Vehicles emit large quantities of carbon monoxide, hydrocarbons, nitrogen oxides (NOx), and other toxic substances such as particle matter (PM) and lead.
Major air pollutants are
- Lead (Pb) and lead scavengers
- Carbon monoxide (CO)
- Nitrogen oxides (NOx) and hydrocarbons (HC)
- Nitrogen dioxide (NO2)
- Ozone (O3)
- Sulfur dioxide (SO2)
- Particulate matter (PM10, PM2.5)
- Air toxics (e.g. benzene, 1,3-butadiene)
These emissions tend to be geographically concentrated and are difficult to disperse. Many people live and work close to traffic, including vulnerable groups such as the young and the old. As the quantity of vehicle emissions increases, the quality of air deteriorates. This is aggravated by the rise in the number of motorized 2- and 3-wheeled vehicles, common in the region, and the proliferation of under-maintained diesel public transport vehicles.
To make things even worse, many cities in Asia far exceed WHO guidelines.
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