xtreme heat episodes result in significant morbidity, especially in northern latitudes or areas influenced by more temperate climates. 1,2 A recent meta-analysis showed that both environmental factors, such as the absence of air conditioning, and population risk factors, such as having cardiovascular or psychiatric co-morbidities, increase the probability of heat-related deaths. 3 Following the European heat wave of 2003, 15,000 excess deaths were reported in 12 European countries during the first week of August and approximately 24,000 during the second week. 4,5 This event prompted many countries to initiate or reinforce heat health watch warning systems to avoid high levels of excess mortality. 6,7 To counter the effect of extreme heat, the Montreal public health department has developed a heat response plan in collaboration with the regional and local public health network and municipal partners. This plan has been in effect since 2004. Its development was prompted by the large increase in mortality following the 2003 heat wave in Europe. Although preventive measures following Environment Canada's heat warnings have been issued to the population since 1994 and a communication campaign was initiated in 2002, the Montreal health department heat plan was undertaken by public health authorities to describe actions under different alert levels with local partners. Indeed, although the heat response plan is addressed to the public health network, public health actions are coordinated with municipal and civil security partners. Health and weather surveillance is an important component of the plan, both for immediate intervention and for updating the plan. These indicators serve as a basis for determination of different levels of action during the summer period. The main objective of the Montreal heat response plan (MHRP) is to reduce heat-related mortality and morbidity. In order to attain this objective, the plan must clearly identify and coordinate actions to be undertaken under different alert levels by partners at the regional public health and municipal level. The MHRP also serves as a guide for the health and social services network (e.g., hospitals or health and social services centres) to develop their own local heat plan for the people they serve. The following paper presents a brief overview of the Montreal heat response plan and its implementation in Montreal during the July 2010 heat wave, which was the first time the Intervention level was

ehicle traffic emissions result in a complex mixture of carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (mainly ultra-fine particles) and air toxics (1,3-butadiene, benzene, formaldehyde, polycyclic aromatic hydrocarbons-PAHs). For the province of Quebec, approximately 75% of NOx and 14% of PM 2.5 (particulate matter with median diameter of less than 2.5 μm) emissions are related to mobile sources. 1 Epidemiological studies that evaluate the relation between longterm exposure to traffic emissions and health outcomes have been reviewed in a number of studies. 2-6 Exposure to traffic-related air pollutants has been linked to premature mortality. 7-10 Epidemiological studies have also linked traffic pollutant exposure to cardiovascular outcomes like myocardial infarction. 11-13 Birth cohort, case-control and cross-sectional studies have also been performed to assess childhood exposure to traffic emissions and incidence and prevalence of asthma and asthma-like symptoms. 3,14-16 According to the Health Effects Institute (HEI) review of the literature, of the many outcomes of traffic-related exposures, asthma in children has been judged to have between sufficient and suggestive evidence to support a causal relationship with traffic exposures. 3 Furthermore, exacerbation of respiratory symptoms in children with asthma was judged sufficient to infer a causal association with traffic exposure. The increasing prevalence and incidence of asthma in Canadian cities, 17 especially in children, is an issue that requires further attention. Computation of asthma risks attributable to exposure to traffic-related pollutants can thus help orient policies and interventions related to transportation and public health. The focus of this study was an attempt to assess the range of prevalent asthma cases in children attributable to residing near a major road or highway on the Island of Montreal. METHODS Initial scoping of health risk functions The study selection on asthma prevalence and proximity to major roads or highways was based on the previous literature review per

The framework proposed in this study revealed valuable information that can be useful to improve plans aimed at reducing heat-related health effects in the population.

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