The Clean Air Status and Trends Network (CASTNET) is a robust, long-term air quality monitoring program with sites operating throughout the United States and Canada. CASTNET sites, located primarily in rural communities, measure air pollutants that can be harmful to human health and cause negative impacts to ecosystems. CASTNET data are used to demonstrate NAAQS compliance, assess spatial and temporal trends in air quality in response to regulatory actions, and evaluate climate-driven impacts on air quality. The U.S. Environmental Protection Agency (EPA) manages CASTNET, in cooperation with the National Park Service, and other partners, including Tribal Nations. In collaboration with the National Atmospheric Deposition Program (NADP), CASTNET also provides data on other air pollutants and precipitation chemistry at most locations.

Through networks like CASTNET and NADP, EPA has developed fruitful relationships with Tribal agencies and continually seeks new partnership opportunities to build monitoring capacity. Establishing a CASTNET or NADP site on Tribal lands helps to address tribal air quality data and training needs without the burden of managing procurements for equipment, developing quality assurance documents, and supporting data management activities. Over the past two decades, EPA has grown the CASTNET tribal program through Federal-Tribal cost-sharing and in-kind support. This expansion of EPA's Tribal air monitoring has resulted in overall improved spatial and temporal representation of air quality in Indian Country and provided a mechanism to ensure accessible air quality data are sustained.

In 2024, the EPA's Science Advisory Board (SAB) released a report prioritizing actions that CASTNET should take to maintain its value and continue to be sustainable. Emphasis was placed on continuing to expand the CASTNET Tribal monitoring program to inform policy decisions in Tribal and other rural EJ communities. The panel noted that CASTNET offers the essential platform and infrastructure for sensors and other monitoring equipment that can be used for the protection of public health, especially with increasing pollution burdens from wildfires, dust, and other extreme weather events.

¹ U.S. EPA, Office of Air & Radiation, Washington D.C.

² WSP USA Environment & Infrastructure Solutions, Inc., Jacksonville, FL

³ WSP USA Environment & Infrastructure Solutions, Inc., Gainesville, FL

*Corresponding Author: sharac.timothy@epa.gov