Lead in petrol and levels of lead in blood: scientific evidence and social policy.

Two aspects of the recent controversy about the health consequences of lead in petrol are considered. Firstly, the evidence is shown to be deficient, largely because the basic epidemiological principles of representative sampling, realistic measurement, and control of confounding variables were not followed so that valid conclusions cannot be drawn from most of the published studies. Secondly, the role of science appeared to be comprised by confusion between science per se and social policy. Relations between the two are explored, and it is concluded that confusing them reduces the contribution that science can make to effective social policy.