Concentrations of selected heavy metals in maternal blood and associated factors in rural areas in Shanxi Province, China

Background: Animal experiments indicate that prenatal exposure to mercury (Hg), lead (Pb), cadmium (Cd) and arsenic (As) can induce fetal neural tube defects (NTDs). The objectives of this study were to determine the levels of maternal exposure to Hg, Pb, Cd and As during early pregnancy in rural areas of Shanxi Province, China, in order to explore factors that were associated with the concentrations of these metals in blood.

Methods: In 2010, we studied 215 pregnant women during their first and second trimesters in two counties with different prevalence levels of NTDs in Shanxi Province, China. Demographic and exposure data were collected from questionnaires. Blood concentrations of Hg, Pb and Cd were measured with ICP-MS; the As concentration was measured using atomic fluorescence spectrophotometry (AFS) in whole-blood specimens.

Results: The median concentrations of Hg, Pb, Cd and As in maternal blood were 0.26 μg/L (interquartile range [IQR]: 0.16-0.45), 24.48 μg/L (IQR: 18.72-32.31), 0.47 μg/L (IQR: 0.33-0.67) and 0.52 μg/L (IQR: 0.32-0.71), respectively. The maternal blood level of Cd was higher in Yushe county (median: 0.54 μg/L) than in Daixian county (0.39 μg/L). Women who lived near a coal combustion factory, used coal as cooking fuel, consumed fish, shrimp or shellfish, and consumed pork, beef or mutton during the week before the investigation had higher blood concentrations of Hg and As than their counterparts (P<0.05) after controlling for confounding variables, including the county of residence, in the logistic regression models.

Conclusions: Blood levels of Cd were higher in Yushe county, which has a higher prevalence of neural tube defects. Higher maternal blood levels of Hg in pregnant women were associated with coal combustion. Higher maternal blood levels of Hg and As were associated with fish, shrimp or shellfish consumption, as well as pork, beef or mutton consumption.