Across the world, air pollution is associated with more early deaths than any other environmental exposure, raising risks of dying from lung cancer, respiratory infection, heart and lung disease and other causes.

Even in Canada, where air pollution is generally considered a low risk, more than 17,000 early deaths and over $140 billion in economic damages each year are linked to it.

Pollution from heavy industry or wildfires, for example, can make outdoor air so polluted that it poses immediate health risks. Climate change can worsen air quality as changes to temperature, winds and rainfall enhance emissions, accelerate their transformation and allow them to build up to unhealthy levels.

In our recently published research, my colleagues and I estimated that, by 2100, 100 million Americans could breathe unhealthy air in the summer, seven times more than in 2000. Without action to keep the air clean, these people would face a regular choice of taking steps to protect themselves, like staying inside, or face higher risks of illness and death.

Our findings are based on models of the global economy,........

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