I don't know all the details, but between heightened public awareness, state-level regulations, and the federal Clean Water Act, overall pollution levels in Ame

I don't know all the details, but between heightened public awareness, state-level regulations, and the federal Clean Water Act, overall pollution levels in American freshwater was improving markedly. It seems plausible to me that we're talking about poisons of all sorts being cleaned from the environment, not just DDT.