Recent scientific research has shown that adverse health effects can be experienced at pollutant concentrations which were previously thought to be safe. In 2001, in response to this, and other technological and policy drivers, the government of Canada, through Environment Canada (EC), initiated a multi-stakeholder process to improve the Canadian Air Quality Index(AQI). The need for a health risk based AQI was determined through the stakeholder process. Using epidemiological research, Health Canada (HC) has developed a health risk based AQI formulation using pollutant co-efficients supported by a meta-analysis of international scientific literature. The pollutants used in the index are PM2.5, ozone, sulphur dioxide and nitrogen dioxide.

Health messages are key to the effectiveness of an AQI. The development of the health risk based index involves the crafting of descriptive and prescriptive messages which inform and empower citizens to takes steps to protect their health and reduce their contribution to the air quality burden. The paper will explain the strategy being employed to develop these messages and integrate them into the presentation of the AQI.

The fact that health effects of some pollutants can be experienced at very low levels increases the importance of timely and accurate air quality forecasts to help citizens take action to protect their health. This paper also deals with the forecasting concerns which will accompany the implementation of a new national AQI program for Canada.