It can still dilute if everybody is releasing different pollutants; it's only a problem in clusters of similar industry that overwhelms intake filtering.

As to your second argument, the EPA's literal purpose is to force citizens to operate their life/business responsibly; if you think their standards are too lenient than take it up with your elected representative. One of my biggest frustrations I see here are people pushing to overthrowing everything for grand new systems, completely ignore the implementation details for such a system, and then get frustrated when the system fails because of the details. The system to accomplish your goals is already fucking there, use it.