What causes ozone to form?
Ozone is not directly
emitted into the atmosphere but forms when oxides of nitrogen (NOx)
and volatile organic compounds (VOCs) are in the air and sunlight is present. Motor
vehicle exhaust and industrial emissions, power plants, gasoline vapors, and
chemical solvents are some of the major human-made sources of NOx
and VOC. Significant natural sources of NOx include lightning, biomass burning,
and soil. Vegetation also releases substantial amounts of VOCs. NOx
and VOCs are gases are referred to collectively as ozone precursors.
Strong sunlight and hot weather cause ground-level ozone to form and reach high
concentrations.
(adapted from “The Health of Our Air”)
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