Evaluation of racial and ethnic disparities in exposure to toxic metals in the United States

Hiroshi Awata, The University of Texas School of Public Health


Asian populations have higher background biomarker levels of certain toxic metals, as compared to other race and ethnic groups in the U.S. However, there is little information on likely exposure pathways in Asians or whether this pattern varies by Asian subpopulations. Using data from the 2011–2012 National Health Nutrition and Examination Survey (NHANES), we achieved two main objectives. First, we compared the biomarker levels of four metals (arsenic, cadmium, lead, and mercury) in the Asian population with those of other U.S. race and ethnic groups. Second, we examined whether differences in biomarker levels between race/ethnic groups are attributable to demographic, physical, dietary, behavioral, socioeconomic, and/or geographic factors. Food consumption (including drinking water) is one of the key exposure pathways for arsenic, cadmium, lead and mercury in the U.S. These metals are bioaccumulative and present ubiquitously in animal and plant tissues that we consume. Hence, one possible cause of increased biomarker levels is the food consumption practices among Asians. Therefore, dietary chemical intake of the aforementioned four metals was also investigated. We presented summary statistics of biomarker levels and dietary metal intake stratified by five NHANES race/ethnic group categories: non-Hispanic white, non-Hispanic black, Mexican American, other Hispanic, and non-Hispanic Asian, and three Asian subgroups: Chinese, Asian Indian, and “Other Asian.” For each race or ethnicity, the weighted geometric mean and 50th and 95th percentiles of biomarker levels and dietary metal intake data were presented by potential determinant or covariate. Further, the association between biomarker levels and dietary metal intake was determined. We confirmed significantly higher biomarker levels of the four metals among Asians as compared to other race/ethnic groups, regardless of demographic, physical, dietary, behavioral, socioeconomic, and/or geographic characteristics. Further, biomarker levels across different Asian subgroups were also significantly different. Many characteristics—namely, sex, age, birthplace, smoking, and fish consumption—were significantly associated with the biomarker levels of these metals. Statistically significant associations between dietary intake and biomarker levels were found for arsenic (both total and inorganic) and mercury; however, such associations were not observed for cadmium or lead. We also observed different food consumption patterns (e.g., levels of fish and rice consumed) and estimated dietary intake across the different race/ethnic groups and Asian subgroups. Fish (for total arsenic and mercury) and rice (for inorganic arsenic) were found to be important dietary sources of arsenic and mercury exposure among Asians. In contrast to our findings for biomarkers, with the exception of arsenic (total and inorganic), estimated dietary intake was generally not significantly different across race/ethnic groups and subgroups, especially for cadmium and lead.

Subject Area

Public health

Recommended Citation

Awata, Hiroshi, "Evaluation of racial and ethnic disparities in exposure to toxic metals in the United States" (2016). Texas Medical Center Dissertations (via ProQuest). AAI10126219.