"Exposure to ozone, a common air pollutant, has been linked to early death, plant and crop damage, and damage to property. The U.S. Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for ground-level ozone to protect human health and welfare with, by law, a 'margin of safety.' States that contain areas with ozone concentrations above these standards must develop plans to reduce emissions and improve air quality. However, states have direct control only over emission sources located within their borders. [...] Some Members of Congress have expressed interest in adverse health effects that occur at or below the current standard, challenges some nonattainment areas may have in meeting current standards, and particularly the responsibilities for meeting the health standard, given interstate and international transport. EPA's review of the ozone NAAQS is underway and set to be completed in 2020, with background ozone contributions suggested as a topic to be addressed. Congress may have an interest in better understanding scientific capabilities, needs, and efforts to improve understanding of contributions from background sources, as well as options for regulatory responses."
CRS Report for Congress, R45482
Congressional Research Service: https://crsreports.congress.gov/