Excretion of arsenic in urine as a function of exposure to arsenic in drinking water

Urinary arsenic (As) concentrations were evaluated as a biomarker of exposu re in a U.S. population chronically exposed to inorganic As (InAs) in their drinking water. Ninety-six individuals who consumed drinking water with As concentrations of 8-620 mu g/L provided first morning urine voids for up t o 5 consecutive days. The study population was 56% male, and 44% was younge r than 18 years of age. On one day of the study period, all voided urines w ere collected over a 24-hr period. Arsenic intake from drinking water was e stimated from daily food diaries. Comparison between the concentration of A s in individual urine voids with that in the 24-hr urine collection indicat ed that the concentration of As in urine was stable throughout the day. Com parison of the concentration of As in each first morning urine void over th e 5-day study period indicated that there was little day-to-day variation i n the concentration of As in urine. The concentration of As in drinking wat er was a better predictor of the concentration of As in urine than was the estimated intake of As from drinking water. The concentration of As in urin e did not vary by gender. An age-dependent difference in the concentration of As in urine may be attributed to the higher As dosage rate per unit body weight in children than in adults. These findings suggest that the analysi s of a small number of urine samples may be adequate to estimate an individ ual's exposure to InAs from drinking water and that the determination of th e concentration of InAs in a drinking water supply may be a useful surrogat e for estimating exposure to this metalloid.