07 October 2015
by Dr. Anthony Horton

The dark side of diesel

It’s fair to say that the Volkswagen diesel emissions revelations have captured the world’s attention. As a scientist with a background in air pollution monitoring and management I must admit that the amount of attention the issue has received intrigues me – from the perspectives of both the media reporting of the issue and of course the public reaction.

I’m particularly interested in the media’s reporting of the issue in terms of what a test method is, what is emitted under test conditions and what an emission standard or limit is. I see the way it has been reported as a public demonstration of the scientific method-questioning the way something is, testing/analysing it, comparing the results against a standard and determining what that means. From my perspective these steps are fundamental, and the more the public can see why scientists do what they do, why they do it and the part science plays in society the better. However this is not really the place for a lesson in the scientific method. Instead, I would like to look at diesel emissions from another perspective.

Diesel emissions from vehicles are comprised of a number of pollutants, with the most significant being nitrogen dioxide (NO2) and particulates. The latter were the first pollutants emitted from vehicle exhaust to be identified as toxic in 1993 by a team from Harvard University in their groundbreaking Six Cities Study which involved more than 8000 adults over more than 14 years.

The study’s findings were significant because the mortality risk in “dirtier” cities (cities that are more heavily polluted) was strongly associated with fine particles, and life expectancy in these cities was reportedly 2-3 years less than “cleaner” cities. The findings also gave rise to new air quality standards which have in turn progressively lowered particulate concentrations and improved health outcomes over the past two decades.

In the time since the Six Cities Study, hundreds of studies have given rise to similar conclusions. One study in the UK estimated that nearly 30,000 people are killed each year from exposure to particulates (more than obesity and alcohol combined and 10 times the number of people killed on roads). The UK Government Committee on the Medical Effects of Air Pollution estimates that it is a factor in an additional 200,000 deaths.

In June 2012, The World Health Organisation (WHO) International Agency for Research on Cancer (IARC) declared that diesel exhaust was a probable human carcinogen, based on sufficient evidence that personal exposure is associated with an increased risk of lung cancer.

Head of the IARC Monographs Section Dr Kurt Straif stated at the announcement that the air we breathe has become polluted with a mixture of cancer-causing substances, and that outdoor air is a leading cause of cancer deaths from an environmental perspective. The scientists conducting the evaluation reviewed in excess of 1000 academic papers on polluted air and small particles in that air. The IARC also reported that in 2010 air pollution was responsible for 223,000 deaths in lung cancer patients worldwide.

France has the highest percentage of diesel cars of any European country’s vehicle fleet as a result of successive Governments subsidising diesel fuel to such an extent that it is cheaper than petrol. In March this year, an increase in air pollution resulted in Paris being the most polluted city in the world for a short time, with the smog being so thick that many of the city’s landmarks including the Eiffel Tower were invisible. In addition, the Volkswagen revelations have increased the pressure on the French Government to act on vehicle emissions and the associated air pollution.

A car free day was implemented in Paris last week (September 27) at the suggestion of the Paris Without Cars group. The car free day was limited to approximately one third of the city, covering an area between Bastille and the Champs Elysees and the outer Bios de Boulogne and Bois de Vincennes between 11 and 6pm. In the remainder of the city, cars were allowed to travel at 20 km/hour. Despite the limited scope, Elisabeth Pagnac who lives in a tower block in the east of the city reported the dramatic difference in the skyline and commented that it had never been as blue and was very different without the layer of pollution that typically hangs in the air.

In addition to implementing the car free day, Mayor of Paris Anne Hidalgo has made a vow to end diesel use on the city by 2020 and promote less car usage and cleaner vehicle. She also plans to extend car free areas further along the Seine River.

Regardless of the extent to which the decision to implement a car free day was or wasn’t influenced by the Volkswagen revelations, I think that implementing such a day was a bold decision. As an Australian I can’t help but wonder how many Mayors would have the courage to do the same in their cities. As a scientist I wonder about three points-1) whether the Volkswagen revelations and in particular discussions on the emissions will cause Regulatory Authorities around the world to rethink/ revise the process they use to assess/audit emissions sources (of all types, not just cars) and any associated data, 2) whether the revelations will cause people to pause and consider the full impacts (eg. environmental, health and economic) of their potential purchase as part of their buying decision process, and 3) the future of diesel vehicles.