alt Hacker NewsClean Air Act was passed in 1963. the Clean Water Act was passed in 1972. The China Shock began in 2000 after PNTR.
Avoiding environmental regulation was one reason to move factories to China, avoiding unions and high wages was another.
But the local communities weren't demanding that their factories be moved overseas so they could have a clean if impoverished towns. Your entire causality is completely backwards.
It isn't 100% causality, but it was definitely one of the ways it was sold to people through PR/propaganda.
Free trade / globalism was the larger "true" move, and yes getting away from unions and high wages to maximize profits was a big part.
Corporations made a change from valuing stakeholder value (employees, communities, customers, suppliers, the nation) to pure shareholder value (profits over everything else, despite the long term result that profits by any and all means hurts all stakeholders and eventually can cannibalize the company unless you have monopolistic moats).