Heavy metals are removed by pollution control equipment in approximately the same ratio as nontoxic particulate. Therefore, the more particulate that is removed, the more toxic metals are removed. Unfortunately, every coal is different in terms of quantities and kinds of heavy metals. Thus, there are two basic variables with the fuel itself being only one. We are at a relatively unsophisticated stage at which we designate a coal as dirty if it is more than 1 percent sulfur, but we completely ignore the quantities of heavy metals and other pollutants, such as chlorine, that are in the coal.
Chlorine possibly is the best example of an unbalanced policy toward pollution reduction.
Ultimately, it would make sense to be able to trade unlike pollutants. This coverage of all pollutants and inter-pollutant trading would have major ramifications on coal selection. The price advantage of low sulfur coals would give way to a price advantage for coals with the lowest combination of pollutants.