On December 11, 2019 3:30pm at 1201 Richcraft Hall, Carleton University, Ottawa-Carleton Chemical and Environmental Toxicology Seminar Series is pleased to host Dr. Ivy Moffat, Senior Evaluator, Water Quality Division, Safe Environments Directorate, Health Canada.

Dr. Moffat will be presenting ‘Guidelines for Canadian Drinking Water Quality: Prioritization Process & Development of a Value for Chromium’.

Health Canada, in collaboration with the Federal-Provincial-Territorial Committee on Drinking Water, develops and publishes the Guidelines for Canadian Drinking Water Quality for chemical and microbiological parameters. For chemicals, the guidelines specify the maximum acceptable concentrations of a chemical(s) in drinking water. As part of our cyclical 5-year chemical prioritization process, Health Canada used a framework that integrates tiered exposure and hazard information into risk plots for iterative rounds of decision making. From 421 potential chemicals for evaluation, we prioritized 62 high, 290 low and 69 wait priority chemicals. This process provides a science-based, methodologically-robust and transparent way to identify and prioritize chemicals/groups requiring the development of a drinking water risk assessment.

Chromium was a chemical that required the development of a drinking water risk assessment. However, the risk assessment of chromium is complex. To better understand this complexity, the essential information on exposure, toxicology and mode of action (MOA) on which agencies based their risk assessments are provided. Humans are exposed to an average of 0.2–2 μg hexavalent chromium per liter in drinking water through natural erosion of soil and rocks or by contamination from industrial sources. Internationally, drinking water limits for total chromium range from 50 to 100 μg/L. These values are based on intestinal toxicity data from experimental animals, since human toxicity data via the oral route are lacking. MOA analysis supports a progression from noncancer to cancer effects via a nonmutagenic MOA and therefore a threshold approach is appropriate for the risk assessment of chromium in drinking water. Drinking water limits derived from this approach are measurable by available analytical methods and achievable by available treatment technologies, and are protective of both cancer and noncancer effects.