Government of Nova Scotia Government of Nova Scotia Nova Scotia, Canada


Drinking Water

Haloacetic Acids in Drinking Water

What are haloacetic acids?

Haloacetic acids (HAAs) are a type of disinfection by-product that are formed when chlorine reacts with natural organic matter in the water. There are five significant HAAs in disinfected water and their combined concentration is referred to as total HAA5.

Is there a drinking water guideline set for HAA5 in drinking water?

The acceptable level, or guideline, for HAA5 in drinking water in Canada is set by Health Canada in consultation with the provinces and territories. The Canadian drinking water guideline for HAA5 is 80 micrograms per litre of water (µg/L). The guideline is based on a locational running annual average of a minimum of four quarterly samples. For more information, go to: Guidelines for Canadian Drinking Water Quality - Supporting Documents.

What are the potential problems of having high HAAs in drinking water?

There is concern that long-term exposure to elevated levels of HAAs may pose a risk in the development of cancer.

How may I be exposed to HAAs?

HAAs are present in chlorinated drinking water supplies due to the presence of naturally occurring organic matter in source water which reacts with chlorine. Water supplies relying on surface water generally have higher levels of chlorinated disinfection by-products than those relying on groundwater.

What if I have my own water well?

Most private well water supplies are not disinfected. The lack of chlorine disinfection means there should be no HAAs present.

Why don't we simply stop chlorinating our drinking water?

Without adequate disinfection of our water supplies, the health risks from micro-organisms would far outweigh the risks from HAAs. Drinking water is disinfected with chlorine to kill bacteria and viruses that can cause serious illnesses and deaths. In fact, chlorination of drinking water is one of the greatest achievements of public health protection having virtually eliminated typhoid fever, cholera and many other diseases.

Can HAAs be eliminated at the source?

The province is working with municipalities to develop strategies for reducing HAAs, including further treatment at the source. Research continues on new treatment methods that will reduce the levels of by-products while maintaining sufficient levels of disinfection to kill micro-organisms.

Which communities have the highest levels?

Levels normally vary within a single water supply depending on the season, water temperature, amount of natural organic matter in the water, pH, amount of chlorine used, time in the distribution system and other factors. For information regarding the HAA levels in your community's drinking water supply, please contact your local water utility or municipality. A listing is available at: Municipal Contacts.

How do I test for HAA5 in my drinking water?

Individuals on municipal water supplies do not need to have their water supply tested. Nova Scotia Environment requires municipalities to regularly monitor water quality. If you have a private well that does not mix chlorine with the water, there should be no need to test for HAA5. However, if you wish to have your water tested, please contact laboratories offering chemical analyses to find out what kind of bottle to use and how to properly collect a water sample. A laboratory listing is available at: Water Testing Labs in Nova Scotia.

For more information

Contact the nearest Nova Scotia Environment office.