Gosh, I could quote you some of the days, which are increasing every summer, when they have levels of smog that have triggered an air quality alert in Toronto, for example. The numbers are increasing. I think that has to do with our increasing trend of warmth, which has to do with climate change as much as emissions.
It's a serious problem principally for people who are predisposed to that problem--for example, people with pre-existing cardiovascular disease, people with pre-existing respiratory disease, small children, the elderly. These are the typical groups that you would say are at most risk from this. Even healthy people perhaps who are working very strenuously outside or jogging outside may notice a decrement in their ability to breathe. The answer to you is that it's a range of problems, depending on how sensitive you are to the issue.
The Ontario Medical Association estimated for all of Ontario--and that's for the whole province--that about 5,800 people die each year from air pollution. And death is at the top of the health effects pyramid. There are many more people affected with lesser outcomes, such as lost workdays, or having to access the health care system and spend money on drugs, and so on. It's a serious problem.