As the Supreme Court heard arguments on the Cross-State Air Pollution Rule (CSAPR), eight Northeast and Mid-Atlantic states petitioned the Environmental Protection Agency (EPA) to force nine “upwind” states to slash their emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs), which contribute to the formation of ozone to the north and east.

EPA modeling shows that interstate air transport of air pollution from the nine upwind states—Illinois, Indiana, Kentucky, Michigan, North Carolina, Ohio, Tennessee, Virginia, and West Virginia—contributes “significantly” to violations of the 2008 ozone national ambient air quality standard (NAAQS), says the petition signed by the governors of Connecticut, Delaware, Maryland, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont.

The eight “downwind” states urged the EPA to add the nine upwind states to the Ozone Transport Region (OTR), which was established by the 1990 amendments to the federal Clean Air Act. The OTR now includes the eight downwind states, as well as Maine, New Jersey, Pennsylvania, the District of Columbia, and portions of the Northern Virginia suburbs.

If added to the OTR, the nine upwind states would each be required to submit state implementation plans that contain the minimum VOC and NOx emission control requirements that are currently applicable to OTR states. The eight downwind states also asked the EPA to require pollution transport reductions by 2015 and begin monitoring attainment by the 2016 ozone season using “readily available control technologies and reliance on cleaner fuels to generate power.”

“We believe expansion of the transport region and implementation of the required controls in upwind states are necessary for all of the OTR to achieve attainment in a timely manner.  We also believe that the consultation process that is such an important part of the OTC’s activities can benefit all states in an expanded OTR in the assessment of the ozone transport problem and result in the development of effective solutions,” the states told EPA Administrator Gina McCarthy.

According to a statement from the Maryland governor’s office, the petition “cites decades of inaction by the upwind states during which time the eight Mid-Atlantic and Northeastern states have spent tens of billions of dollars to reduce their own air emissions.” It is believed that as much as 70% to 98% of the “ozone air pollution problem” is blown in from upwind states. Parts of some downwind states, including Maryland, would remain in violation of the ozone NAAQS even if they eliminated all the pollution generated within their borders, the statement said.

“The cost of removing an additional ton of pollution in downwind states is estimated at between $10,000 to $40,000—compared to as little as $500 a ton in upwind states, where even some basic control technologies have not been installed,” it added.

The EPA administrator is required to approve or reject the petition within 18 months.

The Supreme Court on Tuesday, meanwhile, heard oral arguments on an appeal of a federal court’s decision to vacate the EPA’s July 2011–finalized CSAPR. That rule, designed to replace the EPA’s 2005 Clean Air Interstate Rule, requires a total of 28 states to reduce annual sulfur dioxide (SO2), annual NOx emissions, and ozone season NOx emissions to help attainment of the 1997 ozone and fine particle and 2006 fine particle NAAQS.

At least 24 states have backed industry groups that sued the EPA for its promulgation of CSAPR. Most contend that the federal agency exceeded its authority under the Clean Air Act when it issued the rule.

On Tuesday, arguments for two combined cases disputing CSAPR’s validity (EPA v. EME Homer City Generation and American Lung Association v. EME Homer City Generation) lasted about 90 minutes. But sources saythe eight Supreme Court Justices reviewing the case—Justice Samuel A. Alito, Jr. took himself out without giving a reason—mostly warmed in the EPA’s favor. Challenges from power companies and opposing states found sympathy only from Justice Antonin Scalia.

SCOTUSblog reporter Lyle Denniston noted that with eight justices on the bench, the EPA runs the risk of an even division—which would ultimately uphold the D.C. Circuit’s decision to vacate the rule.

The eight downwind states meanwhile acknowledged the EPA’s legally hampered efforts to address interstate air pollution transport and its effort to move forward on an expedited schedule to complete modeling and develop a new transport regulation. “We support these efforts, but also believe that there is significant additional benefit to be gained through the OTC’s collaborative process in an expanded transport region,” the eight downwind state governors said in a letter to McCarthy.

Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)