EPA’s Revised Endangerment Findings Under the Clean Air Act

New York Law Journal

February 25, 2010

Over the past six months, Environmental Protection Agency (EPA) Administrator Lisa Jackson has issued or proposed new and amended “endangerment” findings under the Clean Air Act (CAA) that are expected to increase the number of sources subject to EPA regulation and ratchet down air emissions standards overall. Under the CAA, EPA must make a finding that an air pollutant may reasonably be anticipated to endanger public health or welfare. The following summarizes the new findings for several “criteria” pollutants subject to National Ambient Air Quality Standards (NA) and the new endangerment finding addressing climate change.

Air Quality Standards

EPA is required to establish primary air quality standards that protect public health with an adequate margin of safety and secondary air quality standards that protect public welfare (e.g., effects on soils, water, crops, vegetation, wildlife, property, etc.).[1] EPA must review existing standards every five years.

Based on recent reviews of the public health and welfare impacts of several criteria pollutants, EPA established a new short-term standard for nitrogen dioxide (NO2) and proposed new standards for sulfur dioxide (SO2) and ozone that are the most stringent air quality standards adopted by any EPA Administrator over the past 40 years.

The tightening of these standards could assist New York in addressing its non-attainment status for fine particulates and ozone because NO2 and SO2 originate from both local and out-of-state sources and serve as precursors to the formation of particulates and ozone. The tightening of these standards would benefit New Yorkers if western states are required to adopt more stringent regulations that can reduce the transport into New York of NO2 and SO2 emissions. Nonetheless, because New York is already not attaining the existing ozone standard, any lowering of that NAAQS would likely require New York to develop additional rules to reduce both NO2 and volatile organic compound (VOC) emissions from stationary and mobile sources, likely increasing requirements not only on large sources but on smaller sources, including small businesses.

Nitrogen Dioxide.  In 1971, EPA established the first primary and secondary NO2 standard at 53 parts per billion (ppb) averaged annually, which remains in effect today. EPA has now established the first hourly NO2 standard, which will take effect on April 12, 2010. See 75 Fed. Reg. 6474 (Feb. 9, 2010). This new one-hour standard is set at 100 ppb and will protect persons from peak short-term exposures that occur primarily near major roads. EPA expects to identify areas attaining or not attaining the new one-hour standard by January 2012 based on existing community-wide ambient air quality monitors. EPA will also require states to set up new monitoring stations near major urban roads by Jan. 1, 2013, and after three years of collecting monitoring data, EPA will then re-designate areas as either attaining or not attaining the new standard by 2016 or 2017.

Currently, there are no areas in the United States designated as non-attainment for the annual NO2 standard; and based on the existing community-wide ambient air quality monitors, no county is predicted to be identified as non-attainment under the new 100 ppb hourly NO2 standard in year 2020.

However, EPA expects some areas will later be designated as non-attainment once data is collected on the new monitors located near major roadways as required by this new regulation.[2] Measures that could reduce NO2 emissions include diesel retrofits on both mobile sources and nonroad engines, elimination of idling from mobile sources, and continuous inspection and maintenance of mobile sources.[3]

Ozone.  Since the 1970s, EPA has periodically revised the ozone NAAQS. In 1971, EPA set the first primary and secondary NAAQS at 0.08 parts per million (ppm) over a one-hour averaging period. The primary and secondary standards were revised upward in 1979 to 0.12 ppm. In 1997, EPA revised the primary and secondary standards back to 0.08 ppm, but changed the averaging period to an eight-hour average concentration. In 2008, the Bush administration lowered the eight-hour primary and secondary standards to 0.075 ppm.[4]

In December 2009, EPA Administrator Lisa Jackson proposed to lower the standards further, including (1) lowering the eight-hour primary standard to a range between 0.06 and 0.07 ppm and (2) establishing a new secondary standard within the range of 7 to 15 ppm-hours based on a cumulative, seasonal standard. See 75 Fed. Reg. 2938 (Jan. 19, 2010). Today, 322 counties violate the current standard of 0.075 ppm. A primary ozone standard of 0.07 ppm would increase the number of non-attaining counties to 515; a primary standard of 0.06 ppm would result in 650 non-attaining counties (with potentially 27 counties impacted in New York State).[5]

EPA proposed revising the 2008 ozone standards based on the 2008 unanimous recommendation of the Clean Air Scientific Advisory Committee (CASAC) that the primary eight-hour ozone standard should be set in the range between 0.06 and 0.07 ppm in order to protect public health with an adequate margin of safety for children and other sensitive populations. In April 2008, CASAC had sent a letter to EPA expressing its strong disagreement with EPA’s 2008 decision to set the primary and secondary eight-hour ozone standard at 0.075 ppm, which in its view did not provide an adequate margin of safety to protect public health as required by the CAA.

In May 2008, states, environmental groups and industry challenged EPA’s 2008 ozone standards. The challenges were consolidated in State of Mississippi v. EPA, No. 08-1200 (D.C. Cir. 2008) and in March 2009, EPA filed an unopposed motion to hold the case in abeyance while the new EPA Administration reviewed the ozone standards. In its notice to the Court, EPA stated that it would propose a new standard by Dec. 21, 2009 (the current proposal) and that the rule would be finalized by August 2010.[6]

In preparing its analysis of the regulatory impact of the proposed ozone standard, EPA assumed certain sectors located in the east and west coasts would be subject to additional emission reductions to meet the 2020 attainment deadline. For electric generating units, EPA assumes lower caps in the east through revisions to its Clean Air Interstate Rule (CAIR), which includes states east of the Mississippi River, and the application of Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) emissions controls on coal fired units in certain non-attainment areas in the east that are in the CAIR region but outside the Ozone Transport Region and Midwest Regional Planning Organization. EPA also predicts NOx and VOC reductions from non-electric generating point sources, area sources, non-road engines, and mobile sources.[7]

Sulfur Dioxide. On Nov. 16, 2009, EPA proposed to establish a new one-hour primary SO2 standard within the range of 50 to 100 ppb and to revoke the existing 140 ppb 24-hour and 30 ppb annual SO2 standards that had existed since 1971. See 74 Fed. Reg. 64810 (Dec. 8, 2009). In 1998, the Court of Appeals for the District of Columbia found that EPA had failed to adequately explain its decision not to revise the SO2 primary standards, or in particular, why short-term SO2 exposures to asthmatics did not constitute a public health problem. See American Lung Ass’n v. EPA, 134 F.3d 388 (D.C. Cir. 1998).

EPA now proposes to create a one-hour standard because scientific evidence demonstrates the shorter-term standard would better protect public health for asthmatics and other at-risk populations than the 24-hour or annual standards. In fact, EPA found that there is little evidence to suggest an association between long-term exposure and public health effects. EPA expects to finalize the new primary standard in June 2010 and then identify which areas meet the new standard by 2012.[8]

Currently six states, including New Jersey, have areas that are not meeting the current SO2 NAAQS. Under a new standard, a one-hour SO2 standard set at 50 ppb would result in 57 non-attaining counties in the United States (including potentially counties in New York State) whereas a standard of 150 ppb would result in six non-attaining counties. The number of non-attaining counties could increase once the new monitoring network is in place.[9] The largest sources of SO2 emissions are electric generating plants and other industrial sources that burn fossil fuels.[10] EPA expects measures to address ozone and fine particulates will likely address any non-attainment areas designated under a newly adopted SO2 NAAQS.

Climate Change

The U.S. Supreme Court held in Massachusetts v. EPA, 549 U.S. 497 (2007), that greenhouse gas emissions are air pollutants and that EPA must determine whether or not greenhouse gas emissions from new motor vehicles cause or contribute to air pollution that may reasonably be anticipated to endanger public health and welfare.

On Dec. 15, 2009, EPA published two findings in the Federal Register. See 74 Fed. Reg. 66496. First, EPA found that greenhouse gases, including carbon dioxide, methane, nitrous oxide, hydroflourocarbons, perfluorocarbons and sulfur hexafluoride, threaten the public health and welfare of current and future generations. In particular, EPA identified the following public health concerns: (a) increased ambient ozone and corresponding public health impacts in ozone non-attainment areas; (b) increased mortality associated with hotter temperatures and more frequent heat waves; (c) increased public risks from hurricanes and flooding; and (d) increased aeroallergens causing more illnesses. Public welfare impacts from greenhouse gas emissions include rising sea levels impacting coastal areas; more extreme weather events, such as wildfires, flooding and drought; and changes in water supplies and quality.[11]

Second, EPA found that greenhouse gases from new motor vehicle engines contribute to the greenhouse gas pollution which threatens public health and welfare. While these findings do not impose any requirements on industry or mobile sources immediately, the findings pave the way for EPA to impose greenhouse gas standards on vehicles and stationary sources.

Even prior to making the endangerment finding, on Sept. 15, 2009, EPA and the Department of Transportation’s National Highway Safety Administration proposed new standards for passenger cars, light-duty trucks and medium-duty passenger vehicles for model years 2012 through 2016 that would require such vehicles to meet an average emissions level of 250 grams of carbon dioxide per mile, which is equivalent to a fuel efficiency of 35.5 miles per gallon.[12]

In addition, on Oct. 27, 2009, EPA proposed changes to its Prevention of Significant Deterioration (PSD) air permitting rules that would require emissions controls on new or modified sources that exceed 25,000 tons per year of greenhouse gases (for most PSD pollutants, the threshold is 250 tpy to be considered a major source).[13]

Overall, with the tightening of several air quality standards and EPA’s climate change endangerment finding, we should expect to see more regulation of sources, including those that had been too small to be subject to CAA requirements or had been grandfathered in the past, and more stringent requirements for those sources already subject to CAA regulatory and permitting programs.

and Ethan I. Strell are attorneys in the environmental practice group at Carter Ledyard & Milburn.

Reprinted with permission from the February 25, 2010 edition of the New York Law Journal © 2010 Incisive Media Properties, Inc. All rights reserved. Further duplication without permission is prohibited. Reprint information for the legal properties relative to content searches and copyright clearance is available at For questions contact, or 347-227-3382.


[1]42 USC §7409 (CAA §109).

[2] See 75 Fed. Reg. at 6476; see also EPA, Final Regulatory Impact Analysis for the NO2 National Ambient Air Quality Standards, January 2010, at ES-4 to ES-8. All final and proposed EPA regulations and regulatory impact analyses referred to herein are available on the EPA Web site at (searching under topics: air pollutants).

[3] See 75 Fed. Reg. at 6476, 6479 (Mobile sources represent 60% of NO2 emissions in the United States.); see also Regulatory Impact Analysis for NO2 at 3-2.

[4] See 73 Fed. Reg. 16436 (March 27, 2008).

[5] See EPA, Counties Projected to Violate Primary 8-hour Ground-Level Ozone Standard in 2020, available with EPA’s Regulatory Impact Statement for Proposed Ozone Standard.

[6] See 75 Fed. Reg. at 2943-46.

[7] See EPA, Regulatory Impact Statement for Proposed Ozone Standard at 3-25 to 3-27.

[8] See 74 Fed. Reg. at 64813-15, 64858.

[9] See EPA, Regulatory Impact Statement for Proposed Sulfur Dioxide Standard at ES-7.

[10] See id. at 1, 3-8 to 3-9.

[11] See 74 Fed. Reg. at 66497-98.

[12] See 74 Fed. Reg. 49454 (Sept. 28, 2009).

[13] See 74 Fed. Reg. 55,292 (Oct. 27, 2009).

Christine A. Fazio

Related practice area:

© Copyright 2020 Carter Ledyard & Milburn LLP