MCL: 0.08 ppm
Source: Water treatment disinfection byproduct, largely from chlorination.
Summary: Trihalomethanes (THM) form as a byproduct of using chlorine in disinfection processes for water treatment. The trihalomethanes are a group comprising four chemicals: chloroform, bromodichloromethane, bromoform, and dibromochloromethane. The total concentration of trihalomethanes may is federally regulated and should not exceed 0.080 ppm.