New research blames early exposure to pollution for higher asthma rates in some Toronto communities.

The study, published Friday in Health and Place by researchers at St. Michael’s Hospital and the Hospital for Sick Children in Toronto, links asthma diagnoses to environmental factors during pregnancy and early childhood.

The study was carried out by examining results from a 2006 study filled out by parents of more than 5,000 Toronto-area children in the first and second grade.

Lead author Ketan Shankardass, a social epidemiologist at St. Michael’s, said a prior study from the same project showed it was possible to predict a child’s risk of developing asthma based on their cumulative exposure to air pollution.

He said this newest paper found a pattern to where those high-risk areas were in Toronto. When examining where children spent the early parts of their lives, four areas in particular seemed to have clusters of childhood asthma.

Asthma map

“When we mapped where they were born, we found that the asthmatic children were more likely to be born in one of these four neighbourhoods,” Shankardass said. “It’s evidence that suggests that where you’re born is going to shape whether or not you get asthma by the time you’re five or six.”

One of the neighbourhoods in question is the area where the Don Valley Parkway and the Gardiner meet, Shankardass said. Higher asthma rates in this space could be blamed on traffic-related pollution, he said.

Other affected neighbourhoods could be partly explained by traffic pollution as well he said, as well as other factors. In Scarborough, where traffic pollution was comparatively low, Shankardass said air pollution was still a likely culprit.

“There’s a lot of industry in that part of the city, historically,” he said. “So even if you’re not being exposed to a lot of traffic pollution, you’re likely getting different types of pollution.”

Shankardass said causation is difficult to prove in this case, because unlike a common cold, taking in one breath of polluted air won’t immediately cause asthma.

He said these types of studies will hopefully help to enact larger social changes -- like pushing for more environmentally-friendly forms of transit -- and create awareness for expecting parents and parents of young children.

“This is evidence that what happens to you when you’re in the womb affects what’s going to happen to you later on in life.”