Since the limit value for urinary arsenic level has not been set in Thailand yet. Therefore the urinary arsenic level in this study used the value recommended by American Conference of Industrial Hygienists (ACGIH) as limit value at< 35 μg/L; it would be the occupational safety and health standard approached. It was a guideline to assist in control of health hazard for 8 hour [2]. Most of farmers work 8 hours per day and every day in farm. If the recommendation of limit value was safe for the worker it should be safe for subjects or farmers who work under similar conditions. The farmer urinary arsenic level (4.5 μg/L) was higher than household resident (2.1 μg/L). There was one of the studies which were similar with this study that arsenic contamination in subject was higher than control group [22].But, it was different from the study of Gebel [23], which found the higher urinary arsenic level in control group. It is remarkably the study consumed traditional food such as seafood, tea and wine 3 days before urinary collection