The principle and methodology of risk assessment was applied to establish the quality standard of potential impurities of drinking water treatment chemicals. The impurities(arsenic, lead, cadmium, chromium, mercury, etc.) are regulated as the contained quantity of chemicals in Korea while they are regulated as the quality standard with the idea of 10% of the national safety drinking water standard in U.S.A(NSF) and Japan(JWWA). According to risk assessment of the current standard implemented in Korea, the excess cancer risk of arsenic and lead were determined in around 10^(-5) and the hazard quotient(HQ) of cadmium and chromium were below 10^(-2), respectively. And the standard concentration of the impurities are regulated as much as 2%~6% of the national drinking water quality standard. The values are more enforced rather than the standards in U.S.A(NSF) and Japan(JWWA) regulating the concentration of impurities the 10% of the national drinking water quality standard. We conclude that the impurities standard of drinking water treatment chemicals should be reconsidered comprehensively concerning the national safety drinking water quality standard and risk assessment.