Diesel fumes: Is the UK’s witch-hunt against diesel cars driven by zealotry and greed, not science?

(Author’s Note: This paper is an example of a relatively new phenomenon; “citizen science.” And citizen science deserves citizen peer review. I would, therefore, greatly appreciate review of this paper by those with the skills to do so; whether or not they live in the UK, or drive diesel cars. Thank you.)

The recent uproar over “toxin taxes” on diesel cars in the UK raises many questions. So, in this (long) essay, I’m going to try to get a handle on how big the cost of pollution from diesel cars really is, and whether the schemes being proposed to ameliorate it are sensible or not. To do that, I’ll try to estimate the so-called “social cost” of particulate matter (PM) and nitrogen oxide (NOx) emissions from diesel cars of different ages in the UK, in pounds per car per year.

If my calculations are right, there is some justification for central London pollution charges for diesel cars built before 2006; for, as I work it out, the social cost of the pollution from these cars is almost £300 per car per year. However, the further schemes in London and countrywide, that are planned to start as early as 2019, are out of all proportion to the reality of the problem. They will cost 8 million or so drivers of diesel cars, first registered between January 2006 and August 2015, orders of magnitude more than the social cost of the pollution their cars emit. Worse, these drivers – including me – may be forced to scrap our cars well before the end of their designed lives. Is this not grossly unjust?

According to my calculations, for a diesel car first registered between September 2010 and August 2015, like mine, the London ULEZ entry fees from 2019 for just two days in a year will be almost as much as the social cost of pollution from that car for the whole year, in comparison to a new (since September 2015) car, which won’t be charged at all. That is both unreasonable and unfair. Indeed, for both these cars and those first registered between 2006 and 2010, it would be far better and easier to collect the social cost of pollution through the yearly licence fee.

If my numbers are correct, this is nothing less than a rip-off. It is greedy, premeditated, zealous extortion, being carried out against the many millions of people, including me, who are unfortunate enough to have bought, in good faith, diesel cars first registered in those periods. And the knock-on effects could be even worse; for example, causing many perfectly good cars to be scrapped prematurely, and the prices of used petrol cars to soar. Some people may even lose their personal mobility entirely because of this rumpus.

Part 1 – The problem

Because this is a very long screed, almost 10,000 words, I’ve divided it into three parts. The first part gives the background to the problem. The second part is the technical bit; it dives into several reports on the issue, and seeks ball-park values of the annual social cost of pollution from diesel cars of various ages. The third part asks some pointed questions about the whole process, and gives some thoughts on how I would seek to deal with the situation if I was in power.

The mayor of London

Let’s start with the mayor of London, Sadiq Khan. On 4th April the Guardian reported that he was launching a crackdown on vehicle pollution. From October 2017, a £10 a day toxicity fee (T-charge) will be introduced for pre 2006 cars, petrol and diesel, entering the London congestion charging zone.

In addition, a new “Ultra Low Emissions Zone” (ULEZ) will be set up. According to the Mayor’s press release [1], it will cost £12.50 per day to drive in this zone a diesel car built before September 2015, or a petrol car built before 2006. This zone was originally scheduled to start in September 2020; but it is now to be brought forward to April 2019. Furthermore, proposals are mooted to extend the zone to the area inside the North and South Circular roads; or even to the entire area covered by the present “Low Emissions Zone” for heavy vehicles, which goes as far out as Heathrow Airport and beyond.

All this is not very surprising. Sadiq Khan’s aims are, first, to be seen to be “doing something” about air quality in London. And second, to haul in as much money as he can to spend on his pet public transport projects. Both these, he thinks, will make him popular with many Londoners. Therefore, he has every incentive to be unfair and unreasonable towards drivers; particularly those from outside London, who can’t vote against him. And if millions of people were to lose their personal mobility as a result, he wouldn’t care a damn; in fact, he’d probably cheer. No; air quality is only an excuse. Khan’s real objectives are money and power.

On top of this, as Christopher Booker has reported [2], some local councils are already charging up to £90 extra a year for residents’ parking permits for diesel cars, and more are planning to follow. It’s hard to avoid the thought that they’re merely riding the political fad du jour, and cynically using any excuse to rake in as much money as possible.

The press release concludes with words to chill the spine of any diesel owner, from one Professor Jonathan Grigg of the Royal College of Paediatrics. “To maximise the effectiveness of this initiative, the Government must now act to remove the current toxic fleet of diesel cars, vans and buses from all our roads.”

The former chief scientist

Next up, Professor Sir David King, formerly chief scientific advisor to Tony Blair’s government. The Daily Mail calls King a “green zealot,” and rightly so. For this is the man that in 2004 publicly asserted that global warming is a greater threat than terrorism. Furthermore, in 2010 he claimed that “peak oil” could happen in just 5 years; a prediction that failed. And it was King that, in about 2001, advised Blair to create incentives for people to buy diesel cars rather than petrol – supposedly because diesels emit less CO2, and so cause less global warming!

On 4th April, King did admit that “we were wrong” to give people incentives to buy diesels. But this did not stop him demonizing diesel drivers. He said that many diesel vehicles were emitting 12 times the latest pollution limits. He blamed the car manufacturers, saying that emissions from diesel cars of all manufacturers (not just Volkswagen, as in the recent scandal in the USA) in on-the-road conditions are many times higher than the standards they’re supposed to meet. And this is so, even when they do meet the standards when tested under laboratory conditions. This accusation, surprisingly given King’s previous record, actually does seem to be justified.

The government’s response

On the same day, 4th April, the Daily Express reported that the government was about to announce a package of “toxin taxes” on drivers of diesels in a bid to crack down on pollution. This would apply, not just in London, but in many other towns and cities too. The Express quoted a figure of £20 a day to enter any of 35 towns and cities. In some cases, there would also be bans on diesel cars driving into cities at certain times of day. They also stated that the bans and charges will target, in essence, any diesel car first registered before September 2015.

On 5th April, prime minister Theresa May stepped in, telling ministers not to “punish” diesel drivers. According to the Sun, she said that the concerns of people, who bought diesel cars in good faith a decade ago, had to be taken into account. It worries me a lot that the issue had to go all the way up to May before anyone questioned the green activist orthodoxy. Particularly since to alienate more than 10 million diesel drivers, many of whom live in the Tory heartlands, would obviously be a quick and easy way to commit electoral suicide.

As background, let’s remember that this issue first blew up in 2014, with a court case brought against the UK by the European Commission [3]. But with Brexit now in the offing, why should anyone care about what the European Commission thinks? Isn’t this exactly the kind of crap we voted for Brexit in order to get away from?

My own interest

I confess to having a personal interest in this matter. Single and in my 60s, my car is my most important possession; my pride and joy. And my policy has always been to buy the very best car I can possibly afford, and run it into the ground. Since I bought my first car in 1975, I have owned just seven cars. And only the latest one has been a diesel.

When my much loved Jaguar S-Type, which I had kept for almost 13 years, died in early 2014, I had to find a replacement. I was looking for a car to last me a decade and more; in effect, for the rest of my driving life. I didn’t intend to buy a diesel; in fact, I would have preferred a petrol car, because they are quieter and perform better. But I couldn’t find a petrol example of the XJ model I wanted. Not only had King and Blair’s mischief caused people to start buying diesels rather than petrol models; it also caused the manufacturers to start making diesels rather than petrol models. So, I had no alternative but to settle for a late 2011 model diesel.

I live on the outskirts of a medium sized town in Surrey. My member of parliament, Jeremy Hunt, happens also to be the current secretary of state for health. (We don’t get on.) Now, I don’t expect to be too badly hit by the immediate ruckus; for I haven’t had reason to drive into central London since 1996. But I’m well aware of the tendency of zealots to push the boundaries as far as they can. Sadiq Khan’s plan to extend his ULEZ area all the way out to Heathrow is a case in point. It seems that we diesel drivers are the witches du jour.

I know well, too, that there’s a vociferous and powerful movement, whose aim is to force us out of our cars altogether. Tony Blair is one of them; as shown by the fact that one of the first bills New Labour brought in was the Road Traffic Reduction Act 1997. Sadiq Khan, David King and Jonathan Grigg are surely all in on this movement, too. My concern is not so much what these zealots have done to us already, than what they might contrive to do to us in the next few years.

Charges and bans for diesel cars in 35 cities, I worry, may prove to be only the tip of an iceberg. So, not surprisingly, I’m fuming. And if the zealots ever manage to extend their charges to my local area, I won’t even be able to afford to drive to the supermarket and back. In my 70s, I’ll have to walk up a 1 in 7 hill with my groceries in my rucksack. The bastards!

Further, it’s unreasonable to charge, from the start, for visits to London by cars built as late as August 2015. For most cars today are designed for a 12 year useful life; bigger cars often for 15 years. Yet by April 2019, Khan’s charges will apply to many cars that at that time will be less than five years old. If anyone believes – as many in the media seem to – that the issue only affects cars more than ten years old, they need to think again. It will be a problem even for some whose cars, right now, are still under the manufacturer’s three year warranty!

As to talk of a scrappage scheme for cars affected by the charges (including mine), the scale of such a scheme beggars belief. For, of the roughly 12.6 million diesel cars now running in the UK, as many as 10 million will be caught by Khan’s charges if they enter London. A scheme to scrap all these cars would need to be about 15 times the size of the 2009 “cash for clunkers” scheme in the USA, whose costs were $1.4 billion greater than its benefits.

Would it really make sense to scrap 10 million cars? Many of which will have run for less than half, or even as little as a third, of their designed lives? What a waste of resources! And what about the costs? At the number I have heard bandied about of £2,000 subsidy per car [4], that’s £20 billion right there. And that’s just costs to the government; it doesn’t include the direct or indirect costs to the people affected. Not to mention the severe disruption it would cause to the used car market, and the “emissions” and “pollution” that would be generated in making enough new cars to cover the shortfall. Or the devastation it would cause to the lives of those unfortunates, who are unable to afford to replace their cars at all.

Numbers, numbers, numbers

I am both naturally cynical about politics, and skeptical about environmentalism and the green agenda. So I felt a need to ask, is the problem that is causing all this brouhaha a real one? Or could it be an exaggeration or even a fabrication, merely another excuse to tax us all out of existence, a pack of convenient lies spread by greedy politicians like Sadiq Khan and green zealots like David King and Jonathan Grigg?

To answer this question, we’ll need to look at some numbers. So, in Part 2 of this essay, I’m going to do some back-of-an-envelope calculations. (It’s a very large envelope!) But first, I’ll give some necessary background.

Emissions standards

First, emissions standards for vehicles [5]. Every five years or so, the EU makes new, tighter standards (a bit like Soviet “five year plans”). These usually come into force one year after issue. UK standards have generally been kept in line with EU ones.

For diesel cars, two pollutants are of main interest to the case: nitrogen oxides (NOx) and particulate matter (PM). Standards for emissions of NOx and PM have been set since the 2001 model year (Euro 3).

In the Euro 4 standard (from the 2006 model year), the limits for both pollutants were halved. This is why 2006 was picked as the cut off point for Khan’s toxicity fee.

Euro 5 or 5A (in effect, applying to cars from September 2010) cut the NOx limit again by almost 30%, and cut the PM limit even more, to only one fifth of its previous value.

Finally, Euro 6, applying to cars registered from September 2015, cut the NOx limit again by 55%, but didn’t change the PM limit. In all, from 2005 to today, the limits have been tightened by a factor of a little more than 6 for NOx, and by a factor of 10 for PM.

Of course, all this is somewhat moot, since for NOx most of the cars don’t actually meet, in the real world, the standards they were supposedly designed for. According to estimates from the RAC [6], cars up to Euro 3 (that is, built before 2006) can be expected to emit around twice as much NOx as they are supposed to. Euro 4 and 5 cars emit about 20% less than Euro 3 ones; roughly 3.2 and 4.4 times the supposed limits, respectively. And many Euro 6 cars, while they may have cut the emissions by roughly another 25%, are expected to be over the latest limit by a whopping factor of 7.5. For NOx, my own car is in the group rated by the Guardian as emitting “6-8 times the Euro 6 limit” [7].That means 2.7 to 3.6 times the Euro 5 limit it should have met when it was built.

Air quality standards

Second, air quality standards. These are supposed to be “acceptable in terms of what is scientifically known about the effects of each pollutant on health and the environment.” In the UK, they are the province of the Department for Energy, Food and Rural Affairs (DEFRA). Why this department has anything to do with air quality in cities, mystifies me. But I digress.

An overview of what it’s all about can be found here [8]. Broadly, there are Limits and Targets. Limits are “legally binding EU parameters that must not be exceeded.” Targets are “to be attained where possible by taking all necessary measures not entailing disproportionate costs.” Both can specify a limit on the average concentration of the pollutant, a time period over which the average is to be calculated, and an allowed number of “exceedences,” that is, the number of times in a year that the limit may be exceeded. For both NOx and PM, there is an annual mean limit, and a higher limit which is used to calculate the number of exceedences.

DEFRA issued in December 2016 a most interesting report entitled “Defra National Statistics Release: Emissions of air pollutants in the UK, 1970-2015” [9]. This covers pollution from all sources, not just cars. For the two pollutants of interest, the take-home message is actually pretty good. Overall, NOx emissions went down by 4% between 2014 and 2015. Road transport emissions of NOx were still going down, by 9% between 2012 and 2015. Moreover, PM emissions were roughly static; nothing to worry about.

But it’s the graph on the second page of the report which really opened my eyes. As of 2015, NOx emissions have gone down to, by my eyeball, 31% of the value they had in 1970. And almost all of that has been achieved since 1990, the point at which catalytic converters were introduced. The decline in PM emissions has been even more spectacular. Taking a composite of the particles of different sizes (PM10 and PM2.5), my eyes tell me that these emissions have gone down to only 25% of their 1970 values. Haven’t we done well? Which prompts the question: having done so well, why should we be expected to make any more sacrifices?

The London Air Quality Network

Third, the London Air Quality Network. This is an organization, set up after the Rio “Earth Summit” of 1992, which reports on the quality of air in London. It issues a report on London’s air quality in each year, which usually comes out about 15 months after the end of the year it refers to. The reports are available here [10].

The key report in this series is report 14, covering 2006 and 2007, and published in June 2009. This states that the EU limit value for NO2 (which results from NOx emissions) was being “consistently exceeded at background sites in inner London and at roadside sites throughout London.” And it says that the increases: “are thought to be due to changes in diesel vehicle technologies … and an increase in the proportion of diesel vehicles on London’s roads.”

Interestingly, the report for 2008 wasn’t published until November 2012. In contrast to earlier reports, it was slim. It had no management summary, had only raw data with very little accompanying text, and drew no conclusions. The 2009 and 2010 reports followed during the next month. It’s hard to avoid the suspicion that Gordon Brown, the prime minister in 2009/10, had the original 2008 report suppressed. And that the Coalition either didn’t find out about it, or continued to suppress it, until 2012.

The latest report, for 2015, was published in March 2017. For NOx, it shows much the same pattern as stated in the 2006/7 report. Most of the roadside and kerbside locations, which collected enough data to complete the test, failed it. But many of these are in places like Holborn, the Hanger Lane gyratory and Brixton Road in Lambeth – right next to very busy roads, where the traffic is often slow moving. Among urban background sites, the only ones to fail the annual average test were at Bloomsbury, the City (only just over the limit) and Victoria; and all three passed the “exceedences” test.

As to PM10 and PM2.5, all sites except one passed the annual average test, and that site was affected by construction in the vicinity. One other site failed the “exceedences” test. So, as far as EU standards are concerned, PM is not an issue. However, the World Health Organization has issued a guideline concentration limit, which is only 40% of the current EU limit; and none of the sites passed that test. It isn’t hard to foresee more trouble coming from this in the future.

I’ll make one more observation. Kerbside and roadside sites are useful for attribution, and to spot future problems. But why are they included in the tests? People don’t spend their lives walking round and round the Hanger Lane gyratory. So, why aren’t just the urban background and industrial sites, supposedly representative of the level of pollution people actually experience, used for the tests? And on that basis, the only problems with NOx in London are inside the congestion charge area.

Part 2 – D(r)iving down into the detail

This is the part of this essay, in which I show my long-ago training as a mathematician, and delve down into the detail.

The mathematically challenged among my readers should skip the numbers, apart from those I tag as Bottom Line. Instead, they should marvel at the way I take a bunch of other people’s numbers, all of which are wrong; masticate them out of all recognition; and end up with a slew of figures, each of which is certain to be far more wrong than any of those which went into the process. But to those of you comfortable with such things, I urge you to seek out any errors I may have made, and to bring them to my attention so I can correct them.

The excess deaths claim

The claim being bandied around in the media is that 40,000 excess deaths in the UK each year are caused by exposure to outdoor air pollution. This claim comes from a 2016 report from the Royal College of Physicians [11]. Even the title is alarmist: “Every breath we take – the lifelong impact of air pollution.” The report has a general tone of rampant greenism and nanny-statism. Its stated recommendations include: “Act now, think long term.” “Promote alternatives to cars fuelled by petrol and diesel. Government, employers and schools should encourage and facilitate the use of public transport and active travel options like walking and cycling.” “Put the onus on the polluters.” “Tackle inequality.” “Protect those most at risk.” And it includes the phrase “climate change” more than 70 times!

This is political zealotry, not science. Though coming from a working group consisting largely of professors of medicine, it surely fails to meet the Hippocratic oath: “First, do no harm.” Indeed, “Act now, think long term” directly contradicts the precautionary principle: “Look before you leap,” or “Think before you act.” And the reason isn’t hard to find. For one of the lead authors, and vice-chair of the working party that produced the report, was Professor Jonathan Grigg; the very same Grigg that provided that quote at the end of the mayor of London’s press release on 4th April!

The claim of 40,000 excess deaths turns out to be a compôte of two ingredients. One comes from a 2010 report by the Health Protection Agency [12], which states a figure of 29,000 excess deaths caused by outdoor air pollution. Specifically, this figure applies only to deaths caused by PM pollution, and doesn’t include any allowance for NOx. The remaining 11,000, a number not even mentioned explicitly in the RCP report, is “justified” by no more than hand-waving.

The HPA report

I read enough of the HPA report to form a broad judgement on it. This looks like real science, done honestly as all science must be. Here’s the Bottom Line, which is on page 1, point 2(c) (bold mine):

“The current (2008) burden of anthropogenic particulate matter air pollution is, with some simplifying assumptions, an effect on mortality in 2008 equivalent to nearly 29,000 deaths in the UK at typical ages and an associated loss of total population life of 340,000 life-years. The burden can also be represented as a loss of life expectancy from birth of approximately six months.”

Dipping into the detail of the report (page 67), their best estimated loss of life expectancy in England and Wales is 203 days for men and 190 for women. (It’s lower in Scotland and Northern Ireland).

Unfortunately, there is very little certainty in these estimates. For page 1, point 2(d) goes on to say: “The uncertainties in these estimates need to be recognised: they could vary from about a sixth to double the figures shown.” That is a factor of 12 between the upper and lower bounds! Imagine if a businessman asked one of his staff to estimate the cost of a project so he could work out whether to go ahead with it or not, and got the answer “between £1 million and £12 million.” Or if an engineer wanted to know how big a plug he needed to stop a particular gap, and was told “between an inch and a foot.”

I’m not blaming the HPA people here – they were obviously doing the best they could under the circumstances. But in the more than five years between their report and the RCP’s, it doesn’t look as if anyone asked them to update their report with more accurately bounded estimates. Numbers with such wide error bounds, it seems, are considered good enough for social engineering; for making political policies which will severely affect, and if got wrong will unjustly hurt, millions of people. They’re “good enough for government work.” Not.


Back to the RCP report. On page 82, we read: “NO2 is linked to 23,500 deaths annually in the UK (with a range of 9,500–38,000), based on pollutant levels in 2013. It is noted that this figure will include some overlap with the impact quantified against exposure to PM2.5.” The reference is to a DEFRA report from 2015 [13]. The error bounds, a factor of 4 between upper and lower, are better than the HPA’s; but they’re still way too big for the number to be fit for purpose.

After that, the following Bottom Line paragraph summarizes the whole (bold mine):

“When quantifying the total impact associated with exposure to both NO2 and PM2.5, it is therefore necessary to account for this overlap in the response functions. Defra estimates that the annual equivalent number of attributable deaths associated with the two pollutants combined is 44,750–52,500, with an associated annual social cost of £25.3 billion – £29.7 billion. However, a subsequent paper issued by COMEAP in December 2015 indicates that the level of overlap in estimates between pollutants may be greater than originally thought. On this basis, while recognising that COMEAP’s research on this issue is continuing, this report adopts a combined estimate of effect of around 40,000 deaths annually with an associated annual social cost of £22.6 billion (both with a range for a central estimate of ±25%).”

That’s where our 40,000 came from. But there’s something odd here. The error range given, ±25%, is way less than the error bounds in either of the numbers we started with – a factor of 12 and a factor of 4 respectively. That won’t fly. It looks as if the ±25% margin is only the overlap, and doesn’t take any account of the uncertainties in the HPA or DEFRA figures themselves. The true uncertainty is far, far bigger.

Separating out PM and NOx

Be all that as it may; we have best estimated figures of 29,000 excess deaths annually caused by PM, and 23,500 caused by NOx. But, as toxicologists know, the effect of the combination of two pollutants isn’t the same as the sum of the effects of the two pollutants separately. In this particular case, it’s known to be substantially less than that sum; in fact, it could even be that NOx adds almost no extra deaths to the 29,000 from PM. See the COMEAP paper mentioned above [14]. This whole matter is, if I may be permitted a pun, “up in the air.”

What seems to have happened is that the RCP, without stating any justification, made an assumption about the size of the overlap between the two. It’s hard to avoid the thought that they went for 40,000 because it was the only round number they thought was credible. 50,000 would have been called out as over the top. 30,000 wouldn’t have been scary enough; and, perhaps more importantly for political purposes, would have suggested that NOx isn’t really the problem, only PM. That said, it’s the best number I have, so I’ll use it.

When I get to crunching the numbers, I’m going to try to work out how much of the effects of PM and NOx pollution is attributable specifically to diesel cars. I’m going to have to assume that the relation of pollutant concentration to health effects is linear, and has no start or cut-off threshold. I understand that this is indeed the current working hypothesis in toxicology. But since the amounts won’t be the same, I’m going to need to work separately with PM and NOx. So first, I need a way of allowing for the overlap, while still preserving the proportions between them. That’s actually not hard. Simply add up the numbers for PM and NOx, then multiply by the factor 40,000/52,500 (about 76.2%) to allow for the overlap.

The NOx deaths figure for 2008

There’s another wrinkle I need to deal with. The HPA study was done using PM levels from the year 2008. The DEFRA study was done using NOx levels from 2013. It doesn’t make sense to treat the 23,500 as though it was a 2008 figure, because there was a significant drop in NOx between 2008 and 2013. According to the graph on page 2 of reference [9], NOx emissions fell from 45% of their 1970 values in 2008 to a little under 35% in 2013. So I need to adjust the 23,500 number, upwards, by a factor which turns out to be almost exactly 30%. Giving a deaths figure for 2008, based on NOx concentrations in that year, of 23,500 * 1.3, or roughly 30,500.

Euan Mearns’ calculations

I am greatly indebted to Euan Mearns for the calculations he has made and published at [15]. But because the HPA’s report focuses on the year 2008, the numbers I use from the fact sheet he links to [16] will be those from that year. In that year, eyeballing the graph on page 6 of the fact sheet, the total fuel consumed by road transport was 37 million tonnes. Diesel cars accounted for 7 million tonnes, diesel LGVs 5 million tonnes, and HGVs and buses together 9 million tonnes. Assuming that petrol and other fuels produce no PM, that means that the fraction of road transport PM emissions due to diesel cars as opposed to trucks, buses and the like is 7/(7+5+9) = 33%.

Now, how much of total PM emissions in 2008 were attributable to road transport? Euan uses a figure of 14%, which is correct for 2015 – see reference [9]. But I went back to the DEFRA report for 2008, here [17]. Since, from the mortality point of view, PM2.5 has greater negative health effects than PM10 (see page 6 of [18]), I’ll use the figure for PM2.5 from [17]. So I’ll use 24% as the proportion of PM emissions due to road transport. Thus the total fraction of PM emissions in 2008 due to diesel cars was 24% * 33%, or 7.9%.

Using the HPA’s best estimate figure of 203 days for loss of life expectancy for a male in England and Wales, I get the Bottom line loss of life expectancy attributable to PM emissions (alone) by diesel cars in 2008 as 203 * 7.9% = 16 days. This is a little higher than Euan’s number, but it’s in the same ball park. The upper bound is 32 days.

But I can go further than Euan could. The DEFRA report at [17] also gives the proportion of NOx emissions attributable to road transport in 2008 – 32%. Not only that, but the RAC paper I linked to as [6] has on page 2 a graph of actual NOx road transport emissions, which – happily – covers the year 2008. Eyeballing this graph gives the following breakdown for 2008: Petrol cars 26%, diesel cars 22%, LCVs 13%, HGVs, buses and coaches 39%. So, the fraction of NOx emissions in 2008 due to diesel cars is 32% * 22% = 7.0%.

Next, how much life expectancy is lost due to NOx on its own, as at 2008? Recall that the original excess death figures were 29,000 for PM (2008) and 23,500 for NOx (2013). The latter figure I adjusted to a 2008 equivalent figure of 30,500. I’d expect the average loss of life expectancy because of NOx alone, then, to be 203 days * (30,500/29,000), and the loss of life expectancy attributable to NOx emissions by diesel cars, on its own, to be 7% of this. That comes to 15 days. The upper bound is 24 days.

To get a ball park estimate of the overall loss of life expectancy due to emission of both pollutants by diesel cars, all we need do is add the two together, then multiply by the overlap factor. The Bottom line result is (16 + 15) * 76.2% = 23.6 days of life expectancy lost due to combined PM and NOx emissions by diesel cars. The upper bound comes out to 42.7 days, or six weeks.

Which would you prefer? To travel where you want, when you want, in the comfort and privacy of a smooth, quiet, spacious car? Or to be granted at an extra 3 to 6 weeks of life, and in exchange to be forced to spend your travelling life waiting at bus stops in the pouring rain or standing on freezing station platforms, and when you finally do get moving it’s often like being in a cattle truck; noisy, rattling, uncomfortable and crowded? I know which I’d pick.

Moreover, wouldn’t you spend a lot more than six weeks of your life at those bus stops and on those platforms? (Exercise for the reader: how many weeks is 5 minutes a day over a lifetime?)

My own calculations

Now, I’m going to try to work out a ball-park monetary value for the social cost, per car per year, of PM and NOx pollution from diesel cars. I take this approach to counter those that would argue, in light of the conclusion of my previous section: “You’d be right if everyone drove a diesel car. But some people don’t have cars. They suffer your pollution, too.”

I’ll say at this point that I entirely agree with the principle of “polluter pays.” It’s a particular case of the general idea of personal responsibility; that people, who unjustly cause damage to others, have a responsibility to compensate those affected.

I have no problem with the idea that someone who engages in a polluting activity should be made to pay the social cost of that pollution. However, I do have a problem with this payment being in the form of taxes to government; so called “Pigovian taxes.” The way I see it, it should be like a “liquidated damages” payment from the polluters to those adversely affected by the pollution. To the extent that individuals sustain damage as a result of this pollution, they deserve to receive compensation in proportion. The only function government should have in this is as a router; making sure the right amounts are collected from the right people, and the right amounts are distributed to the right people.

Another principle I find very important is that, unless there is an intention to cause damage, or recklessness, or bad faith, the amount to be paid by an individual for pollution should never be greater than the social cost of that pollution. To charge any more than this would, in essence, be applying a criminal penalty to someone who has committed no crime. No such penalties should apply in this case; at least not to the drivers, who bought their cars in good faith believing they would meet the emission standards they were supposed to. Whether, and how much, the manufacturers should be punished for what seems to have been a major breach of acceptable conduct, is another matter.

Having taken the trouble to collect all that data for 2008, I’m going to continue using it. But first, I need two more figures. First, how much is a life worth? Or, more accurately, what is the average social cost of the health effects suffered by a victim whose death is caused by pollution? The DEFRA report at reference [13] gives the cost of 23,500 such deaths as £13.3 billion. This gives a social cost, per life lost in this way, of £566,000.

As a cross-check, I divided the HPA’s number of life years lost due to PM (340,000) by their number of deaths (29,000) to give the average number of years of life lost by those killed by PM pollution (11.7). Then I multiplied the result by the £30,000 the NHS uses as the value of a “quality adjusted life year” [19]. That gives a figure of a little under £352,000. So the contribution of the lethal part of the pollution effects is around 62% of the total social cost stated by DEFRA; the remainder must be due to the non-lethal effects. This seems quite believable to me, so I’m happy to use DEFRA’s figure of £566,000 per life lost.

The other figure I need is the number of diesel cars on the road in 2008. At [20], in spreadsheet VEH0203, “Licensed cars by propulsion and fuel type,” I find a figure of 7.16 million, which I’ll round to 7.2 million.

The PM calculation

We’re now ready to work out the social cost, per diesel car per year, of PM pollution as at the year 2008. Take the HPA’s number of deaths (29,000) and multiply by DEFRA’s social cost per death (£566,000) to give the total social cost of PM pollution. That’s about £16.4 billion. Big scary number, heh? Now multiply by 7.9% for the contribution of diesel cars to the whole. That gives us a total social cost of PM from diesel cars of £1.30 billion. Lastly, divide by 7.2 million diesel cars on the roads that year. We come up with a Bottom line social cost of PM pollution, per diesel car per year as at 2008, of £180.

That’s a respectable cost. So, the diesel pollution problem is (or, at least, was in 2008) a real one.

Now, how were these cars, and their costs, distributed among the different Euro standards? Back in 2008, the diesel cars on the road were either Euro 3 or earlier (pre 2006) or Euro 4. To work out what proportion of our 7.2 million were of which type, I’ll use spreadsheet VEH0207, “Licensed cars by first registration,” which is also available at [20]. These figures are not restricted to diesels; but I’m only interested in the proportions here, so using this data should be OK. Adding up the first three columns for 2008 to get the number of cars 3 or less years old gives 6.35 million. Dividing this by the total, 28.2 million, gives 22.5%. So it’s reasonable to assume that our 7.2 million diesel cars in 2008 were made up of 1.6 million Euro 4, and 5.6 million Euro 3.

Next, I note from the emissions standards (assuming every car exactly meets its standard!) that cars built to Euro 4 emit half as much PM as those built to Euro 3. Thus the fraction of our £1.3 billion attributable to Euro 4 will be 1.6 / (1.6 + (2 * 5.6)) = 12.5%. So the Bottom line 2008 social cost per Euro 4 diesel car per year for PM is (£1.3 billion * 12.5%) / 1.6 million, or £101; and for Euro 3, it comes out to £203.

When Euro 5 came in, the PM limit was reduced by a factor of 5; and Euro 6 did not reduce it further. Therefore the Bottom line social cost, per car per year, of PM pollution for diesel cars meeting Euro 5 or 6 standards is one fifth of the value for Euro 4; or £20.

The NOx calculation

The NOx calculation follows the same principles. I take my 2008 adjusted excess deaths figure of 30,500, and multiply it by the social cost per death, £566,000. The result is £17.3 billion. Now multiply by 7.0% for the contribution of diesel cars to the whole. That gives us a total social cost of NOx from diesel cars of £1.21 billion. Lastly, divide by our 7.2 million. We arrive at a Bottom line social cost of NOx, per diesel car per year as at 2008, of £168.

Now, I’m going to apportion the costs for NOx to cars built at different times in two different ways. First, using the RAC [6] paper’s estimates of actual NOx emissions; so that each Euro 4 car is estimated to emit 80% of NOx in comparison to Euro 3. Then the fraction of our £1.21 billon attributable to Euro 3 is 5.6 / (5.6 + (1.6 * 80%)), or 81%. This gives a social cost for Euro 3 cars of £1.21 billion * 81% / 5.6 million, or £176. For Euro 4 it is £1.21 billion * 19% / 1.6 million, or alternatively 80% of the Euro 3 figure, and this works out to £141. This number also applies to Euro 5, since according to the RAC’s figures there was no improvement in NOx between the two. Finally, Euro 6 cars emit only 60% of the NOx that Euro 3 cars do; so we multiply the £176 by 60% to get a figure for Euro 6 cars of £106.

Next, I’ll compare these numbers with those predicated on the assumption that all the cars involved had actually met the standards they were supposed to. I do this to try to separate out the components of the social cost which ought to be borne by drivers and by the car manufacturers. In this scenario, Euro 3 compliant cars should have emitted roughly half the NOx they did, bringing the social cost figure down to £88. With Euro 4 the fraction is one part in 3.2, leading to a cost of £44. For Euro 5 it’s one part in 4.4, leading to a cost of £32. For Euro 6 it’s one part in 7.5, leading to a cost of £14.

The bottom line

Adding our £180 and our £168 together and multiplying by the overlap factor, we get the Bottom line social cost, as at 2008, per diesel car per year, of both PM and NOx together as £265. So, the diesel car pollution problem genuinely was real back in 2008.

It’s also instructive to add up the total costs of pollution by diesel cars as at 2008, and try to compare with the costs of a scrappage scheme. £1.30 billion for PM plus £1.21 billion for NOx is £2.51 billion per year. And most of those cars were Euro 3, so the pollution costs today will be a lot lower, because of the addition of many new Euro 5 and 6 cars. Even to contemplate spending £20 billion, not including the huge personal costs both direct and indirect, on scrapping 10 million cars – including many perfectly good Euro 4 and 5 ones – is sheer madness.

As to the costs associated with cars built (or supposed to be built) to each of the four Euro standards, I summarize the Bottom line in the following table. The “driver” columns represent the costs attributable to the level of pollution which would have obtained if the cars had met the standards they were supposed to. The “manufacturer” columns represent the costs attributable to the RAC’s estimated excess NOx over and above these standards.

Standard Social cost of individual pollutants (per diesel car per year) Social cost of both adjusted for overlap (per diesel car per year)
PM NOx NOx driver NOx manufacturer Total Driver Manufacturer
Euro 3 (from 2001) £203 £176 £88 £88 £289 £222 £67
Euro 4 (from 2006) £101 £141 £44 £97 £184 £110 £74
Euro 5 (from Sep 2010) £20 £141 £32 £109 £123 £40 £83
Euro 6 (from Sep 2015) £20 £106 £14 £92 £96 £26 £70

Well, there you have it. Of course, my numbers aren’t complete. They don’t allow for inflation, for one thing. And the numbers that come out of such a process can never be more accurate than the ones that went in. But assuming there’s no major error in my assumptions or calculations, I can reach a number of conclusions.

First, the manufacturers have consistently lagged behind the NOx standards they are supposed to meet, by approximately the same amount when expressed as a social cost per car per year.

Second, diesel cars first registered before 2006 (Euro 3 standard and earlier) do indeed cause a significant social cost through pollution, about £289 per car per year. It would be fair to charge drivers for most of this social cost. And a T-charge of £10 per day for pre-2006 diesel cars, in central London only, seems not unreasonable. Scrapping may be an alternative option for many, since these cars are all near the end of their normal useful life (12 to 15 years).

Third, for Euro 5 and 6 diesel cars the social cost of the manufacturer’s failure to meet the NOx standards is more than two-thirds of the total costs. Less than a third of the social cost of the pollution can be construed as down to the driver.

Fourth, for a Euro 5 diesel car, the excess social cost of pollution per year over and above a Euro 6 car is only £27. Two £12.50 ULEZ fees would very nearly cover this excess cost for a whole year! Two £20 entry fees to other cities would well more than cover it. And if the manufacturers were held responsible for their share of the pollution caused by their failure to meet the standards, this excess would drop to only £14.

It is grossly unfair and unreasonable to charge fees of this size to drivers of these cars, given that the total social cost of their pollution is less than 30% above that for a Euro 6 car, which even Sadiq Khan has admitted should not be charged at all. It’s hard to avoid the thought that greed and zealotry have gotten the better of Khan and the other city mayors.

Fifth, for a Euro 4 diesel car (first registered from January 2006), the excess social cost is £88. While significant, this is still way lower than the charges many drivers of these cars would be likely to incur.

Sixth, it would be simpler and easier for everyone if Euro 4 and 5 diesel cars were exempted from all proposed charges, and the extra social cost collected through the yearly licence fee.

And last, if the manufacturers were made to retrofit to existing cars systems which meet the standards they were supposed to have been built to in the first place, pollution from diesel cars first registered since 2006 would cease to be a problem at all.

Does all this provide good cause to justify draconian measures against diesel drivers, including threats to force scrappage of perfectly good cars, £20 a day charges to enter every sizeable city in the land, and yet more millions of cameras watching us to catch us out in the tiniest misdemeanour? Is it fair to charge drivers of diesel cars built between 2010 and 2015 – including me – almost as much for two London ULEZ visits, or for a single visit to another city, as the social cost of the extra pollution our cars emit, relative to Euro 6 cars, in a whole year?

We’re being demonized, oppressed and ripped off by greedy, grasping zealots, aren’t we?

Part 3 – Questions, and some answers

I said at the very beginning that the issue raises many questions. If my calculations are right, several of these questions – and the first four, in particular – should be asked in some very high places.

  1. Why are the charges being touted for entry to cities by diesel cars built between 2006 and 2015 several orders of magnitude higher than is warranted by the social cost of the pollution from those cars? Is it fair to charge someone with a 2010 to 2015 model car £20 per day for something whose social cost, relative to someone with a newer car – who isn’t charged at all – is only £27 per year?
  2. Most of the nitrogen oxide pollution from diesel cars built since 2006 results from the manufacturers’ failure to build the cars to meet emissions standards they were supposed to. Why should drivers be expected to pay for a problem whose root causes lie with the EU, the government and the car manufacturers?
  3. How can you expect city mayors, like Sadiq Khan, to behave as anything other than anti-car zealots, when it’s in their political interests to be seen to be “doing something” about air pollution, and to set up schemes that bring in huge sums of money for their pet projects? Particularly when those schemes enable them to impose heavy charges on people who don’t even live in their area, and can’t vote against them?
  4. Why did the matter get all the way up to prime minister level before anyone said “hey, there’s something wrong here?”
  5. Has anyone in the government done a per-car social cost calculation similar to the one I’ve done here? If not, why not? If so, what numbers did it come up with?
  6. Has anyone in the government done estimates of how much the concentration of NOx in different parts of London will actually be lowered as a result of the T-charge? If not, why not? If so, what numbers did it come up with?
  7. Has anyone in the government done estimates of how much the concentration of NOx in different parts of London will actually be lowered as a result of the ULEZ? If not, why not? If so, what numbers did it come up with? How are the expected benefits broken down among Euro 3, Euro 4 and Euro 5 diesel cars?
  8. Has anyone in the government done an objective financial analysis of the proposals to scrap Euro 4 and 5 cars? If not, why not? If so, what numbers did it come up with?
  9. Who decides what an acceptable level of air pollution is? On what basis? Where is the record of their calculations and the assumptions they made? Where is the quality control record on those calculations and assumptions?
  10. How did it happen that the EU imposed on the car manufacturers NOx standards they couldn’t meet? Whose fault was it – the EU, the manufacturers, or a combination of both? Why was this problem, which dates back to at least 2001, not picked up until as late as 2015? Why are the manufacturers not being made to pay for their share of the problem?
  11. Who signed the UK up to an EU program of air quality limits that must be met, regardless of cost? Why did they sign up to any limits at all, without checking that they could be achieved without pain to the general population?
  12. Who decides where and how air quality is to be measured? On what basis? Why is no allowance made for kerbside and roadside sites where poorer air quality is inevitable? Why do the tests include kerbside and roadside sites at all? Don’t urban background and industrial sites reflect far better the actual concentrations to which people are exposed?
  13. Why was the 2008 report of the London Air Quality Network not published until late 2012?
  14. Why was Sadiq Khan allowed to choose, as his cut-off point for ULEZ charging, the Euro 6 standard for diesels, rather than Euro 4 or Euro 5? Particularly given that Euro 6 was introduced so recently, that even some cars still under manufacturer’s warranty were built before it came into effect?
  15. Why is there even talk of extending the ULEZ beyond the congestion charging zone, when all the air quality problems at background sites in London are inside that zone?
  16. How far can we trust the health risk figures, with which we are presented? Where is the record of the calculations and the assumptions made? Where is the quality control record on those calculations and assumptions?
  17. Why does government accept scientific estimates with error margins so wide that they would be laughed at in business or engineering?
  18. Why should people who live in suburbs, in small and medium sized towns and in the countryside suffer unjustly inflated costs, threat of scrappage of their cars, and at worst loss of their personal mobility, for the sake of city dwellers? Where is the quid pro quo?
  19. Having done so well in reducing air pollution over almost 50 years, why should we be expected to make any more sacrifices?
  20. The “polluter pays” principle is an example of the general principle of personal responsibility for actions. If drivers are to be held personally responsible for their share of the negative effects on others of their pollution-causing activities, then why are politicians and their advisers, and Tony Blair and David King in particular, not held personally responsible for their share of the negative effects on others of their policies, when they are shown to have been wrong?
  21. Why does government kow-tow to green activists like David King and Jonathan Grigg, and ignore the interests and the quality of life of the people they are supposed to be serving? Why have anti-car zealots been allowed to exert such a huge influence on transport policy?
  22. What is to stop the zealots doing this whole thing over again? How can people, who replace their diesel cars with petrol models, be sure that in a few years’ time they won’t be forced into replacing those too? 
  23. When will enough be enough? When can we expect an end to this appalling cycle of ever tightening intrusive regulation and ever decreasing quality of life and freedom?

If I ruled the world…

…well, if I was in power in the UK, here’s what I’d seek to do. Of course, some of it might be politically difficult. But without a just solution to this problem, there are going to be ten million or so very angry diesel drivers in the UK, calling for heads to roll. I’d be a fool to let that happen.

First, I’d get David King’s knighthood rescinded. That would be thoroughly deserved, and would send a message that I mean business.

Second, I’d tell the EU where they can insert their air quality standards, that this is exactly the kind of crap we voted for Brexit to be rid of, and that we’re going to fix the problem in our own way.

Third, I’d commission an urgent report from a competent, unbiased source, that would estimate the social cost of pollution from different types of vehicles (not just diesels, and not just cars) accurately enough to be of use in objective cost/benefit analyses and so in policymaking.

Fourth, I’d institute an assisted scrappage and replacement scheme for Euro 3 and earlier (pre 2006) diesel cars only.

Fifth, I’d ensure that neither the T-charge nor the ULEZ brings in any revenue at all for Sadiq Khan. I’d divert all T-charge revenue into a fund to help the people, whose lives and health have been damaged by the pollution that Blair and King caused. If I could, I’d re-direct congestion charge receipts into this fund, too. And I’d forbid any future expansion of the congestion charge area. Furthermore, I’d stop local councils from charging extra for parking spaces for diesel cars.

Sixth, I’d tell Khan, in no uncertain terms, that he has behaved unfairly and unreasonably by choosing Euro 6 as the standard to be met for diesel cars to avoid charges, rather than Euro 4 or Euro 5. And I’d forbid him to levy any charges at all on Euro 4 or 5 cars; we’ll pick up the social cost through the yearly licence fee.

Seventh, I’d tell other city mayors that if they want to institute any T-charge schemes in their own city centres, they’ll have to follow the same rules as London.

Eighth, I’d give the car manufacturers an ear-bashing, and I’d make them pay for their share of the extra NOx pollution caused by their failure to meet the standards they agreed to. On top of that, I’d require them to give timescales and costs to retrofit each of their models from 2006 onwards either to the standards they should have met when they were built, or to the latest standard. I’d give them, say, two years to respond. At that point, I’d set up an assisted scrappage and replacement scheme for those Euro 4 and 5 cars which can’t be converted cost effectively. The manufacturers would be expected to contribute substantial amounts to this scheme, and to supply when they are available cut-price upgrades for those cars which can be cost-effectively converted.

Ninth, I’d institute an honestly and accurately estimated “social cost of pollution” charge, to form part of the yearly licence fee for vehicles which don’t meet the latest emissions standards. This would apply to all vehicle types. It would replace, not be in addition to, any previous pollution taxes on vehicles.

Tenth, I’d establish as a general principle that, absent criminal intent, recklessness or bad faith, no-one who causes pollution should ever be held liable for more than the social cost of the pollution that they cause. In particular, in future drivers of vehicles, which continue to meet the emission standards current when they were built, should not be subjected to further penalties.

Eleventh and last, I’d institute a very high level, wide ranging review of how scientists, government and third parties interact in providing justifications for, and in setting, policy in the areas of environment and energy. It would be chaired by a senior, non-politicized judge. It would include qualified, unbiased and honest scientists, some of them from outside the UK. It would cover all the major environmental issues of the last 25 years, including air pollution and the climate change fiasco. And it would lay out a road map towards ensuring that activist zealots are never again allowed to run, or even to influence, government policy.

[1] https://www.london.gov.uk/press-releases/mayoral/mayor-plans-to-introduce-ulez-in-april-2019
[2] http://www.thegwpf.com/every-climate-initiative-imposed-on-us-by-politicians-has-ended-in-disaster/
[3] http://europa.eu/rapid/press-release_IP-14-154_en.htm
[4] http://www.express.co.uk/life-style/cars/792909/Diesel-scrappage-scheme-2017-what-it-means-for-me-Theresa-May-pollution-emissions
[5] https://en.wikipedia.org/wiki/European_emission_standards
[6] http://www.racfoundation.org/assets/rac_foundation/content/downloadables/Diesel_scrappage_scheme_calculation_Al_PG_Final_March_11_2016.pdf
[7] https://www.theguardian.com/business/2016/apr/23/diesel-cars-pollution-limits-nox-emissions
[8] https://uk-air.defra.gov.uk/air-pollution/uk-eu-limits
[9] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/579200/Emissions_airpollutants_statisticalrelease_2016_final.pdf
[10] https://www.londonair.org.uk/london/asp/reports.asp
[11] https://www.rcplondon.ac.uk/projects/outputs/every-breath-we-take-lifelong-impact-air-pollution
[12] https://www.gov.uk/government/publications/comeap-mortality-effects-of-long-term-exposure-to-particulate-air-pollution-in-the-uk
[13] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/460401/air-quality-econanalysis-nitrogen-interim-guidance.pdf
[14] https://www.gov.uk/government/publications/nitrogen-dioxide-interim-view-on-long-term-average-concentrations-and-mortality
[15] http://euanmearns.com/mortality-from-diesel-car-pollution-in-the-uk/
[16] https://www.gov.uk/government/statistics/sub-national-road-transport-fuel-consumption-2011-factsheet
[17] https://uk-air.defra.gov.uk/assets/documents/reports/cat07/1009030925_2008_Report_final270805.pdf
[18] http://www.euro.who.int/__data/assets/pdf_file/0006/189051/Health-effects-of-particulate-matter-final-Eng.pdf
[19] https://www.wbs.ac.uk/news/the-search-for-a-true-monetary-value-of-a-life/
[20] https://www.gov.uk/government/statistical-data-sets/veh02-licensed-cars


  1. IF this issue were being handled with justice and fairness – which it is NOT, owners who bought diesel vehicles earlier would not be punished for going along with the encouragement of the government to buy them. Just as with the changeover to unleaded fuel, it was the government’s fuel tax policies that helped urge people to buy diesel vehicles and use less total fuel.

    The bills for any special fees charged for using diesel vehicles in London should be sent to Parliament, not to the owners of the vehicles.

    James C. Walker, (US) National Motorists Association, frequent UK visitor to see family in Yorkshire.

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