Determinants of bone and blood lead concentrations in the early postpartumperiod

Objective-This study investigated determinants of bone and blood lead conce ntrations in 430 lactating Mexican women during the early postpartum period and the contribution of bone lead to blood lead. Methods-Maternal venous lead was measured at delivery and postpartum, and b one lead concentrations, measured with in vivo K-x ray fluorescence, were m easured post partum. Data on environmental exposure, demographic characteri stics, and maternal factors related to exposure to lead were collected by q uestionnaire. Linear regression was used to examine the relations between b one and blood lead, demographics, and environmental exposure variables. Results-Mean (SD) blood, tibial, and patellar lead concentrations were 9.5 (4.5) mu g/dl, 10.2 (10.1) mu g Pb/g bone mineral, and 15.2 (15.1) mu g Pb/ g bone mineral respectively. These values are considerably higher than valu es for women in the United States. Older age, the cumulative use of lead gl azed pottery, and higher proportion of life spent in Mexico City were power ful predictors of higher bone lead concentrations. Use of lead glazed ceram ics to cook food in the past week and increased patellar lead concentration s were significant predictors of increased blood lead. Patellar lead concen trations explained one third of the variance accounted for by the final blo od lead model. Women in the 90th percentile for patella lead had an untrans formed predicted mean blood lead concentration 3.6 mu g/dl higher than thos e in the 10th percentile. Conclusions-This study identified the use of lead glazed ceramics as a majo r source of cumulative exposure to lead, as reflected by bone lead concentr ations, as well as current exposure, reflected by blood lead, in Mexico. A higher proportion of life spent in Mexico City, a proxy for exposure to lea ded gasoline emissions, was identified as the other major source of cumulat ive lead exposure. The influence of bone lead on blood lead coupled with th e long half Life of lead in bone has implications for other populations and suggests that bone stores may pose a threat to women of reproductive age l ong after exposure has declined.