What pollutants are given off by gas-powered engines?
Carbon dioxide is the big, unavoidable one. Water vapor may also be called a pollutant, I guess, as it is a greenhouse gas, just not all that persistent. In modern engines and exhaust systems the levels are very low, but there are also oxides of nitrogen and sulfur (NOx and SOx). This depends as much on the quality of the fuel as on the engine. These compounds may be carcinogenic or otherwise harmful, and can be converted in the atmosphere into acids, which fall to earth as acid rain. At low temperatures, those are worse, and you also see higher levels of unburned hydrocarbons (the various components of gasoline, mostly the heavier ones, AFAIK), and carbon monoxide (instead of carbon dioxide). Combustion is more difficult at low temperatures, especially when the engine is just starting, you see. The unburned hydrocarbons can be carcinogenic, especially if the gasoline contains benzene…in many countries, it’s up to 80 percent benzene…in fact in some places the WORD for gasoline is “
