BACKGROUND: The California Environmental Contaminant Biomonitoring Program (www.biomonitoring.ca.gov) was established by legislation in 2006. The Biomonitoring Exposures Study (BEST) within the Program measured levels of blood metals in a sample of adult members of a large HMO living in California’s Central Valley. We aimed to identify demographic differences in exposure within BEST, to compare levels to national estimates, and to identify predictors of exposure in the cohort.
METHODS: Participants (N=395) were recruited in 2013, with an emphasis on recruiting Hispanics and Asians and Pacific Islanders (APIs). A self-administered questionnaire in either English or Spanish captured demographic, occupational, lifestyle, and dietary information. Blood cadmium (bCd), manganese (bMn), mercury (bHg), and lead (bPb) were analyzed in 315 participants by inductively coupled plasma mass spectrometry at the California Department of Public Health Environmental Health Laboratory. We computed descriptive statistics of metal concentrations, and geometric means (GMs) were compared across categories of demographic characteristics with a Wald test, a linear test for trend, or analysis of variance. We also compared our results to a demographically similar NHANES population. We identified factors that predicted elevated exposure using multivariable linear regression.
RESULTS: The bCd GM concentration was 0.27 μg/L (95% CI: 0.25-0.29); bPb was 0.84 μg/dL (95% CI: 0.78-0.91); bMn was 9.55 μg/L (95% CI: 9.24-9.87); and bHg was 0.83 μg/L (95% CI: 0.73-0.93). Overall, bCd and bPb GMs were lower in BEST compared to the NHANES 2011-2012 population of adults ≥ 20 years old. The bMn GM was higher in BEST compared to the NHANES population. Within BEST, APIs had higher levels of bHg, bMn, and bCd compared to other race/ethnic groups; Hispanics had the lowest bCd and bHg levels among all groups; and Blacks had the lowest bMn levels. The strongest predictors for elevated bCd were increasing age, API race/ethnicity, smoking, and being female. Blood Hg levels were associated with API race/ethnicity, greater fish consumption, and being born outside of the United States. Elevated bPb levels were associated with being male, smoking, and increasing age. Being female and API were risk factors for elevated bMn in BEST.
CONCLUSIONS: In a biomonitored California adult cohort, differences in blood metal concentrations were observed by race/ethnicity and gender; smoking and fish consumption were identified as modifiable risk factors for elevated blood Cd, Hg, and/or Pb levels. Future biomonitoring efforts should investigate demographic subgroups at risk for elevated blood metal exposure to elucidate unidentified sources of exposure.