Toxicology of Industrial Compounds

282 TESTING AND EVALUATION FOR REPRODUCTIVE TOXICITY
Figure 20.1 Overlap of toxicity.
only certain way to determine whether reproduction would be affected, but
we need to do the best we can before taking the chance.
The paradox in this is that exposure of humans is facilitated by failure to
demonstrate toxicity in animals. But, lack of activity, being negative, cannot
be proven, only presumed. To make this presumption investigations must
be extensive and comprehensive to convey reasonable assurance that failure
was not due to deficiencies in methodology.
There is an exception. For industrial chemicals, testing of all substances
to these criteria would be a monumental task, therefore, less stringent
testing is allowed according to production volume, which serves as an
approximation for the extent of the population likely to be exposed
(Table 20.1). It is a strategy based on population risk, the downside of
which is an increased risk to the individual. The strategy takes advantage
of the fact that, in a small population, the chance of identifying cause and
effect is poor. At the base set level and level 1, as outlined by the EC, all
tests are equivalent only to the voluntary preliminary studies conducted for