The role of toxicology in evaluating priorities in environmental health.

It is easy to assume that the straightforward explanation of a rational standpoint, based on sound scientific information, will inform public debate in areas of hazard evaluation. However, although toxicology generally provides the basic data that give reassurance, it is also used as a methodology for hazard identification. Once a hazard has been identified, pressure groups will present data that suit their case and ignore those that do not. Any pretence at analysis is abandoned, as shown by the recent MMR (measles--mumps--rubella) vaccine debate in the UK. Toxicologists should not suppose that comparative evaluations of risk, based on data, will result in a rational choice about environmental interventions -- data are few and opinions are a matter of faith. Thus, we might have to be protagonists in a propaganda war for science if irrational misuse of resources is to be avoided.