Mr. Ken Dominie
Assistant Deputy Minister
Environment and Labour
Newfoundland Dept. of Environment
4^th Floor, West Block
Confederation Building
St. John’s, Newfoundland
A1C 5T7

Dear Mr. Dominie:

As you are aware, the disinfection of water supplies is paramount to a healthy Canadian population. The chlorination of drinking water has virtually eliminated water-borne diseases such as cholera and typhoid in the western world.

All levels of government have some responsibility in ensuring the safety of Canada’s drinking water. Provincial governments are responsible for setting and enforcing standards to ensure adequate drinking water treatment and municipalities who are responsible for supplying safe drinking water and conforming to provincial standards. Health Canada provides health and safety advice, sponsors research and cooperates with the provincial/territorial authorities under the auspices of the Federal/Provincial Subcommittee on Drinking Water (DWS) to develop the Guidelines for Canadian Drinking Water Quality.

In 1993 the DWS established a Canadian drinking water guideline of 100 parts per billion (ppb) or micrograms per litre (mg/L) for THMs. The guideline was based on the risk for cancer reported in animals for chloroform, the THM most often present and in greatest concentration in drinking water. To take into account the seasonal variability of THM levels, the guideline was based on an annual average.

Trihalomethanes (THMs) are only one subgroup of the many disinfection by-products formed during chlorination and are used as indicators of overall chlorination disinfection by-product (CDBP) formation.

Since publication of the 1993 guideline, new epidemiologic studies have been published which reported associations between THMs and cancer (e.g., bladder, colon) and adverse pregnancy outcomes (e.g., miscarriage, birth defects, low birth weight). In response to these findings, Health Canada has established a multi-stakeholder Chlorinated Disinfection By-Product Task Group to comprehensively assess and update the health risks from THMs in drinking water and develop recommendations for controlling those risks. This is being done through a series of subgroups to evaluate evidence of health effects from THMs, drinking water quality data and water treatment facility characteristics and options for water treatment upgrades in communities across Canada. The provinces and territories, including Newfoundland and Labrador, are involved in both the Task Group and the Federal-Provincial Subcommittee on Drinking Water. Recommendations of the Task Group are expected to be submitted to the DWS for consideration in 2001.

The CDBP Task Group has prepared Qs and As, in the form of an Information Sheet (attached), on the safety of chlorinated drinking water which it is sharing with the Newfoundland government. This and other information related to Health Canada’s work on the Task Group and on chlorination disinfection by-products can be found on our world wide web site at: //www.hc-sc.gc.ca/waterquality    (/eauqualite).

Further, in order to provide advice to consumers, Health Canada laboratories are currently testing a range of carbon filters and other treatment methods to see if they are able to remove most CDBPs. The results will be made public within a year. In the meantime, consumers wishing to reduce their exposure to chlorination disinfection by-products can use a filter containing activated carbon certified to the NSF Standard 53. Blending and boiling the water will remove some THMs, but does not eliminate all of the disinfection by-products and may actually increase levels of others.

In conclusion, Health Canada strongly supports the disinfection of drinking water to reduce the risk of waterborne infectious diseases. Without adequate disinfection, the proven health risks to Canadians from micro-organisms would outweigh the possible health risks from THMs. The potential risks of cancer and adverse pregnancy outcomes associated with drinking water containing THMs are much lower that the risks of serious illness and death that could result from drinking water that has not been properly disinfected. It is extremely important that water treatment plants ensure that methods used to control chlorination by-products do not compromise the effectiveness of water disinfection.

Yours sincerely,

 

J. Z. Losos, M.D.
Assistant Deputy Minister

Attachment

cc: Beverley Clark, ADM Nfld Health