Not sure about your city, but mostly it's sedans here and those don't do freight. Idling traffic is probably the worst for the air, I'd guess and from talking to bike couriers (wondered why they wear these filtering masks on their faces). Must be due to my mom smoking so I'm used to being around smokers, but largely don't get the disgust people have for them, heh.
Although, considering there's a large cigarette smuggling business here, I wonder how much the drug business would shrink if everything were to be legalized and taxed.