Case-control study of chronic low-level exposure of inorganic arsenic species and non-melanoma skin cancer.

A significant relationship between arsenic exposure and non-melanoma skin cancer (NMSC) is well known. The toxicity of arsenics which develop NMSC is dependent on their species. Accordingly, total arsenic levels are unreliable for risk assessment of NMSC. However, there are few studies on quantitative exposure assessment of arsenic species in NMSC patients. To validate the contribution of each arsenic species to NMSC, we compared the creatinine-adjusted urinary concentration of arsenic species in NMSC patients and community controls. A total of 124 biopsy-proven NMSC cases and 125 age- and sex-matched community controls, drinking tap water with low-level arsenic concentration (<5 μg/L), were included in the study. High-performance liquid chromatography and inductively coupled plasma mass spectrometry were used for the measurement. The NMSC group was found to have significantly higher levels of total inorganic arsenic, trivalent and pentavalent arsenic and monomethylarsonic acid than the control group. Total arsenic, organic arsenic and dimethylarsonic acid levels were lower in the NMSC group. We suggest that inorganic arsenic species, trivalent arsenic and pentavalent arsenic may influence the prevalence of NMSC, in spite of these levels being lower than the Agency for Toxic Substances and Disease Registry-recommended standard or the levels reported by other highly contaminated areas and neighboring countries in East Asia. Furthermore, it also suggests that total arsenic level cannot represent the risk of NMSC.