Air Quality

How the air Canadians breathe has changed: emissions, concentrations, and the rising challenge of wildfire smoke

Air pollution is one of the clearer environmental success stories of the past few decades. Emissions of the classic industrial pollutants have fallen sharply since 1990, and the concentrations Canadians actually breathe have followed for most pollutants. The conspicuous exception is fine particulate matter (PM2.5), which has risen as wildfire smoke reaches populated areas more often. The figures on this page come from Environment and Climate Change Canada’s national air-monitoring and emissions-inventory programs.

Emissions of the main air pollutants

Canada’s Air Pollutant Emissions Inventory tracks how much of each pollutant is released nationally. The declines are large: sulphur oxides (the driver of acid rain) have fallen dramatically since 1990 as smelters and coal plants were controlled or closed. Carbon monoxide and nitrogen oxides have also fallen significantly, largely through tighter vehicle standards. Not all pollutants have declined. Ammonia, mostly from agriculture, has drifted up. (The pollutants are shown as an index, 1990 = 100, so the rates of change are comparable across pollutants of very different size.)

What Canadians breathe

Emissions are what we release into the air. Actual pollutant concentrations are what people breathe. This indicator, built on the National Air Pollution Surveillance (NAPS) network, tracks the population-weighted concentration of each pollutant (indexed to 2009 = 100, the indicator program’s baseline year). Sulphur dioxide, nitrogen dioxide, and volatile organic compounds have all declined; ground-level ozone (a secondary pollutant that forms in the atmosphere) has been roughly flat.

Fine particulate matter (PM2.5) is the exception: it has risen, not fallen. One of the largest current drivers of PM2.5 is wildfire smoke, which the final chart isolates. These are national figures; to pick an individual city and see its pollutants month by month back to the 1970s, see Air Quality by City.

How Canada’s PM2.5 compares internationally

Relative to its OECD peers, Canada’s air is among the cleanest: by mean population exposure to PM2.5, Canada ties New Zealand for 4th of the 16 countries with data. It is behind only Finland, Sweden, and Norway. (This OECD series, derived from satellite and ground measurements, currently runs to 2020 — before the most severe recent smoke years.) The dotted line marks the World Health Organization’s 2021 guideline of 5 µg/m³. That guideline is strict enough that most Canadians still live above it, even though Canada’s air is cleaner than almost every peer country. Very high short-term PM2.5 readings in Canadian cities almost always reflect brief wildfire-smoke episodes rather than the year-round air this annual average measures.

Latest PM2.5 exposure: ranked

Air quality in global context

The peer comparison is among countries with broadly clean air. Globally, the differences are far larger. Mean exposure to PM2.5 in China and India runs several times higher than in Canada, the United States, or any OECD peer. Canada’s air is not only clean by advanced economy country standards; it is among the cleanest in the world. (China and India are shown here for global context; they are not part of the OECD peer group used elsewhere.)

The new challenge: wildfire smoke

The one pollutant becoming more problematic is fine particulate matter, driven by wildfires. This chart pairs the area burned by wildfire each year (bars) with the peak PM2.5 concentration Canadians are exposed to (the 98th-percentile of daily values, indexed to 2009 = 100). The worst smoke years stand out: 2018 and, above all, 2023, when the peak exposure index reached nearly three times its 2009 level. Population-weighted smoke depends on where fires burn relative to where people live, so the link is not exact year to year. 2018 burned far less area than 2023 yet drove a large exposure spike because the smoke settled over British Columbia’s populated southern valleys for weeks. The trend is clear: wildfire smoke is increasingly the dominant source of polluted air on Canada’s worst days. See Wildfire for the long-run wildfire record and 2023 fire map, and FireSmoke.ca for live, interactive smoke forecasts across Canada and the United States.

Download data

Concentrations vs. emissions. Emissions (APEI) measure what is released into the air nationally; concentrations (NAPS/CESI) measure what is actually present in the air where people live. They can diverge. For example, PM2.5 concentrations have risen on smoky days even though directly emitted particulate emissions have changed little, because wildfire smoke is not fully captured in the controllable emissions inventory.

Population-weighting. The concentration indicators weight each monitoring station by the population nearby, so they approximate the exposure of a typical resident rather than a simple average across all monitors.

International series. The OECD PM2.5 figures are modelled from satellite and ground observations on a consistent basis across countries (so they differ slightly from Canada’s own ground-network figures) and currently extend to 2020. South Korea is the one peer without data in this series. All sources are published under the Open Government Licence – Canada or the OECD’s terms of use.