IUPAC Glossary of Terms Used in Toxicology - Terms Starting with T
Abnormally fast heartbeat.
Abnormally fast breathing.
Substance intended to kill tapeworms.
target population (in epidemiology)
- Collection of individuals, items, measurements, etc. about which inferences are required: 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 needed.
- Group of persons for whom an intervention is planned.
See T lymphocyte
Structure which terminates the arm of a chromosome.
Note: A similar term ‘telomer’, with a different meaning is found in the IUPAC Gold Book
temporary acceptable daily
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.
Note: 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.
temporary maximum residue
Regulatory value established for a specified, limited time when only a temporary acceptable daily intake has been established for the pesticide concerned or, with the existence of an agreed acceptable daily intake, the available residue data are inadequate for firm maximum residue recommendations.
Agent that, when administered prenatally (to the mother), induces permanent structural malformations or defects in the offspring.
- Potential to cause the production of nonheritable structural malformations or defects in offspring.
- Production of nonheritable structural malformations or defects in offspring.
Study of malformations, monstrosities or serious deviations from normal development in organisms.
testing of chemicals
- 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.
- In chemistry, qualitative or quantitative analysis by the application of one or more fixed methods and comparison of the results with established standards.
Pertaining to tetanus, characterized by tonic muscle spasm.
theoretical maximum daily intake
Predicted maximum daily intake of a residue, assuming that it is present at the maximum residue level and that average daily consumption of foods per person is represented by assessed regional diets: it is expressed in milligrams of residue per person per day.
Generation and manipulation of stem cells with the objective of deriving cells of a particular organ or tissue to treat a disease.
Ratio between toxic and therapeutic doses (the higher the ratio, the greater the safety of the therapeutic dose).
structure-activity relationship (3D-QSAR)
Quantitative association between the three-dimensional structural properties of a substance and its biological properties.
See quantitative structure-activity relationship
threshold limit value-short term
exposure limit (TLV-STEL)
As defined by ACGIH, concentration to which it is believed that workers can be exposed continuously for a short period of time without suffering from 1) irritation, 2) chronic or irreversible tissue damage, or 3) narcosis of sufficient degree to increase the likelihood of accidental injury, impair self rescue or materially reduce work efficiency, and provided that the daily TLV-TWA is not exceeded.
Note: It is not a separate independent exposure guideline; rather, it supplements the TLV-TWA limit where there are recognized acute effects from a substance whose toxic effects are primarily of a chronic nature. TLV-STELs are recommended only where toxic effects have been reported from high short-term exposures in either humans or animals.
threshold limit value-time-weighted
As defined by ACGIH, time-weighted average concentration for a conventional 8-hour workday and a 40-hour workweek, to which it is believed nearly all workers may be repeatedly exposed, day after day, without adverse effect.
Decrease in the number of blood platelets (thrombocytes).
Condition resulting from excessive concentrations of thyroid hormones, as in hyperthyroidism, characterized by bulging eyes and rapid heart rate.
Quantity of air or test gas that is inhaled and exhaled during one respiratory cycle.
(TWAE), or concentration
Concentration in the exposure medium at each measured time interval multiplied by that time interval and divided by the total time of observation.
Note: For occupational exposure a working shift of eight hours is commonly used as the averaging time.
Continual noise in the ears, such as ringing, buzzing, roaring, or clicking.
Amount of a substance or physical agent (radiation) absorbed by a tissue.
See partition ratio
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.
tolerable daily intake
Estimate of the amount of a potentially harmful substance (e.g. contaminant) in food or drinking water that can be ingested daily over a lifetime without appreciable health risk.
Note 1: For regulation of substances that cannot be easily avoided, a provisionally tolerable weekly intake (PTWI) may be applied as a temporary limit.
Note 2: Acceptable Daily Intake is normally used for substances not known to be harmful, such as food additives.
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.
tolerable weekly intake
Estimate of the amount of a potentially harmful substance (e.g. a contaminant) in food or drinking water that can be ingested weekly over a lifetime without appreciable health risk.
- Adaptive state characterized by diminished effects of a particular dose of a substance: the process leading to tolerance is called “adaptation”.
- In food toxicology, dose that an individual can tolerate without showing an effect.
- Ability to experience exposure to potentially harmful amounts of a substance without showing an adverse effect.
- Ability of an organism to survive in the presence of a toxic substance: increased tolerance may be acquired by adaptation to constant exposure.
- In immunology, state of specific immunological unresponsiveness.
- Characterized by tension, especially muscular tension.
- Medical preparation that increases or restores normal muscular tension.
topical (in medicine)
Applied directly to the surface of the body.
Consequence of application of a substance to the surface of the body which occurs at the point of application.
torsade (de pointes)
potentially lethal form of ventricular tachycardia following chronic abuse of alcohol and mainly due to hypomagnesemia.
- Study designed to establish the pattern of pesticide residue intake by a person consuming a defined diet.
- 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.
- Condition in which the blood contains toxins produced by body cells at a local source of infection or derived from the growth of microorganisms.
- Pregnancy-related condition characterized by high blood pressure, swelling and fluid retention, and proteins in the urine.
See toxic substance
See toxic substance
- 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 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 conditions.
- Adverse effects of a substance on a living organism defined as in 1.
- 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).
toxicity equivalency factor (TEF,
Ratio of the toxicity of a chemical to that of another structurally related chemical (or index compound) chosen as a reference.
toxicity equivalency factor (in
risk assessment) (TEF), f
Ratio of the toxicity of a chemical to that of another structurally related chemical (or index compound) chosen as a reference. Factor used to estimate the toxicity of a complex mixture, commonly a mixture of chlorinated dibenzo-p-dioxins [oxanthrenes], furans, and biphenyls: in this case, TEF is based on relative toxicity to 2,3,7,8-tetrachlorodibenzo-p-dioxin [2,3,7,8-tetrachlorooxanthrene] for which the f = 1.
toxicity equivalent (TEQ), Txe
Contribution of a specified component (or components) to the toxicity of a mixture of related substances.
Note 1: The amount-of-substance (or substance) concentration of total toxicity equivalent is the sum of that for the components B, C … N.
Note 2: Toxicity equivalent is most commonly used in relation to the reference toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin [2,3,7,8-tetrachlorooxanthrene] by means of the toxicity equivalency factor (TEF, f) which is 1 for the reference substance. Hence, where c is the amount-of-substance concentration:
See toxic substance
Study of the influence of hereditary factors on the effects of potentially toxic substances on individual organisms.
- Generally, the overall process of the absorption (uptake) of potentially toxic substances by the body, the distribution of the substances and their metabolites in tissues and organs, their metabolism (biotransformation), and the elimination of the substances and their metabolites from the body.
- In validating a toxicological study, the collection of toxicokinetic data, either as an integral component in the conduct of non-clinical toxicity studies or in specially designed supportive studies, in order to assess systemic exposure.
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.
Note: The data sheet may also include recommendations on protective measures.
toxicologically based pharmacokinetic
See physiologically based pharmacokinetic modeling
Scientific discipline involving the study of the actual or potential danger presented by the harmful effects of substances 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.
Morbid dread of poisons.
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.
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.
Metabolic conversion of a potentially toxic substance to a product that is more toxic.
Poisonous substance produced by a biological organism such as a microbe, animal, plant or fungus.
Note: Examples are botulinum toxin, tetrodotoxin, pyrrolizidine alkaloids and amanitin.
See toxicophoric group
See toxicophoric group
Property of a measurement result whereby the result can be related to a stated reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.
- 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.
- Labeled member of a population used to measure certain properties of that population.
Substance which can be tracked through one or more reactions or systems, often by detecting an incorporated isotope.
Total messenger RNA expressed in a cell or tissue at a given point in time.
- Alteration of a cell by incorporation of foreign genetic material and its subsequent expression in a new phenotype.
- Conversion of cells growing normally to a state of rapid division in culture resembling that of a tumor.
- Chemical modification of substances in the environment.
Gene from one source that has been incorporated into the genome of another organism.
Mobile nucleic acid element.
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).
- Process for sorting people into groups based on their need
for or likely benefit from immediate medical treatment.
Note: Triage is used in hospital emergency rooms, on battlefields, and at disaster sites when limited medical resources must be allocated.
- System used to allocate a scarce commodity, such as food, to those most likely to benefit from it.
- Process in which things are ranked in terms of importance or priority.
Amount of energy in terms of food that an organism needs.
Note: 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.
Able to cause tumors.
- Any abnormal swelling or growth of tissue, whether benign or malignant.
- An abnormal growth, in rate and structure, that arises from normal tissue, but serves no physiological function.
tumor necrosis factor
Protein produced by several of the body's cell types, such as white blood cells, red blood cells, and other cells that line the blood vessels; it promotes the destruction of some types of cancer cells and is a cytokine involved in systemic inflammation.
Gene which serves to protect cells from entering a cancerous state.
Note: According to Knudson’s “two-hit” hypothesis, both alleles of a particular tumor suppressor gene must acquire a mutation before the cell will enter a transformed state.