Everyone knows that feeling. After leaving a building, happy to be outside in the fresh air, your joy is suddenly thwarted by the smelly exhaust of a TTC bus driving by. You grimace and hold your breath for a few seconds before continuing on your way, trying not to think about what you just inhaled.

This goes on all over the city. With millions of cars and buses constantly spewing out toxic fumes, how do our lungs survive? How does this affect our health? And should we avoid outdoor activities like jogging and (gasp!) shopping, that expose us to diesel engine exhaust?

There are no easy answers. Scientists are only beginning to learn how our lungs deal with air pollution. It’s not surprising that preliminary studies have found that pollution negatively affects our overall health, causing higher rates of cardiovascular disease and respiratory problems. But more research is needed, and Toronto is a hot spot for studies of air pollution.

One Toronto expert is Dr. Chung-Wai Chow, an assistant professor of respirology at U of T’s Faculty of Medicine, and a leading researcher in the Southern Ontario Centre for Atmospheric Aerosol Research, or SOCAAR. Recently, Chow gave a public lecture to describe her current research which measures environmental pollutants, where they’re most abundant, and how they affect lung function. Ultimately, her research will identify the most polluted areas of the city, and identify medical treatments to counteract the negative effects of pollution.

Chow began her lecture by reviewing the well-established effects of air pollution on health. For example, people who live in more polluted areas of Los Angeles are more likely to have a faster progression of heart disease than those that live in less polluted areas. Lower levels of air pollution are associated with increased life expectancy in many cities throughout the world. What’s more, the number of immune cells present in the lungs is higher in people living closer to roads, indicating that their immune systems are trying to fight off the harmful pollution.
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Taken together, these and other observations indicate that air pollution is likely to affect our health in ways that are harmful enough to be detected. But should we all run screaming for the countryside? Not necessarily. Rural areas are not without their own potent sources of air pollution. Small engines on tractors and chainsaws, as well as the beloved Zamboni, all offer a powerful punch of air pollution.

Although it isn’t entirely clear how these pollutants affect our lungs, or whether our lungs are able to recover, it is known that pollution increases the amount of inflammation in them. This inflammation is harmful because it causes damage to the lung tissue, ultimately reducing lung function. Such inflammation is even worse for people with pre-existing lung problems such as asthma or cystic fibrosis.

Chow is currently researching the inflammation issue further, using mouse models in her work in order to determine exactly how lungs are most affected by pollutants, and to identify drug targets to reduce inflammation in the lungs. Her laboratory is making great progress, having already identified syk, a protein whose presence is associated with higher levels of lung inflammation. The goal now is to identify chemical inhibitors of syk to reduce the harmful effects of air pollution-induced lung inflammation. Eventually these mouse studies will pave the way for the development of human treatments. But what can we do to protect ourselves in the meantime?

Although air pollution is a health concern, it is important to keep several things in mind. Pollutant levels change over time, even within the same day. Typically, these levels correlate with the amount of diesel fuel being used in the area.

Chow discussed recent research by the SOCAAR group that measured pollutant levels at varying distances from major roads. They found that pollution levels were higher downwind of major roads when compared to the same distance upwind. Similarly, air pollution near highway 404 was highest near the road, and tapered off about 200 meters away.

People on TTC buses and subway platforms have higher pollution exposures than those who are on subway cars or are walking. Areas that have a constantly high level of traffic are unlikely to see much fluctuation, whereas areas that have fluctuations in traffic levels would also have fluctuations in pollutant levels.

Despite these findings, Chow stressed that the health costs of air pollution are unlikely to outweigh the obvious health benefits of being active outside. So don’t be scared to cycle around Toronto, go jogging outside on a nice day, or bask in the sun on a patio!

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