Wednesday, 13 June 2012

Diesel engine exhausts does indeed cause cancer in humans

In an earlier post, Sarah Stephen (April 2012, ) wrote about diesel fuel emissions, its health effects, and the impending International Agency for Research on Cancer (IARC) meeting scheduled for June 2012 at which the labelling of diesel engine exhausts would be evaluated.

IARC is an intergovernmental agency which is part of the World Health Organisation with the role of conducting and coordinating research into the causes and prevention of cancer. The organisation places emphasis on understanding the role of environmental and lifestyle risk factors and studying their interplay with genetic factors in population-based studies and relevant experimental models. A major thrust of the organisation is the IARC Monographs Programme where international experts evaluate the evidence of the carcinogenicity (cancer causing property) of environmental factors.

IARC classifies environmental factors in 5 groups:
• Group 1 - Carcinogenic to humans
• Group 2A - Probably carcinogenic to humans
• Group 2B - Possibly carcinogenic to humans
• Group 3 - Not classifiable as to its carcinogenicity to humans
• Group 4 - Probably not carcinogenic to humans

Over 900 environmental agents have been evaluated by IARC since 1971 of which more than 100 have been identified as carcinogenic to humans (Group 1), and more than 300 as probably carcinogenic, or possibly carcinogenic to humans (Groups 2A, 2B).

As early as 1988, the experts at IARC classified diesel exhaust as ‘probably carcinogenic’
(carcinogenic- that which can cause cancer) to humans. Now, nearly 25 years later, after the emergence of a compelling study that occupational exhaust of miners predisposed them to lung cancer (Silverman et al 2012), the experts reconvened and reviewed all available data on diesel exhaust and cancer. They concluded that there was sufficient evidence that diesel engine exhaust can cause lung cancer. Their review also showed that there was limited evidence showing a link between diesel exhausts and bladder cancers. The experts retained gasoline exhaust in the 'possibly carcinogenic to humans' category which has remained unchanged from the previous evaluation. With the ubiquitous presence of diesel fuel exhaust in the environment contributed by vehicles and power generators and other occupational exposure, the implications of the findings is colossal. The reclassification puts diesel exhausts in the same category as asbestos and tobacco smoke well known lung carcinogens (cancer causing agents). Lung cancer is the most common cancer in the world and the most common cause of death from cancer, with 1.38 million deaths, with the majority of the cases now occuring in the developing countries (55%) which, apart from tobacco consumption, could be attributed to rapid industrialisation and low regulatory standards for vehicular emissions.
In the press release Dr Christopher Portier, Chairman of the IARC working group, said “The scientific evidence was compelling and the Working Group’s conclusion was unanimous: diesel engine exhaust causes lung cancer in humans. Given the additional health impacts from diesel particulates, exposure to this mixture of chemicals should be reduced worldwide.”

One question that emerges is why did it take so long for such a reclassification?  But more importantly, what are we going to do about it now?

Photos: Ruth Stephen 

Silverman DT, Samanic CM, Lubin JH, Blair AE, Stewart PA, Vermeulen R, Coble JB, Rothman N, Schleiff PL, Travis WD, Ziegler RG, Wacholder S, & Attfield MD (2012). The diesel exhaust in miners study: a nested case-control study of lung cancer and diesel exhaust. Journal of the National Cancer Institute, 104 (11), 855-68 PMID: 22393209
Attfield MD, Schleiff PL, Lubin JH, Blair A, Stewart PA, Vermeulen R, Coble JB, & Silverman DT (2012). The diesel exhaust in miners study: a cohort mortality study with emphasis on lung cancer. Journal of the National Cancer Institute, 104 (11), 869-83 PMID: 22393207

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