In 2012, the International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), classified diesel engine exhaust (DEE) as carcinogenic to humans (Group 1). (Earlier post.)
Now, a study by researchers from the Netherlands, the US, and France estimates that approximately 6% of annual lung cancer deaths in the US and UK—combining both environmental and occupational exposures—may be due to DEE exposure. This translates to about 9,000 annual lung cancer deaths in the US and about 2,000 annual lung cancer deaths in the UK that may be attributable to DEE.
An open access paper describing their study is in the journal Environmental Health Perspectives, which is published with support from the US National Institute of Environmental Health Sciences, US National Institutes of Health, and US Department of Health and Human Services.
To derive a meta-exposure-response curve (ERC) for DEE and lung cancer mortality and to estimate lifetime excess risks (ELRs) of lung cancer mortality based on assumed occupational and environmental exposure scenarios, the researchers conducted a meta-regression of lung cancer mortality and cumulative exposure to elemental carbon (EC), a proxy measure of DEE, based on relative risk (RR) estimates reported by three large occupational cohort studies (including two studies of workers in the trucking industry and one study of miners).
Based on the derived risk function, they calculated ELRs for several lifetime occupational and environmental exposure scenarios, and also calculated the fractions of annual lung cancer deaths attributable to DEE.
They estimated that approximately 1.3% and 4.8% of annual lung cancer deaths at age 70 in the US and the UK are due to past occupational and environmental DEE exposures, respectively.
In their paper, the researchers note that the estimates are far from precise, and depend on broad assumptions about proportions exposed to different levels of DEE, and the duration of occupational exposures. However, their attributable fraction AF estimates for occupational and environmental DEE exposure is generally consistent with some previous estimates for traffic-related air pollution and lung cancer mortality and incidence.
Our estimates suggest that stringent occupational and environmental standards for DEE should be set. Fortunately, increasingly stringent on-road emission standards for diesel engines have been introduced in the United States and the European Union (US2010 and Euro 6 standards) with other countries (e.g., China, India, Brazil) following with a delay of about 5 to 10 years. These regulations have resulted in the recent introduction of new diesel engine technologies (integration of wall-flow diesel particulate filter and diesel oxidation catalyst) that on a per-km basis achieve a more than 95% reduction of particulate mass and nitrogen oxides emissions.
However, emission standards for offroad vehicles and industrial applications are generally introduced after those for on-road vehicles and therefore many offroad applications were still largely uncontrolled in 2000. It should also be noted that although new diesel engines are available, it will take still many years before they have a significant penetration into the diesel engine fleet, especially in less developed countries.—Vermeulen et al.
Roel Vermeulen, Debra T. Silverman, Eric Garshick, Jelle Vlaanderen, Ltzen Portengen, and Kyle Steenland (2013) “Exposure-Response Estimates for Diesel Engine Exhaust and Lung Cancer Mortality Based on Data from Three Occupational Cohorts,” Environ Health Perspect doi: 10.1289/ehp.1306880