This bill, titled the "Public Health Air Quality Act of 2025," seeks to enhance clean air protections and public health by expanding air quality monitoring and improving access to information. It establishes a Health Emergency Air Toxics Monitoring Network , requiring the Environmental Protection Agency (EPA) to implement fenceline monitoring for hazardous air pollutants at 100 high-priority stationary sources. These sources are selected based on their emissions and potential health risks to nearby communities, with a focus on specific pollutants like ethylene oxide, benzene, and various metal compounds. The EPA must ensure that monitoring begins within 18 months and continues for at least six years, with results published publicly in an accessible, multi-language format within seven days of collection. The bill mandates the use of best available emissions measurement systems , including continuous, real-time monitoring for the top 20 highest-emitting or highest-risk sources. It also requires regular updates to monitoring methods and the list of monitored sources, along with a report to Congress on the program's effectiveness. Furthermore, the legislation directs the EPA to promulgate regulations for Community Air Toxics Monitoring within two years. These regulations will require specific source categories, particularly those with high-risk emissions or accidental releases, to implement continuous emissions and fenceline monitoring. A key provision is the establishment of corrective action levels for hazardous air pollutants; exceedances will trigger root cause analyses, remedial actions, and public reporting, with violations enforceable under the Clean Air Act. The bill also significantly expands the National Ambient Air Quality Standards (NAAQS) Monitoring Network . It mandates the deployment of 80 additional NCore multipollutant monitoring stations, with at least 40 located in vulnerable communities experiencing higher rates of health conditions or socioeconomic disparities. An additional 100 Federal reference or equivalent method monitors will be deployed in unmonitored or undermonitored areas to detect nonattainment and improve data availability. To further enhance monitoring, the EPA must assess the status of all existing ambient air quality monitors and develop a plan for their repair or replacement. The bill also requires regulations for using satellite monitoring data to calculate design values for certain pollutants, aiding in compliance determinations. State monitoring plans will be subject to increased public notice and comment requirements before EPA approval. For community-level monitoring, the bill directs the EPA to deploy at least 1,000 low-cost air quality systems in clusters, prioritizing communities disproportionately impacted by air pollution. If these systems detect pollution levels nearing national ambient air quality standards, Federal reference or equivalent monitors must be installed. Finally, the EPA is required to update and expand reporting requirements for major and non-major sources, including hazardous air pollutants and PFAS, to improve the national emissions inventory and public access to information, and to restore or create a nationwide geospatial mapping tool like EJSCREEN to integrate all collected data.