Exposure to low levels of arsenic: A comparison of urine and toenails concentrations

Chronic exposure of humans to inorganic arsenic has been associated with increase risk of cancer, skin and cardiovascular disorders, among others. Key diagnostic laboratory tests for arsenic exposure are toenails and urinary arsenic. Toenails samples are used to evaluate three to twelve months of exposure while urinary arsenic is used for recent exposure (24-72 hours). The purpose of this study is to evaluate the differences between urinary and toenails arsenic concentration as biologic markers for low levels of arsenic exposure. A sub-sample of 100 individuals was selected from a bladder cancer case-control study of Southeastern Michigan residents where arsenic in drinking water has been studied. Through summer and fall of 2006, urine, toenails and water samples were collected during a series of home-interviews. Total measurements of arsenic in water, toenails and urine were analyzed using HPLC and ICP-MS. The mean of arsenic in water, urine and toenails were 4.1µg/L, 20.0µg/L and 0.11µg/L, respectively. Among the 100 individuals, a correlation (r) was detected between urine and water: 0.303 (p=0.0029) while a stronger correlation was detected between urine and toenails: 0.364 (p=0.0004). Data stratification by water source concentrations shows a significant correlation between urine and toenails r=0.453 (p=0.0063) in well water. The water source was a significant determinant for arsenic in urine but not in toenails. Urine and toenails are useful tools to measure arsenic exposure but urine may predict the water source of exposure.