The Heat is On for Canadian Health Care

For much of the summer of 2025, the sky in large parts of the Canadian prairies was filled with smoke, reminiscent of a post-apocalyptic Hollywood movie. That year marked the second-worst recorded wildfire season in Canada, eclipsed only by 2023 (when a record 15 million hectares were destroyed by fire). This past year, a total of 5997 individual wildfires were documented. More than 100 communities were evacuated in summer 2025 across the prairies. While the causes of the fires are multifactorial, they occurred on a background of the 11th-warmest summer since 1948, and the Government of Canada declared 85% of the country either abnormally dry or in drought. ¹

The consequences on health care facilities in affected areas were significant. Displaced peoples increased the catchment population of hospitals in receiving regions beyond what was planned for. More importantly, the air pollution which resulted from the fires markedly increased the PM_2.5 (inhalable particulate matter with a diameter of 2.5 µm or less) levels in the air far away from the sites of the fires. Studies have documented a clear increase in all-cause mortality and respiratory morbidity as PM_2.5 levels increase. Asthma and COPD exacerbations increase with decreasing air quality. There is additionally an increase in cardiovascular morbidity, particularly in the elderly population, and less-understood impacts on cancer rates, cognitive function and reproductive health and childhood development. One recent study specifically looking at the effects of wildfire-PM_2.5 in Canada between 2019 and 2023 estimated 1900 attributable premature deaths and a cost to the health care system ranging between $550 million and $6.4 billion over that period of time. ² Needless to say, this spending was not anticipated or accounted for in hospital budgets.

So far, we have discussed the health impact of wildfires, which expert opinion considers a consequence of rising global temperatures. Yet this is just one way in which heat has a negative impact on our health. In the absence of significant coordinated global action to reduce greenhouse gas emissions, experts predict an increase in mean global temperatures in the order of 2.5°C to 2.9°C by the end of the 21st century. This will have both direct and indirect effects on our health. Heat exhaustion and heat stroke have previously been uncommonly-encountered conditions in western countries, but as the population of people who are unhoused or who do not have access to climate control increases, those cases will rise. A substantial body of research has shown several other direct effects. Higher temperatures can exacerbate preexisting cardiovascular disease and lead to an increased incidence of myocardial infarction, uncontrolled heart failure, arrhythmia and stroke, to the point where a 1°C increase in temperature is associated with a 21% increase in the risk of death from cardiovascular disease. Dehydration leads to acute kidney injury, a higher rate of urinary tract infections, and formation of nephrolithiasis. Exacerbations of COPD and asthma can occur even in the absence of fires, purely from higher ambient temperatures. Psychiatric illness can be exacerbated by extreme heat, including anxiety, bipolar disorder or depression. Rates of preterm delivery, stillbirth and intrauterine growth restriction are also increased. Indirectly, heat can affect the viability of crops and reduce sources of potable water, leading to malnutrition and water-borne illness as other less ideal sources of water are utilized. ³

In this issue of the Journal, Dr. Yilmaz and co-authors explore the downstream consequence of these disease exacerbations on diagnostic imaging departments, estimating the excess imaging volumes that departments may face because of increases in temperature. They begin by evaluating the association between imaging utilization and ambient temperature between 2013 and 2022 and then extrapolate that to future. The predictions vary depending on which Shared Socioeconomic Pathway (SSP) is utilized as the foundation for prediction. These SSPs are predictive models which estimate how society may develop under a number of hypothetical scenarios, and how that may affect our environment. Predictive models examined in this paper include SSP1-2.6 (a best-case-scenario situation where there is a global shift toward lower emissions), SSP2-4.5 (what can be considered a continuation of current state) and SSP3-7.0 (a higher-emissions future which may occur due to reduced international cooperation, increased trade barriers and fossil-fuel dependence, and decreased climate innovation and adaptation as a consequence of reduced globalization). A few years ago, SSP3-7.0 seemed implausible but many would say that is no longer the case given current global instability. Under these models the authors report temperature-attributable increased emergency imaging volumes of 0.32% (SSP1-2.6), 0.75% (SSP2-4.5) or 1.25% (SSP3-7.0) by 2083 to 2092. ⁴

Let us not forget that there are dangers to the population of Canada from climate change that we have not even touched on yet. Coastal areas will flood, and natural disasters beyond wildfires are predicted to increase over time. Communicable diseases will rise. As people cluster indoors for climate control, it is easier for infectious diseases to spread. The changing environment may prove more hospitable for ticks and mosquitoes, leading to more cases of Lyme disease and West Nile virus. Hantavirus and parasites normally confined to warmer climates could spread north. Water quality is expected to decrease independent of temperature. Furthermore, these effects will likely be felt more by Canadians of lower socioeconomic status who are less able to mitigate the effects, and this will likely worsen inequality. ⁵

Many may feel a sense of hopelessness in the face of these sobering facts, and wonder what can be done. Dr. Yilmaz highlights the importance of preparation and adaptation for imaging departments as well as broader efforts to combat climate change. ⁴ Radiologists can do their part by being conscious of the energy we use in the course of our job. Increased efforts to power down equipment when not in use, improve appropriateness of diagnostic imaging studies, abbreviate protocols and use lower-energy modalities (magnetic resonance utilization generates more CO₂ than computed tomography, which generates more than ultrasound). We can encourage vendors to prioritize environmental sustainability in their research and development, and to minimize medical waste generated by their products. ⁶ We are not helpless, and it is time to act.