Background: Immune dysregulation associated with mercury has been suggested, although data in the general population are lacking. Chronic exposure to low levels of methylmercury (organic) and inorganic mercury is common, such as through fish consumption and dental amalgams.

Objective: We examined associations between mercury biomarkers and antinuclear antibody (ANA) positivity and titer strength.

Methods: Among females 16–49 years of age ( n = 1,352) from the National Health and Nutrition Examination Survey (NHANES) 1999–2004, we examined cross-sectional associations between mercury and ANAs (indirect immunofluorescence; cutoff ≥ 1:80). Three biomarkers of mercury exposure were used: hair (available 1999–2000) and total blood (1999–2004) predominantly represented methylmercury, and urine (1999–2002) represented inorganic mercury. Survey statistics were used. Multivariable modeling adjusted for several covariates, including age and omega-3 fatty acids.

Results: Sixteen percent of females were ANA positive; 96% of ANA positives had a nuclear speckled staining pattern. Geometric mean (geometric SD) mercury concentrations were 0.22 (0.03) ppm in hair, 0.92 (0.05) μg/L blood, and 0.62 (0.04) μg/L urine. Hair and blood, but not urinary, mercury were associated with ANA positivity (sample sizes 452, 1,352, and 804, respectively), after adjusting for confounders: for hair, odds ratio (OR) = 4.10 (95% CI: 1.66, 10.13); for blood, OR = 2.32 (95% CI: 1.07, 5.03) comparing highest versus lowest quantiles. Magnitudes of association were strongest for high-titer (≥ 1:1,280) ANA: hair, OR = 11.41 (95% CI: 1.60, 81.23); blood, OR = 5.93 (95% CI: 1.57, 22.47).

Conclusions: Methylmercury, at low levels generally considered safe, was associated with subclinical autoimmunity among reproductive-age females. Autoantibodies may predate clinical disease by years; thus, methylmercury exposure may be relevant to future autoimmune disease risk.

Citation: Somers EC, Ganser MA, Warren JS, Basu N, Wang L, Zick SM, Park SK. 2015. Mercury exposure and antinuclear antibodies among females of reproductive age in the United States: NHANES. Environ Health Perspect 123:792–798;  http://dx.doi.org/10.1289/ehp.1408751

Address correspondence to E.C. Somers, University of Michigan, 109 Zina Pitcher Place, BSRB 3018, Ann Arbor, MI 48109-2200 USA. Telephone: (734) 936-3257. E-mail: [email protected]

We thank H. Hu (University of Toronto) and B. Richardson (University of Michigan) for their critical review of the manuscript.

This work was supported by grants K01ES019909 and P30ES017885 from the National Institute of Environmental Health Sciences, National Institutes of Health (NIH), and by grant UL1RR024986 from the National Center for Research Resources, NIH. E.C.S. was supported in part by an Arthritis Foundation Health Professional New Investigator Award.

E.C.S. had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

The authors declare they have no actual or potential competing financial interests.

Received: 29 May 2014 Accepted: 4 February 2015 Advance Publication: 10 February 2015 Final Publication: 1 August 2015