Federal-provincial Subcommittee on Drinking Water - 22nd Meeting - Aylmer, Quebec, April 20-22, 1998

The twenty-second meeting of the Federal-Provincial Subcommittee on Drinking Water (DWS) was held in Aylmer, Quebec, April 20-22, 1998. The development of new guidelines, or the revision of existing guidelines, were discussed for the following parameters:

Aluminum

Comments received during the public comment phase (April to December 1997) were reviewed. A summary of and response to comments received will be developed and sent to all those who provided comments, noting that a specific operational value will not be provided. The response will emphasize that the goal should be the lowest achievable value. The criteria summary will be revised in a similar fashion, emphasizing the lowest achievable value in the guideline statement. The It's Your Health publication will be revised to address home owners with individual wells. The results of the consultation will be presented to the Federal-Provincial Committee on Environmental and Occupational Health (CEOH).

Antimony

The proposed interim Maximum Acceptable Concentration (IMAC) guideline for antimony in drinking water of 0.006 mg/L was approved by CEOH after a lengthy discussion. The guideline value and support document will be published.

Arsenic

The rough draft of the treatment summary concerning arsenic is complete, but a much more exhaustive literature review is required before the summary can be finalized. Health Canada is proposing a research project in Saskatchewan on small water treatment processes, including individual supplies. The practicality of treatment for individual home owners' private supplies needs to be reviewed. Further evaluation has been postponed until spring 1999. The EPA will be consulted regarding the progress of their health re-assessment for arsenic.

Bromate

The document was available on Health Canada's website for public comment until June 30, 1998. Quebec is surveying the remaining ozonated water systems with Health Canada, which will complete sampling of all of Quebec's ozonated water plants. The Secretariat will prepare a summary of consultation comments and a revised criteria summary based on the comments prior to the next meeting.

Chlorate-Chlorite-Chlorine Dioxide

Both WHO and EPA have assessed the health risks associated with, and established limits for, chlorite and chlorine dioxide in drinking water. The Secretariat's literature review is continuing. However, it will be difficult to develop a chlorate guideline from the data available. Currently, over twenty water treatment plants are using chlorine dioxide. An epidemiological study in Quebec (results in 1998) is currently underway related to infants and exposure to chlorite and chlorate in drinking water.

Fluoride

The guideline for fluoride in drinking water was confirmed at a Maximum Acceptable Concentration (MAC) of 1.5 mg/L and was reported to CEOH. The optimum range for fluoride, however, was reduced to 0.8 to 1.0 mg/L (value reported incorrectly in May 1997 minutes). Calgary commissioned an expert review of the guideline and suggested a level of 0.7 mg/L for fluoride addition. The Calgary Review Report will be assessed and a recommendation on the need to re-evaluate the fluoride criteria summary will be provided. A draft report, Drinking Water Fluoridation in Canada: 1996, an update of the 1986 Fluoride report, and its data are currently being verified by Members.

Formaldehyde

The DWS decision to not develop a numerical guideline for formaldehyde in drinking water was reported to CEOH. The EPA has a standard for formaldehyde in drinking water and the value is similar to the limit suggested by the Secretariat's assessment. The value, however, is almost ten fold higher than the highest values found in Canada's drinking water supplies.

Haloacetic Acids

Work is continuing on health assessments for haloacetic acids in drinking water. Data is available for mono-, dichloro-, and trichloro-, but there is limited evidence for the brominated compounds. Overall exposure data in Canada is limited; most of the information available is from the 1995 national survey and from the province of Alberta.

Bacteriological

The few comments received during the comment period will be included in the revised Criteria Summary, where appropriate. The move to the "presence-absence" method reduces the need for a value and, therefore, the need for a guideline statement to determine compliance. The Criteria Summary will be revised, reviewed, published and posted on the website.

Protozoa

Eighteen sets of comments were received during the comment period. Most participants were dissatisfied with the guideline statement stating it was inappropriate to provide an unmeasurable value. A summary of and response to comments received will be developed for DWS review prior to distribution to all participants. The summary will include a risk communication strategy which will provide a brief description on the direction the guideline may take. The Secretariat will revise the Criteria Summary at a later date.

Viruses

The consultant's report in the agenda package will be the basis for drafting the Criteria Summary on viruses in drinking water. Like protozoa, viruses are difficult to monitor and routine monitoring is not possible at this time. Therefore, the Criteria Summary for viruses in drinking water will wait for the development of the protozoa Criteria Summary. A Quebec task-force recently completed a review of virus outbreaks related to food and water. The task- force's recommendations will be forwarded to the Secretariat for distribution.

Boil Water

Few comments were received concerning the draft document. Any instructions must be kept general since so much depends on an understanding of the specific water system and the health of the community. The draft document should suggest that the microbiological quality of the water is most important. The presence of indicator organisms usually does not warrant an immediate order to be issued. The summary will be revised and submitted to DWS for quick review and then will be distributed.

Microcystin-LR

The package for public comment on cyanobacterial toxins in drinking water is now ready for distribution. Hard copies of the package in both English and French were provided to all provincial and territorial DWS members. Copies will be provided to national organizations. WHO is doing a complete monograph on cyanobacteria covering all media.

The Saskatchewan & Partners research project will look for a readily accessible and affordable analytical method with a field capability focussing on the cyanobacterial hepatotoxins. There is a need to determine if the water is safe to drink during and after an algal bloom. Initial support for this research project came from Saskatchewan, Health Canada, Ontario and Manitoba.

Turbidity

The Criteria Summary is still being updated; a revised summary will be ready for the next meeting. An interesting research news clipping suggested a direct link between increased turbidity and increased admissions related to incidents of gastric problems in children.

Uranium

The revised Criteria Summary on uranium in drinking water is based on Dr. Gilman's papers, now published. The document suggests a MAC of 0.01 mg/L with common concentrations of uranium in drinking water, ranging from 0.005 to 0.05 mg/L. Based on a 90 day toxicity study on rats, the proposed guideline was calculated using an uncertainty factor of 100 and an allocation factor of 35%. Since the amount of uranium in food in Canada is fairly constant, the allocation factor is tied directly to the concentration of uranium in the water and is based on Canadian data. The risk assessment presented here is the same assessment used by WHO to establish its guideline at 0.002 mg/L.

Provinces were asked for additional data on cost and exposure. A draft public comment document will be distributed to DWS members for review and comment.THMs & Great Lakes Basin Cancer Risk Assessment (THMs & Chlorinated DBPs Working Group)

The current guideline (1993) was based on the cancer risks for chloroform as found in rodent studies. The trihalomethanes (THMs) guideline value (0.1 mg/L) was established through risk management with qualifications concerning the microbiological quality of the water and to reduce concentrations of THMs to as low a level as possible. Several new epidemiological studies have been conducted since 1993. A 1995 Great Lakes study showed increased risk for bladder cancer in consumers exposed to waters with THMs higher than 0.05 mg/L for 35+ years. In 1997, Health Canada sponsored a workshop, in which expert toxicologists and epidemiologists assessed the available data. The group concluded there was a possible to probable association between chlorinated disinfection by-products (CDBPs) and bladder cancer, but that there was not sufficient data to do a risk/cost/benefit analysis.

A well-conducted 1998 epidemiological study from California reported an increased risk of miscarriages for women drinking > or = 5 glasses/day of water containing > or = 0.075 mg/L THMs. An even higher risk was noted for bromodichloromethane concentrations > or = 0.018 mg/L. Additional recent studies looking at THMs and adverse reproductive and developmental outcomes have been conducted in Nova Scotia/Prince Edward Island and New Jersey. However, recent mechanistic studies on chloroform, the most predominant THM, raise questions about the relevance of the health risks from this compound at concentrations found in drinking water.

Health Canada has proposed a working group on CDBPs to address the issue in two phases. The first phase would try to reconcile the differences between the toxicological and epidemiological data, estimate the health risks and determine if there is a need to revise the THM guideline. The second phase would weigh the estimated costs of health care versus controlling THMs levels and the potential benefits from the control measures.

Chlorinated drinking water is a soup of disinfection by-products (DBPs), therefore the epidemiological studies may not clearly identify what the problem is or which parameter(s) should be addressed for treatment improvements. DWS is already evaluating other DBPs like HAAs which may or may not have an impact on the risk of cancer and adverse reproductive/ developmental effects. Precursor removal, as stated in the THMs guideline, is still the most sensible option, but first a review and risk management information are needed to provide direction. If precursor removal improvements are made, other benefits (microbiological risk reduction) will come about.

DWS Election

The committee unanimously approved G. Jenkins as chair and elected S. Théberge as vice-chair.

Next Meeting

• The next DWS meeting will be held November 1, 2 and 3, 1998.