Citation:

Aylward, L., S. Ramasamy, S. Hays, R. Schoeny, AND C. Kirman. Evaluation of urinary speciated arsenic in NHANES: Issues in interpretation in the context of potential inorganic arsenic exposure. REGULATORY TOXICOLOGY AND PHARMACOLOGY. Elsevier Science Ltd, New York, NY, 69(1):49-54, (2014).

Impact/Purpose:

This is a publication for the peer reviewed press. It describes an application of biomonitoring equivalents to speciated urinary arsenic data from the NHANES database. This work will be useful in determining appropriate biomarkers for exposure to inorganic and organic arsenic. EPA has ongoing reserach and risk assessment activities for various arsenic forms. It is likely that this paper will be of broad interest in this regard. At this point in time, we feel that there is no impact on discussion of existing EPA policy.

Description:

Urinary dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) are among the commonly used biomarkers for inorganic arsenic (iAs) exposure, but may also arise from seafood consumption and organoarsenical pesticide applications. We examined speciated urinary arsenic data from National Health and Nutrition Examination Survey (NHANES) 2009–2010 cycle to assess potential correlations among urinary DMA, MMA, and the organic arsenic species arsenobetaine. Urinary DMA and MMA were positively associated with urinary arsenobetaine, suggesting direct exposure to these species in seafood or metabolism of organic arsenicals to these species, although the biomonitoring data do not directly identify the sources of exposure. The magnitude of association was much larger for DMA than for MMA. The secondary methylation index (SMI, ratio of urinary DMA to MMA) observed in the NHANES program likewise is much higher in persons with detected arsenobetaine than in those without, again suggesting that direct DMA exposure is co-occurring with exposure to arsenobetaine. Urinary MMA was less correlated with organic arsenic exposures than DMA and, therefore, may be a more reliable biomarker for iAs exposure in the general US population. However, given the associations between both MMA and DMA and organic arsenic species in urine, interpretations of the urinary arsenic concentrations observed in the NHANES in the context of potential arsenic exposure should be made cautiously.

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