Total blood mercury concentrations in the U.S. population: 1999-2006

We describe the distribution and demographic characteristics of total blood Hg levels in the U.S. general population among persons ages 1 year and older who participated in the 2003–2006 National Health and Nutrition Examination Survey (NHANES). We also describe trends in the total blood Hg of children ages 1–5 (n=3456) and females ages 16–49 during 1999–2006 (n=7245). In the combined 2003–2006 survey periods, the geometric means for non-Hispanic blacks, 0.853 μg/L (95% confidence interval [CI], 0.766–0.950 μg/L), and non-Hispanic whites, 0.833 μg/L (95% CI, 0.752–0.922 μg/L), were higher than the geometric mean for Mexican Americans, 0.580 μg/L (95% CI, 0.522–0.645 μg/L). Also in 2003-2006, regression analysis of log total blood Hg with age, race/ethnicity and gender showed that total blood Hg levels in the population exhibited a quadratic increase with age (p<0.0001), peaking at ages 50–59 in non-Hispanic blacks and whites, at ages 40–49 in Mexican Americans, and then declining at older ages. Over the four survey periods (1999–2006), regression analysis showed that total blood Hg levels increased slightly for non-Hispanic white children and decreased slightly for non-Hispanic black and Mexican American children. Over the same four survey periods, female children had slightly higher total blood Hg levels than males (0.356 vs. 0.313 μg/L, p=0.0050) and total blood Hg levels in non-Hispanic black women aged 16-49 years were significantly higher than in non-Hispanic white women (1.081 vs. 0.850 μg/L, p<0.0001) and in Mexican American women (1.081 vs. 0.70 μg/L, p<0.0001).