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Clean Air NJ
Federal Standards for Ground-Level Ozone

New Jersey is required to meet air quality standards established by the United States Environmental Protection Agency (USEPA).  These standards are known as National Ambient Air Quality Standards (NAAQS).

On Oct. 1, 2015, the USEPA strengthened the air quality standard for ground-level ozone to improve public health and environmental protection. The NAAQS for ozone was reduced from 75 parts per billion (ppb) to 70 parts per billion, based on extensive scientific evidence about ozone’s effects on public health and welfare. Additional information on the Federal ozone standards can be found at

The USEPA set NAAQS, including the ozone standard, at levels that are protective of human health and public welfare (and that do not damage crops and vegetation or contribute to regional haze).  The USEPA reviews its federal standards every 5 years to evaluate current science and determine if standards should be revised.  As standards are revised, New Jersey is required to evaluate its current air quality and submit plans to the USEPA defining how we will meet the standard as expeditiously as practicable.

A history of the federal Clean Air Act can be found here.

What is ozone season?

Ground-level ozone needs sunlight to form, therefore it is mainly a daytime problem during the summer months. The length of the ozone monitoring season varies across the country according to a number of seasonally-dependent factors (e.g., ambient temperature, strength of incoming solar radiation, length of day, etc.) that affect ozone formation.  Weather patterns have a significant effect on ozone formation and hot, dry summers will result in more ozone formation than cool, wet ones. In New Jersey, the ozone monitoring season runs from March 1st to October 31st.

What is a nonattainment area?

Areas of the country where air pollution levels of are above a NAAQS may be designated by USEPA as "nonattainment."  For additional information on nonattainment areas across the country for the six NAAQS pollutants, visit the EPA’s Green Book.  The map shows the current ozone nonattainment areas that include parts of New Jersey.  New Jersey shares these nonattainment areas with other states.

What is a design value?

A design value is a statistical analysis of actual air quality monitoring data for the specific NAAQS to determine compliance with the federal standard.   The design value varies among the different NAAQS and is used by USEPA to designate and classify nonattainment areas.  It is also used by states and the USEPA to assess progress towards meeting the NAAQS.  More information on design values can be found here.

The NAAQS for ozone are set in such a way that determining whether they are being attained is not based on a single year or on a single exceedance event.  Under the current standard, attainment is determined by taking the average of the fourth highest daily maximum 8-hour average concentration that is recorded each year for three years. This becomes the design value for an area under the current standard.

New Jerset 8-hour Ground-Level Ozone Nonattainment Areas (2008 Standard)

New Jersey has been measuring ozone air quality levels for almost 30 years.
The graph below shows improvement in ozone air quality.