ABSTRACTORAL CONTRACEPTIVE USE AND BLOOD LEAD CONCENTRATIONS IN U.S. PREMENOPAUSL INDIVIDUALS By Arianna Victoria-Elizabeth Foster In the United States, the general population is ubiquitously exposed to toxic metal lead. Lead can adversely affect all organ systems. After exposure, lead is stored within bone, but can still transfer between bone and blood. Estrogen can induce a bone-sparing effect by suppressing osteoclast activity. The majority of oral contraceptives (OCs) contain estrogen and are the most commonly used form of contraception in the United States. Since lead is stored in bone, we hypothesized that current use of estrogen-containing oral contraceptives decreases skeletal mobilization of the toxic metal lead from bone to blood. To test this hypothesis, the aim of this study was to investigate the association between current OC use and blood lead concentrations in a U.S. nationally-representative sample of premenopausal individuals. We conducted a cross-sectional study using five data cycles (2003-2012) from the National Health and Nutrition Examination Survey (NHANES). The study population included premenopausal, non-pregnant individuals ages 20-44 with an intact uterus and at least one ovary who were not currently using injectable contraceptives, with information on current OC use and blood lead concentrations (unweighted n=3,973). We used multivariable linear regression to estimate the percent difference in geometric mean blood lead concentrations and 95% confidence intervals between current OC users and non-users based on self-report, accounting for the complex survey sampling design. We observed that current OC users had lower geometric mean blood lead concentrations (0.68 μg/dl, 95% CI: 0.66, 0.71) than non-users (0.81 μg/dl, 95% CI: 0.79, 0.83). After multivariable adjustment, current OC users had 9% lower (95% CI: -14%, -4%) blood lead concentrations than non-users. We also used prescription medication data to characterize combined oral contraceptive use in the past 30 days and observed a stronger association (-12% lower blood lead concentrations, 95% CI: -18%, -7%). As no safe level of blood lead exists, and lead can adversely affect all organ systems, even in adulthood, further research is warranted to replicate our findings of lower blood Pb concentrations with current OC use.
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