Pollution is a tragedy of the commons. Individually, polluters gain more than they suffer. But collectively, they suffer as well (though I admit it remains to be seen how much, since the IPCC reports on economic impacts leave a lot to be desired [1]).

It is the job of the government to maintain the commons, because it can't get maintained through individual incentives alone.

[1] - https://news.ycombinator.com/item?id=34005635