New research suggests that children who develop asthma in the Toronto area are more likely to have been born in a neighborhood with a lot of pollution.

Canadian researchers found that a higher number of asthma-sufferers were born in a neighborhood that has a high level of traffic-related air pollution, such as Parkdale-Little Portugal, west of downtown Toronto; the neighborhood where the Don Valley Parkway connects to the westbound Gardiner Expressway; and parts of Scarborough, including where the Don Valley Parkway and Highway 401 intersect and around Cliffside-Scarborough Village.

"In this study, high clusters of atopic asthma [asthma related to allergies] were found in children who were born in parts of the southwest, south and northeast of Toronto," Dr. Ketan Shankardass, lead author of the study, said in a statement. "Such clusters support the notion that early life factors at the neighborhood level are relevant to the development of childhood asthma.''

Shankardass, who is also a social epidemiologist at St. Michael;s Hospital, said 70 percent of the children involved in the study had moved from their birth neighborhood, further suggesting the air pollution during pregnancy and shortly after birth was related to developing asthma later in childhood.

While exposure to traffic-related air pollution helped explain some of these clusters, Shankardass said air pollution isn't necessarily acting alone in causing childhood asthma, or else they would have found similar clusters along all the main thoroughfares in Toronto.

Other risk factors that could be associated with the development of asthma include the low socioeconomic status, in Parkdale-Little Portugal and Scarborough, which have average median incomes of $51,767 and $52,944, respectively, compared to $65,047 in the rest of the greater Toronto area.

The findings are detailed in the journal Health & Place.