What's In My Tap Water?

The water that comes out of your faucet looks clean and clear, but you still may wonder, "Is my tap water safe?" This is an excellent question because chlorine and fluoride, the two most common chemicals added to tap water in Canada, have the potential to cause a range of health problems including cancer, pregnancy complications, brain damage and other issues.


Municipalities add chlorine to tap water to kill dangerous microorganisms, but when this chemical comes in contact with organic matter in the water, it reacts to form dangerous compounds called trihalomethanes (THMs). Several studies link these compounds to serious health issues. While many municipalities are beginning to reduce chlorine usage or introducing methods to decrease THM formation, chlorine is still the most widely used disinfectant in Canadian municipal water supplies.

Chlorine and Cancer

Consumer advocacy groups have proposed links between chlorine in tap water and many types of cancer, but the two types of cancer most strongly associated with exposure to chlorinated tap water are bladder and colon cancer. A study published in the American Journal of Epidemiology in 1995 found a link between chlorine byproducts in tap water and colon cancer. A separate study published in 2007 in the same journal found that drinking chlorinated water increased an individual's risk of developing bladder cancer twofold.

Miscarriage, Stillbirth and Birth Defects

A study by the California health department showed a greater than 15 percent increase in the risk of miscarriage among pregnant women who drank five or more glasses of chlorinated water each day. In another study, researchers from Dalhousie University reported that women who drank tap water with high THM levels had twice the risk of stillbirth as those who did not drink water high in THMs. In addition, a study from Norway found a 14 percent increase in the risk of birth defects in babies born to mothers exposed to chlorinated water.

Other Health Problems

Other health problems with proposed links to chlorinated tap water include allergies, heart disease, asthma and fatigue. More research is needed on these topics before scientists can make recommendations.


Health Canada, a federal department responsible for promoting health among Canadians, estimates that 45.1 percent of Canadians have fluoridated tap water in their homes. Municipalities add fluoride to tap water because it decreases the deterioration of tooth enamel to help prevent tooth decay. Unfortunately, the presence of fluoride in water has potential environmental and health consequences.

Bone Cancer

Epidemiological and animal studies have suggested a possible link between fluoridated water and osteosarcoma, a form of bone cancer. A 2006 Harvard study suggested that boys who drink water with fluoride might be at higher risk for developing this aggressive form of cancer.

Brain Damage

High levels of fluoride are toxic to brain tissue in adult humans, and fluoride ingestion also causes memory and learning problems in laboratory animals. A study published in Environmental Health Perspectives in 2012 showed that ingesting fluoride adversely affected brain development in children. Children ingesting water with high fluoride levels had lower IQ scores than those not exposed to high fluoride levels.

Dental Fluorosis

Children exposed to high levels of fluoride when their teeth are forming display signs ranging from small areas of white discoloration on their teeth to pitting in their tooth enamel and brown spots on their teeth. Called dental fluorosis, this problem is cosmetic, but it indicates potentially dangerous exposure to high fluoride levels.

Bone Fractures

Ingestion of water with high fluoride levels might make people more vulnerable to certain fractures. Some epidemiological studies show a potential link between increased risk of hip fractures and ingestion of fluoridated water.

What to do

The best way to answer the question, "Is my tap water safe?" and protect your family is to find out what is in your water. Because chlorine and fluoride usage varies by municipality, you need to contact your local water provider for the most accurate information. Armed with this information, you can choose a water filter that will remove impurities from your water.