Is ozone a primary or secondary air pollutant?

Is ozone a primary or secondary air pollutant?

• A. Primary
• B. Secondary
• C. Tertiary
• D. Quaternary

Answer: (B)

Ground-level ozone is a secondary pollutant: it is not released directly by sources. Sunlight drives photochemical reactions among nitrogen oxides and volatile organic compounds in the atmosphere, forming ozone in situ. Because it arises from reactions of other emissions, ozone is classified as secondary rather than primary. Primary pollutants are emitted directly (like sulfur dioxide, carbon monoxide, and particulate matter). Tertiary and quaternary aren't standard classifications in this context, so they don’t apply.

Ground-level ozone is a secondary pollutant: it is not released directly by sources. Sunlight drives photochemical reactions among nitrogen oxides and volatile organic compounds in the atmosphere, forming ozone in situ. Because it arises from reactions of other emissions, ozone is classified as secondary rather than primary. Primary pollutants are emitted directly (like sulfur dioxide, carbon monoxide, and particulate matter). Tertiary and quaternary aren't standard classifications in this context, so they don’t apply.