by Amanda Peterka, E&E reporter
Originally published by E&E April 17, 2015, and republished here with permissions — Ed.
The National Park Service is asking U.S. EPA to set a more protective standard for ground-level ozone pollution to minimize impacts to plants and ecosystems.
The service said it reviewed EPA’s recent proposal for the secondary ozone standard — a Clean Air Act limit aimed at protecting ecosystems and public welfare — and found it inadequate to prevent harm to natural resources.
EPA in November proposed to tighten the secondary eight-hour standard to between 65 and 70 parts per billion, the same level as the primary standard it’s required to set to protect public health.
“We agree with EPA that the existing secondary standard is not adequate to protect natural ecosystems from adverse impacts due to ozone,” wrote the NPS’s Air Resources Division chief, Carol McCoy, in the letter dated April 14. “We do not believe,” however, that EPA’s proposal “would be effective in addressing ecosystem concerns.”
Under the Clean Air Act, EPA is required to set national ambient air quality standards for six pollutants, including ground-level ozone. The act requires EPA to set two standards — one for public health and one to protect public welfare and the environment.
In the area of ozone, most of the focus has been on the primary standard, which EPA sets to guard against adverse public health effects. EPA has never set a more stringent secondary standard than the primary standard — meaning that the public health standard has always been the effective limit used for compliance.
But the secondary standard is getting more play in the current review, given the increasing data showing that ozone pollution is bad for plant health (Greenwire, March 19). Ozone has been linked to spotting and discoloration on plants, reductions in crop yields, and decreased rates of photosynthesis in trees.
NPS is urging EPA to set a separate and more protective secondary standard at the lower end of the range recommended by EPA’s science advisers. The service also said that EPA needs to change the way the secondary standard is calculated; according to NPS, the current form is not capturing negative effects to natural areas in Arizona, Colorado, New Mexico, Utah and Wyoming.
“That these natural areas are not as protected under an 8-hour standard should be an important consideration in EPA’s determination of the form of the secondary standard,” McCoy wrote.
In 2013, a federal court remanded EPA’s 2008 secondary standard, finding that the agency did not do enough analysis to prove that a 75 ppb secondary standard identical to the public health limit would sufficiently protect the environment.
EPA in its November proposal defended the decision to leave the secondary standard the same as the primary one.
“This proposal is based on a thorough review … of the latest scientific information on ozone-induced environmental effects,” EPA said.
EPA has closed a public comment period on the proposal and is working toward an Oct. 1 court-ordered deadline to issue a final rule.