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Pure Appl. Chem.,
Vol. 65, No. 9, pp. 2003-2122, 1993.
CLINICAL
CHEMISTRY DIVISION
COMMISSION ON TOXICOLOGY
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
macrophage: Large
(10-20 mm diameter) amoeboid and phagocytic cell found in many tissues,
especially in areas of inflammation; macrophages are derived from
blood monocytes and play an important role in host defence mechanisms.
macroscopic (gross) pathology: Study of changes
associated with disease that are visible to the naked eye without
the need for a microscope.
malaise: Vague feeling of bodily discomfort.
malignancy: Population
of cells showing both uncontrolled growth and a tendency to invade
and destroy other tissues; a malignancy is life-threatening.
RT cancer, metastasis,
tumour.
malignant:
1. Tending to become progressively worse and to result in death
if not treated.
2. In cancer, cells showing both uncontrolled growth and a tendency
to invade and destroy other tissues.
AN benign.
mania: Emotional disorder (mental illness)
characterized by an expansive and elated state (euphoria), rapid
speech, flight of ideas, decreased need for sleep, distractability,
grandiosity, poor judgement and increased motor activity.
margin of exposure (MOE), margin of safety (MOS):
Ratio of the no-observed-adverse-effect level (NOAEL) to the theoretical
or estimated exposure dose (EED) or concentration (EEC).
RT therapeutic index.
mass mean diameter: Diameter of a particle
with a mass equal to the mean mass of all the particles in a population.
mass median diameter: Diameter of a particle
with the median mass of all the particles in a population.
IAEA, 1978
material
safety data sheet (MSDS): Compilation of information required
under the US OSHA Hazard Communication Standard on the identity
of hazardous substances, health and physical hazards, exposure limits,
and precautions.
PS hazard communication
standard, safety data sheet.
maximum allowable
(admissible, acceptable) concentration (MAC): Regulatory value
defining the concentration that if inhaled daily (in the case of
work people for 8 hours with a working week of 40 hours, in the
case of the general population 24 hours) does not, in the present
state of knowledge, appear capable of causing appreciable harm,
however long delayed during the working life or during subsequent
life or in subsequent generations.
RT permissible exposure
limit, threshold limit
value.
maximum contaminant level (MCL): Under the
Safe Drinking Water Act (USA), primary MCL is a regulatory concentration
for drinking water which takes into account both adverse effects
(including sensitive populations) and technological feasibility
(including natural background levels): secondary MCL is a regulatory
concentration based on "welfare", such as taste and
staining, rather than health, but also takes into account technical
feasibility. MCL Goals (MCLG) under the Safe Drinking Water Act
do not consider feasibility and are zero for all human and animal
carcinogens.
maximum exposure limit (MEL): Occupational
exposure limit legally defined in GB under COSHH as the maximum
concentration of an airborne substance, averaged over a reference
period, to which employees may be exposed by inhalation under any
circumstances, and set on the advice of the HSC Advisory Committee
on Toxic Substances.
RT ceiling value.
maximum permissible daily dose: Maximum daily
dose of substance whose penetration into a human body during a lifetime
will not cause diseases or health hazards that can be detected by
current investigation methods and will not adversely affect future
generations.
maximum permissible level (MPL): Level, usually
a combination of time and concentration, beyond which any exposure
of humans to a chemical or physical agent in their immediate environment
is unsafe.
RT maximum allowable concentration.
maximum residue limit (MRL) for pesticide residues:
Maximum contents of a pesticide residue (expressed as mg/kg
fresh weight) recommended by the Codex Alimentarius Commission to
be legally permitted in or on food commodities and animal feeds.
MRL's are based on data obtained following good agricultural practice
and foods derived from commodities that comply with
the respective MRL's are intended to be toxicologically acceptable.
Codex
Alimentarius Commission, 1989
maximum residue limit (MRL) for veterinary drugs:
Maximum contents of a drug residue (expressed as mg/kg or :
g/kg fresh weight) recommended by the Codex Alimentarius Commission
to be legally permitted or recognized as acceptable in or on food
commodities and animal feeds. The MRL is based on the type and amount
of residue considered to be without any toxicological
hazard for human health as expressed by the acceptable daily intake
(ADI) or on the basis of a temporary ADI that uses an additional
uncertainty factor. It also takes into account other relevant public
health risks as well as food technological aspects.
Codex
Alimentarius Commission, 1989
maximum
tolerable concentration (MTC): Highest concentration of a substance
in an environmental medium that does not cause death of test organisms
or species (denoted by LC o).
WHO, 1979
maximum
tolerable dose (MTD): Highest amount of a substance that, when
introduced into the body, does not kill test animals (denoted by
LD o).
maximum tolerable exposure level (MTEL):
Maximum amount or concentration of a substance to which an organism
can be exposed without leading to an adverse effect after prolonged
exposure time.
maximum
tolerated dose (MTD): High dose used in chronic toxicity testing
that is expected on the basis of an adequate subchronic study to
produce limited toxicity when administered for the duration of the
test period. It should not induce (a) overt toxicity, for example
appreciable death of cells or organ dysfunction, or (b) toxic manifestations
that are predicted
materially to reduce the life span of the animals except as the
result of neoplastic development or (c) 10 % or greater retardation
of body weight gain as compared with control animals. In some studies,
toxicity that could interfere with a carcinogenic effect is specifically
excluded from consideration.
mean life: Average
lifetime of a molecular, atomic, or nuclear system in a specified
state. For an exponentially decaying system, it is the average time
for the number of molecules, atoms or nuclei in a specified state
to decrease by a factor of e, the base of natural logarithms.
SN mean time.
RT turnover time.
ISO, 1972
median
effective concentration (EC50): Statistically derived
concentration of a substance in an environmental medium expected
to produce a certain effect in 50 % of test organisms in a given
population under a defined set of conditions.
median effective
dose (ED50): Statistically derived dose of a chemical
or physical agent (radiation) expected to produce a certain effect
in 50 % of test organisms in a given population or to produce a
half-maximal effect in a biological system under a defined set of
conditions.
median
lethal concentration (LC50): Statistically derived
concentration of a substance in an environmental medium expected
to kill 50 % of organisms in a given population under a defined
set of conditions.
median lethal
dose (LD50): Statistically derived dose of a chemical
or physical agent (radiation) expected to kill 50 % of organisms
in a given population under a defined set of conditions.
median lethal time (TL50): Statistically
derived average time interval during which 50 % of a given population
may be expected to die following acute administration of a chemical
or physical agent (radiation) at a given concentration under a defined
set of conditions.
median
narcotic concentration (NC50): Statistically derived
concentration of a substance in an environmental medium expected
to cause narcotic conditions in 50 % of a given population under
a defined set of conditions.
median narcotic
dose (ND50): Statistically derived dose of a substance
expected to cause narcosis in 50 % of test animals under a defined
set of conditions.
meiosis:
1. Process of "reductive" cell division, occurring in the production
of gametes, by means of which each daughter nucleus
receives half the number of chromosomes characteristic
of the somatic cells of the species.
RT chromosome, diploid,
gamete, haploid.
2. See miosis.
mercurialism:
Chronic poisoning caused by the excessive use of mercury, by breathing
its vapour, or by exposure in mining or smelting processes.
SN Mad Hatter syndrome.
mesothelioma: Malignant tumour of the mesothelium
of the pleura, pericardium or peritoneum, that may be caused by
exposure to asbestos fibres and some other fibres.
BT tumour.
RT malignant.
metabolic half-life (half-time): Time required
for one half of the quantity of a substance in the body to be metabolically
transformed into a derivative or to be eliminated.
SN metabolic half-time.
RT clearance, elimination.
metabolic model: Analysis and theoretical
reconstruction of the way in which the body deals with a specific
substance, showing the proportion of the intake that is absorbed,
the proportion that is stored and in what tissues, the rate of breakdown
in the body and the subsequent fate of the metabolic products, and
the rate at which it is eliminated by different organs as unchanged
substance or metabolites.
WHO, 1989a
metabolic transformation: Biochemical transformation
of a substance that takes place within an organism.
SN biotransformation.
metabolism: Sum total of all physical and
chemical processes that take place within an organism; in a narrower
sense, the physical and chemical changes that take place in a given
substance within an organism. It includes the uptake and distribution
within the body of chemical compounds, the changes (biotransformation)
undergone by such substances, and the elimination of the compounds
and of their metabolites.
WHO, 1989a
RT biotransformation.
metaplasia: Abnormal
transformation of an adult, fully differentiated tissue of one kind
into a differentiated tissue of another kind.
RT hyperplasia, neoplasia.
metastasis:
1. Movement of bacteria or body cells, especially cancer cells,
from one part of the body to another, resulting in change
in location of a disease or of its symptoms from one
part of the body to another.
2. Growth of pathogenic micro-organisms or of abnormal cells distant
from the site of their origin in the body.
methaemoglobinaemia: Presence of methaemoglobin
(oxidized haemoglobin) in the blood in greater than normal proportion.
methaemoglobin-forming substance: Substance
capable of oxidising directly or indirectly the iron(II) in haemoglobin
to iron(III) to form methaemoglobin, a derivative of haemoglobin
that cannot transport oxygen.
microalbuminuria:
Chronic presence of albumin in slight excess in urine.
microcosm: Artificial
test system that simulates major characteristics of the natural
environment for the purposes of ecotoxicological assessment: such
a system would commonly have a terrestrial phase, with substrate,
plants and herbivores, and an aquatic phase, with vertebrates, invertebrates
and plankton. The term "mesocosm" implies a more complex and larger
system than the term "microcosm" but the distinction is not clearly
defined.
SN experimental
model ecosystem.
micromercurialism: Effects of exposure to
mercury detected at the lowest exposure levels producing a measurable
reaction.
RT mercurialism.
Minamata disease: Neurological disease caused
by ingestion of methylmercury-contaminated fish, first seen at Minamata
Bay in Japan.
mineralization: Complete conversion of organic
substances to inorganic derivatives.
minimum
lethal concentration (LCmin): Lowest concentration
of a toxic substance in an environmental medium that kills individual
organisms or test species under a defined set of conditions.
SN lowest
lethal concentration found.
WHO, 1979
minimum lethal
dose (LDmin): Lowest amount of a substance that,
when introduced into the body, may cause death to individual species
of test animals under a defined set of conditions.
miosis: Abnormal contraction
of the pupil of the eye to less than 2 mm. Alternative spelling
(obsolete): meiosis.
miscible: Liquid substances capable of mixing
without separation into two phases; refers to liquid mixtures.
mitochondri/on (pl -a): Eukaryote
cytoplasmic organelle that is bounded by an outer membrane and an
inner membrane; the inner membrane has folds called cristae that
are the centre of ATP synthesis in oxidative phosphorylation in
the animal cell and supplement ATP synthesis by the chloroplasts
in photosynthetic cells. The mitochondrial matrix within the inner
membrane contains ribosomes, many oxidative enzymes, and a circular
DNA molecule that carries the genetic information for a number of
these enzymes.
mitogen: Substance that induces lymphocyte
transformation or, more generally, mitosis and cell proliferation.
RT transformation.
mitosis: Process by
which a cell nucleus divides into two daughter nuclei, each having
the same genetic complement as the parent cell: nuclear division
is usually followed by cell division.
After Nagel et al. (eds),
1991
modifying factor
(MF): As used by the USEPA, uncertainty factor that is greater
than zero and less than, or equal to 10; the magnitude of the factor
depends upon the professional assessment of scientific uncertainties
of a study or database not explicitly treated with the standard
uncertainty factors (for example the completeness of the overall
database and the number of animals tested); the default value for
the factor is 1.
BT uncertainty factor.
IRIS, 1986
molluscicide: Substance intended to kill
molluscs.
SN limacide.
monitoring: Continuous
or repeated observation, measurement, and evaluation of health and/or
environmental or technical data for defined purposes, according
to prearranged schedules in space and time, using comparable methods
for sensing and data collection. Evaluation requires comparison
with appropriate reference values based on knowledge of the probable
relationship between ambient exposure and adverse effects.
NT ambient monitoring,
biological effect
monitoring, biological
monitoring, environmental
monitoring, health surveillance,
personal monitoring.
After Berlin, Yodaiken, and Henman,1984;
WHO, 1980; Zielhuis
and Henderson, 1986
monoclonal: Pertaining to a specific protein
from a single clone of cells, all molecules of this protein being
the same.
mono-oxygenase:
Enzyme that catalyses reactions between an organic compound and
molecular oxygen in which one atom of the oxygen molecule is incorporated
into the organic compound and one atom is reduced to water; involved
in the metabolism of many natural and foreign compounds giving both
unreactive products and products of different or increased toxicity
from that of the parent compound: such enzymes are the main catalysts
of phase 1 reactions in the metabolism of xenobiotics by the endoplasmic
reticulum or by preparations of microsomes.
SN mixed function oxidase.
RT cytochrome P-420, cytochrome
P-448, cytochrome P-450,
endoplasmic reticulum,
microsome, phase
1 reactions.
morbidity: Any departure, subjective or objective,
from a state of physiological or psychological well-being: in this
sense, "sickness", "illness", and "morbid condition" are similarly
defined and synonymous.
The WHO Expert Committee on Health Statistics noted in its Sixth
Report (1959) that morbidity could be measured in terms of three
units:
1. Proportion of persons who were ill.
2. The illnesses (periods or spells of illnesses) that these persons
experienced.
3. The duration (days, weeks, etc.) of these illnesses.
NT disease.
Last, 1988
morbidity rate: Term used loosely to refer
to incidence or prevalence rates of disease.
IPCS, 1987
morbidity survey:
Method for the estimation of the prevalence and/or incidence of
a disease or diseases in a population: a morbidity survey is usually
designed simply to ascertain the facts as to disease distribution,
and not to test a hypothesis.
Last, 1988
mordant: Substance that fixes a dyestuff
in or on a material by combining with the dye to form an insoluble
compound, used to fix or intensify stains in a tissue or cell preparation.
mortality: Death
as studied in a given population or subpopulation. The word mortality
is often used incorrectly instead of mortality rate.
IPCS, 1987
mortality study: Investigation dealing with
death rates or proportion of deaths attributed to specific causes
as a measure of response.
IPCS, 1987
multigeneration study:
1. Toxicity test in which two to three generations of the test organism
are exposed to the substance being assessed.
2. Toxicity test in which only one generation is exposed and effects
on subsequent generations are assessed.
multiple (or multiphasic) screening: Procedure
that has evolved by combining single screening tests, and is the
logical corollary of mass screening. Where much time and effort
have been spent by a population in attending for a single test such
as mass radiography, it is natural to consider the economy of offering
other tests at the same time. Multiple (or multiphasic) screening
implies the administration of a number of tests, in combination,
to large groups of people.
BT screening.
WHO, 1989a
multistage cluster sampling: Cluster sampling
with more than two stages, each sampling being made on aggregates
(or clusters) in which the clusters already obtained by the preceding
sampling have been divided.
ISO, 1977
multistage model:
Dose-response model for cancer death estimation of the form
P(d) = 1 - exp[-( qo + q 1d 1+
q 2d 2 + ........... + q(k)d k)]
where P(d) is the probability of cancer death from a continuous
dose rate, d, the q's are constants, and k
is the number of dose groups (or, if less than the number of dose
groups, k is the number of biological stages believed to
be required in the carcinogenesis process). With the multistage
model, it is assumed that cancer is initiated by cell mutations
in a finite series of steps. A one-stage model is equivalent to
a one-hit model.
multistage sampling: Type of sampling in
which the sample is selected by stages, the sampling units at each
stage being subsampled from the larger units chosen at the previous
stage.
ISO, 1977
murine: Of or belonging to the family of
rats and mice (Muridae).
mutagen: Any substance that can induce heritable
changes (mutations) of the genotype in a cell as a consequence of
alterations or loss of genes or chromosomes (or parts thereof).
mutagenesis: Introduction of heritable changes
(mutations) of the genotype in a cell as a consequence of alterations
or loss of genes or chromosomes (or parts thereof).
After Nagel et al. (eds),
1991
mutagenicity: Ability of a physical, chemical,
or biological agent to induce heritable changes (mutations) in the
genotype in a cell as a consequence of alterations or loss of genes
or chromosomes (or parts thereof).
mutation: Any relatively
stable heritable change in genetic material that may be a chemical
transformation of an individual gene ( gene or point mutation),
altering its function, or a rearrangement, gain or loss of part
of a chromosome, that may be microscopically visible (chromosomal
mutation); mutation can be either germinal and inherited by subsequent
generations, or somatic and passed through cell lineage by cell
division.
RT chromosome, gene.
RT clastogenesis, genotoxicity.
myasthenia: Muscular weakness.
mycotoxin: Toxin produced by a fungus.
mydriasis: Extreme dilation of the pupil
of the eye, either as a result of normal physiological response
or in response to a chemical exposure.
myelosuppression: Reduction of bone marrow
activity leading to a lower concentration of platelets, red cells
and white cells in the blood.
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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
Page last modified 12 September 2001.
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