Gristmill applauds a report stating that it's actually cheaper for companies to adopt a greener way of making chlorine (mercury-free!) than to continue with their current method.
I am eternally skeptical of such reports. If the company wins by changing, well, why haven't they changed? I give the benefit of doubt to industry in cases like this: they know themselves better than a think-tank with an axe. Even if it is a nice axe.
Since some of the plants have shifted already, this is only proof that the companies know about it. Ergo, I can't summon any reasons, aside from 'it costs more' to explain the mercury-using plants.
Finally, advocating compliance legislation to force the switch instead of a more Pigovian solution to the problem? Apparently Mr. Obama agrees.