Environmental Forensic Investigation of Historical Ethylene Oxide Emissions, Air Dispersion Modeling, and Community Exposure Assessment
Project Overview
Ethylene oxide (EtO) is a highly effective sterilizing agent widely used by commercial sterilization facilities to sterilize temperature-sensitive medical devices, pharmaceuticals, laboratory equipment, and other products that cannot be treated using steam or radiation. While EtO has played a critical role in modern healthcare for decades, it is also recognized as a hazardous air pollutant and human carcinogen, making the evaluation of historical community exposure an important area of environmental forensic science. Assessing historical EtO emissions requires integrating industrial engineering, atmospheric science, environmental chemistry, meteorology, toxicology, epidemiology, air dispersion modeling, and quantitative human health risk assessment to reconstruct past emissions and estimate long-term community exposure (U.S. EPA, 2016; ATSDR, 1990).
RoseyFields conducted a comprehensive environmental forensic investigation involving historical EtO emissions from multiple commercial sterilization facilities operating over several decades. The primary objectives were to reconstruct historical emissions using regulatory reporting data, characterize changes in emissions resulting from evolving sterilization practices and emission controls, evaluate ambient EtO concentrations using regulatory air dispersion modeling, estimate long-term community exposure, and assess potential human health risks associated with chronic inhalation. The investigation incorporated historical Toxic Release Inventory (TRI) reporting, National Emissions Inventory (NEI) emissions data, engineering evaluations, historical process information, atmospheric dispersion modeling, geographic information systems (GIS), meteorological analyses, and quantitative exposure assessment to develop a scientifically supported reconstruction of historical environmental conditions (U.S. EPA, 2017; U.S. EPA, 2024).
A major focus of the investigation involved evaluating long-term trends in EtO emissions across multiple commercial sterilization facilities. Historical emissions data demonstrated that reported releases varied considerably over time because of changes in sterilization throughput, facility expansion, implementation of emission control technologies, revised emissions estimation methodologies, and evolving regulatory requirements. Historical emissions inventories were evaluated together with facility-specific engineering information to develop representative annual source terms for air dispersion modeling. By reconstructing emissions across multiple decades rather than relying solely on current operating conditions, the investigation provided a more scientifically robust evaluation of historical community exposure and cumulative environmental impacts (U.S. EPA, 2017; U.S. EPA, 2024).
The investigation also integrated facility-specific engineering information with atmospheric dispersion modeling to estimate airborne EtO concentrations under representative historical operating conditions. Engineering evaluations included characterization of stack emissions, fugitive releases, emission source configurations, and process-specific release mechanisms identified through regulatory reporting and emissions inventories. Atmospheric dispersion modeling incorporated representative meteorological data, terrain, source characteristics, and historical operating conditions to estimate long-term ambient concentrations throughout nearby residential communities. Integrating historical emissions reconstruction, engineering analyses, atmospheric science, environmental chemistry, and quantitative risk assessment provided a scientifically rigorous environmental forensic evaluation suitable for supporting environmental consulting, regulatory investigations, remediation planning, and expert witness services while maintaining complete confidentiality regarding the underlying projects (American Meteorological Society & U.S. EPA, 2019; National Academies of Sciences, Engineering, and Medicine, 2022).
Chemicals of Concern
The principal chemical of concern evaluated during this environmental forensic investigation was ethylene oxide (EtO), a colorless, highly reactive gas widely used as a sterilizing agent for temperature-sensitive medical devices and as an intermediate in various industrial manufacturing processes. Because EtO readily penetrates packaging materials and effectively eliminates bacteria, viruses, fungi, and bacterial spores, it has become an essential sterilization agent for many products that cannot tolerate conventional steam sterilization. However, its widespread industrial use has also resulted in increasing attention from regulators, scientists, and public health agencies because long-term inhalation exposure has been associated with elevated cancer risks, making it one of the most extensively studied hazardous air pollutants in environmental exposure science (U.S. EPA, 2016; International Agency for Research on Cancer [IARC], 2012).
Unlike contaminants that persist primarily in soil or groundwater, EtO behaves almost entirely as an atmospheric contaminant following release. Once emitted, it disperses rapidly through the atmosphere, with ambient concentrations governed by emission rates, release characteristics, meteorological conditions, atmospheric mixing, and chemical degradation. Because EtO remains in the gas phase rather than adsorbing significantly to particulate matter, atmospheric dispersion modeling represents the primary scientific tool for estimating historical community exposure. Accurate reconstruction of airborne concentrations therefore requires detailed characterization of both point-source emissions, such as stack releases, and fugitive emissions associated with equipment leaks, sterilization chambers, aeration rooms, storage areas, and material handling operations (U.S. EPA, 2017; American Meteorological Society & U.S. EPA, 2019).
A key aspect of this investigation involved distinguishing between stack emissions and fugitive emissions, both of which can contribute substantially to overall facility releases. Stack emissions generally originate from controlled process vents and exhaust systems, whereas fugitive emissions arise from leaks, equipment components, door openings, sterilization chamber operations, aeration activities, vacuum systems, piping, valves, and other process equipment. Historical regulatory reporting demonstrated that the relative contribution of these emission sources changed considerably over time as facilities modified operations and implemented increasingly effective emission control technologies. Evaluating both emission categories independently provided a more complete understanding of historical release patterns and improved the development of representative source terms for atmospheric dispersion modeling (U.S. EPA, 2024; U.S. EPA, 2017).
The investigation also evaluated the influence of changing industrial practices and emission control technologies on historical EtO releases. Over the past several decades, commercial sterilization facilities have increasingly implemented engineering controls designed to reduce emissions, including catalytic oxidizers, thermal oxidizers, acid-water scrubbers, improved process enclosure systems, enhanced leak detection and repair programs, and operational modifications that reduce uncontrolled releases. These engineering improvements have significantly altered historical emission profiles and are an important consideration when reconstructing long-term environmental exposures. Incorporating historical operating conditions rather than assuming present-day emissions provides a more scientifically accurate representation of community exposure over multiple decades (U.S. EPA, 2022; Association for the Advancement of Medical Instrumentation, 2021).
Because EtO is emitted from multiple industrial sectors and measurable background concentrations may also occur from regional and natural sources, evaluating community exposure requires integrating engineering analyses, historical emissions inventories, atmospheric science, environmental chemistry, toxicology, epidemiology, and quantitative exposure assessment. By combining these disciplines within a comprehensive environmental forensic framework, investigators can distinguish facility-related contributions from regional background concentrations, reconstruct historical emissions, evaluate long-term community exposure, and provide scientifically defensible assessments suitable for environmental consulting, regulatory investigations, remediation planning, and expert witness services (ASTM International, 2021; National Academies of Sciences, Engineering, and Medicine, 2022).
Methods
A multidisciplinary environmental forensic investigation was conducted to evaluate historical ethylene oxide (EtO) emissions from a commercial sterilization facility and to estimate long-term community exposure using accepted engineering, atmospheric science, environmental chemistry, toxicology, epidemiology, and quantitative risk assessment methodologies. The investigation integrated historical emissions inventories, Toxic Release Inventory (TRI) reporting, National Emissions Inventory (NEI) source information, engineering evaluations, atmospheric dispersion modeling, meteorological analyses, geographic information systems (GIS), exposure assessment, and toxicological risk characterization to reconstruct historical airborne EtO concentrations over multiple decades. Rather than relying upon a single source of information, the investigation employed a weight-of-evidence approach that combined independent datasets to develop a scientifically robust understanding of historical emissions and community exposure (ASTM International, 2021; U.S. EPA, 2017).
Historical emissions were reconstructed using publicly available regulatory reporting records together with facility-specific engineering information describing emission sources and operating characteristics. Annual TRI reports were evaluated to quantify historical EtO releases over multiple decades, while NEI data were used to characterize emission source locations, release parameters, stack characteristics, and process-specific operating information. Historical reporting demonstrated substantial variation in annual emissions, reflecting changes in production volume, sterilization throughput, emission estimation methodologies, process modifications, pollution control technologies, and regulatory requirements. Reconstructing these changing operating conditions allowed representative annual source terms to be developed for atmospheric dispersion modeling rather than relying solely on current facility operations (U.S. EPA, 2024; U.S. EPA, 2017).
Atmospheric transport was evaluated using the U.S. Environmental Protection Agency’s preferred regulatory air dispersion model, AERMOD, following current federal modeling guidance. Engineering analyses incorporated stack parameters, fugitive emission sources, building downwash, terrain, land-use characteristics, and representative meteorological conditions to estimate long-term ambient EtO concentrations throughout nearby residential areas. Both controlled stack emissions and fugitive releases were modeled because each contributes differently to atmospheric dispersion and community exposure. Geographic information systems were subsequently used to evaluate spatial concentration patterns and identify areas predicted to experience the highest long-term ambient concentrations under representative historical operating conditions (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
Meteorological analyses formed a critical component of the investigation because wind direction, atmospheric stability, mixing height, temperature, and seasonal variability strongly influence the transport and dilution of gaseous contaminants. Representative surface and upper-air meteorological datasets were evaluated and processed using accepted regulatory procedures to generate model-ready atmospheric inputs. Quality assurance evaluations were performed to ensure consistency among meteorological datasets and to verify that atmospheric modeling reflected representative long-term climatological conditions. Integrating detailed meteorological analyses with engineering source characterization substantially improved confidence in predicted ambient EtO concentrations and long-term exposure estimates (World Meteorological Organization, 2018; U.S. EPA, 2017).
Finally, quantitative exposure assessment and human health risk assessment were performed by integrating modeled air concentrations with residential exposure scenarios, toxicological reference values, and current regulatory guidance for chronic inhalation exposure. Lifetime exposure estimates were developed using representative residential occupancy assumptions together with historical emissions reconstruction and atmospheric modeling results. By combining industrial engineering, emissions inventory development, atmospheric science, meteorology, environmental chemistry, toxicology, epidemiology, and quantitative risk assessment within a unified environmental forensic framework, the investigation produced a scientifically defensible evaluation capable of supporting environmental consulting, regulatory investigations, environmental due diligence, remediation planning, and expert witness services involving historical airborne releases of hazardous air pollutants (National Academies of Sciences, Engineering, and Medicine, 2022; U.S. EPA, 1989).
Results
The environmental forensic investigation demonstrated that historical ethylene oxide (EtO) emissions changed substantially throughout the operational history of the commercial sterilization facility as production volumes, sterilization practices, emission estimation methodologies, engineering controls, and regulatory requirements evolved. Historical Toxic Release Inventory (TRI) reporting documented significant variability in annual emissions, with some years exhibiting substantially greater releases than others. These temporal changes demonstrated that evaluating only current operating conditions would not accurately characterize historical community exposure. Instead, reconstructing emissions over multiple decades provided a more scientifically representative estimate of cumulative airborne EtO concentrations experienced by surrounding communities (U.S. EPA, 2024; U.S. EPA, 2017).
Evaluation of historical emissions also demonstrated that both stack emissions and fugitive releases contributed meaningfully to total facility emissions, although their relative contributions varied considerably over time. Engineering evaluations indicated that process modifications, installation of emission control technologies, improvements in equipment design, and operational changes altered the balance between controlled and uncontrolled releases during different reporting periods. As commercial sterilization technology evolved, many facilities implemented catalytic oxidizers, thermal oxidizers, improved process enclosures, leak detection programs, and enhanced operational controls that substantially reduced total EtO emissions. Incorporating these historical engineering changes into the emissions reconstruction improved the scientific accuracy of the atmospheric dispersion modeling and provided a more realistic estimate of historical community exposure than assuming constant emissions over time (Association for the Advancement of Medical Instrumentation, 2021; U.S. EPA, 2022).
Atmospheric dispersion modeling demonstrated that meteorological conditions strongly influenced the transport and distribution of EtO following release. Wind direction, atmospheric stability, mixing height, source configuration, and building downwash all contributed to spatial and temporal variability in predicted ambient concentrations. Modeling results illustrated that community exposure varied across the surrounding area depending upon prevailing atmospheric conditions rather than decreasing uniformly with distance from the facility. Geographic information system analyses further demonstrated how historical emissions combined with local meteorology to produce long-term concentration patterns that could be evaluated using accepted environmental forensic methodologies. Integrating engineering analyses with atmospheric modeling provided an independent line of evidence supporting the reconstruction of historical airborne exposure (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
The investigation also demonstrated the importance of evaluating cumulative exposure over extended time periods rather than relying solely on short-term environmental measurements. Because chronic inhalation exposure is the principal pathway of concern for EtO, long-term average concentrations derived from historical emissions reconstruction and atmospheric dispersion modeling provided a more scientifically meaningful basis for exposure assessment than isolated monitoring events. Engineering analyses, emissions inventories, and atmospheric modeling collectively allowed historical concentrations to be estimated for periods in which direct environmental monitoring was unavailable or limited, thereby improving the completeness of the exposure assessment (National Academies of Sciences, Engineering, and Medicine, 2022; U.S. EPA, 1989).
Overall, the investigation demonstrated that integrating historical emissions inventories, engineering evaluations, atmospheric dispersion modeling, meteorological analyses, GIS, environmental chemistry, toxicology, epidemiology, and quantitative exposure assessment produced a comprehensive environmental forensic evaluation of historical EtO emissions. No individual dataset independently characterized long-term community exposure; however, combining multiple independent scientific disciplines substantially strengthened source attribution, reduced uncertainty, and provided a technically rigorous foundation for environmental consulting, regulatory investigations, environmental due diligence, remediation planning, and expert witness services involving hazardous air pollutants and complex industrial emission sources (ASTM International, 2021; U.S. EPA, 2017).
Conclusions
This environmental forensic investigation demonstrated that evaluating historical ethylene oxide (EtO) emissions from commercial sterilization facilities requires a comprehensive multidisciplinary approach integrating industrial engineering, atmospheric science, environmental chemistry, meteorology, toxicology, epidemiology, air dispersion modeling, exposure assessment, and quantitative human health risk assessment. Because facility operations, emission control technologies, sterilization throughput, and regulatory requirements evolve substantially over time, accurately reconstructing historical community exposure requires more than reviewing contemporary emissions or monitoring data alone. By integrating historical emissions inventories with engineering analyses and atmospheric modeling, the investigation developed a scientifically robust reconstruction of long-term airborne EtO concentrations while reducing uncertainty through the use of multiple independent lines of evidence (ASTM International, 2021; U.S. EPA, 2017).
The investigation demonstrated that historical emissions inventories and engineering evaluations are fundamental to understanding long-term environmental releases of EtO. Annual emissions changed considerably over the operational life of the facility due to variations in production, equipment modifications, implementation of emission control technologies, and improvements in industrial operating practices. Reconstructing these historical changes allowed representative emissions to be modeled for different operational periods, providing a more scientifically accurate estimate of cumulative community exposure than would be possible using present-day operating conditions alone. This historical reconstruction is a critical component of environmental forensic investigations involving hazardous air pollutants emitted over multiple decades (U.S. EPA, 2024; Association for the Advancement of Medical Instrumentation, 2021).
The investigation further demonstrated the importance of combining atmospheric dispersion modeling with engineering analyses and available environmental monitoring information when evaluating chronic community exposure to gaseous contaminants. Air dispersion modeling integrates emissions, source characteristics, terrain, building effects, and meteorological variability over extended periods, providing estimates of long-term ambient concentrations that cannot be obtained from short-duration monitoring alone. When interpreted together, engineering evaluations, historical emissions inventories, atmospheric science, and environmental monitoring provide a more complete understanding of historical exposure conditions while strengthening source attribution and improving confidence in quantitative risk assessments (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
This case study highlights the essential role of environmental forensic science in investigating historical emissions from commercial sterilization facilities and other industrial sources of hazardous air pollutants. By integrating historical emissions reconstruction, industrial process engineering, atmospheric dispersion modeling, meteorological analysis, environmental chemistry, toxicology, epidemiology, exposure science, and quantitative human health risk assessment, RoseyFields provides scientifically rigorous evaluations capable of supporting environmental consulting, regulatory investigations, environmental due diligence, remediation planning, and expert witness services. These multidisciplinary investigations provide objective, evidence-based scientific analyses that improve understanding of historical emissions, atmospheric transport, community exposure, and potential human health risks while remaining consistent with accepted engineering practice, current environmental science, and evolving regulatory guidance (National Academies of Sciences, Engineering, and Medicine, 2022; U.S. EPA, 2016).
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist and environmental forensic expert with extensive experience in ethylene oxide investigations, commercial sterilization facility emissions, hazardous air pollutant exposure assessment, historical emissions reconstruction, air dispersion modeling, and human health risk evaluation. Dr. Rosenfeld’s work focuses on complex environmental contamination matters involving ethylene oxide sterilization operations, stack and fugitive air emissions, Toxic Release Inventory (TRI) and National Emissions Inventory (NEI) data interpretation, atmospheric transport, community exposure assessment, and long-term inhalation risk in residential areas located near industrial and sterilization facilities. His expertise includes reconstructing historical emission scenarios through the integration of industrial process engineering, emissions inventories, atmospheric science, meteorology, geographic information systems (GIS), environmental chemistry, toxicology, epidemiology, and quantitative risk assessment to determine whether historical sterilization operations and emission control practices are consistent with observed environmental conditions and potential human health impacts. Through RoseyFields LLC, Dr. Rosenfeld provides environmental forensic analysis, environmental due diligence, regulatory and compliance support, remediation evaluation, toxic tort and personal injury case assessment, and expert witness testimony involving ethylene oxide contamination, commercial sterilization facility emissions, chronic inhalation exposure, source attribution, and long-term environmental and human health risks associated with hazardous air pollutants.
References
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