Skip to main content

Diesel is not the danger to health some say it is.

One of the biggest challenges for fleet decision makers today is to reconcile the realities of operating vehicles with the mixed signals being sent out by different stakeholders.

Commercial reality for most operators and job-need drivers still emphatically says ‘diesel’ but this knowledge runs contrary to strong signals sent out by last month’s BIK increases <>  and the new toxicity charge <>  in London.

From a commercial point of view, real-world whole life costs will clarify whether a particular business need is best-served by, say, a ULEV, petrol or diesel company car, or indeed via a mobility budget, taking into account business mileage, actual fuel consumption and liability for congestion or T-charges, etc.

But there’s a big environmental dimension as well. Many people have been alarmed by media reports claiming that more than 95% of world’s population breathe “dangerous” air <> . The reports blame diesel as the leading cause of air pollution <>  in cities like London and Los Angeles.

Yet leading UK data scientists and medical professionals publicly questioned both the government’s interpretation of air quality data and its policy responses.

Tony Frew, Professor of Allergy and Respiratory Medicine at the Brighton and Sussex Medical School, told the BBC <>  last month that getting rid of ALL the transport in London would only have a marginal benefit for people who live there.

He said: “At the moment for Millennials, the median life expectancy is in the mid-90s. So you are going to live to 95. If you get rid of all that [transport] pollution and nothing else happens, you might live to 95 and one month. We have to ask ourselves whether that extra month is a worthwhile benefit in return for not having any cars or any public transport or any delivery vehicles.”

Professor Frew was talking about the health impact of very fine particles of matter – so-called PM2.5s – which are emitted by diesels along with many other urban sources, including gas central heating boilers. These can pass through the lungs into body tissue and, over a lifetime, may reduce life expectancy: typically by days in the UK but longer in countries where indoor open fires are used for cooking and heating.

London already meets the World Health Organisation guideline limit for PM2.5s, which is 10 micrograms per cubic metre of air, averaged over a year. By comparison, the once famously-smoggy city of Los Angeles is 11 while Beijing is 85 and Delhi is 122.

Prof. Frew said the high levels in pollution in places like Delhi and Beijing need to be tackled but he questioned how much political and financial capital should be put into bringing places like London or Los Angeles below the WHO guideline.

“Currently everybody’s living longer lives than they did 100 years ago and that is true across the world and that is largely as a result of industrialisation, heating and housing improvements,” he said. “These are all things that generate pollution, so there is a trade-off between doing things that cause pollution and the end result which is that we actually live longer.”

So, it is reasonable for fleet decision-makers to ask the same question about diesel. Since Euro 6 diesels, i.e. the vehicles fleets are acquiring today, are far cleaner than other versions – 76% less NOx than Euro 4, for example – is it correct to say it’s harmful to run them in situations where all the data show they are the best tool for the job?

You can hear Professor Frew, together with Gavin Shaddick, Chair of Data Science and Statistics at the University of Exeter, on Radio 4’s More or Less podcast <>  episode “Are We Breathing Unsafe Air?”