Toxicology Glossary - N
narcotic:- Nonspecific usage - an agent that produces insensibility or stupor
- Specific usage - an opioid, any natural or synthetic drug that has morphine-like actions
natural occurrence: Presence of a substance in nature, as distinct from presence resulting from inputs from human activities. 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 SN autopsy
RT biopsy
necrosis:
- Mass death of areas of tissue or bone surrounded by healthy areas
- Morphological changes that follow cell death, characterized most frequently by nuclear changes
negligible risk:
- 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
RT acceptable risk, accepted risk, risk de minimis
nematocide: Substance intended to kill nematodes
neonat/e n., -al adj.: Infant during the first 4 weeks of postnatal life; for statistical purposes some scientists have defined the period as the first 7 days
neoplas/ia, -m: New and abnormal formation of tissue as a tumour or growth by cell proliferation that is faster than normal and continues after the initial stimulus (i) that initiated the proliferation has ceased
PS tumour
RT hyperplasia, metaplasia
nephritis: Inflammation of the kidney, leading to kidney failure, usually accompanied by proteinuria, haematuria, oedema, and hypertension
nephrotoxic: Chemically harmful to the cells of the kidney
neural: Pertaining to a nerve or to the nerves
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
neurotoxic/ adj., -ity n.: 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
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: 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
RT acceptable daily intake
n-octanol-water partition coefficient: See SN octanol-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. At present, this term tends to be substituted by no-observed-adverse-effect-level (NOAEL) or no-observed-effect-level (NOEL)
RT adverse effect, no-observed-adverse-effect-level (NOAEL), 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
non-effective dose: Amount of a substance that has no effect on the organism. It is lower than the threshold of harmful effect and is estimated while establishing the threshold of harmful effect
SN subthreshold dose
RT threshold
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
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
WHO, 1979
RT adverse effect
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
RTÂ adverse effect
no-response level: Maximum dose of a substance at which no specified response is observed in a defined population and under defined conditions of exposure
IRPTC, 1982
nosocomial: Associated with a hospital or infirmary, especially used of diseases that may result from treatment in such an institution
BT iatrogenic
noxious substance: See SN harmful substance
nuisance threshold: Lowest concentration of an air pollutant that can be considered objectionable
IRPTC, 1982
RT odour threshold, pollutant
nutritional table method: Procedure for evaluating the dietary intake of a large number of people. 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. 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
WHO, 1979
nystagmus: Involuntary, rapid, rhythmic movement (horizontal, vertical, rotary, mixed) of the eyeball, usually caused by a disorder of the labyrynth of the inner ear or a malfunction of the central nervous system