A method to screen U.S. environmental biomonitoring data for race/ethnicity and income-related disparity

Abstract

Background: Environmental biomonitoring data provide one way to examine race/ethnicity and income-related exposure disparity and identify potential environmental justice concerns.

Methods: We screened U.S. National Health and Nutrition Examination Survey (NHANES) 2001-2008 biomonitoring data for 228 chemicals for race/ethnicity and income-related disparity. We defined six subgroups by race/ethnicity-Mexican American, non-Hispanic black, non-Hispanic white-and income-Low Income: poverty income ratio (PIR) <2, High Income: PIR ≥ 2. We assessed disparity by comparing the central tendency (geometric mean [GM]) of the biomonitoring concentrations of each subgroup to that of the reference subgroup (non-Hispanic white/High Income), adjusting for multiple comparisons using the Holm-Bonferroni procedure.

Results: There were sufficient data to estimate at least one geometric mean ratio (GMR) for 108 chemicals; 37 had at least one GMR statistically different from one. There was evidence of potential environmental justice concern (GMR significantly >1) for 12 chemicals: cotinine; antimony; lead; thallium; 2,4- and 2,5-dichlorophenol; p,p'-dichlorodiphenyldichloroethylene; methyl and propyl paraben; and mono-ethyl, mono-isobutyl, and mono-n-butyl phthalate. There was also evidence of GMR significantly <1 for 25 chemicals (of which 17 were polychlorinated biphenyls).

Conclusions: Although many of our results were consistent with the U.S. literature, findings relevant to environmental justice were novel for dichlorophenols and some metals.

Figure 1

Visual overview of GMR for NHANES environmental biomonitoring data for all subgroups. Each cell of the matrix summarizes the outcome of the geometric mean ratio (GMR) test performed. The key to the color codes is located under the matrix. The columns correspond to the five race/ethnicity subgroups (Mexican American/High Income; Mexican American/Low Income; non-Hispanic black/High Income; non-Hispanic black/Low Income; non-Hispanic white/Low Income) that are being compared to the reference subgroup (non-Hispanic white/High Income). The rows of the matrix correspond to 410 studied biomarkers. The chemical groups to which these biomarkers belong (cotinine; halogenated aromatics; metals; polycyclic aromatic hydrocarbons, PAHs; polyfluoralkyl chemicals, PFCs; perchlorate; pesticides; phenols; phthalates; volatile organic compounds, VOCs) are indicated along the right edge of the matrix.