After three decades of epidemiologic research, diesel exhaust was classified as a carcinogen in humans by the International Agency for Research on Cancer (IARC) in 2012 based on evidence of its carcinogenicity to the lung.
Six years after that announcement was made, we will review the actions that have been made across the world to prevent diesel fumes from polluting the air and question whether more should be done by governing bodies.
Diesel exhaust could be carcinogenic due to a combination of mechanisms. First, owing to their microscopic size, PAH’s can be easily inhaled. (The particles from the diesel exhaust are less than 10 micro-metres). These particulate matters penetrate deeper into the lungs and become lodged there – leading to low grade, chronic inflammation.
The resulting inflammation can also influence the rate at which mutated cells divide; more specifically it can put these cells at an increased risk to grow and spread if they happen to pick any random mutations.
The inhaled PAHs could also cause direct damage to the DNA in the lungs’ cells – causing cancer.
Recent studies have found air pollution now kills 3.3 million people prematurely every year – more than HIV, malaria and influenza combined – with emissions from diesel engines among the worst culprits, a joint investigation by the Guardian Newspaper and Greenpeace in 2017 showed hundreds of thousands of schoolchildren across England and Wales are being exposed to illegal air toxicity levels from diesel vehicles.
The European Environment Agency also revealed that nitrogen dioxide (NO2) from diesel fumes had caused around 71,000 premature deaths across the continent in a single year, with the UK experiencing 11,940 annual premature deaths from NO2, the second highest in Europe behind Italy.
Could more be done to tackle the issue?
Governmental regulatory agencies are charged with setting safe levels of exposure for workers such as professional bus drivers, lorry drivers, miners and in the outdoor ambient environment in various countries.
The lung cancer risk exceeds levels that are acceptable in Europe and the U.S., leading investigators to call for the implementation of stringent exposure limits for diesel exhaust.
Casting an eye to future research, several pressing scientific questions merit our attention. First, is the carcinogenicity of diesel exhaust in humans limited to the lung? As we observed for cigarette smoke, a product of combustion and a powerful lung carcinogen that causes cancer of 20 other sites, diesel exhaust may cause cancer of sites such as the urinary bladder, larynx, and colon.
Finally, the gravity of the adverse health effects of air pollution in some metropolitan areas is perhaps best reflected by the recent proposals by mayors of Mexico City, Paris, Madrid and Athens to ban diesel vehicles by 2025, possibly, more cities will follow suit.
An alternative solution raised by Dr. Debra T. Silverman, Chief of the Occupational & Environmental Epidemiology Branch at the National Cancer Institute, was for the replacement of “old” with “new” technology diesel engines, which drastically reduce emissions of many compounds and elemental carbon.
There are many potential solutions to help deal with the problem, but there is no simple solution – diesel passenger cars remain a major part of the auto industry in Europe, they still account for nearly 50% of all new cars sold across the continent. But current statistics show stricter regulations need to be introduced urgently.