If you’re thinking of buying a home at Don Mills and Sheppard or in Riverdale, you might want to take heed. Research carried out at the University of Toronto shows that these neighbourhoods, despite being among the most desirable, are also among the most polluted in the city.

An air pollution map produced by the team pinpoints Toronto’s air-pollution hot spots, showing that areas near highways and major intersections can have three to four times the average amount of ultrafine particles put out by vehicle tailpipes.

High-pollution areas affect both wealthy and poor neighbourhoods in the city, creating an invisible health divide that no one was aware of until now.

“We’ve found that the variability of exposure across the city is quite a bit larger than we expected,” said Greg Evans, a professor of engineering at U of T. “It’s not that there’s one level of air pollution that covers the entire city; it’s that people will have different levels of exposure in different parts of the city, depending on how much surrounding traffic there is.”

Toronto has been declaring citywide smog alerts for years, urging Torontonians from Scarborough to Etobicoke to limit outdoor exercise during these times to protect their health. But Evans’ team focused on unregulated pollutants that aren’t as well understood. Because these ultrafine particulates are a relatively new area of study, exactly what concentration would constitute a health concern isn’t yet known, he said.

“Air pollution itself is quite a complex soup of chemicals, and some of the ones that people pay the most attention to (such as ozone and medium-sized particles) tend to be much more homogeneous across the city,” Evans said. “But when you look at other pollutants that are more specific to traffic (such as ultrafine particles) you start to find that there’s much greater variability.”

Ultrafine particles, linked to diesel vehicles, can be twice as prevalent downwind from major roads as they are upwind, Evans said. The air pollution map accounts for daily variations by using average readings taken over an entire summer.

It shows that the bottom of Highway 427 and its intersection with Highway 401 near Pearson airport are heavily polluted, as well as areas surrounding the junctions of the Don Valley Parkway and Highway 401, Steeles Ave. W. and Highway 400, and Steeles Ave. E and Highway 404.

Scarborough Town Centre is a vicinity of concern, as is the neighbourhood between Keele St. and Dufferin St. south of the 401.

Smaller pockets near the DVP and Eglinton Ave E., Sheppard Ave. W. and Highway 400, and Eglinton Ave. E. and Birchmount Rd. have heavy pollution, as does a swath of the eastern downtown, from the Gardiner Expressway to Dundas St., and from Yonge St. to Leslie St.

The map was produced by U of T students, working alongside scientists from Environment Canada, who walked through the city with hand-held devices. The team also used a mobile lab in a small truck as well as fixed stations to gauge the pollution caused by individual vehicles.

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Similar maps have been produced for Vancouver and Amsterdam, while health concerns over ultrafine particles have led some European cities, including Paris, to propose banning trucks from the city centre.

The Toronto data isn’t yet available to the public, but it could have some interesting applications for public officials looking to locate new schools, sports fields or retirement homes, or for individuals who want to plan their jogging route or decide where to move.

“This is a great resource. It could help people make a better decision on where they want to live,” said John Pasalis, co-founder of Realosophy, a real estate agency and data-driven website that gives people looking to buy a home a wealth of information about neighbourhoods and the ability to create customized maps online.

“There is all this rich information out there; the challenge is to get your hands on it,” said Pasalis. “It’s not going to influence everyone, but if your kids have asthma, it could change your ideas about a neighbourhood.”