[larkery]

I think there are some studies from here in the UK which indicate that air quality may actually be worse inside motor vehicle cabins than it is outside [1].

This may be mitigated in newer vehicles with particulate filters, I am not sure. I don't know whether filters can eliminate NOX as well as PM2.5.

[1] http://www.bbc.co.uk/news/health-35504768

[criddell]

Plus, when I'm on my bicycle I'm breathing much harder than most people in cars and I'm in it for longer because I'm slower.