Ninety Years of Diesel: Quantifying Cancer Risk in America’s Railroad Workforce
By Paul E. Rosenfeld, M.S., Ph.D., Principal Environmental Chemist, RoseyFields LLC, Santa Monica, California
A regulatory gap that litigation has had to fill
Diesel particulate matter has no OSHA permissible exposure limit of its own, unlike benzene or asbestos; only underground metal and non-metal mines are subject to a specific diesel particulate matter standard, set by the Mine Safety and Health Administration at 160 micrograms per cubic meter (30 CFR 57.5060). For railroad workers, litigation has had to establish the exposure and risk analysis largely from first principles, work Dr. Paul E. Rosenfeld, M.S., Ph.D. of RoseyFields LLC has performed in scores of FELA matters.
Federal court admissibility findings on the methodology
In Illinois federal litigation, Dr. Rosenfeld’s opinions on historical diesel exhaust exposure among railroad workers were the subject of Daubert review (Sherman, 2023), and in Colorado federal litigation the court found his EPA-based exposure modeling, use of published emission factors, and cumulative dose calculations to be supported by sufficient facts and data (Abeyta, 2023).
The foundational occupational epidemiology
The scientific foundation for diesel-related railroad worker litigation traces back to a landmark cohort study of 55,407 white male railroad workers, which found a statistically significant elevated lung cancer risk, a relative risk of 1.45 (95% CI 1.11-1.89), among workers with the longest duration of diesel exhaust exposure following the railroad industry’s conversion from steam to diesel locomotives (Garshick et al., 1988).
IARC’s classification of diesel engine exhaust
In 2012, an IARC working group reviewed the accumulated epidemiological and mechanistic evidence, including extensions of the Garshick railroad cohort, and classified diesel engine exhaust as carcinogenic to humans (Group 1), the same classification tier as benzene, based on sufficient evidence of increased lung cancer risk (IARC, 2012/2014).
Translating a cohort relative risk into an individual plaintiff’s exposure
A published cohort relative risk describes population-level association; converting it into an individual plaintiff’s exposure-based risk requires reconstructing that specific worker’s job classification, years of service, and locomotive technology era, since diesel emission factors changed substantially as engine technology and fuel formulations evolved over the twentieth century.
Peer-reviewed quantification of railroad worker cancer risk
Dr. Rosenfeld and coauthors published a peer-reviewed cancer risk assessment specifically addressing diesel exhaust exposure among railroad workers, translating historical occupational exposure reconstructions into quantitative lifetime cancer risk estimates using standard EPA risk-assessment methodology (Rosenfeld et al., 2022).
Why emission-factor selection matters so much in these cases
Diesel locomotive emission factors have declined substantially since the 1960s and 1970s due to engine and fuel improvements, meaning a worker’s total lifetime dose depends heavily on which specific years of service, and which specific locomotive fleet, are used to characterize exposure. Courts crediting Dr. Rosenfeld’s methodology have specifically noted his use of published emission factors integrated with worker-activity data (Gonzales, 2023).
EPA’s health assessment as an independent regulatory benchmark
EPA’s own Health Assessment Document for Diesel Engine Exhaust concluded that diesel exhaust is a likely human carcinogen by inhalation and identified respiratory and cardiovascular effects associated with its particulate components, an independent federal regulatory conclusion that predates and supports the individual litigation-specific risk calculations (US EPA, 2002).
The scale of the affected population
With diesel locomotives remaining the dominant power source across the U.S. freight rail network for the better part of a century, the population of current and former railroad workers with decades of diesel exhaust exposure numbers in the hundreds of thousands, a scale reflected in the volume of FELA litigation nationally.
Why this methodology extends beyond railroads
The same historical emission-factor reconstruction, cohort epidemiology, and quantitative risk-calculation framework developed for railroad diesel exposure applies with modification to other occupational diesel-exposed populations, including truck drivers, dock and warehouse workers, and heavy-equipment operators, an extension Dr. Rosenfeld’s broader diesel exhaust research supports (Rosenfeld et al., 2022).
The continuing evidentiary role of a ninety-year-old cohort study
Nearly four decades after its publication, the Garshick railroad cohort remains a cornerstone of diesel exhaust cancer-risk litigation because of its size, duration, and job-category specificity, illustrating how foundational occupational epidemiology continues to anchor modern exposure reconstruction. For further reading on Dr. Rosenfeld’s diesel exhaust and FELA litigation work, see RoseyFields.com.
References
1. Sherman T, et al. v BNSF Railway Company. Case No. 3:17-cv-01192, US District Court, Central District of Illinois.
2. Abeyta, et al. v BNSF Railway Company. Case No. 1:21-cv-01689-KMT, US District Court, District of Colorado.
3. Gonzales, et al. v BNSF Railway Company. Case No. 1:21-cv-01690, US District Court, District of Colorado.
4. Garshick E, Schenker MB, Munoz A, Segal M, Smith TJ, Woskie SR, Hammond SK, Speizer FE. A retrospective cohort study of lung cancer and diesel exhaust exposure in railroad workers. Am Rev Respir Dis. 1988;137(4):820-825.
5. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Diesel and Gasoline Engine Exhausts and Some Nitroarenes. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 105. Lyon, France: International Agency for Research on Cancer; 2014.
6. Rosenfeld PE, Spaeth K, Hallman R, Bressler R, Smith G. Cancer risk and diesel exhaust exposure among railroad workers. Water Air Soil Pollut. 2022;233:171.
7. US Environmental Protection Agency. Health Assessment Document for Diesel Engine Exhaust. Washington, DC: US EPA; 2002.
8. Mine Safety and Health Administration. Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners. 30 CFR § 57.5060. Washington, DC: US Department of Labor.
9. Gillett S v BNSF Railway Co. Case No. 4:20-cv-03120 (D Neb).
10. 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.
11. Rosenfeld PE. RoseyFields LLC: FELA Occupational Exposure Assessment. Santa Monica, CA: RoseyFields LLC; 2026.
12. Occupational Safety and Health Administration. Hazardous Waste Operations and Emergency Response. 29 CFR § 1910.120.
13. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Diesel Exhaust. Atlanta, GA: US Department of Health and Human Services.
14. Austin v Monsanto. Case No. 2:23-cv-272 (D Vt).