You’re exposed to chlorine by-products when you use water treated with chlorine. This includes drinking chlorinated water and breathing in water vapour during showering, swimming and other activities.
Chlorinated water has chlorine (a chemical) added to it. Chlorine disinfects the water and makes it suitable to drink.
Clean drinking water protects Canadians from illnesses caused by bacteria and other microbes in untreated water. These illnesses include cholera, giardiasis and sickness caused by the bacteria Escherichia coli (E.coli). E. coli can cause diarrhea, abdominal cramps and sometimes more serious illness.
Chlorine is a strong chemical, but the chlorine itself is not the main cause for concern in drinking water. When chlorine interacts with organic matter (such as dead leaves and soil) in untreated water, it forms new chemicals that remain in the water. These are called chlorination by-products. It is chlorination by-products that can increase cancer risk.
The amount of chlorination by-products formed during water treatment depends on the amount of chlorine used and on the amount of organic matter in the water.