1. A cap and trade policy was successfully used to reduce mercury emissions in the United States.

Explain how a cap and trade policy works.

2. The Clean Air Act allows the EPA to set standards for six criteria air pollutants.

With hundreds of possible air pollutants to choose from, why were these six chosen for regulation?

3. The EPA, under the Clean Air Act, regulates particulate matter in the atmosphere. PM2.5 refers to particulate matter with a particle size of 2.5 micrometer in diameter.

From a human health perspective, why is it important that PM2.5 is regulated?

4. Ozone can be found both at ground-level and in the stratosphere.

Which of these is the "good" ozone? Why is this ozone important?

5. Ozone can be found both at ground-level and in the stratosphere.

Why is ground-level ozone a concern?