Particulate matter- fine particles that pose the most serious threat. They can penetrate deep into our lungs, and are usually in the form of soot.

Hydrocarbons- Cam react with nitrogen oxides in the presence of sunlight to form ground level ozone. Can irritate respiratory systems and cause coughing or choking.

Nitrogen oxides- assist in ground level ozone and can cause lung irritation as well as weaken the body's defenses against respiratory infections.

Carbon Monoxide- An odorless, colorless, poisoners gas that can cause the blockage of oxygen to the body.

Sulfur dioxide- can react in the atmosphere to form fine particles that can be a threat to asmatics.

Hazardous air pollutants- chemicals that have been linked to birth defects, cancer and other illnesses, caused by chemicals like Benzene and acetaldehyde.

They also emit green house gases

Emitted gases by Cars