Abnormally fast heartbeat.
Abnormally fast breathing.
Substance intended to kill tapeworms.
target population (in epidemiology)
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.
Study of malformations, monstrosities or serious deviations from normal development in organisms.
testing of chemicals
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.
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.
See toxic substance
See toxic substance
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.
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
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.
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.
Substance which can be tracked through one or more reactions or systems, often by detecting an incorporated isotope.
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).
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.
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.