Projecting the overall heat-related health burden and associated economic costs in a climate change context in Quebec, Canada.

Extreme heat represents a major health risk for the world's population, that is amplified by climate change. However, the health costs associated with these heat events have only been little studied. To stimulate the implementation of effective interventions against extreme heat, a more comprehensive economic valuation of these health impacts is crucial. In this study, a general framework for assessing historical and projected heat-related health costs is presented and then applied to the province of Quebec (Canada). First, heat-related mortality and morbidity, as well as the number of extreme heatwaves, were computed for a historical (∼2000) and projected (∼2050) period under two shared socioeconomic pathways (SSP). Then, these heat-related numbers were converted into 1) direct healthcare costs, 2) indirect productivity costs and 3) intangible societal costs, using the best available cost information. Results showed that historical heat-related health costs were respectively 15M$, 5M$ and 3.6G$ (in 2019 Canadian dollars) annually for the direct, indirect and intangible components in Quebec, Canada. Under a middle-of-the-road scenario (SSP2-4.5), there was a 3-fold increase in total costs due to climate and population change (10.9G$ annually), while under a pessimistic scenario (SSP5-8.5), the increase was 5-fold (17.4G$). Total costs were mostly driven by intangible impacts, such as loss of life (∼90-95%) and of well-being during heatwaves (∼5-10%). Given that heat-related health costs are already significant, and likely to increase substantially in the future, this study has demonstrated the vital need to reduce its burden now and in the future by adopting more measures to mitigate climate change and adapt to heat.