Concentrations and health risk assessment of trichloromethane and carbon tetrachloride in municipal water supply of Beijing

Objective To understand the average concentrations and potential health risks of trichloromethane (CHCl₃) and carbon tetrachloride (CCl₄) in municipal water of supply Beijing after the implementation of South-to-North Water Transfer Project.

Methods The monitoring data of CHCl₃ and CCl₄ in treated water, tap water, and secondary water supply were collected in Beijing during 2015-2019. The four-step health risk assessment model recommended by United States Environment Protection Agency (USEPA) was adopted to assess the health risk of them.

Results A total of 4 292 water samples were collected, the average concentrations of CHCl₃ and CCl4 were 0.003 mg/L and 0.000 62 mg/L, respectively, and the qualified rates were both 100%. The carcinogenic risk values were 3.23×10^-6 for CHCl₃ and 1.51×10^-7 for CCl₄; the non-carcinogenic health risk values were 1.04×10^-2 for CHCl₃ and 5.39×10^-4 for CCl₄.

Conclusion The health risk of CCl₄ in municipal water supply of Beijing was low, and the health risk of CHCl₃ was within the acceptable range. The South-to-North Water Transfer Project has greatly changed the quality of municipal water supply of Beijing, and still needing to continue the monitoring of water quality and propose risk management measures.