Canada's air quality last year was worse than the United States for the first time since a firm started publishing its annual assessment in 2018.

The 2023 World Air Quality report from Swiss company IQAir says raging wildfires were a major influence on Canada's drop in air quality.

The report found that on a list of 15 most polluted cities in both the U.S. and Canada, Canadian communities made up the 13 most polluted cities on the list, topped by Fort McMurray, Alta., and Peace River, Alta.

Data indicates Peace River's pollution concentration, typically below the national average, shot up to levels in May worse than the annual average reported in India, the third-most polluted country in the world.

Canada was less polluted than 92 of the 134 countries, regions or territories surveyed in the report, with about an eighth of the average annual pollution concentration of worst-ranked Bangladesh.

Only seven countries reported average annual pollution concentrations within the World Health Organization's guideline, including Mauritius, Iceland, and Australia.

The report aggregates monitoring data on pollution known as PM2.5, fine particulate matter so small it can travel deep into lungs and pose a risk to human health.