Large Ozone Precursor Cuts Linked to Power Plan

By Patrick Ambrosio

Aug. 5 — The Environmental Protection Agency's first-ever regulation on carbon emissions from existing power plants is also linked to significant reductions in emissions of ozone precursors.

The projected emissions cuts from the Clean Power Plan are comparable to cuts achieved by past EPA air rules, including the Tier 3 motor vehicle emissions and low-sulfur fuel standards. State officials were split over how significant a tool the climate rule will be for states to attain and maintain national ambient air quality standards, but public health advocates called the reductions significant.

“Power plants are a huge source of air pollution that spreads far,” Janice Nolen, assistant vice president of national policy at the American Lung Association, told Bloomberg BNA. “This is one more step to help reduce the serious burden of air pollution that they produce.”

(Click image to enlarge.)

ECR graphic 8/6/2015

The Clean Power Plan (RIN 2060-AR33), signed Aug. 3, is projected to reduce carbon dioxide emissions from the power sector by 32 percent below 2005 levels by 2030.

Additionally, the EPA's cost-benefit analysis attributed billions in annual health benefits to implementing the Clean Power Plan, driven by reductions in emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx). Bill Becker, executive director of the National Association of Clean Air Agencies, described the collateral, non-greenhouse gas pollution reductions as a “big deal” for air quality.

“They're bonus points,” Becker told Bloomberg BNA.

The EPA projected the criteria pollutant reductions attributed to the fully implemented Clean Power Plan will help avoid up to 3,600 premature deaths and 90,000 asthma attacks annually. The Obama administration has repeatedly emphasized the public health benefits of regulating power plant emissions of carbon since the administration proposed the rule in June 2014.

Reductions Compared to Tier 3

The EPA's regulatory impact analysis for the Clean Power Plan assessed two different options: a rate-based compliance strategy and a mass-based compliance strategy. The agency's draft federal plan for Clean Power Plan compliance also proposes a rate-based and a mass-based emissions trading program to achieve necessary carbon reductions from the power sector.

The agency projected that in 2030, a mass-based compliance strategy would cut power plant emissions of sulfur dioxide by 280,000 tons, annual nitrogen oxides emissions by 279,000 tons and ozone-season nitrogen oxides by 121,000 tons. For a rate-based approach, the rule in 2030 would result in annual emissions reductions of sulfur dioxide by 318,000 tons, annual nitrogen oxides emissions by 282,000 tons and ozone-season nitrogen oxides by 118,000 tons.

Becker said the nitrogen oxide reductions from the Clean Power Plan are “in the ballpark” of the reductions expected from implementation of the Tier 3 motor vehicle and fuel rule.

The EPA projected the Tier 3 rule would result in annual nitrogen oxides reductions of about 264,000 tons by 2018 and about 329,000 tons by 2030.

Reductions May Not Occur in Problem Areas

The low-sulfur fuel component of the Tier 3 rule, which goes into effect in 2017, is expected by many state officials to have an immediate positive impact on air quality because removing sulfur from gasoline will improve the effectiveness of catalytic converters in motor vehicles.

Becker said the criteria pollutant reductions will help some areas attain and maintain their air quality standards, but not all state officials were as confident that the Clean Power Plan will be a significant compliance tool.

Clint Woods, executive director of the Association of Air Pollution Control Agencies, was skeptical that the Clean Power Plan will have a similar effect as Tier 3 for the purposes of meeting and attaining national ambient air quality standards.

“I think it's probably less significant than some other things for state programs,” Woods told Bloomberg BNA.

The EPA's benefit calculations are a “bit crude” and make several assumptions about the “linearity” of benefits associated with emissions cuts, Woods explained. For the purposes of air quality planning, the nitrogen oxides and sulfur dioxide reductions achieved under the Clean Power Plan may not occur in areas that have attainment problems, he said.

“Those reductions, while helpful, are not helpful in the area where EPA says there is a problem.” Woods said.

Effects Unclear in the West

It's too soon to tell how the Clean Power Plan will affect air quality across the western U.S., according to Tom Moore, air quality program manager for the Western Regional Air Partnership and the Western States Air Resources Council.

Moore told Bloomberg BNA that emissions of nitrogen oxides and sulfur dioxide from power plants in the West have been “declining precipitously” over the past two decades.

Power plant emissions of sulfur dioxide in the 11-state Western Interconnection fell from more than 550,000 tons per year in 1996 to slightly more than 150,000 tons per year in 2014, according to EPA data cited in an April presentation given by Moore. Over that same time period, Western power plant emissions of nitrogen oxides fell from more than 500,000 tons per year to less than 300,000 tons per year.

Western states will likely wait for the EPA to issue its final decision (RIN 2060-AP38) on revising or retaining the current ozone standards of 75 parts per billion before doing analysis of how the Clean Power Plan will impact ozone levels in the West, Moore said. The agency is under an Oct. 1 court-ordered deadline to determine whether it will revise or retain the standards.

Once that decision is final, western states will conduct their own modeling and determine whether the expected reductions from the Clean Power Plan will have a large effect on Western ozone levels, Moore said.

Possibility of Pollutant Increase

Eric Massey, director of the Air Quality Division in the Arizona Department of Environmental Quality, told Bloomberg BNA that before the final rule was released there was concern that implementation of the Clean Power Plan could actually hurt air quality in some areas.

The proposed version of the Clean Power Plan placed so much of an emphasis on converting from coal-fired electric generation to natural gas that there were concerns that the rule could have driven hydraulic fracturing operations closer to ozone nonattainment areas, Massey said. Arizona is still reviewing the final Clean Power Plan, but Massey noted that the EPA is touting the final plan as “less of a rush” to natural gas as the proposal.

The EPA's decision to establish a Clean Energy Incentive Program to reward states that make early investments in wind and solar power is seen as potentially weakening the role of natural gas, though EPA Administrator Gina McCarthy told reporters Aug. 2 that natural gas will remain a key part of the nation's energy mix.

Some Plants May Boost Operations

The agency does acknowledge in the Clean Power Plan that there may be a “relatively small number of plants” that boost operations as a result of the rule, which would increase criteria pollutant emissions.

The agency said those plants are likely to be the “highest-efficiency natural gas-fired units,” but it encouraged states to evaluate the effects of their compliance plans on low-income communities and communities of color to ensure they benefit from implementation.

The EPA increased its focus on vulnerable communities in the final Clean Power Plan, requiring that states meaningfully engage with those communities on their state compliance plans.

While states were split on whether the anticipated criteria pollutant reductions will help with ozone compliance, supporters of the Clean Power Plan have touted the health benefits of the rule.

Sen. Barbara Boxer (D-Calif.) cited the health benefits during an Aug. 5 markup of a bill (S. 1324) that would block the Clean Power Plan, legislation that she said would harm public health.

“Why would we want to do something that would mean up to 90,000 more asthma attacks, 1,700 more heart attacks, 3,600 more premature deaths, and 300,000 more missed days at school and work?” Boxer said during the markup of the bill, which was eventually approved by the Senate Environment and Public Works Committee. 

Improvements Anticipated

The Clean Power Plan will help improve air quality in the areas that have been burdened the most by power plant emissions, including downwind areas, Nolen said.

She noted that the EPA's cost-benefit analysis “actually underestimated the benefits” of the Clean Power Plan because many benefits couldn't be quantified. Those benefits include the benefits of reducing direct exposure to nitrogen oxides and sulfur dioxide, as well as the benefits of reducing direct particulate matter emissions from power plants.

With assistance from Andrew Childers in Washington

To contact the reporter on this story: Patrick Ambrosio in Washington at

To contact the editor responsible for this story: Larry Pearl at