How much tax? What if they also have a pollution tax? What if they don't, are all exports going to be more expensive now in comparison with countries without t

How much tax? What if they also have a pollution tax? What if they don't, are all exports going to be more expensive now in comparison with countries without this tax? What if they claim to have a pollution tax but are lying at the state level? It gets really complicated really fast. If pollution is taxed at the source how do you calculate how much of a refund to give when exporting? Probably no one can even calculate that for you. And not giving a refund would destroy exports which is an obvious problem.