Specificity & dosimetry of toxicologic responses

Toxicology has two goals. The first is to identify and characterize

the adverse effects that can be produced in biological systems

by exposure to chemicals and the second is to use this

information to predict the type and severity of responses in

other species and exposure situations. The tools that the

toxicologist uses to detect and describe the adverse effects

of chemical exposure include the traditional acute,

subchronic, and chronic studies in animals plus a variety of

special studies designed to demonstrate specific organ

damage, reproductive and teratogenic effects, neurotoxicity,

immunotoxicity, genotoxicity, and other responses. These are

often supplemented with studies of the kinetics and the

mechanism of action and more recently with studies designed to

elucidate the molecular basis for cancer and other effects.

Theses studies together with the information on exposure

provide the basis for subsequent toxicologic predictions.

Although general effects such as weight loss and mortality

are included in toxicity protocols, most of the toxicology

tests are related to specific end-organ toxicity or to

mechanism or behavioral studies. We do not have animal

protocols to study individually the subjective symptoms

described for multiple chemical sensitivity, such as

depression, fatigue, headache, and memory loss, and our tests

lack sufficient specificity to evaluate a syndrome which is

composed primarily of such symptoms. Since all chemicals can

produce adverse effects under some conditions of exposure,

toxicologic predictions are most useful when they specify

both the type of adverse effect anticipated and the dose

required to produce the effect. Multiple chemical sensitivity

does not appear to consistently involve specific chemicals or

specific adverse effects and the effects observed are

reported to lack evidence of a threshold and to occur at

extremely low levels. It is difficult to include these

parameters in any reasonable toxicologic prediction relating

cause and response in multiple chemical sensitivity or

similar conditions.

Doull J

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