Extreme heat: hefty bill to come, warns INRS study

A hefty bill awaits the Quebec health network over the coming decades if nothing is done to mitigate the impact of extreme heat, warns a team from the Institut national de la recherche scientifique that collaborated with the Institut national de santé publique du Québec and Health Canada.

“We have a lot of data on other types of natural disasters, that is to say floods, storms, hurricanes and all that, but we didn’t have a lot of economic data on heat waves,” explained the study’s first author, Jérémie Boudreault, who is a candidate for the customized PhD in data science and environmental health.

“We saw that the impacts on health were well documented, but we had nothing at the economic level.”

However, these data were essential to developing an economic argument for implementing adaptation measures, said Boudreault, especially since the impact of heat waves is more discreet than that of other disasters. “We don’t see monster floods or destroyed houses,” he illustrated.

According to the study, the burden associated with heat in Quebec amounts to $15 million annually in terms of health care (direct costs); $5 million in terms of absenteeism (indirect costs); and $3.6 billion in loss of human life and well-being, that is to say the reduction in activities during periods of extreme heat waves (intangible costs).

These costs are an annual average for the historical period from 1990 to 2019.

But be careful, warn the researchers: if no adaptation measures are taken, these costs are set to explode over the next 50 years, in the context of climate change and population growth.

For example, heat-related mortality and morbidity, as well as the number of extreme heat waves, could increase two-fold or even five-fold by 2050.

As for total costs, these will be multiplied by three, to $10.9 billion, according to a median climate and demographic scenario, and by five, to $17.4 billion, according to a more pessimistic scenario.

If we consider only the costs generated by extreme heat events, the authors say, the amount could be multiplied by three to 8.5, depending on the scenario that materializes.

“We really wanted to identify the costs for the health system,” said Boudreault. 

The authors point out, however, that this is a “hypothetical future,” since “biological acclimatization to heat and socio-economic adaptation” could reduce the impact of heat.

Even under the most optimistic scenario, heat-related health costs increase significantly by 2050 and are amplified by the increase in the population exposed to heat, they point out.

“Yes (the costs) can be higher, but they can also be lower if we put in place adaptation measures,” said Boudreault. “What we are presenting (in our study) is a status quo scenario. These are the costs that we can expect to pay at a minimum if we do not put anything in place.”

The study therefore highlights “the need to improve heat adaptation measures, such as strengthening greening, reducing urban heat islands or new alert systems, among others,” the authors say.

The health costs of extreme heat are as significant as those of other extreme weather events, but are often unrecognized or invisible today, according to this new study.

For example, the 2024 floods caused by Hurricane Debby cost Quebec $2.5 billion in insurable losses, while the intangible costs of heat are around $3.6 billion each summer in Quebec. These could even reach $17 billion in 2050 if no additional adaptation measures are adopted.

“The warmer the climate gets, the more it will cost,” concluded Boudreault. “With this data, we can take into account cost-benefit analyses. Now that we have the information, there is no reason not to act. When we talk about costs, it is difficult not to include them in economic analyses or in public policies. I think that politicians speak the language of money very well.”

The findings of the study, which was published in the journal Science of the Total Environment, were publicly unveiled Tuesday morning as part of the 10th edition of the Ouranos 2025 Symposium.

–This report by La Presse Canadienne was translated by CityNews