A lot of people like emissions trading, but I think it's a bit oversold. Implementing an emissions trading scheme is phenomenally complex, and it doesn't really reduce the regulatory apparatus required. You still have to have people figuring out what the total cap should be on a harmful substance, you still have to have people who go out and enforce to make sure nobody is exceeding their emissions limits, etc. You open yourself up to all sorts of gaming the system--people trying to claim emissions credits for things that don't actually reduce emissions. It also, as the sibling comment mentions, doesn't work for pollutants like lead, sulfur, etc, whose effects are highly localized. It doesn't really do anyone any good if polluters in L.A. buy up all the sulfur credits that result from people in the middle of Montana reducing their emissions.
The EPA generally doesn't ban things. Leaded gasoline was an unusual case because it was so harmful and also, in the grand scheme of things, quite replaceable. Usually what they'll do is specify that polluters that emit particular kinds of air pollution (sulfur, etc) must use a certain level of control technology. This creates certain market incentives for polluters to make this control technology as cheap as possible. However, this approach doesn't really reduce pollution as much as it should, since the EPA is usually quite sensitive to cost issues. But as a practical matter, some polluters should go out of business if the cost of thoroughly cleaning up their emissions outweighs the revenue from the polluting activity.
The EPA generally doesn't ban things. Leaded gasoline was an unusual case because it was so harmful and also, in the grand scheme of things, quite replaceable. Usually what they'll do is specify that polluters that emit particular kinds of air pollution (sulfur, etc) must use a certain level of control technology. This creates certain market incentives for polluters to make this control technology as cheap as possible. However, this approach doesn't really reduce pollution as much as it should, since the EPA is usually quite sensitive to cost issues. But as a practical matter, some polluters should go out of business if the cost of thoroughly cleaning up their emissions outweighs the revenue from the polluting activity.