The EPA is one of the few Federal agencies we actually need. But there is no authority for the Fed govt to actually create and run it. Can't fall under "interstate commerce", or necessary& proper clause, etc.
We need a constitutional amendment authorizing it. And the reason we need the amendment, is also so we can limit it, only to interstate issues (Minnesota pollutes a river that later flows through other states, California pollutes air that later moves through Nevada etc., acid rain is coming into the US from Canada etc.). The Fed govt is forbidden to regulate any other environmental issues. And the scope of things the Fed can do within those confines, is also further limited.
"The social contract exists so that everyone doesn’t have to squat in the dust holding a spear to protect his woman and his meat all day every day. It does not exist so that the government can take your spear, your meat, and your woman because it knows better what to do with them." - Instapundit.com