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Pure Appl. Chem., Vol. 65, No. 9, pp. 2003-2122, 1993.



Glossary for chemists of terms used in toxicology
(IUPAC Recommmendations 1993)


Alphabetical entries

A | B | C | D | E | F | G | H | I | J | K | L | M

N | O | P | Q | R | S | T | U | V | W | X | Y | Z 

tachy-: Prefix meaning rapid as in tachycardia and tachypnoea.
tachycardia: Abnormally fast heartbeat.
AN bradycardia.
tachypnoea: Abnormally fast breathing.
AN bradypnoea.
taeniacide: Substance intended to kill tapeworms.
target (biological): Any organism, organ, tissue, cell or cell constituent that is subject to the action of a pollutant or other chemical, physical, or biological agent.
WHO, 1979
RT receptor.
target (of environmental pollution): Human being or any organism, organ tissue, cell, resource, or any constituent of the environment, living or not, that is subject to the activity of a pollutant or other chemical or physical activity or other agent.
WHO, 1979
RT receptor.
target organ(s): Organ(s) in which the toxic injury manifests itself in terms of dysfunction or overt disease.
WHO, 1979
RT receptor.
target population (epidemiology):
1. Collection of individuals, items, measurements, etc. about which we want to make inferences: the term
   is sometimes used to indicate the population from which a sample is drawn and sometimes to denote any
   reference population about which inferences are required.
2. Group of persons for whom an intervention is planned.
Last, 1988
T cell: See T lymphocyte.
technical directive: See RT standard.
temporary acceptable daily intake: Value for the acceptable daily intake proposed for guidance when data are sufficient to conclude that use of the substance is safe over the relatively short period of time required to generate and evaluate further safety data, but are insufficient to conclude that use of the substance is safe over a lifetime. A higher-than-normal safety factor is used when establishing a temporary ADI and an expiration date is established by which time appropriate data to resolve the safety issue should be available.
RT acceptable daily intake.
After de Koning, 1987
temporary maximum residue limit: Temporary maximum residue limit is established for a specified, limited period when:
1. Only a temporary acceptable daily intake has been established for the pesticide concerned.
2. Although an acceptable daily intake has been established, the residue data are inadequate for firm
   maximum residue recommendations.
WHO, 1976
teratogen: Agent that, when administered prenatally (to the mother), induces permanent structural malformations or defects in the offspring.
teratogenicity: Potential to cause or the production of structural malformations or defects in offspring.
After WHO, 1987
RT developmental toxicity, embryotoxicity.
testing of chemicals:
1. In toxicology, evaluation of the therapeutic and potentially toxic effects of substances by their
   application through relevant routes of exposure with appropriate organisms or biological systems so as to
      relate effects to dose following application.
2. In chemistry, qualitative or quantitative analysis by the application of one or more fixed methods and
   comparison of the results with established standards.
tetanic: Pertaining to tetanus, characterized by tonic muscle spasm.
therapeutic index: Ratio between toxic and therapeutic doses (the higher the ratio, the greater the safety of the therapeutic dose).
threshold: Dose or exposure concentration below which an effect is not expected.
threshold limit value (TLV): Concentration in air of a substance to which it is believed that most workers can be exposed daily without adverse effect (the threshold between safe and dangerous concentrations). These values are established (and revised annually) by the American Conference of Governmental Industrial Hygienists) and are time-weighted concentrations for a 7 or 8 hour workday and a 40 hour workweek. For most substances the value may be exceeded, to a certain extent, provided there are compensatory periods of exposure below the value during the workday (or in some cases the week). For a few substances (mainly those that produce a rapid response) the limit is given as a ceiling concentration (maximum permissible concentration - designated by "C") that should never be exceeded.
thrombocytopenia: Decrease in the number of blood platelets (thrombocytes).
tidal volume: Quantity of air or test gas that is inhaled and exhaled during one respiratory cycle.
time-weighted average exposure (TWAE) or concentration (TWAC): Concentration in the exposure medium at each measured time interval multiplied by that time interval and divided by the total time of observation: for occupational exposure a working shift of eight hours is commonly used as the averaging time.
WHO, 1979
tinnitus: Continual noise in the ears, such as ringing, buzzing, roaring, or clicking.
tissue dose: Amount of a substance or physical agent (radiation) absorbed by a tissue.
T lymphocyte: Animal cell which possesses specific cell surface receptors through which it binds to foreign substances or organisms, or those which it identifies as foreign, and which initiates immune responses.
RT B lymphocyte, immune response, lymphocyte.
tolerable daily intake (TDI): Regulatory value equivalent to the acceptable daily intake established by the European Commission Scientific Committee on Food. Unlike the ADI, the TDI is expressed in mg/person, assuming a body weight of 60 kg. TDI is normally used for food contaminants.
RT acceptable daily intake.
tolerable risk: Probability of suffering disease or injury that can, for the time being, be tolerated, taking into account the associated benefits, and assuming that the risk is minimized by appropriate control procedures.
PS acceptable risk.
1. Adaptive state characterized by diminished effects of a particular dose of a substance: the process
   leading to tolerance is called "adaptation."
2. In food toxicology, dose that an individual can tolerate without showing an effect.
3. Ability to experience exposure to potentially harmful amounts of a substance without showing an adverse
4. Ability of an organism to survive in the presence of a toxic substance: increased tolerance may be
   acquired by adaptation to constant exposure.
5. In immunology, state of specific immunological unresponsiveness.
1. Characterised by tension, especially muscular tension.
2. Medical preparation that increases or restores normal muscular tension.
topical: Pertaining to a particular area, as in a topical effect that involves only the area to which the causative substance has been applied.
total diet study:
1. Study designed to establish the pattern of pesticide residue intake by a person consuming a defined diet.
   WHO, 1976.
2. Study undertaken to show the range and amount of various foodstuffs in the typical diet or to estimate
   the total amount of a specific substance in a typical diet.
   After WHO, 1989a
toxic: Able to cause injury to living organisms as a result of physicochemical interaction.
toxicant: See SN toxic substance.
toxic chemical: See SN toxic substance.
toxic dose: Amount of a substance which produces intoxication without lethal outcome.
SN super-threshold dose.
1. Capacity to cause injury to a living organism defined with reference to the quantity of substance
   administered or absorbed, the way in which the substance is administered (inhalation, ingestion, topical
   application, injection) and distributed in time (single or repeated doses), the type and severity of
   injury, the time needed to produce the injury, the nature of the organism(s) affected and other relevant
2. Adverse effects of a substance on a living organism defined with reference to the quantity of substance
   administered or absorbed, the way in which the substance is administered (inhalation, ingestion, topical
   application, injection) and distributed in time (single or repeated doses), the type and severity of
   injury, the time needed to produce the injury, the nature of the organism(s) affected, and other relevant
3. Measure of incompatibility of a substance with life: this quantity may be expressed as the reciprocal of
   the absolute value of median lethal dose (1/LD50) or concentration (1/LC50).
RT acute toxicity, chronic toxicity, subacute toxicity, subchronic toxicity.
toxicity equivalency factor (TEF): Factor used in risk assessment to estimate the toxicity of a complex mixture, most commonly a mixture of chlorinated dibenzo-p-dioxins, furans and biphenyls: in this case, TEF is based on relative toxicity to 2,3,7,8 -tetrachlorodibenzo-p-dioxin (TEF = 1).
toxicity equivalent (TEQ): Contribution of a specified component (or components) to the toxicity of a mixture of related substances. The amount-of-substance (or substance concentration) of total toxicity equivalent
is the sum of that for the components B, C.....N:
S n(TEQ) = n(TEQ)B + n(TEQ)C + ... n(TEQ)N
Toxicity equivalent is most commonly used in relation to the reference toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3,7,8-TCDD by means of the toxicity equivalency factor (TEF, f) which is 1 for the reference substance, hence:
S n(TEQ) = fBnB + fCnC + ... fNnN
toxicity test: Experimental study of the adverse effects of exposure of a living organism to a substance for a defined duration under defined conditions.
RT acute toxicity test, carcinogenicity test, chronic toxicity test, subchronic toxicity test.
toxic material: See SN toxic substance.
toxicodynamics: Process of interaction of potentially toxic substances with target sites, and the biochemical and physiological consequences leading to adverse effects.
RT adverse effect, pharmacodynamics, target.
toxicogenetics: Study of the influence of hereditary factors on the effects of potentially toxic substances on individual organisms.
RT ecogenetics, pharmacogenetics, polymorphism.
toxicokinetics: Process of the uptake of potentially toxic substances by the body, the biotransformation they undergo, the distribution of the substances and their metabolites in the tissues, and the elimination of the substances and their metabolites from the body. Both the amounts and the concentrations of the substances and their metabolites are studied. The
term has essentially the same meaning as pharmacokinetics, but the latter term should be restricted to the study of pharmaceutical substances.
BT chemobiokinetics.
RT biotransformation, pharmacokinetics.
WHO, 1979
toxicological data sheet: Document that gives in a uniform manner data relating to the toxicology of a substance, its production and application, properties and methods of identification; the data sheet may also include recommendations on protective measures.
PS toxicological profile, toxicological dossier.
IRPTC, 1982
toxicology: Scientific discipline involving the study of the actual or potential danger presented by the harmful effects of substances (poisons) on living organisms and ecosystems, of the relationship of such harmful effects to exposure, and of the mechanisms of action, diagnosis, prevention and treatment of intoxications.
NT chemical toxicology.
toxicometry: Term sometimes used to indicate a combination of investigative methods and techniques for making a quantitative assessment of toxicity and the hazards of potentially toxic substances.
toxicophobia: Morbid dread of poisons.
RT chemophobia.
toxicophoric (toxophoric) group: Structural moiety that upon metabolic activation exerts toxic effects: the presence of a toxicophoric group indicates only potential and not necessarily actual toxicity of a drug or other substances.
SN toxogenic group.
toxicovigilance: Active process of identification, investigation, and evaluation of various toxic effects in the community with a view to taking measures to reduce or control exposure(s) involving the substance(s) which produces these effects.
toxic substance: Material causing injury to living organisms as a result of physicochemical interactions.
SN chemical etiologic agent, poison, toxicant, toxic chemical, toxic material.
toxification: Metabolic conversion of a potentially toxic substance to a product that is more toxic.
toxin: Poisonous substance produced by a biological organism such as a microbe, animal or plant.
PS venom.
toxinology: Scientific discipline involving the study of the chemistry, biochemistry, pharmacology and toxicology of toxins.
RT toxicology, toxin.
toxogenic group: See SN toxicophoric group.
1. Means by which something may be followed; for example a radioactive isotope may replace a stable chemical element in a
   toxic compound enabling the toxicokinetics to be followed.
2. Labelled member of a population used to measure certain properties of that population.
   Gold, Loening, McNaught and Sehmi, 1987
transcription: Process by which the genetic information encoded in a linear sequence of nucleotides in one strand of DNA is copied into an exactly complementary sequence of RNA.
RT reverse transcription.
1. Alteration of a cell by incorporation of foreign genetic material and its subsequent expression in a new phenotype.
RT phenotype.
2. Conversion of cells growing normally to a state of rapid division in culture resembling that of a tumour.
3. Chemical modification of substances in the environment.
transgenic: Adjective used to describe animals carrying a gene introduced by micro-injecting DNA into the nucleus of the fertilized egg.
treatability: In relation to waste water, the amenability of substances to removal without adversely affecting the normal operation of biological treatment processes (such as a sewage treatment plant).
triage: Assessment of sick, wounded and injured persons following a disaster to determine priority needs for efficient use of available medical facilities.
trophic level: Amount of energy in terms of food that an organism needs: organisms not needing organic food, such as plants, are said to be on a low trophic level, whereas predator species needing food of high energy content are said to be on a high trophic level. The trophic level indicates the level of the organism in the food chain.
WHO, 1979
tumorigenic: Able to cause tumours.
1. Any abnormal swelling or growth of tissue, whether benign or malignant.
2. An abnormal growth, in rate and structure, that arises from normal tissue, but serves no physiological function.
SN neoplasm.
tumour progression: Sequence of changes by which a benign tumour develops from the initial lesion to a malignant stage.

turnover time: See SN mean life.


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Alphabetical entries

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N | O | P | Q | R | S | T | U | V | W | X | Y | Z 

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