Chlorine in drinking water can have toxic effects on the human body, according to a study earlier this year. Long-term exposure to chemicals in drinking water can cause cancer. Chlorine is a common chemical used to clean the drinking water supply in the United States. It kills parasites, bacteria, viruses, and germs in our water, but how safe is it? Researchers found that chlorine may create harmful byproducts in water. This happens when chlorine interacts with organic community runoff and phenols. All sources of municipally supplied water contains unwanted chemicals and natural occurring Phenols. If untreated by a water treatment facility, these organics combine with the chlorine to form a chemical group called trihalomethanes which are all carcinogens. Also, phenols are in everyday hygiene products. Phenols may produce carcinogens (substances promoting cancer) upon contact with chlorine.