Objective: Recent studies have shown that generation of reactive oxidants during arsenic metabolism can play an important role in arsenic-induced injury. The purpose of this study was to examine the relationship between arsenic in drinking water and oxidative stress in humans by measuring 8-Hydroxy-2 0 -deoxyguanosine (8-OHdG). Methods: We performed a cross-sectional study in an arsenic-affected village in Hetao Plain, Inner Mongolia, China. A total of 134 of the 143 inhabitants (93.7%) of the village participated in the study. The levels of 8-OHdG, arsenic and its metabolites were measured in urine collected from the participants. Regression analyses were performed to investigate the relationship between arsenic species and 8-OHdG levels in urine. Results: In the polluted village, monomethylarsenic was significantly higher in subjects with arsenic dermatosis than those without dermatosis despite no difference in mean levels of arsenic in well water between both types of subject. For subjects with arsenic dermatosis, arsenic species and metabolites in urine are significantly associated with 8-OHdG, while there was no statistically significant relationship for subjects without arsenic dermatosis. For all residents of the polluted village, the levels of dimethylarsenic and 8-OHdG were significantly higher for those who had been exposed to well water for more than 12 years. Conclusions: These results provide evidence of a link between exposure to arsenic from drinking water and oxidative stress, which may play an important role in arsenic-involved injuries.

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Arsenic removal from contaminated groundwater using microorganisms is a desirable alternative to conventional methods. In this study, Bacillus cereus strain W2, which was isolated from soil in Miyazaki Prefecture, Japan, was examined for its potential to remove arsenic. Strain W2 was capable of removing arsenic from culture medium supplemented with either As(III) or As(V). When grown in medium containing 50.0 mg As (III)/l, strain W2 removed 1.870 mg As per gram of dry cell weight in 12 h. In experiments of arsenic adsorption by dried cells of strain W2, the ratio of As(III) adsorption by strain W2 ranged from 97.3 to 99.1% in solutions containing up to 1.0 mg As/ l. Arsenic concentrations in solution decreased to 0.01 mg As/l or lower with initial concentrations of As(III) up to 0.5 mg As/l. The arsenic-removing capacity of strain W2 is higher than marine bacteria and genetically-modified Escherichia coli reported to date. These promising results indicate that strain W2 can be utilized for the bioremediation of arsenic-contaminated water.

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Biomethylation of arsenic is usually considered as a detoxification of arsenic because toxicity of most organic methylated arsenic is much less than that of inorganic arsenic. We investigated the feasibility of a novel bioremediation using an arsenic methylating bacterium. An arsenic methylating bacterium Bacillus cereus strain R2, isolated from soil in Miyazaki, was evaluated for growth characteristics and arsenic metabolism. The growth of strain R2 was inhibited in 50.0 mg As/l arsenic medium. Strain R2 metabolized arsenite (<5.0 mg As/l) to nonvolatile species such as monomethylarsonic acid, dimethylarsinic acid and trimethylarsenic oxide effectively. The percentage of organic methylated arsenic excreted into the medium by strain R2 showed 89.0% of total arsenic compounds when strain R2 was cultured aerobically in the medium containing 0.1 mg As/l of arsenite and 1.0 g/l of glucose for four days.