THMs in Drinking Water

What are THMs?

THMs are trihalomethanes, chemical compounds that can be formed when water is disinfected with chlorine. THMs occur when chlorine reacts with organic matter, naturally present in water, such as decaying leaves, and for this reason THMs are common in surface water supplies (lake & rivers) throughout Canada.

Is there a drinking water guideline set for THMs in drinking water?
The Canadian drinking water guideline for total THMs is 100 micrograms of THMs per litre of water (µg/L). This is set by Health Canada in consultation with the provinces and territories.
What are the potential problems of having THMs in drinking water?
There is concern among experts in Canada that THMs, may pose a risk in the development of cancer. Some studies report an association between elevated THMs and reproductive effects, though there is presently insufficient evidence to establish a specific relationship, suggesting the need for more studies.
If I'm worried about THM levels in my water supply, what can I do?

To reduce or eliminate THMs in drinking water use a water pitcher with an activated carbon filter, install a tap-mounted carbon filter, or to use bottled water. When using a filter, check to verify that it is certified to NSF Standards for removal of THMs and follow replacement instructions recommended by the manufacturer.
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 THMs present.
What is being done to reduce the levels of THMs in municipal drinking water?
The City of Saint John is working in conjunction with the New Brunswick Departments of Health to monitor the level of THMs so that they are within the guideline of 100µg/l. The City of Saint John is continuing to collect data through THM surveys, analyze data and pursue opportunities (cleaning and lining of pipe infrastructure, watermain flushing, unidirectional flushing) of THM formation reduction.
How can I obtain information about my drinking water quality?
If you are connected to the Saint John Water municipal water system, Saint John Water staff are available at 658-4455.
How do I test for THMs in my drinking water?
Individuals on municipal water supplies do not need to have their water supply tested because the City of Saint John regularly monitors water quality.

Saint John Water currently uses Maxxam Analytics whom is a CALA (Canadian Association of Laboratory Accreditation) accredited laboratory.
If you have a private well that does not mix chlorine with the water, there should be no need to test for THMs.

However, if you wish to have your water tested, please visit the following websites, to obtain the list of accredited labs, as well as to obtain the proper sampling vial as well as information on how to properly collect a representative water sample: CALA Directory of Laboratories

What should you do in the event of a boil water order?

Resources Icon
Environment Canada (Water)
Frozen Pipes - What to do
Saint John Water Annual Reports
Approval to Operate