IUPAC Glossary of Terms Used in Toxicology – T
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tachy-
Prefix meaning rapid as in tachycardia and tachypnoea.
tachycardia
antonym bradycardia
Abnormally fast heartbeat.
tachypnoea
antonym bradypnoea
Abnormally fast breathing.
taeniacide
Substance intended to kill tapeworms.
target (in biology)
Any organism, organ, tissue, cell or cell constituent that is
subject to the action of an agent.
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.
T cell
See T lymphocyte
technical directive
See standard
telomere
Structure which terminates the arm of a chromosome.
Note: A similar term ‘telomer’, with a different
meaning is found in the IUPAC Gold Book
[3]
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.
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
limit
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.
teratogen
Agent that, when administered prenatally (to the mother), induces
permanent structural malformations or defects in the
offspring.
teratogenicity
- Potential to cause the production of nonheritable structural malformations or defects in offspring.
- Production of nonheritable structural malformations or defects in offspring.
teratology
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.
tetanic
Pertaining to tetanus, characterized by tonic muscle spasm.
theoretical maximum daily intake
(TMDI)
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.
After [14]
therapeutic cloning
Generation and manipulation of stem cells with the objective of
deriving cells of a particular organ or tissue to treat a
disease.
therapeutic index
Ratio between toxic and therapeutic
doses (the higher the ratio, the greater the safety of the
therapeutic dose).
three-dimensional quantitative
structure-activity relationship (3D-QSAR)
Quantitative association between the three-dimensional structural
properties of a substance and its biological properties.
[2]
See quantitative structure-activity
relationship
threshold
Dose or exposure
concentration
below which a defined effect will not occur.
See also critical
effect
threshold concentration
See threshold
threshold dose
See threshold
threshold limit value-ceiling
(TLV-C)
As defined by ACGIH, concentration of a potentially
toxic substance that should not be
exceeded during any part of the working exposure.
[2]
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.
[2]
threshold limit value-time-weighted
average (TLV-TWA)
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.
[2]
threshold of toxicological concern
(TTC)
Human exposure threshold value for a group of chemicals below
which there should be no appreciable risk to human health.
thrombocytopenia
Decrease in the number of blood platelets (thrombocytes).
thyrotoxicosis
Condition resulting from excessive concentrations of thyroid
hormones, as in hyperthyroidism, characterized by bulging eyes
and rapid heart rate.
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.
Note: For occupational exposure a working shift of eight hours is
commonly used as the averaging time.
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.
tissue/plasma partition
coefficient
See partition
ratio
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.
tolerable daily intake
(TDI)
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.
[2]
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.
tolerable weekly intake
(TWI)
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.
[2]
- 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.
[2]
topical effect
Consequence of application of a substance to the surface of the
body which occurs at the point of application.
[2]
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.
total terminal residue (of a
pesticide)
Summation of levels of all the residues of a defined pesticide in
a food.
See also residue
After [6]
- 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.
toxic
Able to cause injury to living organisms as a result of
physicochemical interaction.
toxicant
See toxic substance
toxic chemical
See toxic substance
toxic dose
super-threshold dose
Amount of a substance which produces intoxication without lethal
outcome.
- 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,
f)
Ratio of the toxicity of a chemical to that of another
structurally related chemical (or index compound) chosen as a
reference.
[6]
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:
toxicity exposure ratio
(TER)
Ratio of the measure of the effects (e.g., LD50,
LC50, NOEC) to the estimated exposure.
Note: It is the reciprocal of a risk quotient or hazard quotient.
[6]
toxicity test
Experimental study of the adverse effects of
exposure of a living
organism to a substance for a defined duration under defined
conditions.
toxic material
See toxic substance
toxic substance
chemical etiologic agent
poison
toxicant
toxic chemical
toxic material
Material causing injury to living organisms as a result of
physicochemical interactions.
toxicodynamics
Process of interaction of potentially toxic substances with target sites, and the biochemical and
physiological consequences leading to adverse effects.
toxicogenomics
Scientific sub-discipline that combines toxicology with genomics to determine how an
organism’s genetic make-up influences its response to a
toxic substance.
toxicogenetics
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
modeling (TBPK)
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.
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.
toxicophoric group
toxogenic group
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.
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.
toxification
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.
toxinology
Scientific discipline involving the study of the chemistry,
biochemistry, pharmacology and toxicology of toxins.
toxogenic group
See toxicophoric
group
toxophoric group
See toxicophoric
group
traceability (in
metrology)
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.
[7]
tracer
- 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.
tracer substance
Substance which can be tracked through one or more reactions or
systems, often by detecting an incorporated isotope.
[2]
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.
Total messenger RNA expressed in a cell or tissue at a given point in time.
transcriptomics
Global analysis of gene
expression to identify and evaluate changes in synthesis of
mRNA after chemical
exposure.
[2]
- 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.
transformed cell
Cell which has become genetically altered spontaneously or by
incorporation of foreign DNA
to produce a cell with an extended lifetime in culture.
[2]
transformed cell line
See cell line,
transformed cell
Gene from one source that has been incorporated into the genome of another organism.
transgenic
Adjective used to describe animals carrying a gene introduced by micro-injecting
DNA into the nucleus of the
fertilized egg.
translation
Process through which a polypeptide chain of amino acid molecules
is generated as directed by the sequence of a particular
messenger RNA sequence.
transposon
Mobile nucleic acid element.
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).
- 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.
trophic level
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.
trueness
Closeness of agreement between the average of an theoretically infinite number of replicate measured quantity values and a reference quantity value.
tubular reabsorption
Transfer of solutes from the renal tubule lumen to the tubular
epithelial cell and normally from there to the peritubular
fluid.
[2]
tumorigenic
Able to cause tumors.
tumour
neoplasm
- 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
(TNF)
cachectin
cachexin
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.
tumor progression
Sequence of changes by which a benign tumor develops from the initial lesion to a
malignant stage.
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.
two-compartment model
Product of compartmental analysis requiring
two compartments.
[2]
See compartmental modeling,
multicompartment analysis