Relevance of parameters related to fertility and reproduction in toxicity testing.

Toxicity data of 37 compounds tested in both a subchronic study and one or more studies focused on reproduction were evaluated to obtain information on the significance of fertility and reproduction parameters in setting no-effect levels (NEL). It appeared that a) the test system aimed at reproduction and development was more sensitive than the subchronic study for 35% of the selected compounds and was equally sensitive for another 35%; b) for 65% of these compounds parameters related to reproduction and development were at least codecisive in determining the minimal-effect level (MEL); c) for 21% of all compounds, parameters related to reproduction were the most sensitive and therefore decisive for the MEL. It was concluded that reproduction in its broadest sense is a very sensitive tool in toxicity testing. The possibilities of either applying a simple screen of fertility and reproduction at an early stage of toxicity testing or incorporating fertility and reproduction parameters in the current subchronic study are discussed.