Environmental and hormonal risk factors and blood lead levels in adolescent girls

Abstract

BACKGROUND: Lead (Pb) exposure is common in inner-city populations. If ingested, Pb is stored in bone and released into blood when bone demineralizes. Demineralization may occur in adolescents using progestin-only contraceptives such as depot medroxyprogesterone acetate (DMPA) or during pregnancy. We hypothesized that adolescents likely to have had Pb exposure are at risk of endogenous Pb poisoning when treated with a hormone that may result in increased bone absorption.METHOD: We recruited 176 consecutive healthy girls aged 13-21 (x = 17.6 yrs.) seen at an inner-city adolescent clinic: 60% were Hispanic; 27% black; 5% white; and 7% other. Subjects completed an 82-item questionnaire examining current lead exposure, pregnancy, and contraception history. A blood sample for Pb determination by atomic absorption spectroscopy was obtained.RESULTS: Many girls had environmental risk factors for Pb exposure: 67% were born in the inner-city; 58% reported potential occupational exposure either of themselves or a close family member; 18% lived in a building over 35 years of age; 24% reported ongoing building renovations; 10% reported a history of pica, but only 3 subjects had ever been told they had high levels as children. 26 girls (15%) reported 1 or more past pregnancies lasting 6 months or longer; none were currently pregnant. 36 subjects were using DMPA, 28 were taking oral contraceptive pills, and 112 used no hormones. No subject had a blood Pb level ≥ 10 μg/dl, the current level of concern. Mean blood Pb level in the 176 girls was 1.56 μg/dl, SD = 1.05 (range 0-8). Bivariate comparisons of mean blood Pb levels for subjects with and without the various environmental, pregnancy, and contraceptive risk factors were not significantly different. When blood Pb level for the 176 girls was dichotomized to high (≥ 4 μg/dl), i.e. more than 2 standard deviations above the mean, or low (< 4 μg/dl), a higher proportion of girls using DMPA (4/36) than those not using DMPA (3/140) had high levels [χ2 = 6.031 (p = 0.033)]. Past pregnancy was not associated with Pb levels ≥ μg/dl.CONCLUSIONS: Despite reported high risk exposure to lead, toxic blood levels were not found. However, DMPA treated girls were significantly more likely to have higher blood lead levels within the range found than untreated girls. Further assessment and correlation with serum markers for bone demineralization is indicated.