Except for China, all the big coal burning economies have serious scrubbers and other emissions controlling features on coal power plants. China doesn't.
Actually we now know how to build reactors that won't melt down and will use all the long lived radioactive waste from the first generation of light neutron reactors. Unfortunately our regulatory system, including our courts, make it so expensive to even try to build a nuclear plant that no one will even attempt to build an advanced reactor.Coal is a dirty fuel, high in Sulfur and it creates a lot of soot. There are technologies to scrub and capture all products of its combustion, but it is very expensive to operate. Natural Gas is much cleaner burning, but still produces CO2 which is becoming a major player in politics these days. Nuclear power is the only true "green" technology as far as reduction of CO2 emmissions, but then there is the risk of a leak or meltdown.