Chlorination has played a critical role in protecting Canada's drinking water supply from waterborne diseases for nearly a century. According to the World Health Organization, the adoption of drinking water chlorination has been one of the most significant advances in public health protection.

Chlorine-based disinfectants are the only disinfectants that provide lasting residual protection to protect the water from waterborne disease throughout the distribution system from treatment plant to the consumer's tap. Alternatives to chlorination for primary disinfection such as ozone or ultraviolet light can not provide this residual protection. All chemical disinfectants produce by-products. Chlorination by-products have been well studied compared to the by-products of alternative processes which are just beginning to be studied.

According to:

• Health Canada's Health and the Environment Report published in 1997:
  • "Chlorine is a simple, effective, yet relatively inexpensive agent for destroying harmful micro-organisms in tap water, although it can generate potentially harmful by-products, such as THMs [trihalomethanes], which have been linked to certain cancers. A recent Health Canada study found that long-term consumption of chlorinated surface water with elevated levels of THMs is associated with an increased risk of bladder cancer and possibly colon cancer. The health risks associated with drinking unchlorinated water, however, are much higher than the risks posed by chlorination by-products as evident in developing countries with inadequate water treatment systems."
     
• Heath Canada's It's Your Health Fact Sheet on Chlorination March 1999:
  • "Current evidence indicates that the benefits of chlorinating our drinking water - reduced incidence of water-borne diseases - are much greater than the risks of health effects from THMs.
     
• The World Health Organization "disinfection by chlorine is still the best guarantee of microbiologically safe water."
   
• Pollution Probe's Ken Ogilvie - "Chorinated drinking water - Chlorination has eliminated more deaths than anything else." Toronto Star 01/01/00 - Survey of Top Environmental Accomplishments