VANCOUVER—Pollution from cars and trucks is responsible for an estimated 4 million cases of childhood asthma around the world each year — about 13 per cent of all asthma in children, a new global study has found.

That rate is much higher in Canada, where about 20 per cent of asthma in children is tied to traffic-related pollution.

Of 194 countries in the world, Canada had the third highest rate per 100,000 of new cases of childhood asthma tied to traffic pollution, ranking just behind Kuwait and the United Arab Emirates, the study published the journal Lancet Planetary Health found.

“The implication is, if you clean up all the traffic pollution you can reduce asthma by 20 per cent, which is pretty big,” said Michael Brauer, one of the study’s authors and a professor in the University of British Columbia’s school of population and public health.

The findings came as a surprise to Chris Porter, whose two-year-old daughter Astrid has asthma.

“We’ve had 10 hospitalizations now in the last 14 months, where we end up in the emergency room with her asthma. It’s definitely something that impacts our life a lot,” he said.

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“There’s always the fear that the next cold is going to end up in the hospital.”

Astrid’s asthma tends to act up in the winter when she catches a cold. She was also affected by the wildfire smoke that blanketed Vancouver last summer.

But Porter hadn’t thought much about the risks from traffic before.

Now, he said, he hopes the government will start a greater push toward cleaner transportation options. That could be more investments in electric vehicles, more transit, and better walking and biking infrastructure.

“There’s lots of reasons why we should be doing that, but people’s health and asthma is a direct reason why we should be doing it now,” Porter said.

About one third of Canadians live within a couple of hundred metres of a major roadway, putting them at greater risk of exposure to traffic-related pollutants.

The Lancet study focused on nitrogen dioxide as a marker for the pollution from cars and trucks.

Many places, including Metro Vancouver, have guidelines for pollutants such as nitrogen dioxide. However, they may not be strong enough.

The researchers found most childhood asthma linked to traffic-related pollution occurred in areas that were already below the Metro Vancouver and World Health Organization standard.

And nitrogen dioxide isn’t the only concern. Traffic pollution is a toxic mix that has also been tied to other serious health issues, including heart disease.

There are different approaches cities can take to lessen the impact of traffic pollution, Brauer said.

In London, U.K., for instance, the city has adopted an ultra-low emissions zone that only allows low-emissions, such as electric cars, into the city’s downtown. Meanwhile, New York City is bringing in a congestion charge for any cars driving into the city centre.

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Cities could also consider locating bike and walking paths away from heavily-trafficked roadways so people walking or cycling are exposed to less traffic pollution,” he said.

“The bottom line is … reducing reliance on vehicles that are burning (fossil) fuel,” he said.

That would have the added benefit of fighting climate change, which doctors have called a major public health crisis.

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