In Toronto when the temperature goes above 30 degrees Celcius (90 degrees Farenheit), for a few days and without wind, there is smog. I find the smog irritates and makes it difficult to breathe in ...
I'm using my bicycle to ride from home to work and back. Now I face a problem that the air is not so clean: dust, car exhaust etc. So I'm thinking of buying a respirator (i.e., an anti-pollution ...