What indirect benefits were derived from reduced emissions that help to grow the economy?

Limiting Air Pollution

There have been reductions in all of the six criteria air pollutants identified in the 1970 Clean Air Act Amendment. During this time the US economy continued to grow. Explain the programs and processes that led to these reductions. Offer and describe an idea to reduce the emissions of at least two of these pollutants. What indirect benefits were derived from reduced emissions that help to grow the economy?