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Air Quality: EPA's Integrated Science Assessments (ISAs)


Click to download the final report of the Integrated Science Assessment for Ozone and Related Photochemical Oxidants (2013) (PDF)(2228 pp, 1,105 MB)
(PDF, 1251 pp, 40 MB,
About PDF

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 as well as premature death. 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's ozone research efforts are focused on improving emissions estimates, determining health and ecological effects, and improving modeling capabilities. EPA's National Center for Environmental Assessment periodically evaluates the latest research concerning the public health and welfare effects of ozone and publishes the most up-to-date findings in an assessment called an Integrated Science Assessment. This document provides the scientific basis for the establishment of the most current national air quality standards for ozone. EPA released the Integrated Science Assessment for Ozone and Related Photochemical Oxidants in February 2013. [See the history of Ozone for more detailed information]

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