City living and dirty air go together. But when it turns into a killer it's no longer just a vague inconvenience.
Why is air pollution so dangerous?
Smoke from fires causes high concentrations of carbon monoxide (CO, also known as the odourless 'suicide gas'). So do motor vehicle exhaust gases, as the residents of smog-plagued Beijing can attest. Traffic also emits nitrogen oxides (you can smell and see these – they’re a big part of ‘brown haze’); particulates (tiny airborne solids and liquids - the bigger ones add to haze, but the smaller ones penetrate deep into our respiratory systems); and hydrocarbons such as the carcinogen benzene. Hydrocarbons and nitrogen dioxide combine in the presence of sunlight to form ground-level ozone (the ‘bad’ ozone), a major component of smog.