Dilemmas facing regulatory and advisory bodies dealing with conflicting results

Regulatory and advisory bodies have to take into account the possibility th at conventional toxicological screening and testing methods may be failing to pick up relevant effects, with the implication that testing may need to go down to much lower exposure levels and use specifically designed studies . In the paper, attention is focused on the problems of understanding endoc rine disrupting activity. The shape of the dose-response curve for endocrin e disrupters may differ from that normally associated with toxic chemicals (the monotonic sigmoid curve). Thus, prediction of both the nature of the e ffects of potential endocrine disrupters and the intensity of those effects at different doses may be equally difficult. Endocrine effects are not cur rently amenable to analysis by a single apical assay. While existing toxico logical tests can pick up many end-organ and functional effects that are re levant to endocrine disturbances, they are generally poor at exploring appa rently subtle effects such as disturbances of brain endocrine homeostatic m echanisms which may be critical for normal development. (C) 1999 Elsevier S cience Ltd. All rights reserved.