Current air pollution standards for sulfur dioxide (SO2) and nitrogen oxides (NOx) aren't strict enough to prevent damage to the environment, according to a new policy assessment from U.S. EPA that suggests tougher rules could be on the way.
EPA is undergoing a review of the secondary National Ambient Air Quality Standards (NAAQS) for both SO2 and NOx. The welfare-based rules, distinct from the health-based limits on emissions that cause health problems such as asthma, are intended to prevent air pollution that harms the soil, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility and climate.
And according to a draft analysis of recommendations from scientists, the current standards have failed to prevent those types of impacts. Nearly the entire country has achieved attainment with the standards, which have not been changed since they were established in 1971, but emissions continue to harm wildlife, the report by EPA's National Center for Environmental Assessment concludes.
In the Adirondacks of New York and the Shenandoah region of Virginia, populations of acid-sensitive trout are down, the report says. In other places, scientists have found levels of SO2 and NOx that threaten populations of sugar maple and red spruce trees.
"On the basis of the acidification and nutrient enrichment effects that have been observed to still occur under current ambient conditions and those predicted to occur under the scenario of just meeting the current secondary NAAQS," the report says, "we find support for consideration that the current secondary NAAQS are inadequate to protect the public welfare from known and anticipated adverse welfare effects."
The current nationwide limit on airborne NOx, is 53 parts per billion (ppb) averaged over a year -- the same as the health-based standard. The limit on SO2 is 500 ppb averaged over three hours.
In the new policy assessment, agency scientists recommend a different means of limiting SO2 and NOx pollution. Rather than measuring the substances in the air, they say, EPA should examine their effects on bodies of water, where SO2 and NOx are thought to be causing most of their environmental damage.
The limits recommended by the scientists would be based on acid neutralizing capacity, which measures the acidification of lakes, rivers and streams. Using acid neutralizing capacity as a benchmark for success, the report says, several states "have engaged in costly activities" to improve water quality.
When EPA last completed a review of the standards in 1996, the agency chose not to change them. But potential revisions are on the agenda for the Clean Air Scientific Advisory Committee's upcoming meeting, which is scheduled for Oct. 6-7 in Durham, N.C., according to a notice set for publication in tomorrow's Federal Register.
EPA plans to release a proposed rule next July, according to the agency's regulatory agenda, and because the agency has missed few chances to tighten environmental protections, the new report makes it seem more likely that tougher SO2 and NOx standards are on the way.
"In determining the requisite level of protection for the public welfare from effects on aquatic ecosystems," the policy assessment says, "the administrator will need to weigh the importance of the predicted risks of these effects in the overall context of public welfare protection, along with a determination as to the appropriate weight to place on the associated uncertainties and limitations of this information."
Click here to read the second draft policy assessment.