Study on Chlorinated Disinfection Byproducts and the Relevant Health Risk in Tap Water of J City

J City lies in the downstream of Taihu Lake and its water source was micro-polluted by the well-developed industry and agriculture inside the city and in the upper stream.Tap water of J City is characterized as high concentrations of organics and ammonia nitrogen,and chlorinated disinfection byproducts(CDBPs),which has drawn many public concerns for the health risk.Tap water was sampled in May,August,October of 2012 and January of 2013.Four trihalomethanes(THMs) and five haloacetic acids(HAAs) were determined with the gas chromatography.Results revealed that THMs accounted for 88.1% of the sum of THMs and HAAs,with higher concentrations in May,August and January(39.34,50.37 and 28.02 μg.L-1,respectively) while obviously lower in October(19.19 μg.L-1),which were significantly higher than that of HAAs(2.58-4.02 μg.L-1).After boiled for three minutes,THMs were removed over 92.3% but HAAs were largely increased.The health risk of CDBPs was then calculated based on the health risk assessment model recommended by the USEPA.The health risk caused by carcinogenic CDBPs was within a range of 3.1 × 10-6-7.3 × 10-6 in the tap water,all over the recommended level of 1 × 10-6,but after boiled,the value significantly decreased to 7.9 ×10-7,which is below the recommended level.The health risk caused by non-carcinogenic CDBPs absolutely increased from 2.1 × 10-11 to 3.4 × 10-9 after boiled,which is below the reference value of 10-5.