Exhaust[edit]
Main article: Air pollution
Petroleum diesel exhaust from a truck
When oil or petroleum distillates are burned (see combustion), usually the combustion is not complete. This means that incompletely burned compounds are created in addition to just water and carbon dioxide. The other compounds are often toxic to life. Examples are carbon monoxide and methanol. Also, fine particulates of soot blacken humans' and other animals' lungs and cause heart problems or death. Soot is cancer causing (carcinogenic).