A study by researchers at McGill University has found that a microscopic air pollutant generated from vehicles and industry plays a role in the deaths of an estimated 1,100 people in Canada’s two biggest cities each year.

Their study, published recently in the American Journal of Respiratory and Critical Care Medicine, finds that long-term exposure to the ultrafine particles known as UFPs — which are typically less than 100 nanometres in size — increases the risk of mortality.