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Integrated Science Assessment (ISA) for Ozone and Related Photochemical Oxidants

The Issue

Ozone is a gas that occurs both in the Earth's upper atmosphere and at ground level where it is a key component of urban smog. Ground-level ozone causes a variety of effects on human health, vegetation, and ecosystems and it affects climate. Human exposure to ozone is associated with respiratory and cardiovascular effects. Ozone exposure causes visible foliar injury, decreases plant growth and affects ecosystem community composition.

Peak ozone levels typically occur during hot, dry, stagnant summertime conditions. Millions of Americans live in areas where ozone levels exceed EPA's health-based air quality standards, primarily in parts of the Northeast, the Lake Michigan area, parts of the Southeast, southeastern Texas, and parts of California.

EPA Action

EPA scientists are evaluating the latest scientific information to better understand the relationship between exposure to ozone and health and welfare effects, who may be at increased risk to these effects, how particles form in the atmosphere, and what the contributions are from various sources in different regions of the country.

The Clean Air Act requires EPA to periodically review the science for six major air pollutants, including ozone. EPA's Center for Public Health and Environmental Assessment (CPHEA) develops Integrated Science Assessments (ISAs) that summarize the science related to the health and welfare effects of these pollutants. ISAs provide a comprehensive review of the policy-relevant scientific literature published since the last National Ambient Air Quality Standards (NAAQS) review and are necessary for conducting the review of the NAAQS. This ISA represents EPA’s latest evaluation of the scientific literature on the potential health and welfare effects associated with ozone and updates the 2013 Integrated Science Assessment for Ozone and Related Photochemical Oxidants Final Report.

History of the Ozone and Related Photochemical Oxidants Assessments

Date Milestone
Apr 2020 EPA released the final report of the Integrated Science Assessment for Ozone and Related Photochemical Oxidants (EPA/600/R-20/012). [Federal Register Notice Apr 20, 2020] This is the latest version.
Feb 2013 EPA released the final report of the Integrated Science Assessment for Ozone and Related Photochemical Oxidants (EPA/600/R-10/076F).[Federal Register Feb 15, 2013]
Feb 2006 EPA released the final report of the Air Quality Criteria Document for Ozone and Related Photochemical Oxidants (EPA/600/R-05/004). [Federal Register Feb 28, 2006]
1996 EPA released the final report of the Air Quality Criteria for Ozone and Related Photochemical Oxidants (EPA/600/P-93/004).

Peer-Reviewed Literature

While working on the assessment of ozone, EPA used the Health and Environmental Research Online (HERO) database to augment the underlining literature that supported the final assessment.

See: ISA-Ozone and Related Photochemical Oxidants (2019) HERO Project Page