According to what?

"Pollution" is a pretty broad category, but I think underneath that umbrella there are maybe a small handful of profitable private ventures. Recycling comes to mind, which is largely already being done.

So your really talking about centralized solutions at this point, which means you have to analyze the externalities, which is not easy to do. At an individual level, I do not feel pollution is much of a problem in my day to day life, and I doubt I am alone in that sentiment. How are you going to convince my that some externality tax or some new program is better than the opportunity costs? The short answer is you won't. You could try to provide some objective evidence that I do in fact have a shitty life because of pollution, but if the evidence of my own meandering experience says otherwise, I will still reject the analysis.

And here in lies the problem with centralized solutions to abstract problems. You will never have 100% conviction on something like pollution, and the benefit is ultimately subjective, so what you ultimately end up doing is calculating MB = MC for 51% of the people and ignoring the other 49%. Heck, you're actually lucky if you get a solution that calculates MB = MC, more like MB exists within my voter base, therefore solution at whatever the cost is.