Canadian Drinking Water Guidelines Development Process

2. Identification

In order to be considered for guideline development, the following questions regarding Substance X must be asked:

• Could exposure to the substance lead to adverse health effects?
  
  
• Is it frequently detected or could it be expected to be found in a large number of Canadian drinking water supplies?
  
  
• Is the level at which it is detected, or could be expected to be detected, of possible health significance?]

If the answer to these questions is yes, Substance X would receive further consideration for guideline development. It should be noted, however, that the focus of DWS is on parameters of national significance (i.e., substances that are of interest and concern across the country and/or to multiple jurisdictions).

In deciding whether a need exists for a guideline, the DWS Secretariat must establish that controlling the substance in drinking water would have an impact (i.e., does control of Substance X have "clear potential, based on sound research evidence, to significantly improve population health and reduce disparities"?). In order to determine impact, the Secretariat must determine the availability of published literature and national field monitoring data on Substance X. Jurisdictions represented on DWS identify the availability of provincial field monitoring data on Substance X from existing, current or future sampling programs, as well as timelines for providing monitoring data summaries of this information. The provinces also identify additional information that may be needed (e.g., toxicity measurements, cost information, economic statistics) to assist in the assessment of the substance and possible subsequent guideline development process. Impact is verified through further research at the criteria summary preparation and review stages.

In setting the Priority List of substances to be reviewed, the Subcommittee uses a multiple rating system based on frequency and concentration of detection, health effects and professional judgement. DWS members are asked to rate each substance, first by rating how frequently it is detected in drinking water supplies, and then by rating the concentration at which it is usually detected in provincial drinking water supplies. Based on the first two ratings, DWS members rate the substance, using their professional experience and knowledge of water systems, within their jurisdiction. If no monitoring data are available to rate the substance, it is rated using only their experience and knowledge.

The Secretariat provides the health effects rating. Based on pre-health risk assessment or assessments from the U.S. Environmental Protection Agency (EPA) or World Health Organization (WHO), the Secretariat rates each substance (or group of substances) against its potential to cause adverse health effects.

With a summary of both exposure (e.g., concentration, frequency) and heath ratings and provincial data, DWS establishes the Priority List through a consensus process. The Priority List is limited to the six substances that have the most impact on drinking water quality and public health. The list contains the substances the Subcommittee is currently evaluating, priority substances awaiting assignment to an evaluator, and suggested substances that may be given priority at a later date.

f Substance X meets the above criteria, it is placed on the DWS list of substances for assessment or reassessment. The list containing Substance X and other parameters that are under review or scheduled for review by DWS is also reproduced in the Guidelines for Canadian Drinking Water Quality booklet, published once every two or three years.

DWS reviews the list every fall, and then submits it to CEOH for approval. If CEOH agrees with DWS's recommendation, further assessment of Substance X proceeds. If CEOH disagrees with DWS's recommendation, either the substance is dropped from the assessment list or more information is collected on the substance to better justify the initial recommendation.

At this stage, the Secretariat also consults with its partners in other jurisdictions. The Secretariat has a long history of coordinating its evaluations with similar work being undertaken at Health Canada, the U.S. EPA and/or WHO. For instance, the Secretariat is waiting until the EPA concludes its extensive research on arsenic before re-assessing the current Canadian arsenic guideline. Similarly, the EPA deferred its evaluation on uranium until the Secretariat finished its research on this substance.

Based on the information gathered from DWS members and other jurisdictions, the Secretariat establishes a schedule for the review of Substance X. It submits this schedule, along with schedules of other substances, to CEOH for review, comments and approval.