Association of blood arsenic levels with increased reactive oxidants and decreased antioxidant capacity in a human population of northeastern Taiwan

Arsenic is a notorious environmental toxicant known as both a carcinogen an d an atherogen in human beings, but the pathogenic mechanisms are not compl etely understood. In cell culture studies, trivalent arsenic enhanced oxida tive stress in a variety of mammalian cells, and this association may be cl osely associated with the development of arsenic-related diseases. To inves tigate the effect of arsenic exposure on oxidative stress in humans, we con ducted a population study to determine the relationships of blood arsenic t o reactive oxidants and antioxidant capacity at the individual level. We re cruited 64 study subjects ages 42-75 years from residents of the Lanyang Ba sin on the northeast coast of Taiwan, where arsenic content in well water v aries from 0 to greater than or equal to 3,000 mug/L. We used a chemilumine scence method, with lucigenin as an amplifier for measuring superoxide, to measure the plasma level of reactive oxidants. We used the azino-diethyl-be nzthiazoline sulphate method to determine the antioxidant capacity level in plasma of each study subject. We determined arsenic concentration in whole blood by hydride formation with an atomic absorption spectrophotometer, Th e average arsenic concentration in whole blood of study subjects was 9.60 /- 9.96 mug/L (+/- SD) with a range from 0 to 46.50 mug/L. The level of ars enic concentration in whole blood of study subjects showed a positive assoc iation with the level of reactive oxidants in plasma (r = +0.41, p = 0.001) and an inverse relationship with the level of plasma antioxidant capacity (r = -0.30, p = 0.014). However, we found no significant association (p = 0 .266) between levels of plasma reactive oxidants and antioxidant capacity. Our results also show that the lower the primary arsenic methylation capabi lity, the lower the level of plasma antioxidant capacity (p = 0.029). These results suggest that ingestion of arsenic-contaminated well water may caus e deleterious effects by increasing the level of reactive oxidants and decr easing the level of antioxidant capacity in plasma of individuals. Persiste nt oxidative stress in peripheral blood may be a mechanism underlying the c arcinogenesis and atherosclerosis induced by long-term arsenic exposure.