NOx Reduction Plans in Turmoil

NOx Reduction Plans in Turmoil

September 01, 1999

Roy S. Belden, Author

US efforts to reduce nitrogen oxide emissions from power plants and other facilities that burn fossil fuels in 22 states east of the Mississippi River are in turmoil after two recent court decisions.

The decisions have sent the federal government back to the drawing board on efforts to force states to start implementing plans to reduce power plant NOx emissions by an average of 60% to 75% from 1990 levels by May 2003.

In the meantime, the Environmental Protection Agency is poised, in response to pressure from six northeastern states, to take direct action against power plants and other NOx sources in 12 states that are considered upwind from the northeast.


The United States has had in place since the early 1970’s a so-called 1-hour ozone standard that limits pollutants that contribute to smog. The standard limits the amounts of NOx and volatile organic compounds, or VOCs, that can be emitted during each rolling 1-hour period to .12 parts per million.

In 1997, the Environmental Protection Agency issued a new 8-hour ozone standard limiting the same emissions to a total of .08 parts per million per hour on average during each rolling 8-hour period.

In 1998, EPA also issued regulations requiring 22 states east of the Mississippi to submit plans by the end of September 1999 to reduce NOx emissions to levels significantly below 1990 emissions and to start implementing the plans by May 2003. Each state was assigned a target. This “NOx SIP call rule”—or call for state implementation plans (or changes to existing plans where states already had them)—was based on a belief that the existing standards are inadequate by themselves to reduce smog to acceptable levels.

Court Actions

At the end of May this year, the federal appeals court for the District of Columbia issued a stay barring the federal government from enforcing the September 1999 deadline for states to submit their NOx reduction plans. No new deadline has been set. The stay is temporary until the merits of the case can be heard—probably sometime early next year.

Also in May, and potentially more significant, the same appeals court sent the new 8-hour ozone standard—together with a standard on “fine” particulate emissions of 2.5 micrometers or less (PM2.5)—back to the Environmental Protection Agency for further clarification of the legal and scientific bases for the standards. (The court also vacated a separate standard for “coarse” particulate emissions of more than 2.5 micrometers up to 10 micrometers (PM10).) The court said EPA’s reason for selecting the levels of ozone and PM2.5 standards was potentially unconstitutional because the agency failed to base its decision on an “intelligible principle” tied to ensuring the protection of public health. The court concluded that the government’s approach violated a “nondelegation doctrine” of the US constitution that bars Congress from delegating legislative powers to an agency in the executive branch.

The appeals court decision throws the 8-hour ozone standard—which served as a key basis for the NOx SIP call rule—into flux. EPA officials acknowledge that this is an additional barrier to their ability to implement the NOx SIP call rule. The SIP call rule was based on a finding that NOx emissions from upwind states contribute to violations by downwind states of both the old 1-hour and new 8-hour ozone standards.

Northeast Complaints

In an effort to salvage some of its NOx reduction efforts, EPA is now moving to a backup plan to force NOx reductions in 12 of the 22 states. The backup plan is a response to petitions from six states—Connecticut, Maine, Massachusetts, New Hampshire, New York and Pennsylvania—who complained that emissions from the other 12 states contribute to smog in the northeast. The government claims authority to act under section 126 of the Clean Air Act. EPA is expected to take final action on the backup plan this winter, but in the meantime, it has made a final finding that the petitioning states are correct that emissions have been moving downwind. Several midwestern utilities are tying to persuade Congress to block implementation of the backup plan in addition to challenging the plan in court.

The 12 states that would be affected are Delaware, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Virginia and West Virginia.

Under section 126, EPA has authority to implement NOx control reductions directly on specific sources that are alleged to contribute to downwind violations of the 1-hour ozone standard—without working indirectly through the states. NOx emitters in other states have recently been targeted in three new section 126 petitions filed by Delaware, Maryland, and New Jersey, but EPA has not yet acted on them.


The 8-hour ozone standard and the NOx SIP call rule are inextricably linked. If EPA is unable ultimately to save the 8-hour standard in court, then the agency will be left with only the old 1-hour standard. Most of the states are either now in compliance, or soon will be, with the 1-hour standard. EPA might be forced to scale back the NOx SIP call rule substantially or even scrap it altogether.

However, EPA seems determined—regardless of what happens on the SIP call rule—to push through NOx controls on sources in the 12 states that are considered upwind from the petitioning states. EPA may have a stronger hand in using its section 126 authority to implement such controls.

The bottom line is there will ultimately be additional NOx reductions imposed on sources in at least the 12 states, but the mechanism remains unclear and the timing may slip from the May 2003 target date.