evidence not otherwise available in the published literature. On the basis of this review, we will recommend important research initiatives in the field.

Until better evidence is developed, prudent public policy demands that a margin of safety be provided regarding potential health risks from exposures to hazardous-waste sites. We do no less in designing bridges and buildings. We do no less in establishing criteria for scientific credibility. We must surely do no less when the health and quality of life of Americans are at stake.