Air pollution by Carbon monoxide:

Carbon monoxide is produced when organic materials such as gasoline, coal, charcoal, and trash are incompletely burnt. Virtually all stoves, furnaces, fires in open places and forests, factories,  power plants give off carbon monoxide. The other significant source  is from the incomplete burning of  tobacco when smoked. This gas combines with hemoglobin, and reduces the oxygen canying capacity of blood, causing blurred vision, headache, and in extreme cases, unconsciousness, and even death. Automobiles emit a variety of hydrocarbons. These are a group of organic  compound:; consisting  of carbon and hydrogen.

They are either evaporated from the fuel or are the remnants of fuel that did not bum completely. Hydrocarbons in air, are washed down oy rains, and eventually they run off  into surface water. They form an oily film on the surface of water. Hydrocarbons are mostly only a nuisance except when they react to form secondary pollutants.