The impact of the Clean Air Act on the economy is very complex. There are ways in which it can be seen as a drag on the economy and ways in which it can be seen as a benefit.
The law can be seen as a drag on the economy since it places further regulations on businesses. It forces businesses to try to produce goods and services without polluting. This imposes costs on businesses as they try to find cleaner ways to produce. Some would argue that these costs kill jobs and make Americans pay higher prices for various things.
On the other hand, the law can be seen as a benefit to the economy. By reducing pollution, the law has helped us in tangible ways. It has reduced the number of illnesses and deaths connected to pollution. This saves on health care costs and allows people to work instead of being sick (or dead) and unable to contribute to our economy.
This makes determining the exact impact of this law very difficult. It has good and bad effects on the economy and these impacts are hard to measure in any precise way.