Prevalence of Exposure to Environmental Metal Mixtures Among Pregnant Women in the United States National Health and Nutrition Examination Survey (NHANES) 1999-2018.

Although exposure to metals remains a public health concern, few studies have examined exposure to combinations of metals. This study characterized prevalent combinations of cadmium (Cd), mercury (Hg), and lead (Pb) in women (n = 10,152; aged 20-44 years) who participated in the U.S. National Health and Nutrition Examination Survey (NHANES) 1999-2018. To explore relative metal exposures within this population, Cd, Hg, and Pb blood levels were dichotomized as "high" and "low" categories using median values to represent the center of the metal concentrations in the study population, not thresholds for adverse health effects. The prevalence of the three metal combinations at "high" levels (singular, binary, tertiary combinations) was calculated. Multinomial logistic regression was used to calculate odds ratios for each combination relative to none of these combinations after adjusting for potential confounders. Among the pregnant women (n = 1297), singular Hg was most prevalent (19.2% [95% CI 15.0-23.3]), followed by singular Cd (14.7% [95% CI 11.2-18.2]), tertiary combination Cd/Hg/Pb (11.0% [95% CI 8.7-13.2]), binary combinations Cd/Pb (9.8% [95% CI 7.4-12.2]), Hg/Pb (9.2% [95% CI 6.5-11.8]), Cd/Hg (7.8% [95% CI 6.0-9.6]), and singular Pb (5.5% [95% CI 4.1-6.9]). We found significantly lower odds of having Cd/Hg/Pb (adjusted odds ratio (adjOR) = 0.49: