Taipei Water Department

THMs stand for trihalomethanes. They are by-products of chlorine disinfection. When chlorine mixes with certain organic substances in water, THMs are formed. Animal studies have shown that high concentrations of THMs are a potential carcinogen. The National Drinking Water Regulations currently set the MCL (maximum contaminant level) for THMs as 80ppb (parts per billion). The tap water in Taipei has been tested regularly. All the data indicate that the level of THMs in your tap water is less than 10ppb, well below the MCL.