Children, the environment and cancer

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Specific environmental contaminants - VI

Chlorinated water

What you can do
at home
Ask your municipal water supplier for a report on your water quality. If you are still concerned, you may be able to reduce your intake of these chlorine by-products somewhat by drinking filtered tap water. If you use point-of-use filtration devices (usually activated carbon filter systems in your water pitcher or attached to your tap) or point-of-entry devices (for whole house water treatment), make sure the products are certified to NSF standards and that the filters are changed according to the manufacturer’s instructions to avoid contamination from bacteria and other microbes.

Levels of disinfection by-products may not be reduced by all types of products mentioned here. In addition to this, you can still be exposed to disinfection by-products via showering and other activities. If you are concerned, the best solution is to advocate for changes within your municipality.

Bottled water does not have to be completely free of bacteria, and bacteria can re-grow during storage and transport. The low levels of bacteria are not generally a concern for healthy individuals, but those with a compromised immune system (such as people undergoing chemotherapy) may wish to avoid certain types of bottled water. Other bottled drinks fall under similar legislation. All individuals should regularly clean and disinfect their water coolers to avoid bacterial build-up.

In your municipality
The level of THMs and HAAs in your tap water can depend on where your municipality gets its water. Ask your municipality whether your water supply depends on ground or surface water. Ground water sources (from wells) will generally mean lower levels of THMs and HAAs in your tap water than surface water sources (from lakes, rivers).


The level of THMs and HAAs in your tap water can depend on where your municipality gets its water. Ask your municipality whether your water supply depends on ground or surface water. Ground water sources (from wells) will generally mean lower levels of THMs and HAAs in your tap water than surface water sources (from lakes, rivers).

• Ask your water treatment facility if they are meeting the Guidelines for Drinking Water Quality , especially regarding total levels of THMs and HAAs. Ideally, the levels of THMs and HAAs will be as low as possible while still disinfecting the water.
• The proposed guideline for total THMs is 0.1mg/L (100 parts per billion). If the level of total THMs in your water is higher than 0.1mg/L, ask your municipality what can be done to fix this.


• Currently, the proposed level of HAAs is 0.08mg/L (80 parts per billion), but is under discussion.


• Ask your municipality to publish its water-testing results if it doesn’t already do this.

If your THM and HAA levels are high, your municipality may be able to:

• remove or reduce the amount of organic matter while pre-treating the water


• provide better protection against contamination from organic matter (such as run-off from farms) for the current water supply


• use an alternative water supply, or move the water intake pipe to a more suitable location


• modify its disinfection strategies and use alternative disinfectants





Please note that alternate methods for water treatment can be very expensive to implement properly, and these costs generally are paid for by your local municipality. Larger municipalities may be able to make these changes more easily than smaller ones. Proper drinking water disinfection prevents many illnesses and deaths, and so improvements to your local facility must be made carefully.

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