We don't know how much the EPA affected anything. In the past people didn't realize how bad pollution was so they didn't see why to care: people have been dumping trash in rivers for thousands of years to no noticeable ill effect (such trash was mostly organic matter that the fish could eat and in small quantities until the very end of that). Companies are directed by people, and they started caring: they did two things in parallel: start the EPA and clean up their act. We can only guess how things would be different if the EPA had been ruled unconstitutional (I can't even think how you could construct a parallel universe where the people running a company didn't care but the EPA existed and had teeth).

I do know the EPA fines are a cost of doing business to some. A few of them have decided that the public relations problems were getting too bad and cleaned up their act.