I don’t know if the number of incidents is vastly out of proportion to normal but pollution, accidental or deliberate, is hardly new. It may be a change in coverage, which may be using narratives to new ends. As coverage of fires on the Cuyahoga River over the last 110 years may show, even when things are improving, narratives and selective increase in news stories can make things seem worse than they are. See an example of manipulations in this bit of history: