1989 Alice Hamilton lecture. Lead and human health: background and recent findings.

This paper, prepared in tribute to Dr. Alice Hamilton on her 120th birthday, reviews her pioneering studies of occupational lead poisoning and its control, her largely unheeded warnings about the possible consequences of widespread lead exposure to the general public through the use of leaded fuel, and the results of recent studies of human exposure to and health effects of lead in the general environment. Evidence is presented for dose-related non-threshold effects for children with blood lead concentrations below 25 micrograms/dl for a variety of effects including verbal IQ; mental development; physical size; and age at physical milestones such as first steps, hearing thresholds, and postural sway. For adults, various studies have produced associations between blood pressure and blood lead concentrations below 35 micrograms/dl, suggesting possible effects on cardiovascular health. While the biological mechanisms responsible for these effects remain poorly understood, recent and current efforts to reduce exposure to lead by the virtual elimination of lead in gasoline and food packaging show that we have learned one of Dr. Hamilton's important lessons, i.e., that the most effective means of reducing excessive exposures are through control of the environmental sources.