Reconstructing the Past: How Dr. Paul E. Rosenfeld Turns Decades-Old Industrial Emissions Into Quantifiable Human Exposure
By Paul E. Rosenfeld, M.S., Ph.D., Principal Environmental Chemist, RoseyFields LLC, Santa Monica, California
The evidentiary gap at the center of every legacy contamination case
Toxic-tort and environmental litigation frequently turns on a deceptively simple problem: a facility operated, emitted chemicals, and people lived nearby for years or decades, but no one was standing in the affected neighborhood with an air monitor at the time. Dr. Paul E. Rosenfeld, M.S., Ph.D., founder and principal environmental chemist of RoseyFields LLC in Santa Monica, California, has spent more than 25 years developing and applying historical emissions and exposure reconstruction methods that close that gap. His approach combines facility operating history, meteorology, environmental chemistry, atmospheric dispersion modeling, geographic and land-use data, and quantitative dose assessment into a single, defensible reconstruction of what a community actually breathed, drank, or contacted decades before litigation began (Rosenfeld, 2026).
AERMOD as the regulatory backbone of historical reconstruction
The technical foundation of this work is AERMOD, the steady-state dispersion model that the U.S. Environmental Protection Agency has designated as its preferred model for regulatory air-quality analysis of stationary industrial sources (US EPA, 2017). Because AERMOD is the same model EPA itself uses to evaluate permit compliance, its use in litigation carries a regulatory pedigree that is difficult for opposing experts to dismiss as ad hoc or result-driven. Dr. Rosenfeld’s reconstructions typically combine historical meteorological data, facility-specific source parameters, and terrain data to estimate pollutant concentrations at specific residential or community receptor locations for years, and sometimes decades, before any monitoring program existed.
Judicial description of the methodology in Alabama mill litigation
In the consolidated Alabama litigation arising from the International Paper Prattville mill, the U.S. District Court for the Middle District of Alabama described Dr. Rosenfeld as an environmental chemist retained to assess community exposure to the mill’s emissions, and detailed his use of AERMOD together with 1992 meteorological data and facility-specific source parameters to estimate short-term airborne concentrations of PM10, nitrogen oxides, sulfur dioxide, and volatile organic compounds across a grid of receptor points surrounding the site (Brantley, 2017). Dr. Rosenfeld also provided exposure-related opinions in a companion case brought by a different set of plaintiffs against the same facility (Benefield, 2011).
Using dispersion modeling to define the geographic boundary of a case
A related but distinct use of dispersion modeling is defining who was exposed in the first place. In the consolidated refinery litigation against BP Products North America arising from the 2010 Texas City ultracracker unit emissions event, Dr. Rosenfeld’s air-dispersion analysis was used to help delineate the geographic area within which the plume was estimated to have traveled, providing a scientific basis for identifying the population plausibly affected by the release (Cannon, 2013). This kind of plume-based boundary work turns an abstract emissions event into a mapped, receptor-specific exposure footprint that a judge or jury can evaluate visually as well as quantitatively.
Peer-reviewed foundation: attic dust as a historical exposure archive
Dr. Rosenfeld’s litigation reconstructions are grounded in his own peer-reviewed environmental-forensics research, not invented for trial. Working with colleagues, he investigated PCB and dioxin/furan contamination in attic dust near former PCB-production and secondary-copper facilities in Sauget, Illinois, using attic dust as a long-term, largely undisturbed archive of historical atmospheric deposition (Gonzalez et al., 2010). That same underlying principle, that certain environmental media passively record decades of historical emissions, recurs throughout his litigation work whenever contemporaneous air monitoring does not exist.
Extending the method to occupational diesel exhaust exposure
The same reconstruction logic applies to occupational settings. Dr. Rosenfeld has been retained in scores of FELA cases brought by railroad workers alleging injury from decades of diesel exhaust exposure, reconstructing historical exposure using published emission factors, locomotive and engine-technology histories, and worker-activity data. Federal courts have found this methodology admissible under Daubert: in Nebraska, the court held that his opinions on historical diesel-exhaust exposure, environmental forensics, source attribution, and dose reconstruction were grounded in reliable scientific principles (Gillett, 2022), and in Colorado, the court found that his EPA-based exposure modeling, use of published emission factors, and cumulative-dose calculations were supported by sufficient facts and data (Gonzales, 2023).
Grounding the exposure numbers in low-dose epidemiology, not just modeling
A dispersion model only tells part of the story; its output has to be compared against dose-response evidence to mean anything to a jury. For benzene, one of the most litigated FELA and refinery-emission constituents, Dr. Rosenfeld’s reports draw on the low-dose occupational epidemiology showing that hematologic effects, reduced white blood cell and platelet counts and impaired progenitor-cell colony formation, have been documented in workers exposed to benzene at levels below 1 part per million (ppm) in air, the current U.S. occupational permissible exposure limit (Lan et al., 2004; OSHA, 29 CFR 1910.1028). The International Agency for Research on Cancer classifies benzene as carcinogenic to humans (Group 1), a classification grounded in an extensive epidemiological and mechanistic record (IARC, 2018), and EPA’s own noncancer toxicological review establishes reference concentrations intended to be protective at chronic, sub-ppm exposure levels (US EPA, 2003).
Quantifying disease risk once exposure has been reconstructed
Reconstructing exposure is only useful if it can be connected to a quantitative risk estimate. In peer-reviewed work published after years of FELA litigation experience, Dr. Rosenfeld and coauthors modeled cancer risk associated with diesel exhaust exposure among railroad workers, translating historical occupational exposure estimates into lifetime cancer-risk figures using standard EPA risk-assessment methodology (Rosenfeld et al., 2022). That publication demonstrates the same analytical chain used in his litigation reports: historical exposure reconstruction feeding into a transparent, peer-reviewed dose-response and risk calculation, rather than a bare assertion that exposure occurred.
Extending historical reconstruction to drinking-water pathways
The reconstruction methodology is not limited to air. Dr. Rosenfeld has applied comparable historical modeling techniques to contaminated drinking-water pathways, including a peer-reviewed cancer-risk assessment for U.S. Marines and their families exposed to contaminated drinking water at Camp Lejeune between 1955 and 1987, decades before the exposure became the subject of litigation and eventual federal legislation (Rosenfeld et al., 2024). The cross-media consistency of the approach, air, soil, dust, and water, illustrates why courts across multiple states and several categories of contamination have found the underlying methodology, rather than any single application of it, to be reliable.
Judicial acceptance of the resulting dose and risk calculations
Courts evaluating Dr. Rosenfeld’s exposure calculations directly, rather than only his source modeling, have reached similar conclusions. In Vermont federal litigation, the court upheld his calculations of Average Daily Dose and hazard quotients, his use of EPA default exposure assumptions, his reliance on statistically supported upper confidence limits, and his integration of air, dust, and exposure-duration variables, finding the methodology scientifically reliable and admissible (Austin, 2025). Methodologies of this kind have been evaluated under Daubert and analogous state standards in multiple jurisdictions; RoseyFields does not represent that any methodology is immune from challenge in a future case, only that the specific analyses described here were evaluated and admitted in the cases cited.
Why historical exposure reconstruction remains central to modern toxic-tort litigation
As industrial facilities close, change hands, or install new emission controls, the population of plaintiffs whose exposure occurred entirely in the past, with no contemporaneous monitoring, continues to grow. Dr. Rosenfeld’s combination of regulatory-grade dispersion modeling (AERMOD), environmental-forensic sampling strategies developed in peer-reviewed research, and dose calculations tied to current low-dose epidemiology and EPA/OSHA/IARC benchmarks gives plaintiffs a scientifically transparent way to answer the question defendants most often raise: how do you know what reached this specific plaintiff, at this specific time, when no one measured it? RoseyFields.com includes further material on Dr. Rosenfeld’s exposure-reconstruction methodology, including his air-dispersion modeling practice and case history.
References
1. Benefield JK, et al. v International Paper Company. Civil Action No. 2:09-cv-232-WHA-TFM (MD Ala).
2. Brantley TL, et al. v International Paper Company. Civil Action No. 2:09-230-DCR-TFM, Memorandum Opinion and Order (MD Ala May 24, 2017).
3. Cannon K, Donovan E, Ramirez G, Sassler C, Walton H, et al. v BP Products North America, Inc. Case No. 3:10-cv-00622 (SD Tex).
4. Gillett S v BNSF Railway Co. Case No. 4:20-cv-03120 (D Neb).
5. Gonzales v BNSF Railway Co. Case No. 1:21-cv-01690 (D Colo).
6. Austin v Monsanto. Case No. 2:23-cv-272 (D Vt).
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9. Gonzalez J, Feng L, Sutherland A, Waller C, Sok H, Hesse R, Rosenfeld P. PCBs and dioxins/furans in attic dust collected near former PCB production and secondary copper facilities in Sauget, IL. Procedia Environ Sci. 2010:113-125.
10. Rosenfeld PE, Spaeth KR, McCarthy SJ, et al. Camp Lejeune Marine cancer risk assessment for exposure to contaminated drinking water from 1955 to 1987. Water Air Soil Pollut. 2024;235:124.
11. US Environmental Protection Agency. Revisions to the Guideline on Air Quality Models. 40 CFR Part 51, Appendix W. Fed Regist. 2017;82(10):5182-5235.
12. Occupational Safety and Health Administration. Benzene. 29 CFR § 1910.1028. Washington, DC: US Department of Labor.
13. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Benzene. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 120. Lyon, France: International Agency for Research on Cancer; 2018.
14. US Environmental Protection Agency. Toxicological Review of Benzene (Noncancer Effects). Integrated Risk Information System (IRIS). Washington, DC: US EPA; 2003.