4. Conclusion
This study investigated the human health risk from radon concentration and toxic elements in drinking and irrigated water collected from different locations of Sungai Petani, Malayisa. High radon concentrations were observed in well water sources with the highest observed value of (17.0 ± 1.67) Bq/l and low radon concentrations were observed in tap water sources with the hightest value of (7.0 ± 0.71) Bq/l. Average radon concentration in water collected from rivers was found higher then tap water. Values of radon concentration in well water exceed the EPA recommended level of 11 Bq/l but are below the action level of 100 Bq/l recommended by WHO, while in case of tap and stream water all samples were found below the action level of both US EPA and WHO. However it is recommended to boil the well water before use for drinking in order to decrease the level of radon concentration. The results reveal the fact that values of annual effective doses are below the permissable limit of ICRP and WHO. The order of distribution of toxic elements was Ni > Pb > Cd > As > Cr (5.63 > 5.18 > 2.81 > 2.51 > 2.19 mg/l, respectively) and found within recommended levels