5 May - Thinking about ULEZ, Part 7 - The Endgame
Before Part 7 of @tonyofsidcup’s dissection of the opposition to Khan’s new car tax the usual word of dissent…
I am quite pleased to know one of the ULEZ rebels who a couple of months ago asked me
if there was any danger of electrocution from snipping a cable or two. I was
able to give reassurance that professional grade security cameras operate on 48
volt DC, so wear gloves but the worst you would get is a not too severe jolt.
In the end of
the previous post, we talked about Bexley’s air-quality monitoring stations, and were
going to check just how clean Bexley’s air is. Before we do that, let’s think about what “clean” means.
Recall that discussions of air quality tend to focus on two pollutants - nitrogen dioxide and
particulate matter. The two “villains” are very different in their origin, behaviour and impact.
Nitrogen dioxide is mainly produced by combustion engines, “stays local”, and hits the lungs.
Scientists’ best guess is that long-term exposure to NO2 increases one’s chances of dying in the next
year by 1-2% for every 10 micrograms-per-cubic-metre (“mgcm”) of NO2 concentration. Particulate
matter has more sources - motor vehicles are an important one, but not as dominant as with NO2 -
travels far and wide, and affects both respiratory and cardiovascular health, as smaller PM particles
(2·5 microns is the established cut-off, hence “PM2·5”) can pass from the lungs into the bloodstream.
Scientists think that every 10 mgcm of PM2.5 exposure raises one’s “hazard rate” by 6-8%. (To
provide some reassurance after this morbid talk, one’s “baseline” hazard rate - the chance of dying in
the next year - reaches 1% only after 70. That tiny number gets multiplied by 1·02 or 1·06, etc.)
In 2005 and again in 2021, the World Health Organization published a set of “guidelines” for NO2 and
PM pollution levels. They are 10 mgcm for NO2 and 5 mgcm for PM2·5. A guideline level answers the
question: “Based on what we know, what is the lowest pollution level that, with long exposure,
affects health?” To clarify, a value below a guideline level does not mean that “everything is good”, it
just means “We don’t have enough proof that it is bad”. Likewise, a value above the limit does not
mean that “everything is bad”: the higher the pollution level, the higher the hazard rate. In the end,
there is no “clean” and “not clean”, only “less clean” and “more clean”.
And now, finally, the Bexley numbers. Please review the charts below. Note that red lines stand for
roadside monitoring sites, and green lines denote residential settings. What are we to make of this? I
see two main take-aways.
Everywhere we look, measured NO2 and PM2·5 pollution levels exceed the WHO guidelines - about
10 mgcm too high for NO2, and about 5 mgcm too high for PM2·5. (It sounds more dramatic if we
express the gap in relative terms: for both NO2 and PM2·5, the Bexley levels are double the WHO
guidelines). If these values were fixed long-term, this would mean a Bexley resident’s hazard rate to
be elevated by about 5%. However, they definitely haven’t been fixed - and so we get to the next finding.
(Someone like Gareth Bacon, waxing lyrical about the meadows of Biggin Hill, ought to notice that
PM2ܕ5 pollution levels are essentially the same next to a highway and in a residential neighbourhood.
As noted earlier, particulate matter travels far and wide. There’s a very good chance that if PM2·5
were measured in Biggin Hill - it hasn’t; as we know from Part 6, London’s largest borough has a
single monitoring site - the reading wouldn’t be particularly low).
Both NO2 and PM2·5 charts display a clear downward trend. Should it continue, it looks like WHO
guidelines will be reached within a few years, maybe by 2030.
“Will they, even without ULEZ?” is the million-dollar question. Here, we get into guesswork territory.
My guess is that they will. On the other hand, I believe that the ULEZ expansion will *ensure* that
they do, and drive pollution to an even lower level. (What about the Independent Impact
Assessment commissioned by TfL, which forecast only a negligible air-quality impact? The forecast
applied only to the first 12 months, whereas the policy’s effect will develop over many years).
If the trajectory of pollution levels is permanently shifted downward, and not just short-term but
long-term exposure to NO2 and PM2·5 is reduced, we “slide down” the
hazard-rate curve and save
lives. Importantly, we save them year after year, whereas the costs of ULEZ expansion are largely
transient. Accumulated over many years, even a tiny public-health improvement eventually compensates for the initial pain.
“Easy for you to say - it’s not your pain. You are not an already-struggling
low-income worker facing
an extra £300 pm expense”. I have no comeback to that, and pointing to the Tories who refused to
fund a bigger scrappage scheme (or develop public transport and “active travel”, or generally
promote the clean-air agenda - looking at you, Bexley Tories) would be a deflection tactic. It is what it
is. ULEZ creates winners and losers. If you are on the winning side, you want the blow on the losers
to be softened. Unfortunately, the Tory politicians in charge have opposite incentives, hoping to
convert suffering into votes.
So that’s my “defence of the Red Dictator”, as the gracious host of this series introduced it, done. We
may have reached the end with our views unchanged, but we definitely have learned something new.
Links
World Health Organisation, Global Air Quality Guidelines, 2021
https://apps.who.int/iris/bitstream/handle/10665/345329/9789240034228-eng.pdf
COMEAP, “Mortality Effects of Long-Term Exposure to Particulate Air Pollution in UK”
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/304641/COMEAP_mortality_effects_of_long_term_exposure.pdf
Glutton for punishment? All seven pro-ULEZ articles on one page.