Canada is being called on to adjust to recently established global guidelines for air pollution.
In an editorial, the Canadian Medical Association Journal advocates following the lead of the World Health Organization, which in May updated the acceptable levels of small particulate matter, nitrogen dioxide and ground-level ozone.
The CMA is particularly concerned about the impact of air pollution on children.
"We see increases in admissions to hospital for respiratory illnesses such as asthma [in children]," Dr. Moneeza Walji, one of the co-authors of the editorial, told CBC News.
That can increase the risk of developing respiratory or cardiac disease as an adult, she said
Canadian standards dated
The Canadian standard for ground-level ozone is 65 parts per billion, 15 ppb above the recently established WHO guideline. The Canadian standard for peak 24-hour concentration of fine particulate matter is 28 micrograms per cubic metre (µg/m3), four micrograms higher than the WHO guideline.
The Canadian standards were endorsed by the country's environment ministers in 2000.
Health Canada was involved in the drafting stages of the WHO's air-pollution resolution.
"In the end, the Canadian delegation made known Canada's desire to co-sponsor the air-pollution resolution," a Health Canada spokesperson told CBC News.
Air pollution is a "silent killer" and is unique in that it affects the entire population, according to Dr. Michael Brauer, professor at the school of population and public health, University of British Columbia. Brauer was the co-author of a 2008 editorial in which CMAJ attributed more than 20,000 deaths annually in Canada to air pollution.
Small particles can travel deeply into our lungs, medical experts say, and the body's response to fight the particles will keep continuing, even though it's not a living particle that can be combatted. It can lead to inflammation that spills over into the bloodstream, causing health complications.
The problem is variable across Canada, and can change from year to year, Walji said.
"There is a lot of geographic variation when it comes to the improvement in air pollution," Walji said. "There are some areas that have seen vast strides, and other places that are still striving from high pollution levels"
That's because the sources of air pollution include such diverse factors as diesel transportation, oil and gas industry activity, forest fires, smoke from wood-burning stoves and air pollution in neighbouring provinces and states.
Ontario and Quebec, for example, score poorly on ozone measurements due to their own industrial activity, but pollution arriving from northeastern U.S. states contributes to the problem.
National guidelines are important, but the issue can be fought locally with better planning by municipalities, according to University of Toronto chemical engineering Prof. Greg Evans, who has studied sources of air pollution.
Houses and schools downwind or close to highway corridors often see adverse air-pollution measurements, as can downtown areas, where particles can become trapped.
Canadian provinces regularly out-perform the newly adopted WHO guidelines, in addition to long-held national standards.
But medical experts believe that significantly reducing air pollution can lessen the frequency of heart attacks, chronic lung disease and emphysema in Canada, as well as the mortality rate.
The original version incorrectly identified Greg Evans as a University of Toronto chemistry professor, when he in fact works in the field of chemical engineering.Jul 22, 2015 10:36 AM ET