Ozone precursors react in the atmosphere to form ozone. These precursors include volatile organic compounds and nitrogen oxides..
Criteria Air Pollutants (CAP) are six common air pollutants: carbon monoxide, ozone, sulfur oxides, nitrous oxides, lead, and particulate matter.
Benzene, toluene, ethylbenzene, and xylene (BTEX) are volatile organic compounds harmful to human health