Our country is far to connected, as one would expect of the environment, for any state to make decisions that will affect other areas without their input.
Any decisions made about the environment need to be maintained on a national level.
Our health depends on the health of the environment. Without the EPA, regulations favoring corporations will allow pollutants to damage this health, which will result in rising healthcare costs associated with increased health problems.
The only reason to abolish the EPA is for corporate interests. That's it. This is, inherently, shortsighted and does not take into account future generations.