Polychlorinated biphenyls, lead, and mercury are associated with liver disease in American adults: NHANES 2003-2004

Abstract

Background: High-level occupational exposures to some industrial chemicals have been associated with liver diseases, including nonalcoholic fatty liver disease (NAFLD). However, the potential role of low-level environmental pollution on liver disease in the general population has not been evaluated.

Objective: We determined whether environmental pollutants are associated with an elevation in serum alanine aminotransferase (ALT) activity and suspected NAFLD in U.S. adults.

Methods: This cross-sectional cohort study evaluated adult participants without viral hepatitis, hemochromatosis, or alcoholic liver disease from the National Health and Nutrition Examination Survey (NHANES) for 2003-2004. ALT elevation was defined in men as ≥ 37 IU/L (age 18-20 years) and ≥ 48 IU/L (age ≥ 21 years) and in women as ≥ 30 IU/L (age 18-20 years) and ≥ 31 IU/L (age ≥ 21 years). Adjusted odds ratios (ORs) for ALT elevation were determined across exposure quartiles for 17 pollutant subclasses comprising 111 individual pollutants present with at least a 60% detection rate. Adjustments were made for age, race/ethnicity, sex, body mass index, poverty income ratio, and insulin resistance. Individual pollutants from subclasses associated with ALT elevation were subsequently analyzed.

Results: The overall prevalence of ALT elevation was 10.6%. Heavy metals and polychlorinated biphenyls (PCBs) were associated with dose-dependent increased adjusted ORs for ALT elevation. Within these subclasses, increasing whole-blood levels of lead and mercury and increasing lipid-adjusted serum levels of 20 PCBs were individually associated with ALT elevation.

Conclusions: PCB, lead, and mercury exposures were associated with unexplained ALT elevation, a proxy marker of NAFLD, in NHANES 2003-2004 adult participants.

Figure 1

Schematic diagram depicting adult NHANES 2003–2004 subjects and pollutant subclasses analyzed. n_homa refers to the subset of subjects with HOMA-IR scores, which were required for data adjustment, and represents the maximum number of subjects available for each subpopulation for analysis by the primary model that adjusted for insulin resistance. The actual numbers used varied by analyte primarily because of missing response variables required for the other adjustments. The final numbers used for each analyte or chemical subclass are given in Tables 2–5 and in the Supplemental Material, Tables 2–5 (doi:10.1289/ehp.1002720). Volatile organic compounds were measured in selected subjects from subpopulations B and D.