similar individual of the species under consideration, often causing pallor and fatigue.

Substance which produces loss of feeling or sensation: general anesthetic produces loss of consciousness; local or regional anesthetic renders a specific area insensible to pain.

Cell or organism with missing or extra chromosomes or parts of chromosomes and thus an abnormal number of chromosomes which is not an exact multiple of the haploid number.

Strictly total absence of oxygen but sometimes incorrectly used instead of hypoxia to mean a decreased oxygen supply in tissues.

antagonism (in toxicology)
Combined effect of two or more factors which is smaller than the solitary effect of any one of those factors.
Note: In bioassays, the term may be used when a specified effect is produced by exposure to either of two factors but not by exposure to both together.

antagonist (in toxicology)
antonym agonist
Substance which binds to a cell receptor normally responding to a naturally occurring substance and which prevents a response to the natural substance.

  1. n., Substance intended to kill or cause the expulsion of parasitic intestinal worms, such as helminths.
  2. adj., Acting to expel or kill parasitic intestinal worms.

anthracosis (coal miners' pneumoconiosis)
Form of pneumoconiosis caused by accumulation of anthracite carbon deposits in the lungs due to inhalation of smoke or coal dust.

  1. Caused by or influenced by human activities.
  2. Describing a conversion factor used to calculate a dose or concentration affecting a human that has been derived from data obtained with another species, e.g. the rat.

See sympatholytic

Substance produced by, and obtained from, certain living cells (especially bacteria, yeasts and moulds), or an equivalent synthetic substance, which is biostatic or biocidal at low concentrations to some other form of life, especially pathogenic or noxious organisms.

Protein (immunoglobulin) produced by the immune system in response to exposure to an antigenic molecule and characterized by its specific binding to a site on that molecule (antigenic determinant or epitope).

  1. adj., Preventing transmission of parasympathetic (acetylcholine releasing) nerve impulses.
  2. n., Substance which prevents transmission of parasympathetic nerve impulses.

See cholinesterase inhibitor

Substance which prevents blood clotting, e.g., warfarin.

Substance capable of specifically counteracting or reducing the effect of a potentially toxic substance in an organism by a relatively specific chemical or pharmacological action.

Substance or a structural part (epitope) of a substance which causes the immune system to produce specific antibody or specific cells and which combines with specific binding sites (epitopes) on the antibody or cells.

Substance that blocks or counteracts the action of histamine.

See anthelmint(h)ic

Substance, structurally similar to a metabolite, which competes with it or replaces it, and so prevents or reduces its normal utilization.

  1. n., Substance inhibiting or preventing the actions of muscarine and muscarine-like agents, e.g., atropine, on the muscarinic acetylcholine receptors.
  2. adj., Inhibiting or preventing the actions of muscarine and muscarine-like agents on the muscarinic acetylcholine receptors.

Substance used to kill a fungus or to inhibit its growth.

  1. n., Substance inhibiting or preventing the actions of nicotine and nicotine-like agents, e.g., suxamethonium chloride, on the nicotinic acetylcholine receptors.
  2. adj. Inhibiting or preventing the actions of nicotine and nicotine-like agents on the nicotinic acetylcholine receptors.

Substance which relieves or reduces fever.

Substance used as an additive to a pesticide formulation in order to reduce the resistance of insects to the pesticide, e.g., an antimetabolite that inhibits metabolic inactivation of the pesticide.

Serum containing antibodies to a particular antigen either because of immunization or after an infectious disease.
Note: Usually the antibodies are polyclonal.

See virucide

Loss or impairment of the power of speech or writing, or of the ability to understand written or spoken language or signs, due to a brain injury or disease.

Substance intended to kill aphids.

Common name for a harmful plant parasite in the family Aphididae, some species of which are vectors of plant virus diseases.

Lack of development of an organ or tissue, or of the cellular products from an organ or tissue.

apopto/sis n., tic adj.
Active process of programmed cell death, requiring metabolic energy, often characterized by fragmentation of DNA, and cell deletion without associated inflammation.
See necrosis

Substance intended to kill trees and shrubs.

area source
Widespread origin of emissions.

area under the concentration-time curve
See area under the curve

area under the curve (AUC)
Area between a curve and the abscissa (horizontal axis), i. e., the area underneath the graph of a function: often, the area under the tissue (plasma) concentration curve of a substance expressed as a function of time.

area under the moment curve (AUMC)
Area between a curve and the abscissa (horizontal axis) in a plot of (concentration x time) versus time.

Pathological condition characterized by grey-bluish or black pigmentation of tissues (such as skin, retina, mucous membranes, internal organs) caused by the accumulation of metallic silver, due to reduction of a silver compound which has entered the organism during (prolonged) administration or exposure.

Any variation from the normal rhythm of the heartbeat.

Chronic arsenical poisoning.

Observation, effect, or result which is inaccurate because it is produced by the methodology used in scientific investigation or by experimental error

Hardening and thickening of the walls of the arteries.

Pain in a joint.

Chronic inflammation of a joint, usually accompanied by pain and often by changes in structure.

Disease of a joint.

Joint or articulation.

Form of pneumoconiosis caused by inhalation of asbestos fibers.

Substance intended to kill roundworms (Ascaridae).

Condition resulting from insufficient intake of oxygen: symptoms include breathing difficulty, impairment of senses, and, in extreme, convulsions, unconsciousness and death.

Substance that blocks the transport or use of oxygen by living organisms.
Note: Examples include both physical (nitrogen gas) and chemical (carbon monoxide) asphyxiants.

  1. Process of quantitative or qualitative analysis of a component of a sample.
  2. Results of a quantitative or qualitative analysis of a component of a sample.

Uptake and incorporation of substances by a living organism.

Weakness; lack or loss of strength.

Chronic respiratory disease characterized by bronchoconstriction, excessive mucus secretion and edema of the pulmonary alveoli, resulting in difficulty in breathing out, wheezing, and cough.

  1. Adj. Causing contraction, usually locally after topical application.
  2. N. Substance causing cells to shrink, thus causing tissue contraction or stoppage of secretions and discharges; such substances may be applied to skin to harden and protect it.

Unsteady or irregular manner of walking or movement caused by loss or failure of muscular co-ordination.

Pathological condition in which there is thickening, hardening, and loss of elasticity of the walls of blood vessels, characterized by a variable combination of changes of the innermost layer consisting of local accumulation of lipids, complex carbohydrates, blood and blood components, fibrous tissue and calcium deposits. In addition, the outer layer becomes thickened and there is fatty degeneration of the middle layer.

Wasting away of the body or of an organ or tissue, involving a decrease in size and (or) numbers of cells.

attenuation (in genetics)
Regulation of gene expression in bacteria by premature termination of transcription of a biosynthetic operon.

Substance which attracts animals. Some attractants fulfill natural biological functions such as mating or predation: others may be used to attract animals for monitoring or for control.
See also pheromone

attributable risk
Part of a risk that is identified as due to exposure to a defined substance.

auto-immune disease
Pathological condition resulting when an organism produces antibodies or specific cells which bind to constituents of its own tissues (autoantigens) and cause tissue injury: examples of such disease may include rheumatoid arthritis, myasthenia gravis, systemic lupus erythematosus, and scleroderma.

See autoxidation

Membrane-bound body (secondary lysosome) in which parts of the cell are digested.

Post-mortem examination of the organs and body tissue to determine cause of death or pathological condition.

Any chromosome other than a sex chromosome.

Reaction with dioxygen at moderate temperatures.

autoxidation (in food chemistry)
Apparently spontaneous, usually slow reaction of foodstuff components with dioxygen in an aerobic environment at moderate temperatures.

Organism unable to synthesize an organic molecule which is required for its growth: when the compound is given to the organism with the other nutrients it requires, growth of the organism may occur.

Inability of a micro-organism to synthesize a particular organic compound required for its growth.

Substance intended to kill birds.

axenic animal
See germ-free animal

  1. Absence of live motile spermatozoa in semen.
  2. Failure to form live spermatozoa.