Human exposure assessment of different arsenic species in household water sources in a high risk arsenic area.

Understanding arsenic speciation in water is important for managing the potential health risks associated with chronic arsenic exposure. Most arsenic monitoring studies to date have only measured total arsenic, with few looking at arsenic species. This study assessed 228 ground water sources in six unstudied villages in Pakistan for total, inorganic and organic arsenic species using ion chromatography inductively coupled plasma collision reaction cell mass spectrometry. The concentration levels approached 3090μgL-1 (95% CI, 130.31, 253.06) for total arsenic with a median of 57.55μgL-1 , 3430μgL-1 (median=52) for arsenate (As+5 ) and 100μgL-1 (median=0.37) for arsenite (As+3 ). Exceedance of the WHO provisional guideline value for arsenic in drinking water (10μgL-1 ) occurred in 89% of water sources. Arsenic was present mainly as arsenate (As+5 ). Average daily intake of total arsenic for 398 residents living in the sampled houses was found up to 236.51μgkg-1 day-1 . This exposure estimate has indicated that 63% of rural residents exceeded the World Health Organization's provisional tolerable daily intake (PTDI) of 2.1μgkg-1 day-1 body weight. Average daily intake of As+5 was found to be 15.63μgkg-1 day-1 (95% CI, 5.53, 25.73) for children ≤16 and 15.07μgkg-1 day-1 (95% CI, 10.33, 18.02) for adults. A mean daily intake of 0.09μgkg-1 day-1 was determined for As+3 for children and 0.26μgkg-1 day-1 for adults. Organic arsenic species such as monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and Arsenobetaine (AsB) were found to be below their method detection limits (MDLs).