Estrogen-containing contraceptive use and blood lead concentrations in a cohort of premenopausal individuals

After exposure, toxic metal lead is stored in the skeleton and is mobilized to systemic circulation with bone turnover. Given the bone-conserving properties of estrogen, we investigated whether current use of estrogen-containing contraception is associated with lower blood lead concentrations. We conducted a cross-sectional analysis using enrollment data from the Study of Environment, Lifestyle & Fibroids (SELF), a cohort of 1693 Black women ages 23-35 years enrolled in years 2010-2012. The study population was restricted to non-users of injectable hormonal contraception with questionnaire data on hormonal contraceptive use and laboratory data on whole blood lead concentrations (n = 1549). The geometric mean blood lead concentrations for current users of estrogen-containing contraception and non-users were 0.41 μg/dl (95 % CI: 0.39-0.43) and 0.51 μg/dl (95 % CI: 0.50-0.52), respectively. After adjusting for age, education, current smoking status, alcohol consumption, recency of injectable contraceptive hormone use, and recent birth using a multivariable linear regression model to estimate the percent difference in blood lead concentrations, current use of estrogen-containing contraception was associated with an 11 % lower blood-lead concentrations (95 % CI: -16 %, -5 %). In exploratory analyses considering contraceptive type, current combined oral contraceptive users (n = 187) had 10 % lower blood lead concentrations (95 % CI: -16 %, -4 %) and contraceptive vaginal ring/transdermal patch users (n = 33) had 18 % lower blood lead concentrations (95 % CI: -29 %, -5 %) compared with non-users. Given the known toxic effects of lead and the common use of estrogen-containing contraception, further research is warranted to confirm our observation of lower blood lead concentrations with current use of estrogen-containing contraception.