Is there a drinking water guideline set for THMs in drinking water?
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.
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?
- DO NOT DRINK THE WATER WITHOUT BOILING IT FIRST. Bring water to a rolling boil, let it boil for at least one minute, and let it cool before using, or use bottled water.
- Boiled or bottled water should be used for drinking, brushing teeth, making ice, juice, coffee, tea or washing vegetables that will not be cooked.
- Boiling kills bacteria and other organisms in the water.
- People whose immune system is compromised, such as the elderly, infants and people with transplanted organs, on dialysis, with HIV/AIDS, etc. should pay attention to the use of a safe source of drinking water. Water that has been properly boiled is considered a safe source.
- It is safe for people to take showers, bathe and use swimming pools.
- It is safe to wash dishes in hot, soapy water and then air dry. It is safe to use a dishwasher.
- The presence of low chlorine means that disinfection may not be effective and thus there may be bacteria in the water that can cause illness in humans. These organisms can cause diarrhea, cramps, nausea, headaches, or other symptoms. They may pose a special health risk for infants, young children, some of the elderly, and people with severely compromised immune systems.
- Organisms in drinking water are not the only cause of the symptoms above. If you experience any of these symptoms and they persist, you may want to seek medical advice. People at increased risk should seek advice about drinking water from their health care providers.