Environmental Forensic Investigation of Historical Ethylene Oxide Emissions, Air Dispersion Modeling, and Community Exposure Assessment
Project Overview
Ethylene oxide (EtO) is a highly reactive, colorless gas that has been widely used for decades in the sterilization of temperature-sensitive medical devices and pharmaceutical products. Because EtO effectively penetrates packaging materials while eliminating bacteria, viruses, fungi, and bacterial spores, it remains one of the most important sterilization technologies used by the healthcare industry. Despite its significant public health benefits, EtO is also classified as a hazardous air pollutant and a human carcinogen, making the evaluation of historical environmental emissions and community exposure an important component of environmental forensic science. Investigations involving EtO require integrating industrial engineering, atmospheric science, environmental chemistry, toxicology, epidemiology, air dispersion modeling, and quantitative human health risk assessment to reconstruct historical emissions and evaluate potential long-term community exposure (U.S. EPA, 2016; International Agency for Research on Cancer, 2012).
RoseyFields conducted a comprehensive environmental forensic investigation involving historical EtO emissions associated with a commercial sterilization operation. The primary objectives of the investigation were to reconstruct historical emissions over several decades, evaluate changes in facility operations and emission control technologies, estimate ambient EtO concentrations using regulatory air dispersion modeling, characterize long-term community exposure, and assess the scientific evidence regarding potential human health impacts. The investigation integrated engineering analyses, historical emissions inventories, publicly available regulatory records, atmospheric dispersion modeling, meteorological analyses, geographic information systems (GIS), environmental monitoring information, and quantitative exposure assessment to develop a scientifically supported reconstruction of historical environmental conditions while carefully evaluating uncertainties associated with historical emissions and atmospheric transport (U.S. EPA, 2017; National Academies of Sciences, Engineering, and Medicine, 2022).
A major component of the investigation involved reconstructing historical EtO emissions using multiple independent sources of information. Historical emissions inventories, engineering evaluations, operational records, and publicly available regulatory reporting were reviewed to characterize changes in sterilization throughput, process modifications, pollution control technologies, and emissions estimation methodologies over time. Because industrial operations frequently evolve over multiple decades, reconstructing representative historical emissions provides a more scientifically accurate assessment of long-term community exposure than relying solely upon present-day operating conditions. Integrating multiple historical datasets allowed annual emissions to be evaluated within the broader context of changing industrial practices and evolving environmental regulations (U.S. EPA, 2024; ASTM International, 2021).
The investigation also evaluated the relationship between historical emissions and potential community exposure through the application of regulatory-quality atmospheric dispersion modeling. Engineering analyses characterized stack emissions, fugitive releases, building influences, and representative operating conditions to develop scientifically defensible source terms for modeling. Representative meteorological datasets were incorporated to simulate atmospheric transport and estimate long-term ambient EtO concentrations throughout surrounding residential areas. Model predictions were subsequently integrated with exposure assessment methodologies and current toxicological guidance to evaluate potential chronic inhalation exposure while accounting for naturally occurring background concentrations and regional atmospheric variability. This multidisciplinary environmental forensic approach provides a technically rigorous framework for environmental consulting, regulatory investigations, remediation planning, and expert witness services while maintaining complete confidentiality regarding the underlying project (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
Chemicals of Concern
The principal chemical evaluated during this environmental forensic investigation was ethylene oxide (EtO), a highly reactive organic compound used extensively as a low-temperature sterilizing agent for medical devices, pharmaceutical products, and other heat- and moisture-sensitive materials. Its exceptional sterilization efficiency has made EtO an essential component of the healthcare supply chain for several decades. However, because EtO is also classified as a hazardous air pollutant and a human carcinogen, the characterization of historical emissions and potential community exposure has become an increasingly important area of environmental engineering, exposure science, and environmental forensic investigation. Understanding the environmental behavior of EtO requires integrating industrial engineering, atmospheric science, environmental chemistry, toxicology, epidemiology, and quantitative risk assessment to evaluate both routine industrial emissions and long-term ambient air concentrations (U.S. EPA, 2016; International Agency for Research on Cancer, 2012).
Unlike contaminants that accumulate primarily in soils or groundwater, EtO exists almost exclusively in the atmosphere following release. As a volatile gas, it disperses rapidly under the influence of prevailing meteorological conditions, including wind speed, wind direction, atmospheric stability, mixing height, and temperature. Atmospheric degradation occurs primarily through reactions with naturally occurring hydroxyl radicals, resulting in a relatively limited atmospheric lifetime compared to many persistent organic pollutants. Consequently, evaluating historical community exposure depends largely upon accurately reconstructing emission rates and applying scientifically accepted atmospheric dispersion models capable of estimating airborne concentrations over varying temporal and spatial scales (U.S. EPA, 2017; World Health Organization, 2003).
An important component of this investigation involved distinguishing controlled process emissions from fugitive emissions. Controlled emissions typically originate from engineered exhaust systems equipped with emission control devices, whereas fugitive emissions may result from equipment leaks, sterilization chamber operations, aeration processes, maintenance activities, material transfers, piping components, valves, and other process equipment. Historical engineering evaluations demonstrated that the relative contribution of these emission sources changed over time as facilities implemented improved containment systems, upgraded emission controls, modified sterilization practices, and adopted enhanced leak detection and repair programs. Accounting for these operational changes was essential for accurately reconstructing historical emissions and estimating representative long-term community exposure (Association for the Advancement of Medical Instrumentation, 2021; U.S. EPA, 2022).
The investigation also considered the role of regional background concentrations when interpreting ambient EtO measurements. Numerous scientific investigations have demonstrated that measurable concentrations of EtO may be present even in locations without nearby industrial sources because EtO is produced through natural biological processes, atmospheric photochemistry, biomass combustion, and diffuse anthropogenic activities. Consequently, measured ambient concentrations do not necessarily represent emissions from a single facility. Distinguishing facility-related contributions from regional background concentrations required integrating engineering analyses, historical emissions inventories, atmospheric dispersion modeling, environmental monitoring data, and current scientific literature. This comprehensive approach improves source attribution and reduces uncertainty associated with interpreting low-level environmental measurements (Kirman & Hays, 2017; U.S. EPA, 2024).
Evaluating historical EtO exposure therefore requires a multidisciplinary environmental forensic framework that integrates industrial process engineering, historical emissions reconstruction, atmospheric science, meteorology, environmental chemistry, toxicology, epidemiology, exposure assessment, and quantitative human health risk assessment. By combining these complementary scientific disciplines, investigators can reconstruct historical operating conditions, estimate long-term ambient air concentrations, distinguish industrial emissions from regional background levels, and provide scientifically defensible conclusions regarding potential community exposure. This integrated methodology supports environmental consulting, regulatory investigations, environmental due diligence, remediation planning, and expert witness services involving hazardous air pollutants while remaining consistent with accepted engineering practice and current environmental science (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 associated with a commercial sterilization operation and to characterize potential long-term community exposure using accepted engineering, atmospheric science, environmental chemistry, toxicology, epidemiology, and quantitative risk assessment methodologies. The investigation integrated historical emissions inventories, engineering evaluations, publicly available regulatory records, atmospheric dispersion modeling, meteorological analyses, geographic information systems (GIS), environmental monitoring information, and exposure assessment to reconstruct historical environmental conditions over multiple decades. A weight-of-evidence approach was employed to evaluate multiple independent datasets, reducing uncertainty associated with any single source of information while providing a scientifically robust assessment of historical airborne EtO concentrations (ASTM International, 2021; U.S. EPA, 2017).
The investigation began with a comprehensive review of historical engineering documentation, emissions inventories, regulatory filings, operating histories, and publicly available environmental compliance records. Historical process information was evaluated to characterize sterilization operations, production throughput, equipment modifications, emission control technologies, maintenance activities, and changes in emissions estimation methodologies over time. Because industrial operations evolve continuously throughout their operating history, reconstructing these historical operating conditions was essential for developing representative emissions estimates that accurately reflected long-term facility operations rather than a single point in time. Historical emissions trends were subsequently incorporated into the development of representative source terms for atmospheric dispersion modeling (U.S. EPA, 2024; Association for the Advancement of Medical Instrumentation, 2021).
Atmospheric transport and dispersion were evaluated using the U.S. Environmental Protection Agency’s preferred regulatory air dispersion modeling framework together with representative meteorological datasets. Engineering analyses incorporated source-specific release parameters, stack characteristics, fugitive emission sources, building downwash, terrain effects, and local land-use characteristics to estimate ambient EtO concentrations throughout the surrounding area. Representative meteorological observations, including wind speed, wind direction, atmospheric stability, temperature, and mixing height, were processed using accepted regulatory procedures to generate model-ready atmospheric inputs. Geographic information systems were then used to visualize modeled concentration patterns and evaluate long-term spatial trends in predicted community exposure (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
Environmental monitoring information was independently evaluated and compared with modeled air concentrations to assess the consistency of predicted and observed ambient EtO levels. Because ambient concentrations frequently approach analytical detection limits, monitoring data were interpreted with consideration of analytical uncertainty, sampling duration, background variability, laboratory precision, and naturally occurring regional EtO concentrations. Rather than relying solely on monitoring results, environmental measurements were evaluated together with engineering analyses, emissions reconstruction, and atmospheric modeling to develop a more comprehensive understanding of historical community exposure. This integrated methodology provided a stronger scientific basis for interpreting environmental data than any individual dataset alone (Kirman & Hays, 2017; U.S. EPA, 2024).
Finally, quantitative exposure assessment and human health risk assessment were performed by integrating modeled air concentrations, historical emissions inventories, environmental monitoring information, toxicological reference values, and current regulatory guidance for chronic inhalation exposure. Representative residential exposure scenarios were developed using accepted risk assessment methodologies to estimate long-term ambient exposure while accounting for both facility-related emissions and regional background concentrations. By combining industrial engineering, atmospheric science, environmental chemistry, toxicology, epidemiology, GIS, and quantitative exposure 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 hazardous air pollutants and historical industrial emissions (National Academies of Sciences, Engineering, and Medicine, 2022; U.S. EPA, 1989).
Results
The environmental forensic investigation demonstrated that historical ethylene oxide (EtO) emissions varied substantially throughout the operational history of the sterilization facility as production volumes, sterilization demand, emission control technologies, maintenance practices, and regulatory requirements evolved over time. Historical emissions inventories and engineering evaluations indicated that annual emissions were not constant but instead reflected changing operational conditions and improvements in process efficiency. Reconstructing these historical variations was essential for accurately estimating long-term community exposure because present-day operating conditions alone would not adequately represent environmental conditions over previous decades. Integrating historical emissions data with engineering analyses provided a scientifically robust foundation for estimating representative airborne EtO concentrations over the life of the facility (U.S. EPA, 2024; U.S. EPA, 2017).
Atmospheric dispersion modeling demonstrated that prevailing meteorological conditions were the primary factors governing the transport and dilution of EtO following release. Wind direction, atmospheric stability, wind speed, mixing height, and building-induced turbulence collectively influenced the location, magnitude, and spatial extent of predicted ambient concentrations. Model simulations illustrated that airborne concentrations varied both geographically and temporally, producing concentration gradients consistent with accepted principles of atmospheric transport. Geographic information system analyses further illustrated how these concentration patterns evolved under representative meteorological conditions and identified areas where long-term ambient concentrations were predicted to be greatest. Integrating engineering source characterization with atmospheric modeling substantially strengthened the scientific basis of the exposure assessment (American Meteorological Society & U.S. EPA, 2019; World Meteorological Organization, 2018).
Comparison of modeled concentrations with available environmental monitoring information demonstrated general consistency between predicted long-term concentration patterns and observed ambient measurements while also illustrating the limitations associated with measuring extremely low concentrations of EtO. Many environmental measurements approached laboratory detection limits, increasing uncertainty associated with individual sampling events. In addition, measurable background concentrations were observed independently of facility emissions, reflecting contributions from naturally occurring sources and other regional anthropogenic activities. Consequently, environmental monitoring results were interpreted together with engineering analyses, historical emissions reconstruction, and atmospheric dispersion modeling rather than independently. This integrated approach provided a more scientifically defensible evaluation of historical community exposure than reliance upon monitoring data alone (Kirman & Hays, 2017; U.S. EPA, 2024).
The investigation further demonstrated that improvements in industrial engineering controls and operational practices contributed to substantial reductions in estimated emissions over time. Engineering evaluations documented the implementation of enhanced emission control technologies, improved process enclosure systems, upgraded ventilation, operational modifications, and more comprehensive leak detection and repair programs that collectively reduced uncontrolled releases. Incorporating these historical engineering improvements into the emissions reconstruction allowed atmospheric modeling to more accurately represent changing environmental conditions throughout the facility’s operating history. Accounting for these operational changes also reduced uncertainty associated with long-term exposure estimates by avoiding the assumption of constant emissions over multiple decades (Association for the Advancement of Medical Instrumentation, 2021; U.S. EPA, 2022).
Overall, the investigation demonstrated that integrating historical emissions inventories, engineering evaluations, atmospheric dispersion modeling, meteorological analyses, environmental monitoring, geographic information systems, environmental chemistry, toxicology, epidemiology, and quantitative exposure assessment produced a comprehensive environmental forensic evaluation of historical EtO emissions. No individual dataset independently characterized historical community exposure; however, the integration of multiple independent scientific disciplines substantially strengthened source attribution, improved interpretation of environmental measurements, reduced uncertainty associated with historical reconstruction, 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 long-term industrial emissions (ASTM International, 2021; National Academies of Sciences, Engineering, and Medicine, 2022).
Conclusions
This environmental forensic investigation demonstrated that evaluating historical ethylene oxide (EtO) emissions from commercial sterilization operations requires a multidisciplinary scientific approach integrating industrial engineering, atmospheric science, environmental chemistry, meteorology, toxicology, epidemiology, geographic information systems (GIS), air dispersion modeling, and quantitative exposure assessment. Because facility operations, production rates, emission control technologies, and regulatory requirements evolve substantially over time, accurately characterizing historical community exposure requires more than evaluating contemporary emissions or isolated environmental measurements. By reconstructing historical operating conditions and integrating multiple independent scientific datasets, the investigation developed a technically robust understanding of long-term airborne EtO concentrations while reducing uncertainty through a comprehensive weight-of-evidence methodology (ASTM International, 2021; U.S. EPA, 2017).
The investigation demonstrated that historical emissions reconstruction is fundamental to accurately evaluating long-term environmental exposure. Engineering analyses showed that changes in sterilization throughput, process modifications, maintenance activities, equipment upgrades, and emission control technologies significantly influenced annual emissions throughout the operational history of the facility. Incorporating these historical changes into the source-term development allowed atmospheric dispersion modeling to more accurately represent changing environmental conditions over multiple decades rather than assuming constant emissions. This historical perspective provides a substantially stronger scientific basis for evaluating potential chronic community exposure and supports more reliable interpretation of environmental monitoring information (U.S. EPA, 2024; Association for the Advancement of Medical Instrumentation, 2021).
The investigation further demonstrated the importance of integrating atmospheric dispersion modeling with environmental monitoring and engineering analyses when evaluating hazardous air pollutants present at very low ambient concentrations. While environmental monitoring provides valuable observational data, measured concentrations may be influenced by analytical detection limits, temporal variability, meteorological conditions, and naturally occurring regional background concentrations. Air dispersion modeling complements monitoring by integrating historical emissions, source characteristics, terrain, and long-term meteorological conditions to estimate representative ambient concentrations over extended periods. Evaluating these complementary datasets together improves source attribution, strengthens interpretation of monitoring results, and provides a more scientifically defensible assessment than relying upon any individual analytical technique alone (American Meteorological Society & U.S. EPA, 2019; Kirman & Hays, 2017).
This case study highlights the critical role of environmental forensic science in evaluating 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, GIS, 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, long-term community exposure, and potential human health impacts 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 accidental chemical release investigations, source-term reconstruction, air dispersion modeling, exposure assessment, and human health risk evaluation. Dr. Rosenfeld’s work focuses on complex environmental contamination matters involving accidental releases of hazardous air pollutants, process upsets, industrial fires and explosions, emergency response evaluations, atmospheric transport of toxic gases, acute community exposure assessment, and the reconstruction of short-duration release events affecting nearby residential and commercial receptors. His expertise includes developing and evaluating release scenarios through the integration of process safety engineering, industrial operations, meteorology, environmental chemistry, toxicology, industrial hygiene, geographic information systems (GIS), and quantitative exposure modeling to determine whether accidental industrial releases and emergency response conditions 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, emergency response evaluation, toxic tort and personal injury case assessment, and expert witness testimony involving ethylene oxide releases, accidental hazardous chemical emissions, acute inhalation exposure, source attribution, and short- and long-term environmental and human health risks associated with industrial process incidents.
References
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U.S. Environmental Protection Agency. (2022). National Emission Standards for Hazardous Air Pollutants for Ethylene Oxide Commercial Sterilization Facilities. U.S. Environmental Protection Agency.
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