LA was one of many. New York was supposed to be bad. Many cities used residential coal heating. Not only in the USA, but there are many stories that all of London simply turned BLACK. To the point that local moths even turned black through selective breeding.
Here in Springfield, OR we had a paper mill that STUNK. Mostly noted as one drove along HWY 126. Yet, there had to be local land owners that also were impacted by it.
There was a big kerfuffle in Albany, Oregon about Wah Chang.
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I remember about a mile of driving along I-5. It wasn't every once in a while, but the place always stunk. To the point I'd try to hold my breath while passing the plant.
Both the Paper plant in Springfield, and Wah Chang in Albany remain today, but they've made changes to reduce their stench.
I don't want to go back.
When I was young, we always had pretty orange sunsets. I haven't noticed them for quite some time, except while there are wildfires. I'm pretty sure those pretty orange sunsets we were looking at was air pollution.
I don't want to go backwards. Yet, at some point one might decide that the current air pollution regulations are good enough. So, we can go ahead with Tier 4, but not move onto Tier 5.
If electric vehicles take over in the next couple of decades, then gas and diesel exhaust will become less of a problem.