>We need to flip the approval process on its head -- from "safe until proven otherwise" to "unsafe until (independently) proven safe". The tally of harm to all life caused by these chemicals is on a massive scale that any mass murderer would be proud of.

That isn't always practically feasible and its a really tough problem to solve. Consider all the ways a compound released into the environment can break down and how long it might take for any exposure or even low levels of exposure might take to have any adverse health affects. The type of evidence you'd need to gather to demonstrate any compound is fully safe with that bar would make it nearly impossible to declare anything safe.

Microplastics, PFAS, and other compounds with potential long-acting health impacts are very hard to predict far in advance. Strong evidence against any adverse health effects would take considerable effort to gather while in the mean time they would offer massive clear benefits and solve so many problems. Plastics have massively reduced costs in almost every industry and have become almost irreplaceable in some applications such as medical equipment (think packaging for syringes, surgical tools, or anything that requires contamination control). Yet how they break down into microplastics in the environment and then eventually bioaccumulate in our tissues through the food chain is something that would've been extremely hard to predict at the onset of their creation. Even now we don't know if they're necessarily harmful.