Lead and mercury exposure in pregnant women in the UK: a cross-sectional observational study (the PEAR Study)

OBJECTIVES : Lead and mercury are recognised as critical determinants of population health, especially for children and pregnant women. Few UK cohorts have measured lead or mercury in pregnant women since 1990. The aims of this study are to: (1) quantify lead and mercury exposures in a sample of pregnant women in the UK; (2) document concentrations over time in pregnant women in the UK; and (3) compare concentrations with international data. DESIGN: Whole blood samples were obtained from pregnant women in a quantitative arm of the Pregnancy, the Environment And nutRition Study in a cross-sectional observational study design. The samples were analysed by inductively coupled plasma mass spectrometry (Health and Safety Executive, Buxton, UK). SETTING : Community-based with recruitment through a hospital antenatal clinic in south-west England. PARTICIPANTS : Women ≥18 years old and ≥11 weeks pregnant by last menstrual period. PRIMARY OUTCOME MEASURES: Whole blood lead and speciated mercury concentrations. RESULTS : The whole blood lead concentration was: mean 5.8 (SD 6.2), median 4.6 (IQR 3.5, 5.9), range 1.7-78.1 µg/L (n=262; gestational age range by scan 8.3-15.9 weeks). These values are about 84% lower than in pregnant women in the UK Avon Longitudinal Study of Parents and Children (ALSPAC; 1991-1992), about 47% lower than in the UK Born in Bradford (BiB) study (2007-2011) and about 34% lower than in White women in the UK Mother's and Baby's Exposure to Lead study (MaBEL; 2011). Blood total mercury concentration was: mean 0.83 (SD 0.64), median 0.69 (IQR 0.34, 1.19), range 0.07-3.40 (about 60% lower than in pregnant women in ALSPAC and about 37% lower than in BiB). These results are similar to contemporary concentrations found in Europe and the USA. CONCLUSIONS: Blood concentrations of lead and mercury in pregnant women in the UK have declined considerably since the early 1990s. However, no safe levels have previously been identified for adverse effects on cognition, preterm birth rate or coronary heart disease prevalence. These data will contribute to the ongoing development of public health advice. STUDY REGISTRATION: ISTCTN92638336.