Toxicology Glossary - L
lachrymator: See lacrimatorlacrimator: Substance that irritates the eyes and causes the production of tears or increases the flow of tears.
larvicide: Substance intended to kill larvae.
laryngospasm: Reflex spasmodic closure of the sphincter of the larynx, particularly the glottic sphincter.
larynx: Main organ of voice production, the part of the respiratory tract between the pharynx and the trachea.
lassitude: Weakness; exhaustion.
latent effect: See SN delayed effect.
latent period: Delay between exposure to a disease-causing agent and the appearance of manifestations of the disease: also defined as the period from disease initiation to disease detection.
SN latency.
Last, 1988
lavage: Irrigation or washing out of a hollow organ or cavity such as the stomach, intestine or the lungs. laxative: Substance that causes evacuation of the intestinal contents.
SN cathartic, purgative.
lesion:
- Area of pathologically altered tissue.
- Injury or wound.
- Infected patch of skin.
WHO, 1979
RT effective concentration, lethal dose.
lethal dose: Amount of a substance or physical agent (radiation) that causes death when taken into the body by a single absorption (denoted by LD).
RT effective dose, lethal concentration.
lethal synthesis: Metabolic formation of a highly toxic compound from one that is relatively non-toxic (bioactivation), often leading to death of affected cells.
SN suicide metabolism.
leukaemia: Progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leucocytes and their precursors in the bone marrow and blood.
leukopenia: Reduced concentration of leukocytes in the blood.
lgKOW: See SN lgPow.
lgPow: Logarithm of base 10 of the partition coefficient of a substance between octan-1-ol and water: as an empirical measure for lipophilicity used for calculating bioaccumulation, fish toxicity, membrane adsorption and penetration etc.
RT lipophilicity, octanol-water partition coefficient, partition coefficient.
SN lgKOW
life-long exposure: Subjection to a potentially toxic substance during the whole lifetime.
limacide: Substance intended to kill mollusca including the gastropod mollusc, Limax
limit recommended: See recommended limit
limit test: Acute toxicity test in which, if no ill-effects occur at a pre-selected maximum dose, no further testing at greater exposure levels is required
Brown, 1988
RT fixed dose test
limit value (LV): Limit concentration at or below which Member States of the European Community must set their environmental quality standard and emission standard for a particular substance according to Community Directives
NT threshold limit value
limited evidence: According to the US EPA's guidelines for Carcinogen Risk Assessment, "limited evidence" is a collection of facts and accepted scientific inferences that suggests that an agent may be causing an effect, but this suggestion is not strong enough to be considered established fact.
IRIS, 1986
RT carcinogenicityclassificationaccordingtoIARC
linearized multistage model: Sequence of steps in which (a) a multistage model is fitted to tumour incidence data; (b) the maximum linear term consistent with the data is calculated; (c) the low-dose slope of the dose-response function is equated to the coefficient of the maximum linear term; and (d) the resulting slope is then equated to the upper bound of potency.
BT multistage model.
lipophilic/ adj., -ity n.: Having an affinity for fat and high lipid solubility: a physicochemical property which describes a partitioning equilibrium of solute molecules between water and an immiscible organic solvent, favouring the latter, and which correlates with bioaccumulation.
RT bioaccumulation, bioaccumulation factor, bioconcentration, octanol-water partition coefficient.
SN hydrophobicity.
AN hydrophilicity, lipophobicity.
lipophobic/ adj., -ity n.: Having a low affinity for fat and a high affinity for water.
RT bioaccumulation, bioaccumulation factor, bioconcentration, octanol-water partition coefficient.
SN hydrophilicity.
AN hydrophobicity, lipophilicity.
liposome: Originally a lipid droplet in the endoplasmic reticulum of a fatty liver. Now applied to an artificially formed lipid droplet, small enough to form a relatively stable suspension in aqueous media and with potential use in drug delivery.
local effect: Circumscribed change occurring at the site of contact between an organism and a toxicant.
RT systemic effect.
logit transformation: Mathematical transformation that relates response to a stated dose or concentration of a toxicant to the response in the absence of the toxicant by the formula:
Logit = lg [B/(B0-B)]
where B is the response to the stated dose or concentration and B0 is the response in the absence of the toxicant. Plotting the logit function against the logarithm of base 10 of the dose or concentration usually gives a linear relationship.
long-term effect: See SN chronic effect
long-term exposure: Continuous or repeated exposure to a substance over a long period of time, usually of several years in man, and of the greater part of the total life-span in animals or plants.
IRPTC, 1982
SN chronic exposure.
lowest lethal concentration found: See SN minimum lethal concentration.
lowest-observed-adverse-effect-level (LOAEL): Lowest concentration or amount of a substance, found by experiment or observation, which causes an adverse alteration of morphology, functional capacity, growth, development, or life span of a target organism distinguishable from normal (control) organisms of the same species and strain under defined conditions of exposure.
RT adverse effect, lowest-observed-effect-level, no-observed-adverse-effect-level, no-observed-effect-level
lowest-observed-effect-level (LOEL): Lowest concentration or amount of a substance, found by experiment or observation, that causes any alteration in morphology, functional capacity, growth, development, or life span of target organisms distinguishable from normal (control) organisms of the same species and strain under the same defined conditions of exposure
RT adverse effect, lowest-observed-adverse-effect-level, no-observed-adverse-effect-level, no-observed-effect-level
lymphocyte: Animal cell that interacts with a foreign substance or organism, or one which it identifies as foreign, and initiates an immune response against the substance or organism. There are two groups of lymphocytes, B lymphocytes and T lymphocytes
NT B lymphocyte, immune response, T lymphocyte
lymphoma: General term comprising tumours and conditions allied to tumours arising from some or all of the cells of lymphoid tissue
lysimeter: Laboratory column of selected representative soil or a protected monolith of undisturbed field soil with which it is possible to sample and monitor the movement of water and substances
lysosome: Membrane-bound cytoplasmic organelle containing hydrolytic enzymes