IUPAC Glossary of Terms Used in Toxicology – B
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back-mutation
Process which reverses the effect of a mutation which had inactivated a gene; thus it
restores the wild phenotype.
bacterial artificial chromosome (BAC)
DNA vector into which large DNA fragments can be inserted and
cloned in a bacterial host.
bactericide
Substance intended to kill bacteria.
bagassosis
Lung disease caused by the inhalation of dust from sugar-cane
residues.
basal lamina, pl -ae
Triple-layered structure on which epithelium sits: it consists of
an electron dense layer (lamina densa) between two electron
transparent layers (lamina lucida). The lamina densa is composed
of type IV collagen and the lamina lucida contains the
glycoprotein laminin.
base pairing
Linking of the complementary pair of polynucleotide chains of
nucleic acids by means of hydrogen bonds between complementary
purine and pyrimidine bases, adenine with thymine or uracil,
cytosine with guanine.
basement membrane
Specialized layers of extra-cellular matrix (basal laminae) that separate epithelial
tissue from underlying connective tissue: cancer cells must break
through the basement membrane in order to migrate to other parts
of the body and form metastases.
Bateman function
Equation expressing the build up and decay in concentration of a substance (usually in plasma)
based on first order uptake and elimination in a one compartment
model, having the form
C =
[ƒDκa/V(κa
- κe)][exp(-κet) -
exp(-κat)]
where C is the concentration and D the dose of
the substance, ƒ the fraction absorbed, and V the
volume of distribution.
κa and κe) are the first order
rate constants of uptake and
elimination, respectively, and t is time.
[2]
B-cell
See B lymphocyte
benchmark concentration (BMC)
Statistically calculated lower 95% confidence limit on the
concentration that produces a defined
response (called the benchmark response or BMR, usually 5 % or 10 %) for an adverse effect
compared to background, often defined as 0 % or 5%.
[2]
benchmark dose (BMD)
Statistically calculated lower 95 % confidence limit on the
dose that produces a defined
response (called the benchmark
response or BMR, usually 5 % or 10 %) of an adverse effect
compared to background, often defined as 0 % or 5 %.
[2]
benchmark guidance value
Biological
monitoring guidance value set at the 90th percentile of
available biological
monitoring results collected from a representative
sample of workplaces with good occupational hygiene
practices.
[2]
benchmark response
Response, expressed as an
excess of background, at which a benchmark dose or benchmark concentration is set.
[2]
benefit
Advantage to or improvement in condition of an individual or a
population.
benign
antonym malignant
- Of a disease, producing no persisting harmful effects.
- Tumor which does not invade other tissues (see metastasis),
having lost growth control but not positional control.
Note: Such a tumor is not carcinogenic but may cause mechanical damage to adjacent tissues.
berylliosis
See beryllium
disease
beryllium disease
berylliosis
Serious and usually permanent lung damage resulting from chronic
inhalation of beryllium.
bias
- Deviation of results or inferences from the truth, or processes leading to such deviation.
- Any trend in the collection, analysis, interpretation, publication, or review of data which can lead to conclusions which are systematically different from the truth.
biased sample
antonym random sample
Any sample which is not a random
sample.
bilirubin
Orange-yellow pigment, a breakdown product of heme-containing
proteins (hemoglobin, myoglobin, cytochromes), which circulates in the
blood plasma bound to
albumin or as water soluble glucuronide conjugates, and is
excreted in the bile by the liver.
bio-accessibility
Potential for a substance to come in contact with a living
organism and then interact with it. This may lead to
absorption.
Note: A substance trapped inside an insoluble particle is not
bio-accessible although substances on the surface of the same
particle are accessible and may also be bio-available. Bio-accessibility,
like bio-availability, is a function of both chemical speciation
and biological properties. Even surface-bound substances may not
be accessible to organisms which require the substances to be in
solution.
bio-accessible
Able to come in contact with a living organism and interact with
it.
See bio-accessibility
bio-accumulation
Progressive increase in the amount of a substance in an organism
or part of an organism which occurs because the rate of intake
exceeds the organism's ability to remove the substance from the
body.
Note: Bio-accumulation often correlates with lipophilicity.
See also bioconcentration, biomagnification
bio-accumulation potential
Ability of living organisms to concentrate a substance obtained
either directly from the environment or indirectly through its
food.
bio-activation
Metabolic conversion of a
xenobiotic to a more toxic
derivative or one which has more of an effect on living
organisms.
bio-assay
Procedure for estimating the concentration or biological activity of
a substance by measuring its effect on a living system compared
to a standard system.
bio-availability (general)
biological availability
physiological availability
Extent of absorption of a
substance by a living organism compared to a standard system.
[2]
bio-availability (in toxico- or
pharmacokinetics)
Ratio of the systemic exposure from extravascular (ev) exposure to that
following intravenous (iv) exposure as described by the
equation:
F = AevDiv /
Biv Dev
where F (fraction of dose absorbed) is a measure of the
bioavailability, A and B are the areas under the (plasma)
concentration time
curve following extravascular and intravenous administration
respectively, and Dev and
Div are the administered extravascular and
intravenous doses.
[2]
bio-available
Able to be absorbed by living organisms.
See bio-availability
biochemical mechanism
Reaction or series of reactions, usually enzyme-catalysed,
associated with a specific physiological event in a living
organism.
biochemical (biological) oxygen demand (BOD)
Amount concentration of oxygen taken up through the respiratory activity of
micro-organisms growing on organic compounds present when incubated at a specified temperature (usually 20° C) for a
fixed period (usually 5 days). It is regarded as a measure of that organic pollution of
water which can be degraded biologically but includes the oxidation of inorganic material such as sulfide and iron(II). The
empirical test used in the laboratory to determine BOD also measures the oxygen used to oxidize reduced forms of nitrogen
unless their oxidation is prevented by an inhibitor such as allyl thiourea.
biocid/e n., -al adj.
Substance intended to kill living organisms.
bioconcentration
Process leading to a higher concentration of a substance in an
organism than in environmental media to which it is exposed.
See bioaccumulation
bioconcentration factor (BCF)
Measure of the tendency for a substance in water to accumulate in
organisms, especially fish.
Note 1. The equilibrium concentration of a substance in
fish can be estimated by multiplying its concentration in the
surrounding water by its bioconcentration factor in
fish.
Note 2. This parameter is an important determinant for human
intake of aquatic food by the ingestion route.
bioconjugate
See conjugate
bioconversion
See biotransformation
biodegradation
Breakdown of a substance catalysed by enzymes in vitro or in
vivo. This may be characterized for purposes of
hazard assessment as:
- Primary. Alteration of the chemical structure of a substance resulting in loss of a specific property of that substance.
- Environmentally acceptable. Biodegradation to such an extent as to remove undesirable properties of the compound. This often corresponds to primary biodegradation but it depends on the circumstances under which the products are discharged into the environment.
- Ultimate. Complete breakdown of a compound to either fully oxidized or reduced simple molecules (such as carbon dioxide/methane, nitrate/ammonium, and water. It should be noted that the products of biodegradation can be more harmful than the substance degraded.
bio-elimination
Removal, usually from the aqueous phase, of a test substance in
the presence of living organisms by biological processes
supplemented by physico-chemical reactions.
bio-equivalen/ce n., -t
adj.
Relationship between two preparations of the same drug in the same dosage form that have a
similar bioavailability.
bio-inactivation
Metabolic conversion of a
xenobiotic to a less toxic
derivative.
[2]
bioinformatics
Discipline encompassing the development and utilization of
computational facilities to store, analyse and interpret
biological data.
biokinetics (in toxicology)
Science of the movements involved in the distribution of substances.
[2]
biological absorption
See absorption,
biological
biological accessibility
See bio-accessibility
biological acclimatization
See acclimatization,
biological
biological assessment of exposure
See biological
monitoring
biological availability
See bioavailability
biological cycle
Complete circulatory process through which a substance passes in
the biosphere. It may involve transport through the various media
(air, water, soil), followed by environmental transformation, and
carriage through various ecosystems.
biological effect monitoring (BEM)
Continuous or repeated measurement of early biological effects of
exposure to a substance to
evaluate ambient exposure
and health risk by
comparison with appropriate reference values based on knowledge
of the probable relationship between ambient exposure and
biological effects.
biological exposure indices (BEI)
Guidance values recommended by ACGIH
for assessing biological
monitoring results.
[5]
biological half life
For a substance the time required for the amount of that
substance in a biological system to be reduced to one half of its
value by biological processes, when the rate of removal is
approximately exponential.
[2]
biological half time,
t1/2
See biological half life
biological indicator
Species or group of species which is representative and typical
for a specific status of an ecosystem, which appears frequently
enough to serve for monitoring and whose population shows a
sensitive response to changes, e.g., the appearance of a toxicant
in an ecosystem.
[6]
biological marker
See biomarker
biological monitoring
biological assessment of exposure
biomonitoring
Continuous or repeated measurement of any naturally occurring or
synthetic chemical, including potentially toxic substances or their metabolites or biochemical effects in tissues,
secreta, excreta, expired air or any combination of these in
order to evaluate occupational or environmental exposure and health risk by comparison with
appropriate reference values based on knowledge of the probable
relationship between ambient exposure and resultant adverse health effects.
biological oxygen demand
See biochemical oxygen
demand
biological preparation
biological
biopreparation
Compound derived from living organisms and their products for use
in medicine or as a pesticide etc.
biological specimen
- Organ, tissue (including blood), secretion or excretion product taken from an organism as a sample reflecting the state of the whole organism.
- Organism taken as a sample reflecting the state of a population or their environment.
biological warfare
Military operations using any organism (bacteria, virus or other
disease-causing organism) or toxin found in nature, to kill,
injure or incapacitate human beings, animals, or plants.
biomagnification
ecological magnification
Sequence of processes in an ecosystem by which higher
concentrations are attained
in organisms at higher trophic levels (at higher levels in the
food web); at its simplest, a process leading to a higher
concentration of a substance in an organism than in its food.
biomarker
Indicator signaling an event or condition in a biological system
or sample and giving a
measure of exposure, effect,
or susceptibility.
Note: Such an indicator may be a measurable chemical,
biochemical, physiological, behavioral or other alteration within
an organism.
[2]
biomarker of effect
effect biomarker
Biomarker that, depending upon
the magnitude, can be recognized as associated with an
established or possible health impairment or disease.
[2]
biomarker of exposure
exposure biomarker
Biomarker that relates
exposure to a xenobiotic to the levels of the
substance or its metabolite, or of
the product of an interaction between the substance and some
target molecule or cell that can be
measured in a compartment
within an organism.
[2]
biomarker of susceptibility
susceptibility biomarker
Biomarker of an inherent or
acquired ability of an organism to respond to exposure to a specific substance.
[2]
biomass
- Total amount of biotic material, usually expressed per unit surface area or volume, in a medium such as water.
- Material produced by the growth of micro-organisms, plants or animals.
biomineralization
Complete conversion of organic substances to inorganic
derivatives by living organisms, especially micro-organisms.
biomolecule
Substance that is synthesized by and occurs naturally in living
organisms.
biomonitoring
See biological
monitoring
biopesticide
Biological agent with pesticidal activity, e.g., the bacterium
Bacillus thuringiensis when used to kill insects.
After [6]
biopsy
Excision of a small piece of living tissue for microscopic or
biochemical examination; usually performed to establish a
diagnosis.
biosphere
Portion of the planet earth which supports and includes life.
biostatic
Adjective applied to a substance which arrests the growth or
multiplication of living organisms.
biota
All living organisms as a totality.
biotransformation
bioconversion
Chemical conversion of a
substance that is mediated by living organisms or enzyme
preparations derived there from.
2,3-bis(sulfanyl)propan-1-ol
British anti-Lewisite
dimercaprol
2,3-dimercaptopropan-1-ol
Metal chelator which has been used in the treatment of arsenic,
antimony, gold, mercury and lead poisoning.
blastocyst
Mammalian embryo at the stage at which it is implanted into the
wall of the uterus.
[9]
blood-brain barrier
Physiological interface between brain tissues and circulating
blood created by a mechanism that alters the permeability of
brain capillaries, so that some substances are prevented from
entering brain tissue, while other substances are allowed to
enter freely.
After [2]
blood-placenta barrier
Physiological interface between maternal and fetal blood
circulations that filters out some substances which could harm
the fetus while favoring the passage of others such as nutrients:
many fat soluble substances such as alcohol are not filtered out
and several types of virus can also cross this barrier.
Note: The effectiveness of the interface as a barrier varies with
species and different forms of placentation.
blood plasma
See plasma (in biology)
blood substitution
See exchange transfusion
blood-testis barrier
Physiological interface between the blood supply and the
spermatozoa of the seminiferous tubules.
Note: This interface consists of specific junctional complexes
between Sertoli cells.
After [2]
B lymphocyte
B cell
Type of lymphocyte which synthesizes
and secretes antibodies in response to the
presence of a foreign substance or one identified by it as
foreign. The protective effect can be mediated to a certain
extent by the antibody alone (contrast T
lymphocyte).
body burden
Total amount of a substance present in an organism at a given
time.
bolus
- Single dose of a substance, originally a large pill.
- Dose of a substance administered by a single rapid intravenous injection.
- Concentrated mass of food ready to be swallowed.
botanical pesticide
Substance with activity against pests, that is produced naturally
within a plant and may act as a defense against predators.
botulism
Acute food poisoning caused by botulinum toxin produced in food
by the bacterium Clostridium botulinum and characterized
by muscle weakness and paralysis, disturbances of vision,
swallowing, and speech, and a high mortality rate.
brady-
antonym tachy-
Prefix meaning slow as in bradycardia or bradypnoea.
bradycardia
antonym tachycardia
Abnormal slowness of the heartbeat.
bradypnoea
antonym tachypnoea
Abnormally slow breathing.
breathing zone
Space within a radius of 0.5 m from a person’s face.
British anti-Lewisite (BAL)
See 2,3-bis(sulfanyl)propan-1-ol
bronchoconstriction
antonym bronchodilation
Narrowing of the air passages through the bronchi of the
lungs.
bronchodilation
antonym bronchoconstriction
Expansion of the air passages through the bronchi of the
lungs.
bronchospasm
Intermittent violent contraction of the air passages of the
lungs.
builder (in chemistry)
Material which enhances or maintains the cleaning efficiency of a
surfactant, in a detergent, principally by inactivating water
hardness; complex phosphates (especially sodium tripolyphosphate,
i.e. pentasodium triphosphate), sodium carbonate, and sodium
silicate are the builders most commonly used.
byssinosis
Pneumoconiosis caused by inhalation of dust and
associated microbial contaminants and observed in cotton, flax,
and hemp workers.
bystander exposure
Liability of members of the general public to come in contact
with substances arising from operations or processes carried out
by other individuals in their vicinity.