Speciation of Arsenic in Urine from the Health Effects of Arsenic Longitudinal Study (HEALS) Revealing New Arsenic Species and Individual Variability.

More than 100 million people around the world are exposed to arsenic in drinking water that exceeds the World Health Organization guideline level of 10 μg/L. Ingestion of water and food is the main route of human exposure to arsenic. Arsenic species excreted into urine serve as a useful biomarker of exposure and a potential marker of susceptibility, which requires speciation of arsenic in population studies. We report here the determination of arsenic species in 1873 urine samples from the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh. This double-blind research involved detection of inorganic arsenite (iAsIII), arsenate (iAsV), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), tetramethylarsonium ion (TMI), and 12 new arsenic species that are yet to be fully identified. The total arsenic concentrations in urine, ranging from 0.9 to 2634 μg/L, were in good agreement (R 2 = 0.99) with the sum of all arsenic species. DMA was the major arsenic metabolite, and its concentrations ranged from 0.3 to 1599 μg/L, with a mean of 79 μg/L. The mean concentration of MMA was 12 μg/L, and its maximum concentration was 278 μg/L. The mean and maximum concentrations of inorganic arsenic (the sum of iAsIII and iAsV) were 16 and 611 μg/L, respectively. There was no statistically significant difference in urinary concentrations of arsenic species between the female (n = 1156) and male (n = 714) participants. On average, the relative proportions of individual arsenic species were 71.7% DMA, 11.0% MMA, 14.8% iAs (sum of iAsIII and iAsV), 1.9% AsB, and 1.6% unidentified arsenic species. Unidentified arsenic species were detected in 751 urine samples (40% of the 1873 urine samples), and their concentrations ranged from 0.4 to 42 μg/L (mean 1.8 μg/L). A subset of participants (n = 76) with skin lesions, compared to those (n = 74) without skin lesions, had higher urinary concentrations of DMA (4.1-728 vs 1.4-354 μg/L, p = 0.013), MMA (1.2-278 vs 0.3-87 μg/L, p = 0.0048), inorganic arsenic (sum of iAsIII + iAsV) (not detectable to 141 μg/L vs 0.3-83 μg/L, p = 0.016), and total arsenic (7.1-1231 vs 3-581 μg/L, p = 0.0093). These results of individual arsenic species in human urine, arsenic speciation patterns, and arsenic metabolite profiles, along with observations of health outcomes, demonstrate potential for establishing biomarkers of effect and susceptibility.