I found this fascinating quote today:

"Recent research suggests that lung cancer risks are higher among trucking industry workers because of diesel fume exposure.  According to a new study published in the January issue of the journal Environmental Health Perspectives, workers in the trucking industry with an estimated 20 years on the job have an elevated risk of lung cancer with each increasing year of work due to their diesel fume exposure."

Lung Cancer, whats that got to do with Delivery Drivers
This is a logical approach in the same way that number of pack years is relevant to the risks of developing lung cancer from smoking.  What does other research say?  Is there anything to back this assertion up? 

Schneider National Carriers 2006 Freightliner ...Image via Wikipedia

"In 2002 the U.S. Environmental Protection Agency (EPA) released a Health assessment Document for Diesel Engine Exhaust. The objective of this assessment was to examine the possible health hazards associated with exposure to diesel engine exhaust (DE). The assessment concludes that long-term inhalation exposure is likely to pose a lung cancer hazard to humans as inferred from epidemiologic and certain animal studies."

Source: Inhalation Toxicology, 19(Suppl. 1):229–239, 2007

However, the US EPA research was somewhat flawed in that:

"Estimation of cancer potency from available epidemiology studies was not attempted because of the absence of a confident cancer dose-response and animal studies were not judged appropriate for cancer potency estimation."

Instead, chronic human health hazard is inferred from rodent studies which show dose-dependent inflammation and histopathology in the rat lung, so relative particle overload needs to be accounted for.

The EPA assessment conclusions are based on studies that used exposures from engines built prior to the mid 1990s. More recent engines without high-efficiency particle traps would be expected to have exhaust emissions with similar characteristics.  The results of more recent trials from 2007-8 will help address some of the questions.

Interestingly, there are some reviews that concluded that there was insufficient evidence to support a cancer link, however the papers are potentially biased in that the lead authors were from the International Truck and Engine Corporation, so there was little incentive for them to declare such a link, anymore than a tobacco company would concede that smoking cigarettes is hazardous to health.

Scientifically and epidemiologically, one of the many things affecting the analyses is the significant changes over the last 20 years in engine emissions such as nitrogen oxide and other by products that may be hazardous to health.  These have occurred with improvements and changes in the composition of the fuel and exhaust filters.  There are currently new studies underway to evaluate the impact of newer fuels now that TDE has been removed from the fuel mix. One might postulate that as fuels have become cleaner, the risks associated with cancer may have lessened but time will tell.

Hopefully, cleaner fuels will offer fewer health hazards from emission by-products and lower the risk of cancer.  The advent of hybrid cars is also a step in the right direction; who knows this may well help the US auto industry in the long run too.

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