IUPAC Glossary of Terms Used in Toxicology – N
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nanoparticle
Microscopic particle whose size is measured in nanometers, often
restricted to so-called nanosized particles (NSPs; < 100 nm in
aerodynamic diameter), also called ultrafine particles (see
separate entry).
nanotoxicology
Scientific discipline involving the study of the actual or
potential danger presented by the harmful effects of
nanoparticles 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.
- Nonspecific usage - an agent that produces insensibility or stupor.
- Specific usage - an opioid, any natural or synthetic drug that has morphine-like actions.
natriuretic
Substance increasing the rate of excretion of sodium ion in the
urine.
natural occurrence
Presence of a substance in nature, as distinct from presence
resulting from inputs from human activities.
Note: The contamination of the natural environment by some
man-made compounds may be so widespread that it is practically
impossible to get access to biota with a truly natural level;
only ‘normal’ levels can be measured, those which are
usually prevalent in places where there is no obvious local
contamination.
necropsy
See autopsy
necro/sis n., /tic
adj.
Sum of morphological changes resulting from cell death by lysis
and (or) enzymatic degradation, usually accompanied by
inflammation and affecting groups of cells in a tissue.
Note: Not to be confused with apoptosis
[2]
- Probability of adverse effects occurring that can reasonably be described as trivial.
- Probability of adverse effects occurring that is so low that it cannot be reduced appreciably by increased regulation or investment of resources.
nematicide
nematocide
Substance used for the control of nematodes.
neonat/e n., /al adj.
Infant during the first 4 weeks of postnatal life
Note: For statistical purposes some scientists have defined the
period as the first seven days of postnatal life. The precise
definition varies from species to species.
neoplas/ia, -m
New and abnormal formation of tissue as a tumor or growth by
cell proliferation that is faster than normal and continues after
the initial stimulus (i) that initiated the proliferation has
ceased.
nephritis
Inflammation of the kidney, leading to kidney failure, usually
accompanied by proteinuria,
hematuria,
edema,
and hypertension.
nephropathy
renopathy
Any disease or abnormality of the kidney.
nephrosis
Disease of the kidneys marked by degeneration of renal tubular
epithelium.
nephrotoxic
Chemically harmful to the cells of the kidney.
neural
Pertaining to a nerve or to the nerves.
neurologic shellfish poisoning (NSP)
Serious illness which is a consequence of consumption of toxic
bivalve shellfish (mollusks) such as mussels, oysters and clams
that have ingested, by filter feeding, large quantities of
micro-algae containing brevetoxin; symptoms include gastroenteritis;
rectal burning; paresthesias
of the face, trunk, and limbs; myalgias;
ataxia;
vertigo; and
reversal of hot/cold sensation.
See also amnesic
shellfish poisoning, diarrheal
shellfish poisoning
neuron(e)
Nerve cell, the morphological and functional unit of the central
and peripheral nervous systems.
neuropathy
Any disease of the central or peripheral nervous system.
Able to produce chemically an adverse effect on the nervous system: such effects may be subdivided into two types.
- Central nervous system effects (including transient effects on mood or performance and pre-senile dementia such as Alzheimer's disease).
- Peripheral nervous system effects (such as the inhibitory effects of organophosphorus compounds on synaptic transmission).
nitrification
Sequential oxidation of ammonium salts to nitrite and nitrate by
micro-organisms.
nitrosative stress
Adverse effects occurring when the generation of reactive
nitrogen species in a system exceeds the system’s ability
to neutralize and eliminate them; nitrosative stress may lead to
nitrosylation reactions that can alter protein structure thus
inhibiting normal function.
no-acceptable-daily-intake-allocated
This expression is applicable to a substance for which the
available information is not sufficient to establish its safety,
or when the specifications for identity and purity are not
adequate, or when the available data show that the substance is
hazardous and should not be used.
Note: The basis for the use of the expression should be
determined before action is taken; in the first two cases above,
not being able to allocate an ADI does not mean that the
substance is unsafe.
n-octanol-water partition
coefficient
Obsolete for octan-1-ol-water
partition coefficient
See octan-1-ol-water
partition coefficient
nodule
Small node or boss that is solid and can be detected by
touch.
no-effect level (NEL)
Maximum dose (of a substance) that produces no detectable changes
under defined conditions of exposure.
Note: This term tends to be substituted by no-observed-adverse-effect level (NOAEL) or
no-observed-effect level (NOEL).
non-bioenvironmental transformation
Change in the chemical or physical nature of a substance
occurring as a result of physicochemical conditions and
independent of any biological system.
no-effect dose (NED)
subthreshold dose
Amount of a substance that has no effect on the organism.
Note: It is lower than the threshold of harmful effect and is
estimated while establishing the threshold of harmful effect.
non-ionizing radiation
Electromagnetic radiation of low energy that is not capable of
causing ionization.
non-occupational exposure
Environmental exposure
outside the workplace to substances that are otherwise associated
with particular work environments and (or) activities and
processes that occur there.
nonstochastic
See deterministic.
non-target organism
Organism affected by a pesticide
although not the intended object of its use.
no-observed-adverse-effect level
(NOAEL)
Greatest concentration
or amount of a substance, found by experiment or observation,
which causes no detectable adverse alteration of morphology,
functional capacity, growth, development, or life span of the
target organism under defined conditions of exposure.
no-observed-effect level (NOEL)
Greatest concentration
or amount of a substance, found by experiment or observation,
that causes no alterations of morphology, functional capacity,
growth, development, or life span of target organisms
distinguishable from those observed in normal (control) organisms
of the same species and strain under the same defined conditions
of exposure.
no-response level (NRL)
Maximum dose of a substance at which
no specified response is observed in a defined population and
under defined conditions of exposure.
nosocomial
Associated with a hospital or infirmary, especially used of
diseases that may result from treatment in such an
institution.
noxious substance
See harmful
substance
nucle/us (in cell biology) sing.,
/ei pl.
Compartment in the interphase eukaryotic cell bounded by a double
membrane and containing the genomic DNA, with the associated
functions of transcription and processing.
nuisance threshold
Lowest concentration
of an air pollutant that can be considered objectionable.
nutritional table method
Procedure for evaluating the dietary intake of a large number of
people.
Note 1: The accuracy of the method depends on the accuracy with
which records of the food consumption can be established and the
accuracy of the nutritional tables specifying the concentration
of various nutrients, vitamins, essential, and non-essential
substances including pesticide residues.
Note 2: For each record of quantity of food consumed during a
certain time period, the daily intake of the substance in
question is calculated by multiplying the substance concentration
in the food item (as obtained from the nutritional table) by the
quantity of food consumed and dividing by the time of
observation.
nychthemeral
circadian
Relating to or exhibiting a nychthemeron or 24-hour period.
nystagmus
Involuntary, rapid, rhythmic movement (horizontal, vertical,
rotary, mixed) of the eyeball, usually caused by a disorder of
the labyrinth of the inner ear or a malfunction of the central
nervous system.