"If someone decided he didn't want to pay for a sewer hookup or a septic field and decided to pipe his sewage out into the street in your neighborhood, would you be in favor of infringing on his choice and his freedom?"
There are local zoning laws which he would violating. But before technology allowed for such things as sewage systems and running water to be affordable, that's what was done, except it was a pail instead of a pipe. It wasn't laws which were improved this condition; it was technology.

"This is the kind of question, writ large, that is being raised. It's not about trying to enforce some sort of "will of the elite" on everybody else. It's about making sure that we have sane laws protecting the quality of the air, water, soil, and so on, that we all require to live, in spite of what might be less expensive and more convenient for some people."

Your above example would not be cheaper nor more convenient- just dumber.

"In case you hadn't noticed, the financial elite already have expressed their will on environmental matters. It's called buying summer homes in the mountains where the air is better, organizing home owners' associations to control the environment in their neighborhoods (even down to the matter of whether people may have the choice and the freedom to hang laundry outside in their own yards), and making sure that nasty power plants, refineries, etc., are not built where the rich and powerful have their homes. Let somebody else's kid get cancer."

Indoor air is far worse than outdoor air- in terms of health than compared to any outdoor air in US. The air in the mountains will be cooler but not neccessarily better than air in cities. As far as home owners this has largely to do with appearance and is about as much about the environment is what clothes people choose to wear.
So far you not discussed anything to do with FEDERAL laws required for this.

"The benefits are not distributed equally. There's not much to be done about that. Let's see if we can do something about the risks, hm?"

A rich guy living in the mountains is probably more a risk than someone living is the lowly cities- because increased radiation this may add or subtract from this risk it might be worse [though distance to medical care is probably much larger factor]. But environmental conditions directly related to air quality are not safer.