Trihalomethanes (THMs) are a byproduct of the water treatment process. Trihalomethanes (THMs) can be be found in chlorinated water supplies. The disinfection byproducts of the chlorination process include a group of chemicals known as Trihalomethanes (THMs). THMs include four chemicals: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. The U.S. Environmental Protection Agency (EPA) has mandated public water systems check for THMs on a regular basis and that the level of THMs in the water should be less than 80 parts per billion (ppb). The EPA has set standards for THMs in water because there is a slight possibility of an increased risk of bladder or colorectal cancer over a lifetime of drinking water with THMs above 80 parts per billion. THMs are also environmental pollutants, and many are considered carcinogenic. They are Cancer Group B carcinogens (shown to cause cancer in laboratory animals). THM's are not only ingested by the water that we drink but also by inhaling them in the shower. The recommended treatment for THMs is activated carbon filtration or Reverse Osmosis.