Keywords: 
• urinary arsenic /
• skin lesions induced by arsenic exposure /
• risk /
• arsenic methylation /
• logistic regression /
• coal-burning arsenism

Abstract: Population exposed to arsenic either by drinking water or by burning coal for cooking/heating have been diagnosed with skin lesions in many rural villages in China. Studies on the risk of skin lesions and their relationship with urinary total arsenic (U-TAs) have been presented in some drinking-water contaminated areas, but few studies have been done in the villages burning arsenic contaminated coal. This study was conducted in a village in Shaan'xi Province, where the people sustained burning a kind of local arsenic contaminated coal for cooking or heating. Skin lesions induced by arsenic exposure were diagnosed by specialist following the diagnostic criterion of endemic arsemism of China (WS/T211-2001). Morning urinary samples of the exposed population were collected to analyse total arsenic (TA) and four species of arsenic, e. g. arsenite (As³⁺), arsenate (As⁵⁺), monomethylarsonic acid (MMA⁵⁺) and dimethylarsinic acid (DMA⁵⁺). Percents of inorganic arsenic (iAs%), monomethylarsonic acid (MMA⁵⁺%) and dimethylarsinic acid (DMA⁵⁺%), as well as the primary arsenic methylation index (PMI, MMA⁵⁺/iAs) and secondary arsenic methylation index (SMI, DMA⁵⁺/MMA⁵⁺) were calculated for analyzing their relations with the risks of skin lesions. The logistic regression analysis results show that U-TAs is a risk factor of skin lesions (OR=1.038, 95% CI:1.003~1.073), while DMA⁵⁺% and SMI are protecting factors (OR=0.883, 95% CI:0.798~0.976; OR=0.724, 95% CI:0.535~0.978). Population with higher U-TAs and lower DMA⁵⁺% and SMI face higher risk of skin lesions.