Full link here.
Name: The Sheep Look Up, by John Brunner. E-book pdf here.
Written in: 1972
Set in: Not really clear, but can't be after 1978. The 'hero' of the book (Austin Train, last seen being blown up while more or less masturbating to the idea of America being under a toxic pollution cloud) was listed as being born in 1938 and being almost forty at the time of the novel's events.
Why it's a dystopia: Pollution, to the nth degree. Water rationing, air pollution at toxic levels, dead species everywhere, resource insecurity. At the end of the book half of America is in civil insurrection, and most of it is on fire.
Why it's significant: It scratches an itch in the Left-SF community, apparently. They keep reprinting the book.
What happened? From Wikipedia: "On July 9, 1970, citing rising concerns over environmental protection and conservation, President Richard Nixon transmitted Reorganization Plan No. 3 to the United States Congress by executive order, creating the EPA as a single, independent agency from a number of smaller arms of different federal agencies. Prior to the establishment of the EPA, the federal government was not structured to comprehensively regulate environmental pollutants." Unfortunately, in 1972 and afterward the American Left was sufficiently blinded by rage and anticipatory revenge towards anything that could be described as 'Nixonian' that they completely failed to incorporate the idea that the EPA might actually succeed.
This may be because Brunner was a bit of a hardcore Lefty - I assumed at first that he was a full-blown Communist, which would handily explain why he managed to get societal trends so badly wrong in just four years' worth of projection; Marxism is after all intellectualism for stupid people - and thus not quite as insightful as Brunner was often told that he was (this comment showing the rather fundamental flaw in Brunner's casual analysis of Starship Troopers* demonstrates the problem that can arise when people tell you once too often that your excrement doesn't reek). Or it may just have been that he couldn't believe that we'd stop fouling our nests while the Commies would just keep on polluting. Hard to say.
PS: The Brown Pelican's doing all right, Brunner. Since you were worried, and everything.
*While lots of people do seem to skip past the fact that the Federal Service requirements for the franchise in Heinlein's book is not the same as 'only military veterans can vote,' it's not because Heinlein didn't make it clear, in several different places in said book, that the vast majority of franchises were earned by non-military service. I will be polite about why a certain subset of the SF community persists about getting that one wrong, and merely refer you to a certain observation that's a few paragraphs above.