DIETARY AND ENVIRONMENTAL DETERMINANTS OF BLOOD AND BONE LEAD LEVELS IN LACTATING POSTPARTUM WOMEN LIVING IN MEXICO-CITY

Despite the recent declines in environmental lead exposure in the Unit ed States and Mexico, the potential for delayed toxicity from bone sto res remains a significant public health concern. Some evidence indicat es that mobilization of lead from bone may be markedly enhanced during the increased bone turnover of pregnancy and lactation, resulting in lead exposure to the fetus and the breast-fed infant. We conducted a c ross-sectional investigation of the interrelationships between environ mental, dietary, and lifestyle histories, blood lead levels, and bone lead levels among 98 recently postpartum women living in Mexico City. Lead levels in the patella (representing trabecular bone) and tibia (r epresenting cortical bone) were measured by K X-ray fluorescence (KXRF ). Multivariate linear regression models showed that significant predi ctors of higher blood lead included a history of preparing or storing food in lead-glazed ceramic wave, lower milk consumption, and higher l evels of lead in patella bone. A 34 mu g/g increase in patella lead (f rom the medians of the lowest to the highest quartiles) was associated with an increase in blood lead of 2.4 mu g/dl. Given the measurement error associated with KXRF and the extrapolation of lead burden from a single bone site, this contribution probably represents an underestim ate of the influence of trabecular bone on blood lead. Significant pre dictors of bone lead in multivariate models included years living in M exico City, lower consumption of high calcium content foods, and nonus e of calcium supplements for the patella and years living calcium cont ent foods, and nonuse of calcium supplements for the patella and years living in Mexico City, older age, and lower calcium intake for tibia bone. Low consumption of milk and cheese, as compared to the highest c onsumption category (every day), was associated with an increase in ti bia bone lead of 9.7 mu g Pb/g bone mineral. The findings of this cros s-sectional study suggest that patella bone is a significant contribut or to blood lead during lactation and that consumption of high calcium content foods may protect against the accumulation of lead in bone.