Environmental Forensic Investigation of Creosote Wood-Treatment Emissions, Odor Nuisance, Air Dispersion Modeling, and Community Exposure Assessment
Project Overview
RoseyFields conducted an environmental forensic investigation involving chemical emissions and odor nuisance impacts from a historical wood-treatment facility in Eugene, Oregon. The investigation evaluated whether creosote-related emissions from wood-preservation operations migrated into surrounding residential neighborhoods and interfered with residents’ use and enjoyment of their homes and community spaces. The analysis combined facility-history review, chemical fate-and-transport evaluation, odor-complaint analysis, ambient naphthalene monitoring, regulatory and permit-review materials, and demonstrative AERMOD air dispersion modeling to characterize the geographic extent and persistence of off-site odor impacts (ATSDR, 2002; U.S. EPA, 2017).
The facility treated wood products such as railroad ties, crossarms, and utility poles using water- and oil-based preservatives, including creosote-based formulations. The site was located in an industrial corridor with residential neighborhoods directly north, northeast, and northwest of the facility, creating a source-to-receptor setting in which routine emissions from treatment retorts, drip pads, tank systems, treated wood storage, and fugitive process releases could affect nearby communities (ATSDR, 2002; WHO, 2004).
A major focus of the investigation was the evaluation of long-term odor complaints submitted by residents to the Lane Regional Air Protection Agency. The complaint record showed thousands of odor complaints over more than four decades, with residents reporting noxious creosote-type odors, headaches, dizziness, nausea, eye irritation, respiratory irritation, and interference with daily activities such as opening windows, spending time outdoors, sleeping, and feeling comfortable inside their homes (ATSDR, 2024; Shusterman, 1992).
The investigation also incorporated air monitoring and concentration-trend analysis for naphthalene, a volatile and odorous polycyclic aromatic hydrocarbon associated with creosote emissions. Air quality data from the Highway 99 and Amazon Park monitoring stations were evaluated for temporal trends, maximum concentrations, mean concentrations, and concentration spikes corresponding to suspected excess-emission periods. This analytical framework helped connect resident odor complaints, ambient PAH measurements, and wood-treatment emission sources within a unified environmental forensic exposure assessment (ATSDR, 2005; WHO, 2004).
Chemicals of Concern
The principal chemical mixture evaluated in this investigation was coal tar creosote, a complex wood preservative derived from coal tar distillation and composed of hundreds of organic compounds. Creosote is a thick oily material commonly used to protect wood from biological degradation, and it is associated with a sharp, smoky, tar-like odor that can be detected by surrounding communities when volatile and semi-volatile constituents migrate offsite (ATSDR, 2002; WHO, 2004).
The primary chemical class of concern within creosote was polycyclic aromatic hydrocarbons, or PAHs. PAHs make up a large fraction of coal tar creosote and include compounds such as naphthalene, methylnaphthalenes, fluorene, acenaphthene, phenanthrene, anthracene, fluoranthene, and pyrene. These compounds vary in volatility, odor potency, environmental persistence, and toxicological relevance, which makes creosote odor investigations chemically complex and unsuitable for evaluation using a single odor threshold or a single marker compound alone (ATSDR, 2002; WHO, 2004).
Naphthalene was an important indicator compound in this case because it is one of the most volatile and odorous PAHs associated with creosote emissions. The report identified naphthalene as the most frequent and significant detection in long-term and short-term air samples, with long-term samples showing naphthalene in 100% of samples and short-term samples showing detections in 73% of samples. The median long-term naphthalene concentration was reported as 3.1 µg/m³, which was more than 160 times the highest background concentration identified for the area between December 2001 and 2005 (ATSDR, 2005; WHO, 2004).
Creosote odor impacts cannot be fully characterized by naphthalene alone because creosote vapors contain a mixture of PAHs, tar acids, aromatic amines, sulfur-containing heterocycles, and oxygen-containing heterocycles. Odor thresholds also vary by compound, study design, and human sensitivity, and odor detection is influenced by repeated exposure, odor familiarity, stress response, and individual susceptibility. As a result, the investigation treated odor complaints, ambient monitoring, chemical composition, and dispersion modeling as complementary lines of evidence rather than relying solely on a numeric odor-threshold comparison (Ruth, 1986; Shusterman, 1992).
Methods
RoseyFields applied a multidisciplinary environmental forensic methodology that integrated facility-history reconstruction, air monitoring evaluation, odor-complaint analysis, source-term estimation, AERMOD dispersion modeling, GIS-based receptor assessment, and community exposure interpretation. The report relied on records from the facility, EPA, LRAPA, Oregon DEQ, Keystone Environmental Resources, odor-complaint records, air monitoring data, and public health materials to evaluate the source, transport, and community impacts of creosote-related emissions (ASTM International, 2021; U.S. EPA, 2017).
The facility-history review evaluated operational units and emission-generating processes associated with wood preservation. The facility included multiple retorts, wood-drying kilns, boilers, an evaporator, drip pads, a wood yard, incisor units, process wastewater treatment, stormwater treatment, groundwater treatment, and tank farms. These operations created multiple potential emission pathways, including retort venting, treated-wood handling, drip-pad volatilization, wastewater handling, tank emissions, fugitive process releases, and treated-wood storage emissions (ATSDR, 2002; U.S. EPA, 1992).
The odor-complaint analysis evaluated the frequency, timing, location, and qualitative descriptions of odor complaints submitted by nearby residents. The complaint record was used as a community-level exposure indicator because odor nuisance is inherently receptor-based and because resident complaints can capture real-world odor episodes that may not coincide with scheduled sampling events. The investigation considered complaint volume over time, complaints within the relevant limitations period, reported symptoms, and behavioral responses such as remaining indoors or closing windows (ATSDR, 2024; Shusterman, 1992).
The air monitoring component evaluated ambient naphthalene data from the Highway 99 and Amazon Park monitoring stations. Mean and maximum naphthalene concentrations were compared by monitoring location and year, with Highway 99 generally showing higher concentrations than Amazon Park, consistent with its closer proximity to the Baxter facility. This monitoring comparison provided spatial evidence of a concentration gradient away from the facility and temporal evidence of episodic concentration spikes associated with facility-related emission events (ATSDR, 2005; WHO, 2004).
The investigation also used AERMOD for demonstrative dispersion modeling of creosote emissions. The modeling was performed using EPA AERMOD methods and ODEQ modeling guidance, with model inputs including emission data from Baxter and AP-42, USGS terrain data, BREEZE meteorological data, and ESRI basemapping. AERMOD was used to estimate 1-hour high and annual average creosote concentrations, evaluate plume behavior, and develop a proposed class boundary based on modeled annual average creosote exposure and historical odor-complaint patterns (U.S. EPA, 2017; ODEQ, 2022).
The receptor grid was developed using variable-density spacing to provide higher spatial resolution near the facility and broader coverage farther away from the source. The grid included 25-meter spacing from 0 to 200 meters, 50-meter spacing from 200 to 1,000 meters, 100-meter spacing from 1,000 to 2,000 meters, 200-meter spacing from 2,000 to 5,000 meters, and 500-meter spacing from 5,000 to 10,000 meters, resulting in 6,529 receptor points across a 20-by-20-kilometer domain. Terrain was processed using AERMAP and National Elevation Dataset files to account for local elevation effects on plume transport and ground-level concentrations (U.S. EPA, 2017; ODEQ, 2022).
Meteorological data were obtained from BREEZE using Eugene Airport data, located approximately five miles northwest of the facility. The BREEZE data team reviewed meteorological data for 2017 through 2022 and identified 2021 as the most complete year for modeling. The use of representative meteorological data allowed the analysis to evaluate plume transport under realistic local wind speed, wind direction, atmospheric stability, and dispersion conditions (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
The modeling results were visualized using BREEZE 3D Analyst to prepare still images showing maximum hourly creosote plume directions during June through September, the months that consistently showed high odor-complaint activity. The modeling also included annual average creosote dispersion results, which were used to illustrate the geographic extent of community impacts and to support a proposed class boundary that captured more than 90% of historic odor complaints filed with LRAPA from 1977 through 2022 (U.S. EPA, 2017; ODEQ, 2022).
Results
The environmental forensic investigation demonstrated that creosote-related emissions from the Baxter facility were persistent, variable, and capable of affecting surrounding residential communities. Demonstrative AERMOD modeling showed modeled creosote plumes extending into neighborhoods around the facility, including areas in and around Bethel, Trainsong, and River Road. The modeled annual average plume and historic odor-complaint record supported a proposed class boundary representing a contiguous zone of off-site odor impact (U.S. EPA, 2017; ODEQ, 2022).
The odor-complaint analysis showed that nearby residents filed more than 3,000 complaints against the facility over more than 40 years. Complaints described persistent odors that disrupted residents’ ability to feel healthy, enjoy their homes, spend time outside, sleep soundly, and use private and public spaces comfortably. Residents also reported headaches, nausea, vomiting, eye irritation, nose irritation, throat irritation, lung irritation, dizziness, and difficulty breathing in connection with creosote-type odor events (ATSDR, 2024; Shusterman, 1992).
The complaint record provided important receptor-based evidence because odor nuisance is defined by interference with comfort, health, or safety rather than by the exceedance of a single chemical threshold. The report emphasized that complaints were a stronger indicator of nuisance than naphthalene odor thresholds alone because creosote emissions contain hundreds of compounds and because odor thresholds vary widely across studies and individuals. This interpretation is consistent with odor-science principles recognizing that odor impact depends on frequency, intensity, duration, offensiveness, location, and receptor response (Ruth, 1986; Shusterman, 1992).
Ambient air monitoring supported the conclusion that the facility affected local air quality. At the Highway 99 monitoring station, mean naphthalene concentrations were 329.94 ng/m³ in 2015, 128.96 ng/m³ in 2018, 271.87 ng/m³ in 2019, 127.51 ng/m³ in 2020, 106.08 ng/m³ in 2021, and 125.18 ng/m³ in 2022, while maximum values reached 2,121.5 ng/m³ in 2015 and 2,670 ng/m³ in 2019. At Amazon Park, mean concentrations were lower, ranging from 24.48 to 50.74 ng/m³, with maximum values reaching 564 ng/m³ in 2020 and 389 ng/m³ in 2019 (ATSDR, 2005; WHO, 2004).
The spatial pattern of monitoring results supported a source-gradient interpretation. The Highway 99 station showed higher naphthalene concentrations than Amazon Park, which was interpreted as consistent with the Highway 99 station’s closer proximity to the Baxter facility. The 2019 monitoring data also showed a pronounced spike during early October, corresponding with a weekend when reported facility mishaps resulted in excess emissions and numerous odor complaints; Highway 99 naphthalene concentrations increased from below 500 ng/m³ to more than 2,500 ng/m³, while Amazon Park also increased at a lower magnitude (ATSDR, 2005; WHO, 2004).
The investigation also identified a history of noncompliance and permit-related deficiencies relevant to air emissions and odor impacts. The facility was cited for issues including failure to submit operations records, exceeding allowable No. 6 fuel oil use, failure to take reasonable measures to prevent particulate emissions, failure to conduct emissions testing, failure to submit an amended operations and maintenance plan, failure to demonstrate required carbon adsorption efficiency, and failure to notify LRAPA of an excess-emissions event. These regulatory findings supported the conclusion that historical operational practices and control failures contributed to community air-quality impacts (U.S. EPA, 1992; ASTM International, 2021).
The aerial-image record further supported the environmental forensic reconstruction by documenting the facility area over time from 1994 through 2022. The images show the Baxter facility located immediately south of residential areas and within a mixed industrial-residential setting, reinforcing the source-to-receptor context for odor nuisance and air dispersion analysis. This spatial relationship was important because the facility’s proximity to residential neighborhoods increased the likelihood that routine and episodic emissions could be detected by nearby residents (U.S. EPA, 2017; ASTM International, 2021).
Overall, the investigation demonstrated that the odor impacts surrounding the Baxter facility were supported by multiple independent lines of evidence: facility operations involving creosote-treated wood, thousands of odor complaints, ambient naphthalene monitoring, documented concentration spikes, regulatory and permit violations, aerial source-to-receptor mapping, and AERMOD plume modeling. Together, these evidence streams supported the conclusion that creosote emissions migrated beyond the facility boundary and interfered with neighboring residential communities (ASTM International, 2021; U.S. EPA, 2017).
Conclusions
This environmental forensic investigation demonstrated that historical creosote emissions from wood-treatment operations can create long-term odor nuisance impacts in surrounding residential communities. The Baxter case required an integrated technical approach because creosote is not a single compound but a complex mixture of PAHs and other odorous organic constituents that vary in volatility, persistence, odor potency, and toxicological significance. By integrating odor complaints, naphthalene monitoring, facility-history reconstruction, regulatory records, aerial imagery, and AERMOD dispersion modeling, RoseyFields developed a scientifically defensible assessment of off-site creosote odor migration and community impact (ATSDR, 2002; ASTM International, 2021).
A principal conclusion of the investigation was that odor complaints provided strong receptor-based evidence of nuisance. More than 3,000 complaints over more than 40 years showed that residents repeatedly experienced odors that interfered with comfort, health, sleep, outdoor activity, and use of their homes. Because creosote emissions contain hundreds of chemicals and because odor thresholds are variable and subjective, the complaint record was an important analytical dataset for evaluating nuisance impacts and should not be discounted simply because individual monitoring samples did not exceed a single odor-threshold value (Ruth, 1986; Shusterman, 1992).
The investigation also concluded that ambient naphthalene monitoring supported the existence of facility-related air-quality impacts. Highway 99 concentrations were consistently higher than Amazon Park concentrations, and episodic spikes in naphthalene aligned with reported excess-emission periods and odor complaints. These results supported the interpretation that naphthalene was an appropriate marker compound for creosote-related air impacts and that the Baxter facility was a likely contributor to elevated PAH concentrations in nearby air (ATSDR, 2005; WHO, 2004).
The AERMOD analysis provided additional support for a geographically coherent exposure area. The model used a variable-density receptor grid, USGS terrain processing, Eugene Airport meteorological data, and BREEZE 3D Analyst visualization to evaluate creosote plume behavior under annual average and maximum hourly conditions. The resulting demonstrative plume maps showed impacts extending into residential neighborhoods in multiple directions from the facility and supported a proposed class boundary based on annual average modeled creosote concentrations and historic odor complaints (U.S. EPA, 2017; ODEQ, 2022).
This case study highlights the role of environmental forensic science in evaluating odor nuisance, creosote emissions, PAH air monitoring, and community exposure near historical wood-treatment operations. By integrating environmental chemistry, odor science, AERMOD air dispersion modeling, GIS-based receptor analysis, regulatory compliance review, and exposure assessment, RoseyFields provides technical evaluations capable of supporting environmental consulting, nuisance litigation, class-boundary analysis, regulatory investigations, and expert witness services involving industrial odor emissions and community air-quality impacts (ASTM International, 2021; U.S. EPA, 2017).
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist and environmental forensic expert with extensive experience in chemical fate and transport, air dispersion modeling, odor science, human health risk assessment, exposure assessment, wood-treatment facilities, creosote contamination, PAHs, volatile and semi-volatile organic compounds, and community nuisance evaluations. Through RoseyFields LLC, Dr. Rosenfeld provides environmental forensic analysis, air quality modeling, odor-impact assessment, contaminant exposure reconstruction, regulatory review, remediation support, and expert witness testimony involving industrial emissions, hazardous air pollutants, nuisance odors, and long-term community exposure.
References
Agency for Toxic Substances and Disease Registry. (2002). Toxicological profile for wood creosote, coal tar creosote, coal tar, coal tar pitch, and coal tar pitch volatiles. U.S. Department of Health and Human Services.
Agency for Toxic Substances and Disease Registry. (2005). Toxicological profile for naphthalene, 1-methylnaphthalene, and 2-methylnaphthalene. U.S. Department of Health and Human Services.
American Meteorological Society, & U.S. Environmental Protection Agency. (2019). AERMOD: Description of model formulation. U.S. Environmental Protection Agency.
ASTM International. (2021). Standard guide for environmental forensic investigations. ASTM International.
Oregon Department of Environmental Quality. (2022). Recommended procedures for air quality dispersion modeling. Oregon Department of Environmental Quality.
Ruth, J. H. (1986). Odor thresholds and irritation levels of several chemical substances: A review. American Industrial Hygiene Association Journal, 47(3), A142–A151.
Shusterman, D. (1992). Critical review: The health significance of environmental odor pollution. Archives of Environmental Health, 47(1), 76–87.
U.S. Environmental Protection Agency. (1992). AP-42: Compilation of air pollutant emission factors. U.S. Environmental Protection Agency.
U.S. Environmental Protection Agency. (2017). Guideline on air quality models (40 CFR Part 51, Appendix W). U.S. Environmental Protection Agency.
World Health Organization. (2004). Concise international chemical assessment document 62: Coal tar creosote. World Health Organization.