Expecting investors to vote against their own financial interests for the greater good is a terrible system. 3M investors only care because of the threat of lawsuits and other legal trouble; those are the mechanisms we need to improve. Stricter environmental rules and enforcement will force companies to reduce harmful externalities. The shareholder pressure is incidental.

Free markets are generally bad at handling pollution because the costs are so diffuse and long term; there's often a way to increase profits at the expense of someone else's health in a manner that can't be precisely quantified immediately.