The Air Quality Health Index and all emergency department visits.

Through a variety of media formats, the Air Quality Health Index (AQHI) has served as a valuable communication tool for the general Canadian population for several years. This index, calculated and communicated to the public on an hourly basis, is designed to provide important information on the impact of air quality on health. This presentation outlines the association between AQHI values and, for the first time, all-cause emergency department (ED) visits (over one million diagnosed ED visits). It is assumed that a higher AQHI value, reflecting increased health risk, will encourage people to take steps to reduce their exposure, by limiting the duration and intensity of outdoor activity. The case-crossover methodology was used to assess the associations between the considered exposure and ED visits. The results, the estimated odds ratios, are presented as non-linear concentration-response functions. We argue that air health effects, measured as the total number of all-cause ED visits, are related to the values of the AQHI. We postulate that there are differences in this association between males and females, possibly due to gender-specific behavior and/or health conditions.