DISCUSSIONS
In this study the soil arsenic contamination both of household resident and farmers was higher than limit value of Nation Environment Board (NEB), Thailand at 3.9 mg/kg [9]. The median of soil arsenic contamination in household resident soil, farmer resident soil, and farm soil was 56.4, 42.3 and 25.3 mg/kg, respectively. The farmers and household resident were living in high soil arsenic contamination area. This result was agreed with the survey of ERTC, Thailand that arsenic concentration in soil was higher than limit value (NEB) at 380.1 mg/kg [8]. Arsenic compound might be the natural background of soil in this area. It was supported by the geology and mineral resources survey of S.A.P company ltd that Ongphra Subdistrict was rich of tin ore and there were two tins mine located. The consequence of mining operation was arsenic contamination that was found high level in soil [19]. But the level of