Ground level ozone is not emitted directly into the air. Instead, it is created by a chemical reaction when volatile organic compounds (VOCs) and nitrogen oxides (NOx) react in the presence of sunlight. The major source of VOCs and NOx are emissions from industrial facilities, electrical utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents.
Ozone is particularly likely to reach unhealthy levels on hot sunny days in urban environments and is a major component of urban smog. However, even rural areas can experience high ozone levels when ozone is transported by the wind.
As summer approaches, ground-level ozone is more of a concern due to the high heat and low precipitation that occur during this time. Ground-level ozone forms when Nitrogen Oxide (NOx) and Volatile Organic Compounds (VOCs) react in the presence of sunlight and heat. To help keep us “in-attainment,” we must target NOx emissions to prevent ozone from forming. By removing either VOCs, NOx, sunlight, or heat, ground-level ozone cannot form. Since VOCs are produced largely from vegetation, the only element we have some control over is the amount of NOx being emitted.