The National Ambient Air Quality Standards

EPA'S PROPOSED OZONE AIR QUALITY STANDARDS AND AGRICULTURE: FACT SHEET

OVERVIEW OF ACTION

•	On Nov. 25, 2014, the U.S. Environmental Protection Agency (EPA) proposed to strengthen the
National Ambient Air Quality Standards (NAAQS) for ground-level ozone, based on extensive
scientific evidence about ozone's effects on public health and welfare. The proposed updates will
improve public health protection, particularly for children, the elderly, and people of all ages who
have lung diseases such as asthma. Today's proposal will expand the ozone monitoring season for
many states, and update the Air Quality Index to ensure people are notified when air quality is
unhealthy. And it will improve the health of trees, plants and ecosystems.

•	States would have time to develop and implement plans to meet revised standards, and existing and
proposed federal rules will help by making significant strides toward reducing ozone-forming
pollution. EPA projections show the vast majority of U.S. counties would meet the proposed
standards by 2025 just with the rules and programs now in place or under way.

•	EPA has proposed to set both the primary (health) and the secondary (welfare) standards as 8-hour
standards in a range from 65 to 70 parts per billion (ppb). The existing standards are both 75 ppb.
The agency is taking comment on alternative levels for the standards.

•	The Clean Air Act requires EPA to set secondary standards to protect the public welfare, which
includes trees, plants, crops and ecosystems. EPA analyses show that reducing ozone can improve
yields for timber and some crops, such as soybeans and winter wheat.

•	EPA will take public comment for 90 days after the proposal is published in the Federal Register. The
Agency will hold three public hearings.

•	EPA will issue final standards by Oct. 1, 2015.

WHAT THE EXISTING OZONE STANDARDS HAVE MEANT FOR AGRICULTURE

•	Ozone, a key component of smog, forms in the atmosphere when emissions of nitrogen oxides and
volatile organic compounds "cook" in the sun. Emissions from sources such as cars, trucks, buses,
engines, industries, power plants and products such as solvents and paints are among the major
manmade sources of ozone-forming emissions. Farm dust does not contribute to ozone formation.

•	Protecting and improving the nation's air quality is the work of a federal-state partnership
established in the Clean Air Act. EPA issues national standards and designates the "nonattainment
areas" that must reduce pollution in order to meet the standards. States then determine what those
pollution reduction steps will be and outline those steps in plans known as "state implementation
plans."

•	Like all national air quality standards, the existing ground-level ozone standards set the amount of
ozone pollution allowed in the outdoor air. But the standards do not establish emission control
requirements for any particular industry, including agriculture. Each state determines how to reduce
an area's pollution to meet the standards in a way that makes the most sense for that area.

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•	The vast majority of states have not required the agriculture industry to take any actions that require
emission reductions, instead focusing their efforts on reducing emissions of the pollutants that form
ozone from sources such as industrial processes and consumer products.

•	In California, some nonattainment areas are addressing ozone-forming emissions from agriculture by
incorporating conservation management practices developed with growers and USDA into ozone
implementation plans for those nonattainment areas. These include a menu of options growers can
choose from, such spray application technologies or integrated pest management strategies, and
limiting combustion emissions from engines by combining or reducing tillage operations to reduce
the number of passes through fields. These commonsense practices also reduce emissions of VOCs
and NOx.

•	In addition, the USDA Environmental Quality Incentives Program is helping reduce ozone-forming
nitrogen oxides (NOx) emissions by providing financial assistance to farmers for replacing diesel
engines that power agricultural equipment with lower-emitting models.

WHAT EPA HAS PROPOSED

Strengthening the primary (health) standard to improve public health protection

•	A significantly expanded body of scientific evidence shows that ozone can cause a number of
harmful effects on the respiratory system, including difficulty breathing and inflammation of the
airways. For people with lung diseases such as asthma and COPD (chronic obstructive pulmonary
disease), these effects can lead to emergency room visits and hospital admissions. Ozone exposure
also is likely to cause premature death from lung or heart diseases.

•	In addition, evidence indicates that long-term ozone exposure is likely to result in harmful
respiratory effects, including the development of asthma. Asthma disproportionately affects
children, families with lower incomes, and minorities, including Puerto Ricans, Native
Americans/Alaska Natives and African-Americans.

•	EPA is proposing that the current 8-hour ozone standard of 75 ppb is not adequate to protect public
health as the law requires and that the standard should be revised to improve public health
protection for millions of Americans.

•	EPA is proposing to set the health standard within a range from 65 to 70 ppb and is seeking
comment on levels for the primary standard as low as 60 ppb. The agency will accept comments on
all aspects of the proposal, including on retaining the existing standard.

Strengthening the secondary (public welfare) standard to improve protection for trees, plants and
ecosystems

•	New studies since the last review of the standards add to evidence showing that repeated exposure
to ozone reduces growth and has other harmful effects on plants and trees. These types of effects
have the potential to impact ecosystems and the benefits they provide.

•	EPA is proposing to revise the level of the secondary standard to a level within the range of 65 to
70 ppb, the same range proposed for the primary standard. The agency is proposing that a
standard in this range would provide appropriate protection against the cumulative ozone
exposures that can affect ecosystems through damage to plants and trees.

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•	In July 2013, the U.S. Court of Appeals for the D.C. Circuit upheld the 2008 primary ozone standard
but remanded the secondary standard to EPA, on the grounds that the agency had not specified the
level of air quality that was requisite to protect public welfare as required by the Clean Air Act, and
had not clearly shown how the secondary standard provided this protection. The proposed revisions
to the ozone standards respond to this remand.

•	EPA is proposing to identify the appropriate level of protection for trees, plants and ecosystems
using a seasonal index that scientists often use to assess the impact of ozone on ecosystems and
vegetation. This index is known as a W126 index, named for the equation used to calculate it.

•	EPA is proposing that air quality meeting a W126 index value between 13 and 17 parts per million-
hours (ppm-hours), averaged over three years, would provide the degree of protection that the
Clean Air Act requires. Ppm-hours is a measurement unit used to express the sum of weighted
hourly ozone concentrations, combined over the 12-hour daylight period. EPA is proposing that this
protection could be achieved by setting an 8-hour secondary standard in the range of 65 to 70 ppb.

•	EPA is seeking comment on this target level of protection. In addition, EPA is seeking comment on
achieving the necessary protection by revising the secondary standard to a W126-based standard
within a range of 13 to 17 ppm-hours, averaged over three years. EPA also is seeking comment on
retaining the current secondary standard.

FOR MORE INFORMATION:

•	More detail on the proposed standards: http://epa.gov/glo/pdfs/20141125fs-aqi

•	Proposal and additional fact sheets visit http://www.epa.gov/glo/actions.html

•	Commenting instructions: http://epa.gov/glo/pdfs/20141125fs-comment.pdf

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