EPA Research Partner Support Story: Exploring the cause of persistent high ozone in the New York City region

Partners: Northeast States for Coordinated Air Use Management (NESCAUM), Connecticut Department of Energy and Environmental Protection (CTDEEP), New Jersey Department of Environmental Protection (NJDEP), New York State Department of Environmental Conservation (NYSDEC), New York State Energy Research and Development Authority (NYSERDA)
Challenge: Better understanding the causes of ground-level ozone formation and transport in the New York City metropolitan area
Resource: Deployment of advanced air quality monitoring tools at eight sites as part of the Long Island Sound Tropospheric Ozone Study (LISTOS) and subsequent data analysis in collaboration with NASA, NOAA, University of Maryland, SUNY-Albany, SUNY-Stony Brook, City College of New York, and Yale University
Project Period: 2018 – Present

Surface-level ozone is formed when nitrogen oxides and volatile organic compounds react with one another in the presence of sunlight. While air pollution levels have dropped over the years across the United States, the New York City (NYC) metropolitan area and surrounding region continue to persistently exceed both past and recently revised federal health-based air quality standards for ground-level ozone.

“ORD's coordination with and support of LISTOS has helped New York better understand precursors of ground level ozone in the New York City area so that we will be able to better address it." – NYSDEC Division of Air Resources Research Scientist Dirk Felton

To better understand and address this challenge, EPA scientists collaborated in a multi-agency field study in spring and summer 2018 called the Long Island Sound Tropospheric Ozone Study (LISTOS). Data collected during LISTOS provided scientists and decision makers more detailed information on the sources of ground-level ozone photochemical formation and its transport downwind of NYC. Measurement assets supporting this field study included a combination of aircraft and ground-based measurements from numerous research organizations.

The main part of the study ran from June – August 2018, but many ORD supported measurements are continuing in collaboration with the states to address their need to develop and carry out an enhanced monitoring plan with EPA. Since the summer of 2018, information garnered from the study and its subsequent analysis have help guide discussions about emission control scenarios for reducing ground-level ozone formation with the aim of eventually meeting the national standards.

EPA and its partners have continued to collect and analyze enhanced ozone monitoring measurements seeking to improve understanding of the persistent challenge to address ozone air pollution. These activities include measurements to support validation of the NASA TEMPO mission launched in April 2023 that is collecting hourly maps of ozone and ozone precursors across the contiguous United States, Puerto Rico, Canada and Mexico. Additionally, data collected since 2018 are supporting a R1/R2 ROAR project assessing regional NOx emissions inventories and an R1 R2P2 project investigating the relationship of ozone pollution to measured boundary layer mixing depths. For more information on the Long Island Sound Tropospheric Ozone Study, go to the Northeast States for Coordinated Air Use Management webpage.