Lung Cancer and Vehicle Exhaust in Trucking Industry Workers

Article excerpt

BACKGROUND: An elevated risk of lung cancer in truck drivers has been attributed to diesel exhaust exposure. Interpretation of these studies specifically implicating diesel exhaust as a carcinogen has been limited because of limited exposure measurements and lack of work records relating job title to exposure-related job duties.

OBJECTIVES: We established a large retrospective cohort of trucking company workers to assess the association of lung cancer mortality and measures of vehicle exhaust exposure.

METHODS: Work records were obtained for 31,135 male workers employed in the unionized U.S. trucking industry in 1985. We assessed lung cancer mortality through 2000 using the National Death Index, and we used an industrial hygiene review and current exposure measurements to identify jobs associated with current and historical use of diesel-, gas-, and propane-powered vehicles. We indirectly adjusted for cigarette smoking based on an industry survey.

RESULTS: Adjusting for age and a healthy-worker survivor effect, lung cancer hazard ratios were elevated in workers with jobs associated with regular exposure to vehicle exhaust. Mortality risk increased linearly with years of employment and was similar across job categories despite different current and historical patterns of exhaust-related particulate matter from diesel trucks, city and highway traffic, and loading dock operations. Smoking behavior did not explain variations in lung cancer risk.

CONCLUSIONS: Trucking industry workers who have had regular exposure to vehicle exhaust from diesel and other types of vehicles on highways, city streets, and loading docks have an elevated risk of lung cancer with increasing years of work.

KEY WORDS: diesel exhaust, lung cancer, occupational exposure, particulate matter, traffic. Environ Health Perspect 116:1327-1332 (2008). doi:10.1289/ehp.11293 available via http://dx.doi.org/[Online 30 May 2008]

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Diesel exhaust is a complex mixture of particulate matter (PM) and gases and includes particles [less than or equal to]1.0 [micro]m diameter ([PM.sub.1]) with mutagenic and polycyclic aromatic hydrocarbon (PAH) carcinogenic compounds adsorbed to a carbon core and ultrafine particles made up of condensed organics (Kittelson et al. 2002). Approximately 40 epidemiologic studies have described an association between lung cancer risk and occupations with some degree of diesel exhaust exposure, including railroad workers, construction workers, port workers, and truck and other professional drivers (Bhatia et al. 1998; Diesel Working Group 1995; Lipsett and Campleman 1999; Office of Research and Development 2002). However, this association has been questioned (Bunn et al. 2004; Hesterberg et al. 2006; Valberg and Watson 2000) because of uncertainties regarding the link between the occupational records used to assess work history, specific job duties, and exposure. In particular, the likelihood that truck drivers and other workers in trucking industry jobs were exposed to diesel exhaust depends on job duties and historical driving patterns. Previous studies in the trucking industry have lacked detailed work records identifying specific trucking industry-related jobs and had a limited ability to assess job related exposure differences.

To address these uncertainties, we conducted a retrospective assessment of lung cancer mortality of workers employed by four large unionized (Teamster) carriers. In this study, we used the detailed work records available in this industry to describe the relationship with years of work in specific trucking industry jobs that have different current and historical exposure patterns. We have previously identified elevated standardized mortality ratios (SMRs) for lung cancer mortality in this cohort (Laden et al. 2007). In this industry, the association between job and specific exposure-related duties has remained stable over time, and the dates of diesel and other equipment use are known (Garshick et al. …