Effect of long-term lead exposure on hematology, blood biochemistry, and growth curves in monkeys.

A total of 90 monkeys (Macaca fascicularis), comprising four study cohorts born over a seven-year period, were hand reared and dosed orally with lead or vehicle according to one of several protocols, in most cases from birth to 9-14 years. Blood lead concentrations of lead-exposed groups ranged from 10 to 90 micrograms/dl depending on dose and age. Routine hematology and blood biochemistry analyses were performed regularly. Comparison of treated groups at various ages to the appropriate control group revealed no strong indication of lead-related effects. In addition, body weight increase was modeled from days 30-3500 of age in subset of this larger group, including 52 monkeys exposed to vehicle or lead during development according to one of four regimens: vehicle, lead from birth onward, lead to 400 days of age, or lead beginning at 300 days of age. No effect of lead on body weight was found. These results suggest that lead exposure beginning early in life and continuing for as long as 14 years resulted in no overt toxicity, as measured by these parameters.