Risk Assessment of Chlorination Disinfection Byproducts from Ingestion of Municipal Tap Water Supply in Khon Kaen, Thailand
Keywords:
trihalomethanes (THMs), haloacetic acids (HAAs), dissolved organic carbon (DOC), free chlorine, rainy seasonAbstract
Introduction This study aimed at assessing for human health risk of disinfection by-products (DBPs) from chlorination of public tap water supply since DBPs have been reported of harms to human health. Methods Water samples were collected from 5 collection points along the municipal tap water supply route during rainy (September-October 2014) and after-rainy periods (November-December 2014). Analysis for THMs (Trihalomethanes) was by Purge and Trap and GC-ECD, for HAAs (Haloacetic acids) by LCMSMS.
Results Our study found THMs occurrence in water from the chlorination process and the concentrations were highest at the last collection point of water supply route. After-rainy periods water had significantly higher THMs than in rainy periods. Comparison of THMs levels from the best case scenario (finished water at the treatment plant) to US.EPA guideline values found the safety factors <1, i.e., for chloroform=0.95, for total THMs=0.72. The risk assessment found the threshold
toxicity of THMs in water was within acceptable range, but the lifetime excess cancer risk (non-threshold toxicity) from ingestion exceeded 243 fold the acceptable rate in the best case calculation and 363 fold in the worst case. However, the risks of HAAs in water were all in acceptable range.
Conclusion the cancer risk from THMs was of great concern for consumers of
Khon Kaen municipal tap water and people living at the last collection point of the water supply route were at greater risk compared to people living near the water treatment plant, particularly in the dry season.
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