I'm lucky enough to work in a building with showers, attached to a small gym. I think it's a bit ironic that I can go downstairs to change into my cycling clothes to ride home, on a gorgeous summer day, and find people in the gym riding stationary bikes to nowhere. I want to scream: "Winter will be here before you know it!! You can do that when it's -35ºC outside!!!" (And yes, I'm a bit of a fair weather cyclist. I take the train when it's that cold)
A few years ago someone measured air pollution in various places and found that the worst place to be, in terms of exhaust fumes, was inside a car at rush hour. The fumes get inside and don't easily get out again. So, you're actually breathing less pollution on a bike.
Where I live, people who can least afford cars are pushed further and further from the city core into outlying neighborhoods where public transit is bad to non-existent. Living in inner city downtown neighborhoods is now this chic expensive yuppie thing. Bad urban planning can force people into cars as much as any perception of safety.