Canada cut nitrogen dioxide air pollution 79.5% since 1976 despite population and vehicle growth

Canada's air is now the cleanest it's been in generations, a reversal that defies decades of growth in population, vehicle numbers, and energy production.

Over the past 50 years, Canada's population has grown from 23 million to more than 41 million. Motor vehicles on Canadian roads have more than doubled since 1975, from 11.3 million to 26.8 million. Oil and gas production has reached record heights. Yet between 1976 and 2023, Canada's national average levels of nitrogen dioxide—a pollutant with serious consequences for human health and the environment—fell by 79.5 per cent, meaning average levels today are roughly one-fifth what they were in the 1970s. Since 2004, average outdoor levels of nitrogen dioxide have consistently remained below current Canadian health guidelines for air quality.

Nitrogen dioxide can make breathing more difficult and worsen or induce respiratory conditions. Prolonged exposure raises the risk of developing heart disease. The pollutant combines with other pollutants to create smog and acid rain.

Motor vehicles have historically been the biggest source of nitrogen oxide pollution in Canada. When fuel is burned incompletely, gas and diesel cars emit nitrogen oxides as tailpipe exhaust. Between 1990 and 2023, nitrogen oxide emissions from transportation decreased by 71 per cent, largely because of technological improvements: catalytic converters, mandatory for Canadian vehicles since 1988, use precious metals such as platinum and palladium to convert nitrogen oxides and other pollutants into less harmful substances. Cars are generally more fuel-efficient than in the past, meaning less fuel is burned per kilometre driven and less nitrogen oxide pollution is released.

Changes in electricity generation have also helped. The shift toward lower-emission sources of electricity, along with improvements in pollution-control technology, has reduced nitrogen emissions from the sector. Emissions from electric power generation fell by 72 per cent between 2000 and 2023.

Even oil and gas production, a sector often associated with nitrogen oxide releases, has made measurable strides in reducing emissions relative to output. From 1999 to 2023, Canadian oil and gas production approximately doubled while nitrogen oxide pollution fell by 12 per cent—meaning less pollution is released per unit of oil and gas produced.