While sophistication in public health research has been increasing substantially in the past few decades, sophistication in decision making about public health and environmental issues has not been increasing in parallel. Measures that are inexpensive tend to be implemented and measures that are expensive tend not to be implemented by makers of public policy. That is often independent of the degree of public health protection afforded by the measures. Understanding and addressing this pattern is crucial to the control of lead exposure of critical populations. People are still exposed to lead in our society not because anyone believes that exposure is good, but because reducing exposure costs money. Maintaining exposure also has its costs, however. It is more difficult to measure them, and they are often ignored in decision making--but they are not small, and attempts to measure them have been made. The high cost of reducing lead exposure of critical populations is the reason that progress in reducing lead-paint exposure has been minimal in the 18 years since the passage of the Lead-Based Paint Poisoning Prevention Act and that it took from the time of the initial proposal in 1973 until 1986 before lead was substantially eliminated from gasoline. In its 1986 rule making, the EPA estimated that the elimination of lead from gasoline would cost more than $500 million per year. Removing leaded paint is estimated to cost billions of dollars. The difference is that the EPA promulgated its rule of removing lead from gasoline, whereas HUD has had little success in removing leaded paint from housing. One reason that the EPA was successful in implementing such an expensive regulation was that it provided detailed estimates of the health and welfare benefits that would accrue and the monetary value of some of the benefits. The EPA cost-benefit analysis demonstrated that the monetary benefits of its regulation far exceeded the costs. That neutralized the cost issue and focused the debate over the regulation on questions of timing. A detailed benefit analysis of reducing lead in drinking water has caused the EPA to consider tighter water lead standards than initially envisioned. Despite years of concern about the consequences of leaded paint poisoning, children continue to be poisoned by leaded paint because it will cost billions of dollars to abate the hazard, and demand for these dollars has lost out to competing needs.(ABSTRACT TRUNCATED AT 400 WORDS)