FACT SHEET
Extension of Deadline for Promulgating Designations for the
2015 National Ambient Air Quality Standards for Ozone
ACTION
•	On June 21, 2017, the Administrator of the U.S. Environmental Protection Agency (EPA)
extended the deadline for designating areas for the 2015 national ambient air quality
standards (NAAQS) for ground-level ozone by 1 year. The new deadline for area
designations is October 1, 2018.
•	After establishing a new or revised NAAQS, the EPA must take steps to ensure that the
standard is met. An important initial step is to identify areas of the country as meeting or not
meeting the new or revised NAAQS. This step is known as the initial area designations.
•	According to the Clean Air Act, the EPA must complete the initial area designations in 2
years. However, the EPA Administrator may extend that period by up to 1 year in the event
he determines he has insufficient information to complete the designations in 2 years.
•	The Agency is currently evaluating a host of complex issues regarding the 2015 ozone
NAAQS and its implementation, such as understanding the role of background ozone levels
and appropriately accounting for international transport. In addition, the Administrator is
establishing a Task Force to develop additional flexibilities for states to comply with the
ozone NAAQS.
•	Given the analyses currently underway at the Agency, the Administrator has determined he
needs additional time to consider completely all designation recommendations provided by
state governors, including full consideration of exceptional events impacting designations.
Also, agency officials are currently reviewing the 2015 ozone NAAQS rule. The
Administrator has determined that in light of the uncertainty of the outcome of that review,
there is insufficient information to promulgate designations by October 1, 2017.
BACKGROUND
•	On October 1, 2015, EPA strengthened the primary and secondary air quality standards for
ground-level ozone to 0.070 parts per million, based on extensive scientific evidence about
ozone's effects on public health and welfare.
•	The primary ozone standard is designed to protect public health with an adequate margin of
safety. Breathing air containing ozone can reduce lung function and increase respiratory
symptoms, thereby aggravating asthma or other respiratory conditions. Ozone exposure also
has been associated with increased susceptibility to respiratory infections, medication use by
asthmatics, doctor visits, and emergency department visits and hospital admissions for
individuals with respiratory disease. Ozone exposure also increases the risk of premature
death.

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•	The secondary ozone standard is designed to protect against adverse welfare effects,
including impacts on vegetation and forested ecosystems. Repeated ozone exposure can
interfere with a plant's ability to produce and store food, leading to reduced tree growth;
reduced crop yields; visibly injured leaves; and increased susceptibility to disease, damage
from insects, and harsh weather.
•	After EPA designates ozone nonattainment areas, the states are required to take additional
actions to improve air quality, including developing implementation plans outlining how the
areas will attain and maintain the standards by reducing air pollutant emissions contributing
to ground-level ozone concentrations.
FOR MORE INFORMATION
•	To download a copy of this notice, go to EPA's Web Site at:
https://www.epa.gov/ozone-designations. The docket number for this action is Docket ID No.
EPA-HQ-OAR-2017-0223.

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