Which of the following is listed as a major secondary pollutant?

• A. Ozone
• B. Volatile Organic Compounds
• C. Sulfuric Acid
• D. Lead

Answer: (B)

The main idea is that secondary pollutants form in the atmosphere through chemical reactions, not by being released directly. Volatile organic compounds are a broad group of reactive organic gases that readily participate in sunlight-driven reactions with nitrogen oxides. These reactions produce ozone and secondary organic aerosols, which are major components of secondary pollution. So, VOCs are listed as major contributors to secondary pollution because of how effectively they drive the formation of these secondary pollutants. For context, ozone itself is a classic secondary pollutant formed this way, while lead is typically emitted directly, and sulfuric acid forms after sulfur dioxide reacts in the atmosphere.