Trends in blood mercury concentrations and fish consumption among U.S. women of reproductive age, NHANES, 1999-2010

Background: Consumption of finfish and shellfish is the primary exposure pathway of methylmercury (MeHg) in the US. MeHg exposure in utero is associated with neurodevelopmental and motor function deficits. Regulations and fish advisories may contribute to decreased exposure to mercury over time.

Objectives: Combine fish tissue mercury (FTHg) concentrations and 1999-2010 NHANES blood mercury concentrations and fish consumption data to investigate trends in blood mercury concentrations, fish consumption, and mercury intake in women of reproductive age.

Methods: Blood MeHg was calculated from the blood total and inorganic concentrations. Dietary datasets were combined to estimate 30-day fish consumption, then combined with FTHg concentrations to estimate mercury intake and mercury concentration in the fish consumed. Non-linear and logistic regression analyses were used to evaluate trends over time.

Results: Regression analysis found NHANES 1999-2000 to have higher blood MeHg concentrations than the mean of the later releases (p<0.0001) and a positive quadratic trend since 2000 (p=0.004). No trend was observed in fish consumption amount or mercury intake. A decreasing trend was found in the ratio of mercury intake to fish consumed (p=0.04).

Conclusions: The analyses found blood MeHg concentrations in NHANES 1999-2000 to be significantly higher than the mean of the later releases. There was no trend in fish consumption amount across the study period. The analysis found a decreasing trend in the ratio of mercury intake to fish consumed, consistent with women shifting their consumption to fish with lower mercury concentrations.