Hazard assessment of lead.

Exposure to lead (Pb) continues to be a source of concern for the US Food and Drug Administration and other United States federal regulatory agencies. Blood lead levels as low as 10 micrograms/dl have been associated with impaired neurobehavioural and cognitive development and electrophysiological deficits in children and reduced gestational age and birth weight in infants. Blood lead levels of 10 micrograms Pb/dl are also of concern in pregnant women because of exposure to the fetus. Blood lead levels of 30 micrograms Pb/dl have been associated with elevated blood pressure and other adverse effects in adults. Thus, the values of 10 and 30 micrograms Pb/dl represent lowest-observed-effects levels for developing and adult populations, respectively. The ingestion levels that result in these blood levels of concern were estimated to be 60 micrograms Pb/day for children ages 6 years or younger, 150 micrograms Pb/day for children aged 7 years or older, 250 micrograms Pb/day for pregnant women and 750 micrograms Pb/day for adults. Provisional total tolerable intake levels for lead were derived from these blood lead levels for each group by applying the Renwick approach to obtain a tolerable exposure level.