EPA for the first time has set air quality standards geared to protecting ecosystems from the impact of pollutant deposition, but the final rule falls well short of an independent advisory panel’s majority recommendations.
The rule, posted online Wednesday morning following a lengthy review, bundles together three classes of pollutants — sulfur oxides (SOx), nitrogen oxides (NOx) and fine particles — whose fallout can harm crops, trees and aquatic life.
But while the rule revamps the SOx secondary standard from a three-hour average of 500 parts per billion to a yearly threshold of 10 ppb, it makes no change to the comparable limits for NOx and particles.
The 10 ppb SOx limit is in line with the recommendations of the Clean Air Scientific Advisory Committee, a group of independent experts. Most members of the panel last year, however, had endorsed significant cuts in the benchmarks for the other two pollutants as well.
