Levels of urinary total and speciated arsenic in the US population: National Health and Nutrition Examination Survey 2003-2004

Objective: To provide levels of total and speciated urinary arsenic in a representative sample of the US population. Methods: For the first time, total arsenic and seven inorganic and organic arsenic species were measured in the urine of participants (n = 2557) for the 2003-2004 National Health and Nutrition Examination Survey (NHANES). Data were compiled as geometric means and selected percentiles of urinary arsenic concentrations (mu g/l) and creatinine-corrected urinary arsenic (mu g/g creatinine) for total arsenic, dimethylarsinic acid, arsenobetaine, and a sum of the inorganic related species. Results: Arsenic acid, arsenous acid, arsenocholine, and trimethylarsine oxide were detected in 7.6%, 4.6%, 1.8%, and 0.3% of the participants, respectively (the limits of detection of 0.6-1.2 mu g/l). Monomethylarsonic acid was detected in 35% of the overall population. For all participants aged >= 6 years, dimethylarsinic acid (geometric mean of 3.71 mu g/l) and arsenobetaine (geometric mean of 1.55 mu g/l) had the greatest contribution to the total urinary arsenic levels. A relatively greater percentage contribution from arsenobetaine is seen at higher total urinary arsenic levels and from dimethylarsinic acid at lower total urinary arsenic levels. For all participants aged >= 6 years, the 95th percentiles for total urinary arsenic and the sum of inorganic-related arsenic (arsenic acid, arsenous acid, dimethylarsinic acid, and monomethylarsonic acid) were 65.4 and 18.9 mu g/l, respectively. For total arsenic and dimethylarsinic acid, covariate-adjusted geometric means demonstrated several slight differences due to age, gender, and race/ethnicity. Conclusions: The data reflect relative background contributions of inorganic and seafood-related arsenic exposures in the US population. Arsenobetaine and dimethylarsinic acid are the major arsenic species present with arsenobetaine, accounting for a greater proportion of total arsenic as total arsenic levels increase.