British Columbia

Dense development: is building along busy corridors unhealthy?

Experts say pollution from traffic has a very localized impact, so is it a good idea to build densify corridors?

Experts say pollution from traffic has a very localized impact, so why build along busy corridors?

Dense development along the Cambie Corridor is part of the City of Vancouver's plan for the area. (CBC)

The City of Vancouver has an ambitious plan to add 18,100 units of housing to the Cambie corridor in the next 25 years, many of them along Cambie Street itself.

But experts warn the impact from traffic emissions is far worse right next to high traffic areas.

Michael Brauer is a professor at the University of British Columbia's School of Population and Public Health. He says there are certainly environmental and health benefits to building density into a city — especially at transit hubs — but there are also risks people should consider.

According to Brauer, the dangerous pollution from vehicles travelling along busy corridors like highways and arterial routes like Cambie Street has a very localized impact.

"It's not like people are dropping dead," he said. 

"We look at this as another contributing factor to the typical diseases that affect us. We have seen that people who live closer to these major roads ... are more likely to die earlier than people that live farther away from roads."

According to Brauer, things like lung cancer, increased asthma rates in children, women giving birth to lower birth weight babies, and premature babies are all tied to living close to pollution from traffic.

"For many pollutants, things drop off quite rapidly," he said. "Like 150 metres [away from the busy street], which is a block and a half or so."

A map shows the level of nitric oxide (parts per billion) detected in a 2010 study in Vancouver. (Michael Brauer)

"Mostly we look at some of the gases, nitrogen dioxide which is a gas ... that comes out of the exhaust of the car," said Brauer. "There's also what we call black carbon, so that's soot, these very, very small particles, and we see higher levels of those along these corridors."

Beyond what comes out of the tailpipe, Brauer said that brake and tire wear releases metallic particles into the air, which are believed to be bad for health.

Finally, according to Brauer, the noise from heavy traffic comes with its own health impacts.

"Many people don't realize noise is a risk factor for things like heart attacks," he said.

How to plan for pollution

Francis Ries, senior project engineer with Metro Vancouver's air quality and climate change division, is involved in monitoring air quality in the region.

"Absolutely, exposure to traffic emissions should be folded into planning, I think there's no question about that," said Ries.

"We're always striving to reduce the exposure of the population to air pollution. And with something like [fine particulate matter], particularly, the science at this point basically says there is no safe level, so lower, always lower is going to be better."

Both Ries and Brauer say there are large health benefits of building dense, walkable communities. When people get out of their cars, it reduces emissions and keeps people active.

But Brauer has some ideas about avoiding the worst of the pollution, when developing new community plans.

He says building back from the busy street is key. As long as the walkability is still there, building a block or two away can make a big difference. Brauer also says building upward adds a considerable advantage.

"Most of the action going up was in the first two storeys or so," he said, adding that in Hong Kong, where he's looked at the issue, many developments included two floors of retail space.

Nobody from the City of Vancouver was available to comment on how the risk associated with direct exposure to traffic emissions along the Cambie corridor has been taken into account in community planning, but the city highlights the green space and overall emphasis on emission reduction in the plan.

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Rafferty Baker

Video journalist

Rafferty Baker is a Video journalist with CBC News, based in Vancouver, as well as a writer and producer of the CBC podcast series, Pressure Cooker. You can find his stories on CBC Radio, television, and online at