Bike mask for urban pollution

After most of my commutes both in the morning and afternoon I often cough a lot and can be heard wheezing. I do suffer from seasonal allergies, but even in the winter I was caught with some of the symptoms aforementioned. This leads me to believe that a lot my problems are from road pollution. And indeed I do feel it in the lungs. It's horrible. I hate to think what it's doing to my health.

I'm considering buying a mask for usage here in Toronto. Is this a realistic thing to do, and does anybody else use one? I commute mainly on midtown arterials during rush hour.