The EPA changes the standards for acceptable pollution every year or so. That’s really bad since it’s industry that influences the decision not science or rationality. The EPA does something even worse, too. They change the procedures for sampling pollution levels frequently in response to pressure from industry.
The EPA most important and defining role is to at least monitor pollution. But if you test a mile from the road one year, then the next year, three, you can’t really compare those results and look for trends.
There are corporations who fail to meet the EPA standards year after year but just pay fines.