Toxicology concepts

Dose-response relationship 1 he toxicological concept that the toxicity of a substance depends not only on its toxic properties, but also on the amount of exposure or dose. 

Mulvey M, Diamond SA. 1991. Genetic factors and tolerance acquisition in populations exposed to metals and metalloids. In Newman MC, McIntosh AW, editors. Metal eco-toxicology concepts and applications. Chelsea (MI) Lewis Publishers, p 301-321. 

In the case of lethal effects, the goal of chronic toxicity studies is to estimate the stress level that would kill half the test organisms after an exposure period approximately equal to their natural lifetime. Since in practice it is often impractical to monitor the test organisms for such a long time, survival may be monitored for shorter time periods and the results extrapolated to time infinity. This approach leads to two important toxicological concepts median survival times and incipient lethal levels. 

Brief yourself on how the PEL, TLV, DNEL and other exposure limits are derived, in most cases, and particularly with the DNEL, there may be a huge safety factor buUt into the number. More than ever, you need to be able to explain this toxicological concept to employees to help them better appreciate that being above a DNEL does not necessarily mean harm will result. 

Wegener, A., Hockwin, O. Animal models as a tool to detect the subliminal cocataractogenic potential of drugs in Hockwin, O. (Ed) Drug-induced ocular side effects and ocular toxicology. Concepts Toxicol. Basel, Karger, 4, 250-262 (1987) a. 

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