There was a time in the not too distant past that the so-called "smokestack industries" belched pollutants into the air without much regard to the harmful effects on humans and the environment. Even so, jobs were plentiful, and people learned to live with the pollution in industrial areas. It's not a vote for pollution. It's just the way it was.
However, the first stirrings of environmental concern began in the 1960s and led to the Clean Air Act in the 1970s. Much in the way of cleaning up the environment has been accomplished since then, as those of you who lived in a heavy industrial area before the 1970s know. The vastly improved air that we breathe today has not come without a cost though.