As I write this post, Toronto is enveloped by haze from wildfires burning in northern Ontario and the Prairie provinces. The air quality is poor, and it is hot—so hot that dogs are finding shade and refusing to continue to walk and heat warnings have been issued.
The twin health hazards of polluted air and extreme heat will surge in the coming years, and the frequency of days when it is both hot and dangerously polluted will increase with climate change.
Globally, and in Canada, temperatures are getting hotter, faster. According to the 2024 update of global climate change indicators, “human induced warming has been increasing at a rate that is unprecedented in the instrumental record”. Average temperatures will continue to increase, extremely high temperatures will occur more often, and extreme heat will last longer because we are continuing to emit more and more greenhouse gases into the atmosphere.
Higher temperatures from climate change will increase the frequency, duration, and intensity of wildfires. In 2023 fire weather conditions doubled the risk of fire that burned more than 13 million hectares in Eastern Canada and pumped out health harming air pollutants that worsened the air quality in many parts of Canada and the United States.
It is well established that exposure to air pollution and extreme heat are associated with increased mortality and morbidity. (More about that later.) But, in addition, it’s recently been shown that exposure to both factors at the same time amplifies mortality levels making their individual harmful impacts even worse.
According to a study of over 22 million deaths in 620 cities around the world, higher air temperature increased mortality, and there was an even stronger association between higher temperature and mortality on days with high air pollution.
Several factors converge to amplify health risks during hot days. These risks are heightened when it is extremely hot for several days. This is more likely when there is a heat dome, a high-pressure system that gets stuck over an area. When that happens the temperature of the air increases under the heat dome and the air becomes more and more polluted because it cannot be blown away.
Hot sunny weather also increases ground-level ozone levels, a pollutant harmful to human health formed by chemical reactions of nitrogen oxide and volatile organic compounds, two substances released from the use of fossil fuels, in the presence of sunlight and heat.
The impacts of air pollution and extreme heat on health are worse for several different groups of people. A detailed investigation of the over 600 heat-related deaths in British Columbia during the 2021 heat dome revealed that most of those deaths occurred indoors. Many of those who died were older, lived alone, were poor, or had health problems. Almost none had access to air conditioning.
Another study showed that extreme heat when combined with high levels of air pollution increased cardiovascular and respiratory mortality, was particularly deadly for individuals over age 75, and for those with pre-existing cardiovascular and respiratory conditions.
People living in urban areas will also be particularly vulnerable since urban areas are warmer during the day and night than rural areas because of the heat-trapping effects of concrete and pavement. In addition, air pollution is worse in urban areas because of the higher levels of air pollution from cars, buildings, and industrial processes. And these two factors when combined will amplify mortality rates.
Separate Effects of Air pollution and Extreme Heat on Health
According to the World Health Organization, air pollution, most of which results from burning fossil fuels, is responsible for the deaths of 6.7 million people per year. The impacts of air pollution are much more serious in low- and middle-income countries than in high income countries.
In Canada it’s estimated 15,300 premature deaths occur annually. To put this number in context, Canadians are about eight times more likely to die prematurely from air pollution than from a motor vehicle accident.
Air pollution affects people at all stages of life from fetal and early stages of child development to old age. It is linked to a wide range of acute and chronic diseases. It increases risk of heart disease, chronic obstructive pulmonary disease, stroke, asthma, diabetes, contributes to dementia, and impacts cognitive and mental development in children.
Extreme Heat
Extreme heat is an important environmental and occupational health hazard, and its risks are growing exponentially with the increasing intensity, duration, and frequency of heat waves with climate change. Such heat waves can result in a spike in the number of premature deaths. For example, the European heat wave in the summer of 2022, was estimated to result in the premature deaths of 61,672 people. At elevated risk were older adults, people with cardiovascular and respiratory disease, women, socially isolated, and socio-economically disadvantaged individuals.
What We Can Do
Several steps can be taken to reduce air pollution. The first law of digging holes is to stop digging a deeper hole by continuing to burn fossil fuels. Canada needs to shut down its existing coal-fired power plants, stop constructing new gas-fired power plants, and reduce our consumption of fossil fuels to heat and cool homes and buildings, and power our vehicles.
The impact of taking these actions on improving the health of Canadians could be substantial. This was demonstrated in a study examining the health of Beijing residents after the government had taken a variety of steps to reduce air pollution. It reduced the number of cars on the road, replaced coal-fired boilers with gas or electric heat for homes and buildings, and reduced the number of industrial processes emitting dangerous pollutants.
The effect of taking these steps reduced air pollution by half in 2022 compared to its very substantial levels in 2013. The study concluded residents in Beijing could be expected to live 4.6 years longer, provided these improvements in air quality were sustained.
Canadians will increasingly experience extreme heat in the coming years because of climate change. Fortunately, we can take practical steps to prepare for extreme heat. Seniors for Climate Action Now! has prepared a useful fact sheet for ways to prepare for heat, keeping hydrated and, suggesting ways to try to stay cool. And it lists different types of heat illnesses, and for each illness, what to look for, and how to treat.
While these tips are useful, they are insufficient, and governments need to become more actively involved. Here is a partial list of some actions they should take: give access to everyone for cooling, identify hot zones and locations of vulnerable people, pass more stringent workplace heat stress regulations, and pass laws on maximum temperatures in apartment buildings. These laws would have prevented many of the 600 heat-related deaths during the 2021 heat dome in British Columbia. For a more complete list of actions, click here.
Until we are successful in getting governments to take these actions, individuals who can afford it, especially those with cardiovascular disease, respiratory problems including asthma, and those living with children having asthma should consider installing air conditioning and an air purifier, or better yet get a heat pump with a filter appropriate for their needs. Justification of this purchase becomes even more compelling for people living in areas with extreme heat, high levels of pollution from burning fossil fuels or from wildfires.
There is no denying that air pollution and extreme heat increase the risk of premature death and when the two occur simultaneously the risks of dying prematurely increase even more. Fortunately, there are straightforward, well-known actions we can immediately take to reduce levels of air pollution and to adapt to extreme heat. What’s missing is the political will to make changes.
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Norman W. Park is Professor Emeritus, Clinical Psychology, York University, and a member of SCAN!’s Education Committee.