Abstract

Because of the long half-life of lead stored in bone (years), skeletal lead stores may be a source of endogenous lead exposure during periods of increased bone demineralization, such as menopause. To test the hypothesis that postmenopausal bone resorption increases blood lead levels, the authors examined cross-sectional associations of bone density-related factors with blood lead levels among women aged 40-59 years from the Third National Health and Nutrition Examination Survey (1988-1994). Factors related to bone turnover were significant predictors of blood lead level. Bone mineral density was significantly inversely related to blood lead levels in log-linear multivariate models that adjusted for age, race/ethnicity, smoking, education, household income, alcohol use, and residence (urban/rural). With menopausal status added to the model, naturally and surgically menopausal women had adjusted median blood lead levels that were 25% and 30% higher, respectively, than those of premenopausal women (2.0 microg/dl). Current use of hormone replacement therapy was associated with significantly lower adjusted median blood lead levels (1.8 microg/dl) than past use (2.6 microg/dl) and never use (2.2 microg/dl). Lead stored in bone may significantly increase blood lead levels in perimenopausal women because of postmenopausal bone mineral resorption. Attention to factors that prevent bone loss may lessen or prevent this endogenous lead exposure.