Lead poisoning: the implications of current biomedical knowledge for public policy.

New information on the nature and extent of lead poisoning, as well as on sources and toxicokinetics of lead, is relevant to the development of effective public health policy. Lead at low levels of exposure is now recognized to be toxic, and it is difficult to discern a threshold for lead toxicity in populations exposed to lead at levels nearly 200 times those experienced by pre-industrial humans. Although some sources of lead have been controlled, notably lead in gasoline, there are persistent lead sources associated with past uses of lead in paints, plumbing, and gasoline. In Baltimore City, nearly 50% of children screened in 1993 had blood lead levels in excess of guidelines issued by the Centers for Disease Control and Prevention. Much of this exposure is associated with lead-based paint in housing.