The cap-and-trade program introduced in 1990 targeted which pollutant?

• A. Sulfur dioxide
• B. Lead
• C. Ozone
• D. Particulate matter

Answer: (A)

A market-based cap-and-trade approach works by setting a fixed total limit on emissions and letting sources trade allowances to meet that limit. In 1990, the Clean Air Act Amendments created the Acid Rain Program, which specifically capped sulfur dioxide emissions from coal-fired power plants. By issuing tradable permits equal to the cap, emissions could be reduced where it was cheapest, driving down sulfur dioxide and acid rain over time. Lead, ozone, and particulate matter are controlled by different programs and standards, not this particular cap-and-trade initiative, even though they are important pollutants addressed in other ways.