Getting the Lead Out at the Tap: Corrosion Control Guidance for Canada

摘要

Health Canada has proposed a Corrosion Control Guideline, based on lead, which is undergoing public consultation and expected to be finalized in 2007. In Canada, there are no regulations and little guidance to address corrosion problems and existing sampling methods are inappropriate for developing corrosion control strategies. In Canada, responsibility for drinking water quality falls primarily under the jurisdiction of the provinces/territories. Health Canada works in partnership with the provinces/territories to develop the Guidelines for Canadian Drinking Water Quality (Guidelines). The Guidelines establish limits for substances at levels found in drinking water known or suspected to be harmful. They are published by Health Canada and used by all Canadian jurisdictions to establish their requirements for drinking water quality. The effects of corrosion and potential impacts on health are complex and varied. Corrosion is a common problem in Canadian drinking water distribution systems since many municipalities have aged iron pipes, lead service lines, leaded brass fittings/components and lead solder. Lead corrosion has been documented in a number of Canadian cities where lead levels exceeded the current lead Guideline. The proposed Guideline gives consideration to all materials and corrosion-related contaminants in distribution systems. However, lead is the contaminant with the most significant potential health effect and since there is no single, reliable method to measure corrosion in distribution systems, the level of lead at a consumer's tap is the primary focus of the Guideline. The Guideline proposes action levels and a two-tier approach for both residential and nonresidential buildings. For residential sites, the first action level is intended to assess the lead contributed from the home's interior plumbing and the lead service line, by collecting a 1L first flush sample after 6 hrs of stagnation. The second action level is intended to assess average exposure to lead and trigger corrosion control measures when the lead Guideline is exceeded. At sites exceeding the first action level, the system is flushed and a 2L sample collected after 30 min of stagnation. This sampling method is derived from a European Commission study that concluded that this was the best approach to identify the source of lead and provide a representative average of ingested lead.