This is actually somewhat common too. Like chlorine being replaced by other disinfectants in drinking water. https://www.npr.org/2011/01/07/132743638/disinfect

This is actually somewhat common too. Like chlorine being replaced by other disinfectants in drinking water. https://www.npr.org/2011/01/07/132743638/disinfectant-to-clean-water-has-problems-of-its-own https://www.npr.org/2011/01/07/132743638/disinfectant-to-cle... Basically you have some popular chemical so it gets studied extensively and we learn about the bad things it does. It then starts being replaced by things that have been less studied, so there's less evidence of the bad things they do but could be equally bad, better or worse.