Approximately 292 million tons or more of municipal solid waste (MSW) is produced annually in the United States, and over 50% of this waste is landfilled. Municipal solid waste landfills are known stationary sources of air pollution and public health concerns for surrounding communities. For more than 40 years, the Agency for Toxic Substances and Disease Registry (ATSDR) completed more than 300 municipal solid waste landfills or open dumps (MSWLFs) site-specific public health assessments (PHAs). The purpose was to review ATSDR’s history evaluating air pathway concerns at MSWLFs and identify factors that were associated with public health hazards due to toxic chemical exposures or unsafe landfill gas accumulations over time. We reviewed ATSDR PHAs, health con-sultations (HCs), and exposure investigations (EIs) completed between 1988 and early 2025. In-depth discussions focused on 125 reports that evaluated the air exposure path-way out of more than 300 inhalation and oral route of exposures assessments. We re-trieved documents from ATSDR’s internal and external databases and organized them in a Microsoft Excel Spreadsheet. Site-specific environmental data and information on health concerns were generally provided by the United States Environmental Protection Agency (EPA), other governmental agencies, businesses, and the public. ATSDR devel-oped science-based procedures for estimating exposure and its potential for harmful health effects through the PHA process. When necessary, ATSDR recommended further assessments to determine health hazard category, protect public health, and prevent fu-ture exposures or health effects. Of 125 MSWLFs assessments that focused on an inhala-tion exposure pathway, mostly were located in the Midwest and Northeast of the U.S. Only 25 percent were active and accepting waste. In 86 percent of the documents, ATSDR concluded that the site did not present a public health hazard by the air exposure path-way. In the documents that identified air-related public health hazards, common indica-tors included (a) potentially harmful levels of toxic substances found in outdoor air (4 sites); (b) unhealthy levels of toxic substances found in indoor air, because of vapor intru-sion from site-related subsurface contamination (2 sites); and (c) unsafe accumulations of methane at or near the landfill (11 sites). Major contaminant of concerns included sulfur compounds (RSCs) [e.g., hydrogen sulfide (H2S)], volatile organic compounds (VOCs) [(e.g., benzene)], halogenated organic compounds (e.g., trichloroethylene), and trace heavy metals [e.g., mercury (Hg)]. Factors that contributed to public health hazards included sites constructed and operated prior to promulgation of EPA regulations, sites without ef-fective landfill gas collection systems, sites experiencing underground fires or smoldering events, and sites with homes located very close (< 100 feet) to landfill property lines. At every site with a public health hazard, corrective actions were recommended to effectively reduce toxic chemical exposures or methane accumulation and eliminate the public health hazards. The evaluated sites that posed no public health hazards by inhalation, likely because they are properly sited, constructed, and maintained MSWLFs best practice operations or more sensitive and sophisticated assessment methods are needed. Over the years, more MSWLFs are closing and alternative solid waste management technologies such as recycling, composting and combustion with energy recovery are becoming avail-able and the demand of waste landfilling is steadily increasing. Future studies are war-ranted to assess current and predict exposure levels and controls consistent with the new clean and sustainable technologies.

Over 292 million tons of municipal solid waste (MSW) are generated annually in the United States, with more than half disposed of in landfills. Municipal solid waste landfills (MSWLFs) are stationary sources of air pollution and potential health risks for nearby communities. The Agency for Toxic Substances and Disease Registry (ATSDR) has completed over 300 public health assessments (PHAs) and related investigations at MSWLFs and open dumps since the 1980s. This paper reviews the ATSDR’s evaluations of air pathway concerns at 125 MSWLF sites assessed between 1988 and early 2025, with many being evaluated during the 1990s. Most sites were located in the Midwest and Northeast, and only 25% remained active. The ATSDR found no air-related public health hazard at 86% of sites. At sites where hazards were identified, common issues included elevated outdoor or indoor toxicants (e.g., hydrogen sulfide, benzene, trichloroethylene, and mercury) and unsafe methane accumulations. Contributing factors included older site designs, inadequate gas-collection, subsurface fires, and distance from nearby residences. Corrective actions effectively reduced exposures at the affected sites. Results suggest that well-located and maintained landfills minimize public health hazards, while aging or poorly managed sites pose risks. Continued monitoring and research are warranted as waste management shifts toward reducing, reusing, recycling, composting, and energy-recovery technologies to improve efficiency, advance technologies, and address systemic public health challenges.