Environmental Forensic Investigation of Industrial Petrochemical Fire Emissions Using Air Dispersion Modeling, Atmospheric Monitoring, Exposure Assessment, and Environmental Forensics
Project Overview
Industrial petrochemical facilities manufacture, process, and store large quantities of volatile hydrocarbons that serve as feedstocks for plastics, synthetic rubber, fuels, and numerous chemical products. Although these facilities are designed with multiple engineering safeguards, equipment failures, accidental releases, fires, and explosions can result in the rapid release of hazardous airborne contaminants capable of affecting both workers and surrounding communities. Environmental forensic investigations of these incidents require integration of engineering records, emissions inventories, meteorological observations, environmental monitoring data, air dispersion modeling, toxicological literature, and regulatory documentation to reconstruct release events and evaluate potential human exposure. Such investigations are routinely conducted to understand the nature of chemical releases, identify contaminants of concern, evaluate atmospheric transport, reconstruct historical exposure conditions, and assess the consistency of multiple independent sources of technical evidence.
This environmental forensic investigation involved a comprehensive technical evaluation of a major petrochemical facility fire and explosion involving the release of 1,3-butadiene and other combustion-related contaminants. The investigation integrated regulatory emissions reports, engineering documentation, meteorological observations, ambient air monitoring results, aerial remote sensing data, air dispersion modeling, exposure assessment, epidemiological literature, and published toxicological information to evaluate the environmental conditions associated with the incident. Rather than relying upon a single source of information, the investigation compared multiple independent datasets to develop a scientifically supported understanding of contaminant releases, atmospheric transport, and potential community exposure. The reviewed materials included governmental investigation reports, continuous stationary monitoring data, airborne monitoring conducted by the U.S. Environmental Protection Agency, emissions inventories reported to state regulators, meteorological analyses, and quantitative air dispersion modeling developed using accepted environmental engineering principles.
The investigation was conducted using accepted principles of environmental forensics, atmospheric science, exposure assessment, environmental engineering, industrial emissions evaluation, and historical event reconstruction. The objective was to evaluate the available scientific and technical evidence describing the release, transport, monitoring, and potential exposure associated with airborne contaminants generated during the incident. Particular emphasis was placed on integrating emissions data with meteorological conditions and measured environmental concentrations to understand how changing atmospheric conditions influenced contaminant movement throughout the duration of the event. This multidisciplinary approach reflects standard environmental consulting practice for evaluating complex accidental chemical releases involving multiple contaminants, evolving fire conditions, and extended emergency response activities.
Because the incident involved both an initial catastrophic release and an extended period of continuing emissions during the subsequent fire, the investigation also considered how emission characteristics evolved throughout the event. Immediate vapor releases, ongoing combustion emissions, prolonged equipment failures, and changing fire conditions can each influence contaminant concentrations, plume behavior, and potential exposure patterns. Accordingly, the investigation evaluated multiple emission scenarios using engineering calculations, reported emissions inventories, air dispersion modeling, environmental monitoring data, and meteorological analyses to reconstruct changing environmental conditions over the course of the incident.
Chemicals of Concern
The principal chemical evaluated during this investigation was 1,3-butadiene, a highly flammable volatile organic compound widely used in the manufacture of synthetic rubber, plastics, elastomers, and other petrochemical products. Under normal industrial conditions, 1,3-butadiene is handled within closed processing systems because of its volatility, flammability, and recognized health hazards. Accidental loss of containment can rapidly produce vapor clouds capable of dispersing over considerable distances before ignition. If ignition occurs, both the unburned vapor and the products of combustion become important considerations in evaluating environmental exposure. The reviewed documentation identified 1,3-butadiene as the primary released material associated with the initiating event and subsequent fire.
From an environmental fate and transport perspective, 1,3-butadiene possesses physical properties that strongly influence its behavior following release. The compound rapidly volatilizes under ambient conditions, allowing airborne transport to become the dominant environmental pathway immediately after loss of containment. Once released into the atmosphere, dispersion is governed primarily by meteorological conditions including wind speed, wind direction, atmospheric stability, mixing height, and turbulence. Because the compound is chemically reactive, atmospheric degradation and photochemical reactions gradually reduce concentrations over time while simultaneously contributing to the formation of secondary atmospheric products. These characteristics make meteorological reconstruction and atmospheric dispersion modeling essential components of environmental forensic investigations involving large butadiene releases.
The investigation also considered combustion-related contaminants generated during the prolonged facility fire. Burning petrochemical products can produce complex mixtures of volatile organic compounds (VOCs), particulate matter (PM₂.₅ and PM₁₀), soot, carbon monoxide, nitrogen oxides, polycyclic aromatic hydrocarbons (PAHs), and other combustion by-products. The specific composition of emissions depends upon the chemical inventory involved, combustion efficiency, oxygen availability, fire temperature, and the duration of burning. Consequently, evaluation of the incident required consideration of both the original chemical release and the contaminants produced during sustained combustion. The reviewed technical documentation identified benzene, toluene, xylene, particulate matter, nitrogen oxides, carbon monoxide, and hydrogen sulfide among the contaminants considered during environmental monitoring and exposure evaluation.
The toxicological significance of 1,3-butadiene has been extensively evaluated through occupational epidemiology, toxicology, and environmental health research. Regulatory agencies including the U.S. Environmental Protection Agency, the National Toxicology Program, the International Agency for Research on Cancer (IARC), and other public health organizations classify 1,3-butadiene as a known or probable human carcinogen based primarily upon inhalation exposure. In addition to long-term cancer risk, occupational studies have evaluated respiratory effects, hematological changes, reproductive toxicity, immunotoxicity, and other adverse health outcomes associated with prolonged exposure. The supporting literature reviewed during this investigation included epidemiological studies evaluating occupational exposure among petrochemical workers, toxicological reviews describing both cancer and non-cancer effects, and investigations of biological monitoring in exposed populations.
An important aspect of the investigation involved distinguishing between acute exposure associated with the accidental release and chronic exposure evaluated in occupational epidemiology studies. Industrial accidents typically produce relatively short-duration airborne releases characterized by rapidly changing concentrations, whereas epidemiological studies often examine workers exposed repeatedly over many months or years. Nevertheless, occupational exposure research provides valuable scientific information regarding inhalation pathways, toxicological mechanisms, dose-response relationships, and biological effects that can inform environmental exposure assessments conducted following accidental releases. Accordingly, peer-reviewed occupational studies were incorporated to provide scientific context regarding the environmental significance of airborne 1,3-butadiene and its recognized health effects.
The investigation further recognized that community exposure depends not only upon the quantity of chemical released but also upon atmospheric transport processes occurring after the release. Wind direction, atmospheric mixing, terrain, release height, and fire behavior all influence whether contaminants remain near the source or disperse toward surrounding neighborhoods. Consequently, airborne monitoring data, meteorological observations, aerial remote sensing, and air dispersion modeling each provide complementary information regarding contaminant movement and potential exposure. Evaluation of these multiple independent datasets represents a core component of modern environmental forensic investigations because no individual source of information completely characterizes atmospheric contaminant transport during complex industrial incidents.
Finally, the reviewed documentation demonstrated that accidental petrochemical releases frequently involve multiple exposure pathways operating simultaneously. Direct inhalation of volatile chemicals during the initial release may be followed by exposure to combustion products generated during prolonged fires. Environmental monitoring therefore commonly includes measurement of volatile organic compounds, combustion gases, and particulate matter while atmospheric models estimate the potential geographic extent of chemical transport. Integrating these complementary sources of information provides a more complete understanding of environmental conditions than evaluating any individual contaminant or monitoring program independently.
Methods
The investigation was conducted using accepted principles of environmental forensics, environmental engineering, atmospheric science, exposure assessment, industrial emissions analysis, and historical event reconstruction. Because the incident involved an accidental chemical release followed by an extended industrial fire, the evaluation required integration of multiple independent technical datasets describing emissions, meteorology, environmental monitoring, engineering information, and toxicological evidence. Rather than relying upon a single category of information, the investigation synthesized regulatory documentation, engineering calculations, governmental monitoring programs, peer-reviewed scientific literature, air dispersion modeling, and historical meteorological observations to reconstruct environmental conditions and evaluate potential community exposure. This multidisciplinary approach is consistent with accepted environmental consulting practices for evaluating accidental releases of hazardous airborne contaminants from petrochemical facilities.
A primary component of the investigation involved review of regulatory documentation describing the incident, including official emissions event reports submitted to state environmental regulators. These records documented the timing of the release, reported emission quantities, affected process units, contaminant inventories, and the duration of the event. Regulatory emissions inventories were evaluated to characterize both the initial catastrophic release and the prolonged emissions associated with the subsequent facility fire. Because emissions continued for an extended period following the initial explosion, the investigation evaluated how release rates varied over time and how these changing emission characteristics influenced atmospheric transport and potential exposure. Regulatory documentation also provided detailed inventories of 1,3-butadiene and associated volatile organic compound emissions originating from multiple process units throughout the incident.
Engineering evaluation of reported emissions represented another important component of the investigation. The technical documentation reconstructed several release scenarios based upon reported chemical inventories, estimated release durations, and emissions reported by regulatory agencies. Separate emission scenarios were developed to evaluate the initial vapor release, sustained combustion during the facility fire, variable emission rates during different stages of the incident, emissions occurring before schools reopened, and total emissions over the complete duration of the regulatory event. Evaluating multiple engineering scenarios allowed the investigation to examine how different release assumptions influenced predicted contaminant transport and potential exposure while remaining consistent with reported emissions inventories.
Air dispersion modeling formed a central component of the environmental forensic evaluation. Atmospheric dispersion analyses were performed using the Areal Locations of Hazardous Atmospheres (ALOHA) model, an emergency response modeling program developed by the U.S. Environmental Protection Agency and the National Oceanic and Atmospheric Administration. ALOHA predicts the movement and dilution of hazardous airborne releases using source characteristics, chemical properties, and meteorological conditions to estimate potential downwind concentrations. Within this investigation, multiple modeling scenarios were developed to evaluate the geographic extent of potential airborne 1,3-butadiene concentrations under different release conditions. Model output included predicted Acute Exposure Guideline Level (AEGL) footprints corresponding to increasing levels of potential health concern and demonstrated how varying release rates influenced the spatial distribution of airborne contaminants. These modeling results were evaluated together with environmental monitoring data rather than interpreted independently, reflecting accepted environmental forensic practice for assessing atmospheric contaminant transport.
The investigation also incorporated airborne monitoring conducted by the U.S. Environmental Protection Agency using the Airborne Spectral Photometric Environmental Collection Technology (ASPECT) system. ASPECT combines airborne Fourier Transform Infrared (FTIR) spectroscopy, infrared line-scanning imagery, aerial photography, and geospatial analysis to evaluate active chemical incidents from a safe distance. The system was deployed during the emergency response to provide situational awareness, identify thermal anomalies, screen for airborne chemicals, and estimate plume characteristics. Review of the ASPECT documentation included evaluation of aerial infrared imagery, flight paths, meteorological observations collected during the missions, and FTIR screening results. Although significant thermal signatures associated with the fire were observed, automated and manual review of the airborne FTIR spectral data did not identify detectable airborne chemical concentrations during the monitoring flights conducted after weather conditions improved. Evaluation of these findings provided important context when interpreting atmospheric conditions during later stages of the incident.
Ground-based ambient air monitoring provided an additional independent source of information describing environmental conditions throughout the incident. Stationary monitoring stations operated by regulatory agencies continuously measured airborne concentrations of selected contaminants, including 1,3-butadiene, at locations surrounding the facility. These data were reviewed to evaluate temporal trends in measured concentrations, identify periods of elevated airborne contaminants, and compare observed environmental measurements with predicted dispersion patterns. Continuous stationary monitoring provides valuable information because it documents actual ambient concentrations over time and allows investigators to compare modeled contaminant transport with measured environmental conditions. Integration of measured monitoring data with air dispersion modeling represents a fundamental principle of environmental exposure assessment because each source of information independently contributes to understanding atmospheric behavior during complex industrial incidents.
Meteorological analysis represented another essential component of the investigation. Atmospheric transport of airborne contaminants depends upon continually changing weather conditions, including wind speed, wind direction, atmospheric stability, humidity, temperature, mixing height, and precipitation. Historical meteorological observations collected during the incident were evaluated together with airport weather records and operational weather information collected during emergency response activities. Particular attention was given to hourly wind direction because changing wind patterns directly influence the direction of plume transport and the communities potentially affected during different periods of the event. Rather than assuming constant atmospheric conditions, the investigation reconstructed changing meteorological conditions throughout the incident to better understand variations in downwind exposure. This approach reflects accepted atmospheric science principles and improves interpretation of both environmental monitoring results and air dispersion model predictions.
The technical evaluation further incorporated review of peer-reviewed toxicological and epidemiological literature concerning 1,3-butadiene exposure. Occupational health studies evaluating petrochemical workers, toxicological reviews, biomonitoring investigations, and human health risk assessments were examined to provide scientific context regarding inhalation exposure pathways, dose-response relationships, respiratory effects, hematological changes, and carcinogenicity. Environmental forensic investigations routinely integrate toxicological evidence with engineering analyses because understanding contaminant toxicity is necessary for interpreting the environmental significance of measured or modeled airborne concentrations. The reviewed epidemiological literature also provided information regarding both cancer and non-cancer health outcomes associated with occupational exposure, allowing the investigation to place environmental measurements within the broader framework of accepted exposure science.
Finally, the investigation employed a weight-of-evidence methodology that integrated engineering analyses, regulatory documentation, atmospheric modeling, environmental monitoring, meteorological reconstruction, and peer-reviewed scientific literature into a unified environmental forensic framework. Each category of technical information contributed unique insight regarding the release, transport, monitoring, and environmental behavior of airborne contaminants. By evaluating these independent datasets collectively rather than in isolation, the investigation reduced uncertainty associated with any individual source of information and developed a technically supported reconstruction of environmental conditions throughout the incident. This multidisciplinary methodology represents current best practice within environmental consulting, expert witness investigations, and environmental forensic science for evaluating accidental industrial releases involving hazardous airborne chemicals.
Results
Review of the available technical documentation demonstrated that evaluation of complex petrochemical incidents benefits substantially from integrating engineering analyses, regulatory records, environmental monitoring, meteorological reconstruction, toxicological literature, and atmospheric dispersion modeling into a single environmental forensic framework. Although each source of information independently described only one aspect of the incident, collectively the reviewed materials provided a comprehensive scientific basis for reconstructing contaminant releases, evaluating atmospheric transport, and assessing potential community exposure. The investigation demonstrated that the integration of multiple independent technical datasets provides a more complete understanding of accidental chemical releases than reliance upon any individual source of information alone.
One of the principal findings of the investigation involved the characterization of the initial accidental release and the prolonged emissions associated with the subsequent industrial fire. Regulatory documentation described an initial loss of containment involving approximately 6,000 gallons of 1,3-butadiene that rapidly vaporized and formed a flammable vapor cloud before ignition. Following the initial explosions, damaged process equipment continued releasing process fluids that sustained fires for an extended period, resulting in emissions over many weeks rather than a single short-duration event. This distinction significantly influenced the environmental evaluation because the atmospheric conditions affecting the initial release differed substantially from those governing prolonged combustion emissions occurring throughout the response period. Consequently, multiple emission scenarios were required to characterize the full range of environmental conditions associated with the incident.
Review of the reported emissions inventories further demonstrated the magnitude and complexity of the release. Regulatory reports documented emissions from multiple process units in addition to the primary fire area, with the overwhelming majority of reported 1,3-butadiene emissions associated with the sustained fire. These inventories provided the engineering basis for estimating release rates used in subsequent air dispersion modeling and exposure assessment. Because emissions were reported for multiple facility components rather than a single release point, the investigation considered both localized fugitive releases and sustained combustion emissions when evaluating atmospheric contaminant transport.
Evaluation of the ALOHA air dispersion modeling demonstrated how release duration and emission rate substantially influenced the predicted geographic extent of airborne 1,3-butadiene concentrations. Rather than relying upon a single release assumption, multiple modeling scenarios were developed representing the initial catastrophic release, sustained fire emissions, variable release rates during different phases of the incident, and emissions occurring over progressively longer periods. These scenarios produced differing plume geometries and predicted concentration footprints, illustrating the sensitivity of atmospheric transport predictions to engineering assumptions regarding source strength and release duration. The modeling also incorporated Acute Exposure Guideline Level (AEGL) thresholds to estimate areas potentially associated with increasing levels of acute health concern, providing a structured framework for evaluating the potential spatial extent of airborne exposures.
The investigation also demonstrated the value of integrating modeled predictions with measured environmental data. Continuous stationary monitoring documented temporal variations in ambient 1,3-butadiene concentrations throughout the monitoring period, identifying both relatively low background periods and intervals of elevated concentrations. Because environmental monitoring provides direct measurement while atmospheric models estimate predicted concentrations, comparison of these independent datasets allows investigators to evaluate the consistency of engineering assumptions with observed environmental conditions. The reviewed monitoring records therefore served as an important validation component within the broader environmental forensic evaluation rather than functioning solely as a standalone dataset.
Airborne monitoring performed by the U.S. Environmental Protection Agency provided an additional independent perspective on environmental conditions during the response. ASPECT infrared imagery documented thermal activity associated with the facility while airborne FTIR screening was used to evaluate the presence of airborne chemicals within the monitored plume. Although significant thermal signatures and active firefighting operations were evident, automated and manual review of the FTIR data collected during the later monitoring missions did not identify detectable airborne chemical concentrations within the instrument’s screening capabilities. These findings illustrate an important principle of environmental forensics: the absence of chemical detections during a specific monitoring period does not necessarily imply that releases did not occur earlier or under different atmospheric conditions. Rather, monitoring results must be interpreted within the context of sampling location, meteorological conditions, instrument sensitivity, fire behavior, and the timing of data collection relative to the evolving incident.
Meteorological reconstruction further demonstrated that atmospheric transport conditions varied considerably throughout the incident. Hourly changes in wind direction and wind speed altered the orientation and movement of airborne contaminants over time, resulting in changing downwind exposure patterns rather than a single persistent plume direction. Review of historical weather observations indicated that regional wind variability required evaluation of the complete meteorological record rather than reliance upon isolated observations. These findings underscore the importance of reconstructing meteorological conditions throughout an incident when evaluating environmental exposure because even relatively modest changes in wind direction can substantially alter the communities affected by airborne releases.
Review of the toxicological and epidemiological literature further demonstrated that 1,3-butadiene has been extensively studied in occupational settings, providing a substantial scientific foundation for interpreting inhalation exposure. Peer-reviewed investigations consistently identify inhalation as the principal exposure pathway and document both cancer and non-cancer health outcomes associated with prolonged occupational exposure. The reviewed studies also described respiratory effects, hematological changes, pulmonary function changes, reproductive toxicity, and immunological effects among exposed populations. Although these occupational investigations involve different exposure durations than those associated with accidental industrial releases, they provide important scientific context for evaluating the environmental significance of airborne 1,3-butadiene concentrations and understanding the toxicological basis underlying human health risk assessments.
Collectively, the reviewed materials demonstrated the importance of integrating engineering analyses, emissions inventories, atmospheric modeling, environmental monitoring, meteorological reconstruction, and toxicological evidence when evaluating accidental petrochemical releases. Each category of technical information independently contributes valuable insight regarding contaminant release, atmospheric transport, environmental persistence, and potential exposure. Considered together, these datasets provide a scientifically supported framework for reconstructing complex environmental incidents and evaluating community exposure using accepted principles of environmental forensics and exposure assessment.
Conclusions
The available technical documentation provides a comprehensive scientific foundation for evaluating accidental petrochemical releases using accepted principles of environmental forensics, atmospheric science, environmental engineering, exposure assessment, and historical event reconstruction. Although large industrial incidents involve numerous uncertainties associated with rapidly changing fire conditions, evolving emissions, and variable meteorological influences, the integration of multiple independent technical datasets allows investigators to reconstruct environmental conditions using scientifically accepted methodologies.
The investigation demonstrated that environmental monitoring, engineering analyses, regulatory documentation, atmospheric dispersion modeling, aerial remote sensing, and meteorological reconstruction each contribute unique information regarding contaminant behavior following accidental releases. When evaluated collectively through a weight-of-evidence framework, these independent datasets provide a technically defensible understanding of contaminant fate and transport, atmospheric dispersion, and potential human exposure that is substantially more robust than reliance upon any individual source of information.
Review of the available documentation also illustrates the importance of considering the temporal evolution of industrial incidents. Initial catastrophic releases, prolonged combustion emissions, changing meteorological conditions, emergency response activities, and ongoing environmental monitoring each describe different phases of an evolving event. Environmental forensic investigations that integrate these changing conditions into a unified reconstruction provide a more accurate representation of historical environmental conditions than evaluations based solely upon isolated measurements or simplified release assumptions.
More broadly, this investigation demonstrates how modern environmental consulting combines environmental chemistry, atmospheric science, industrial emissions evaluation, exposure assessment, toxicology, engineering analysis, meteorology, regulatory review, and air dispersion modeling to investigate complex accidental releases of hazardous chemicals. These multidisciplinary investigations provide scientifically supported evaluations of contaminant behavior and potential exposure while remaining grounded in objective technical analysis, peer-reviewed science, and accepted environmental engineering methodologies.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist, environmental forensic expert, and exposure assessment specialist with more than twenty-five years of experience evaluating industrial emissions, atmospheric contaminant transport, environmental contamination, occupational exposures, and human health risk. Throughout his career, Dr. Rosenfeld has investigated chemical releases involving volatile organic compounds, petroleum hydrocarbons, hazardous air pollutants, combustion products, particulate matter, asbestos, metals, pesticides, PFAS, ethylene oxide, and numerous other contaminants affecting both occupational and community environments. His expertise encompasses environmental forensic investigations, air quality modeling, contaminant fate and transport, historical exposure reconstruction, environmental monitoring, regulatory compliance evaluation, quantitative risk assessment, and expert witness testimony in complex environmental litigation.
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