Federally, who monitors air quality?

Question

Federally, who monitors air quality and what are some major policy changes over the past few decades that address the issue

Answer 1

Since Bush took office, enforcement is slack and usually regulated to the state level.
Here in Texas, since Bush, the agency responsible for inspecting things such as air pollution, water pollution, and water quality does little.
They no longer do suprise inspections, they call and set an appointment date to come out and take samples.
Gives operators warning and allows time for them to go back into compliance.

It is actually the EPA, Enviormental Protection Agency that is supposed to watch after this.

Answer 2

Believe it or not, but individual companies also monitor air and water quality. Certain manufacturers, for example, are monitored by the state and federal EPA offices. If a company uses water in it's processing, for example, and discharge water into a stream or river, they are required to measure the quality of the water upstream of where they discharge and downstream of where they discharge. These measurements are turned into the state EPAs on a monthly basis. Same with air quality.