China has 350 million electric two-wheelers, 20 million EVs. China reduced air pollution from transportation by 80% in a decade.
Delhi: 442. Lahore: 334. Beijing: 16. These are the levels of PM 2.5, one of the principle measures for air pollution, on November 19. How China cleaned up its air pollution – and what that meant for the climate: https://theconversation.com/how-china-cleaned-up-its-air-pol...
1. London when the ULEZ was brought in was already a lot less polluted than historically.Are there gains from that? London was not that bad by global standards.
2. This was followed by the benefits of COVID lockdowns (not a phrase often used!) as pollution dropped much further.
3. Is this effect even across London? Suburbs vs centre, different types of housing etc.? I grew up a the edge of London and the difference in pollution was visible (i.e. you did not need instruments to see signs of it).
4. There was also a reduction in sales of diesel cars which had been heavily encouraged (because of lower CO₂ emissions) in previous decades.
5. As the articles notes, there have been a lot of other changes at roughly the same time. It only mentions one, but there have been significant lifestyle changes, so a lot of potential confounding variables.
1. Less than historically still has a quite high baseline compared to after ULEZ - if it was more polluted, presumably the change seen here would be more dramatic.
2. Definitely kickstarted it, but we're looking at taking that impact and continuing it for some 5 years after covid ended now.
3. You can look at the ULEZ map and it really covers everything but the outer tube line suburbs [1].
5. The control group in Luton, presumably, has the same lifestyle changes - it's not that far away (about 30 miles), so it is as close as you can get to a one to one comparison, not accounting for the fact that Luton is likely to be more deprived than London (especially in the council estates, which have horrible reputations).
Anecdata I was living very close to a busy highway, and my young daughter was wheazing when she had a cold, we had to give her medicine via a nebulizer. When we moved out to the country more, far away from any major roads, these issues all disappeared within a couple months.
Living very close to busy highways is known to generate poor air quality. I recommend anyone in those locations buy an air purifier for their kids' rooms.
I bought a couple reasonably priced HEPA purifiers and I change the filters on schedule. Replacement HEPA filters are very cheap.
Also watch out for things that we do indoors that can generate bad air quality. I had a friend who bought a VOC meter and noticed very high readings in his kid's room. He traced the source to his chemical and paint cabinet nearby, which he never considered because he couldn't smell anything. Throwing out a lot of the old containers dropped the measurements to the unmeasurable range.
HEPA filters are counterproductive in standard air purifiers. Air purifiers pump their cleaned air directly into the dirty air of the room. It doesn't matter if that cleaned air is extremely clean, because it's immediately mixed with dirty air. What actually matters is how much clean air you produce: the "clean air delivery rate" (CADR).
The more effective the filter the more it restricts airflow. If a filter is only 99% effective instead of 99.99% but allows double the airflow, it provides nearly double the CADR. To benefit from HEPA you need a clean side and dirty side, like in a clean-room setup.
A reasonable compromise is achieved by an air purifier that has the outlet on top because it’s blowing the filtered air well away from the inlet side and generally circulates the air in the room.
I used to work in the cleanest room in the state, that wasn’t a lab, back when I lived in Adelaide, and top-inlet button-outlet in a raised floor data centre is how the air handling units in the main data hall worked, so you can simulate that to a certain extent.
> The more effective the filter the more it restricts airflow.
This isn’t the whole story. Surface area and flow rate are factors.
A residential home is aiming to improve air quality, rather than grow flawless silicon ingots etc.
If you only use 99% it means there are small particles you can't catch. Being faster is meaningless if you can never clean the air.
Air purifiers are designed to run 24/7 and all they do is catch particles. Eventually all the particles will be caught. The one I got also detects if there is a lot of particles and will spin faster accordingly.
If the purifier can filter the air more quickly than air leaves the room it'll still reduce the amount of pollutants in the air. Most people aren't going to create a "clean side" and "dirty side" setup for filtering the air in a room.
I think that is what they're saying: the point is that if you're doing this, you don't want to optimize for the cleanest air leaving the filter, but more for throughput.
If you’re so inclined, you can build your own air purifier with laser cut panels or 3d printed panels and use a cheap ikea air filter and standard PC fans. All the parts are readily available, and user repairable.
If you pair if with an Apollo AIR-1 you can have home assistant ramp up and down the fans with a PC fan controller based on live readings of PM2.5 in your home. I did this with the help of Claude code.
Didn’t the Apollo 13 crew make an air scrubber out of duct tape and hope? Surely a cardboard box, a box fan and a hepa filter covered in tape gets you 90% there
I really wish the DIY folks would measure the airflow and sound levels on this sort of thing. CADR and decibels are going to vary wildly with fan choice
I came across this site which has pretty comprehensive data about PQ curves (the chart for determining CADR given filter impedance) at different noise and power levels: https://www.cybenetics.com/evaluations/fans/204/ (many other fans tested as well but I've been liking the value of P14 Pro PST)
However they look somewhat commercial and I'm not sure the funding/incentives so definitely corroborate with other sources.
It's a good start, but for VOCs and gases you'll need activated carbon. Those 2-in-1 filters do exist but cost more. And many are scams because they don't have enough volume of activated carbon.
Getting rid of the VOC source, if possible, is much easier than trying to filter it.
> Those 2-in-1 filters do exist but cost more. And many are scams because they don't have enough volume of activated carbon.
Any filter with a little bit of carbon added is going to be useless after a few days, or maybe even hours.
The only VOC filters that work have multiple pounds of carbon, with the good filters having upwards of 10-20 pounds. It also has to be replaced regularly.
Because it’s not obvious to most customers that a corner’s been cut. Same reason most new construction in the US sucks.
You can safely put a washer and dryer on the upper floor of a house if you add a proper floor drain, but you’re unlikely to see anyone add a floor drain in new construction because buyers aren’t looking for it. Now multiply that by everything a buyer isn’t looking for and you’re talking real money.
> You can safely put a washer and dryer on the upper floor of a house if you add a proper floor drain
European here, we've always been placing washer/dryer stacks in our bathrooms without needing floor drains. We have machines with a system called Aquastop [1] that stop the water flow if the machine detects a leak inside the system.
You have companies choosing the component that cost 10 cents instead of 15 cents even if the 10 cents component will break 10 times faster than the more expensive one.
And manufacturers do a sneaky swap too, my Coway 150 which is a great air filter by the way, came with a nice thick grid of hexagonal cells each filled with carbon granules - that insert alone weighs like half a kg. I ordered official filter and carbon filter replacements off their website ....got a thin carbon "foam" that weighs maybe 50g instead.
Agreed, just buy air purifiers with HEPA filters and change them regularly. The main expense is buying one for every room, but it's one of those expenses you wish you had made sooner.
NO2 is a very hazardous air pollutant which doesn’t get a ton of attention. The main sources are combustion engines and gas stoves. Asthma looks to be mostly caused by gas stoves.
I’ve got a sensor that can detect no2 and it noticeably spikes when using gas. Switched to induction after that.
Do you have a source for that? Because as far as I can see, asthma isn't _that_ less common in countries where gas stoves are barely used, such as germany. Still has like 60-70% of the asthma cases the US has. There's also a ton of other pollutants the US hasn't yet forbidden, but the EU has, which could also explain a lot of the difference in rates.
Don't get me wrong, it's certainly a good idea to get rid of gas stoves. I just think it's a bit much to declare them the primary cause of asthma.
I’ve never once been in a property that had an exhaust fan sufficient. I’ve had the exhaust on full blast and the spike on the air quality sensor on another floor of the house is rapid and massive.
I suspect a sufficient ventilation would require something more like a lab fume hood that can pull a negative pressure on the area around the stove.
And from what I have seen, a good number of exhaust fans are straight up fake and just ventilate back in to the room rather than ducted outside.
I wanted to long for the time when people hated "Malaria" and wanted to move to "Beunos Aires". But they believed the arrows chase us at daytime and the plague engulf us at night, like in the Psalm.
I don't understand why we keep on building right next to highways which are some of the worst things for our health. You don't need to live in the countryside for that. Just stay roughly 1km away from them and the situation is significantly better.
There is evidence of a lot of ugly diseases caused by this, without even mentioning the constant 40+ dB background noise.
A friend of mine does research on air pollution from cars - the TL;DR is you should not live within a third of a mile of a highway. The falloff is pretty sharp, but you don't want to be in that zone.
Shame you cant remember the source. Ive long since wondered if its actually more deleterious for my health to cycle to work in London due to air quality. I came to the conclusion that youre damned if you do and damned if you dont in the end, as in London at least, many of the tube lines have particulates higher than is considered safe
Probably depends on the tube line; one of them, can't remember which now as I left the country in 2018, left me with black snot on each use. Cycling wasn't that bad, but neither were the other lines.
Generations of men have been taught that when walking with a woman on a pavement, they should always take the side closer to the road allowing her to keep further away from the traffic.
But Dr Iarla Kilbane-Dawe claimed that Londoners should avoid walking too near the kerb because on busy streets, air pollution can be up to a third higher than on the inside of the pavement.
EV's have 100% reduction of NOx/tailpipe VOCs, 100% reduction in soot/tailpipe particulates, 70% reduction in brake pad dust (due to regenerative braking), in exchange for 25% increase in tire wear.
Vehicles are capped at emissions of 3mg/mile of particulates and 30mg/mile of VOC's. Something like 1-2mg of tire material actually becomes airborne PM10 particles every mile (and only about 10% of that for PM2.5 particles).
So, EV's really do a great job reducing emissions from 35mg/mile to <2mg/mile (PM10) or even <0.1mg/mile for PM2.5. A 95%-99.8% reduction in air pollution near highways would seem absolutely fantastic for me and my children!
> EV's have 100% reduction of NOx/tailpipe VOCs, 100% reduction in soot/tailpipe particulates, 70% reduction in brake pad dust (due to regenerative braking), in exchange for 25% increase in tire wear.
I replaced the tires on my Tesla model 3 at 74,000 km and they still had tread above the indicator bars. I'm now at 140,000 km and the tires look great, the back ones look like they're only about halfway done. I might be an outlier but my previous Subaru needed tires every 50,000 to 60,000 km.
Needless to say, the brake pads have never been touched and when I saw the left front one at around 110,000 to 120,000 to patch that tire, it looked like it was just installed. The regen braking almost completely eliminated the brake pad or rotor as a wear item.
Notably, most major cities have been building tons of housing (especially ‘affordable housing’) right next to highways, as it is the only areas that aren’t already built out with tons of high value houses.
Woke activists love the word "systemic" for a reason.
If a bunch of good people acting in good faith produce a result an evil mastermind would want does it matter if they are good? On many levels obviously yes, on some practical levels the system and the incentives still need to change.
Same. I visit my family in London and my sleep improves because of no hay fever. Though then I get black boogers, horrible chalky hair, a renewed sense of misanthropy etc
'"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC."'
I agree. Though they did at least put it in quotes in the first sentence, which I hope doesn't indicate how far people are generally getting through an article before commenting on it on Hacker News.
Smokers don't magically undo the damage they did to their lungs after they stop smoking. Stunned might be hyperbole, but it is at least a little bit surprising.
The lifetime risk is approximately 1.3% for women and 1.8% for men. For regular smokers: 11.2% for women and 14.8% for men. So about 15 to 30 more likely to get lung cancer. Bringing that down to 4x is close to "almost the same".
Might be that I am not reading probabilities correctly, but how do 1.3% -> 11.2% and 1.8% -> 15% become "15 to 30 times more likely"? Sounds like less then ten times?
They absolutely do! Not all the way, but if you'd have smoked a pack a day for 15 years and then have given up for the last 15, there's absolutely no way you'd be saying this!
"Stunned" isn't really a scientific term. It's the sort of editorializing you should expect to come from people who aren't the scientists themselves. More than hyperbole, it is classic click bait.
Also, quitting smoking definitely eases a number of symptoms, especially if you're not at the point of chronic emphysema. The reduction of inflammation triggers alone after a bit of time is fairly significant. Less coughing, less mucus buildup, etc.
But this isn't that at all. "Stunned" is used here because it's the word one of the study's authors actually used.
'"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC.'
I'd like to imagine the stunned scientist is a scientist from another field, they show some medical findings to a guy who looks at snail butts all day and he's the one "stunned" by the findings
I'm obviously supportive of less pollution etc etc but looking at the actual graph results I wouldn't describe them as 'stunning', the needle barely moved. But of course, they have to have something to make headlines after spending so many million on the study and who knows how many billion on ulez.
I'm not one of these anti ulez people I think it's good. But you can imagine the pressure to spin tepid results into headlines.
The entities with a ton of money tied up in the ULEZ are, perhaps with a layer or two of indirection, are likely the same ones funding this research, or if not this research then the guy across the hall in the same lab.
> strongest evidence yet that local clean air zones could help reduce some of the harm caused by pollution during childhood.
It's incredible this is even in debate. It's one of those intuitive things well known since the reduction of coal burning and smog during the industrial revolution in London?
ULEZ massively reduced the amount of NO2, which is a trigger for asthma. It also seems to have reduced the hospital admissions for heart related emergencies.
Yup, especially on the older lines (Northern, Victoria, Jubilee, Bakerloo). Particulate pollution can be two orders of magnitude higher than at street level. This tends to be glossed over when trumpeting the success of ULEZ measures pushing people away from cars and onto public transport, and I say that as a non-car-owner.
People tend to walk 10-15 mins at either end when taking the tube, and will walk more through the day. My understanding is this activity is net positive despite the extra particulates while on the tube. I might be misremembering this with a study I read on cycling in road pollution though
Anecdotal, but similar situation here for me (I don't need an inhaler, but visiting London around 2015 meant blowing my nose to black snot for a week, and then back in 2024 it was completely fine)!
I grew up in a small town in the mountains in Norway. There is a children's "hospital" there (Geilomo Barnesykehus), where kids come to live because they can't live in the cities. Kids with severe asthma, eczema and some other conditions. It started as far back as the 1930s, still unfortunately a problem so kids have to come live there away from their families.
My anecdata: I have a Japanese friend who was born in 1964. She grew up in Yokohama for the first ten years. Japan didn't pass its first (serious) environmental protection law until 1967. She said many, many of her friends had asthma. Fast forward 50 years, very few children have asthma in Yokohama.
I will never forget watching this documentary about a Canadian man, Doug Rogers, who went to Japan in 1964 to train martial arts at a dojo. This YouTube video[1], watch it from 1:00 to 1:10. The air pollution is simply stunning. It shows you just how terrible the air pollution was in Tokyo in 1964. Today, it is night and day. The same is true for most large cities in highly industrialised nations.
completely anecdotal. my earliest childhood memories in india were of asthma, sinusitis and constant cold. this was consistent until i was 26 and since then I've moved to the US and lived in New York with 0 days of sinusitis or breathing trouble. and i fallback to trouble breathing when i go home again.
even New York is so much more better than Bangalore or my small village in the middle of coffee farms
Bangalore has historically (over decades) been known to have a high incidence of asthma due to the high pollen in the air. It's been made worse in recent years due to pollution. The pollen is present for a significant portion of the year while other pollen regions in the world tend to have it for a smaller duration.
During my childhood, I lived across the street from a brewery. I suffered from chronic sinusitis for years, and no one understood the cause.
When I moved to a different part of town, the problem immediately stopped.
The same thing happened to one of my classmates who lived in the apartments next to me.
I just made a comment about having good air quality but with summer fires we were getting smoke for weeks at a time so I got an air purifier. My kid wasn't struggling horribly but I did notice right away after putting one in his room that he slept better and his breathing seemed so much more relaxed at night and it just felt like it made a noticeable improvement to me.
What is more amazing to me is I thought this wouldn't be localized. I thought we have on earth and one atmosphere but clearly not? Like the standard of living can wildly change if we change our own local area. We don't need people in Montreal or Paris to come up with a plan?
So unlike greenhouse gases, which can last in the atmosphere for years, seems like NO2 and particulates only stay in the air for less than a day or a few days. This is an amazing little fact because we can start small and call for meaningful reform where we live without requiring a global coordination. Maybe there will be a global consensus later but it doesn't matter because we can start making improvements today within our own local context. The bonus is we will likely also lower our own carbon footprint as we reduce our other emissions. I think this is the "selfish" breakthrough we need to convince people.
When I say it doesn't matter, I don't mean like cross border contamination does not happen but rather that we can improve our own lives with our own action regardless of what others do.
The obvious actionable thing that you can do for your own life is to stop using or being around gasoline or petrol powered two stroke engines such as in a leaf blower. But we can do more. We can completely ban these two stroke engines from being sold at all and that will bring meaningful improvements in weeks, not years.
The problem is to make more impact, we will need to actually get people to give up or retrofit their existing equipment. We will need to educate people about the harms that these things cause and why the change is good. However, in today's siloed world, I don't think it will be easy at all. So perhaps the most difficult part ironically in a very connected and yet siloed world is the marketing of this idea and connecting the required change in behavior with the benefits.
As we saw with the leaf blower example, the costs are concentrated, yes but so are the benefits! The benefits are NOT at all diffuse because guess who benefits the most from not inhaling in gasoline fumes? The person operating the leaf blower!
The localisation of it struck me when I read an Irish EPA report on traffic-related air pollution a few years ago that recommended carrying your child if you were walking regularly near heavy traffic. The air at 0.8m (their breathing height) has 5-15% more NOx in it than the air at 2m (the height they would breath at being carried by you).
I remember reading something similar about walking on the part of the pavement furthest from the road, because being an extra meter or so away makes a big difference
Link to the original study below, free to access [0]. The key data appear to be this:
>At baseline, 184 (14%) of 1280 children with successful FEV1 measurement in London had a clinically low FEV1 (pre-bronchodilator FEV1 <80% of predicted value) compared with 126 (9%) of 1339 children in Luton (appendix p 8). At the end of the study, these values had dropped to 51 (9%) of 585 children in London and 41 (7%) of 606 children in Luton (appendix p 8).
So the proportion of children with low lung function dropped from 14% to 9% in London, and from 9% to 7% at the comparator site in Luton. It's not that much different, though any improvement is obviously welcome.
Seems electric cars produce the same or sometimes more non combustion particulates than ICE cars, eg. bits of road and tire that are flung into the air while driving.
So EVs are better than ICE for air quality, but fewer cars even better.
I think it’s mostly break dust. Electric cars are heavier but can also hopefully mostly use regenerative breaking instead of break pads. Road vibrations (and wear?) tend to go as the fourth power of weight over the axle and so it tends to be worse for (naturally heavier) electric cars but even worse for goods vehicles.
It was news to me that the lung damage from pollution isn't necessarily permanent in children, if a change in environment happens early enough. Up until reading this, I was under the impression it would be.
We had a lot of construction work in the neighborhood, our house covered in fine dust particles each day. My kid got asthma in the same period, keeps asking when she can stop taking the medicines, and I say "I don't know" thinking "probably never". But maybe now the construction work is over, there is hope? (And if construction starts again, we know that it is better to move, because there is hope.)
There is a big difference between believing something is true, and demonstrating it is true and measuring the effect. One is a vibe. The other can drive policy.
The sad thing is... when the ULEZ went into effect, there were some wild conspiracy theories about it. Suddenly even my father was an expert and viewed it as sinister government intervention - all because of youtube crackpots. I couldn't get him to relate to my view that cleaner air must be a good thing.
I bet if some youtube weirdos pushed out videos against "big soap" for making us unnecessarily clean our hands after pooping... we'd have a growing following of angry "freedom from big soap" people.
> I bet if some youtube weirdos pushed out videos against "big soap" for making us unnecessarily clean our hands after pooping... we'd have a growing following of angry "freedom from big soap" people.
At one point during Covid, I tried (not very hard at all) to float a conspiracy that the vaccine was in fact not the poison, but the antidote. That Covid was deliberately designed by governments to filter the 'independent thinkers' (who won't take the vaccine) from the sheep (those who do take the vaccine). So by not taking the vaccine, you were giving the governments what they wanted.
This was because the conspiracy that governments were killing the loyal sheep with the vaccine, therefore only leaving the 'independent thinkers' behind, made absolutely no sense at all to me.
When I talk about health implications I often end up saying "but it's less bad than living next to a street" which statistically many things we spend time optimizing about are.
However most people live next to a busy street ...
The street isn't the problem. Cars and trucks are. If those streets were filled with people walking, cycling, etc., the health penalty of living next to one would vanish overnight.
Why not? A lot of streets often seem busy simply due to the incredible space inefficiency of cars. What I like to do sometimes, when I wait at a traffic light with my bicycle, is to count the actual number of cars that cross during a phase. The amount feels large, but when you count, it's often not more than the amount of cyclists that cross in the next phase, and they take up just a tiny fraction of what cars need.
Sure it absolutely makes sense. But for me and my eyes 200 people passing by are somehow still less "busy" than 25 loud and stinky cars. That's what I mean with I need better wording
Generally, the busiest streets are pedestrianised; you just can't move that volume of people in cars.
(Actually, the _very_ busiest streets are probably major bus gates (where, again, there are no cars), those can have fairly ridiculous density at peak times.
"TNO tested in-use vehicles directly at the tailpipe. Three diesels with DPFs emitted: 3.9–5.3 million particles/cm³ at warm low idle. The same report measured warm Euro 5 direct-injection gasoline cars without gasoline particulate filters at: 50,000–60,000 particles/cm³ at low idle."
"In 2017, the highest diesel was approximately 12 g black carbon/kg fuel, versus roughly 0.4 g/kg for the highest gasoline car.
In 2023, the highest diesel was roughly 8 g/kg, versus approximately 0.7 g/kg gasoline."
"approximately 5% of measured Euro 5b/Euro 6 diesel vehicles exceeded one million particles/cm³, and this small group produced more than 90% of the particle emissions from the tested diesel group"
If you click the link at the top you'll find it goes to an article. The article will often expand upon the text in the link!!!
In this case:
"While we would expect children's lungs to grow year on year, our results indicate that the London children's lung growth had accelerated during the four years to 'catch up' with the control group in Luton to reach similar levels of lung capacity," researchers say.
"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC.
"The speed of catch up in lung capacity in the London group was surprising and impressive."
While having something done at Stanford's hospitals, at one point I was placed in a room with signs indicating it was on a heavily filtered ventilation system rated for COVID, etc. It was striking to be in an environment with air almost to clean room quality.
This is a reminder that getting an air purifier with high airflow filters (NOT HEPA!) is lifechanging in cities with high pollution levels.
I recommend getting one of these https://www.youtube.com/watch?v=sQGfO4hNb60 and just slapping a MERV 12 to 16 filter on it, you can get a whole roll off aliexpress for cheap and replace them monthly if you wanted to and it would be cheaper than 1 hepa filter replacement. They can also filter vastly more air, while you can keep hepa for 6 to 12 months MERV will filter a lot more air.
I've been meaning to do some data mining on how much PM2.5 differs with even a few hundred feet of elevation. I have a theory that even around Silicon Valley, living even up a little bit in the foothills would have you breathing massively cleaner air most of your life vs living in the pits of the valley. I see it all the time when I'm out there for recreation or just driving, the smoggy haze all over that just sits in the valley and the Bay. It's probably not too tough of a data processing challenge to compare the stats on Purple Air AQI sensors in reasonably close geo proximity vs elevation to get some statistically-significant data on this.
100%,
and not just due to no emissions / minimal break dust.
The noise reduction is a massive dividend. I used to live in london 10+ years ago, and when I come back I’m stunned by the noise difference, it really is so much quieter especially in central london. EVs everywhere especially replacing the horribly noisy diesel black cabs and buses. Very noticeably different and much more pleasant, and improving all the time as EV adoption continues to accelerate, hooray
London's also been putting effort into improving safe bicycle routes lately. I visit London every few weeks and if I'm going somewhere in central, I'll often just grab one of the Santander hire bikes instead of the tube. Well, most of London (looking at you, Royal Borough of Kensington and Chelsea)
In some areas of London the ULEZ has been so successful that the measured NOx is now coming mostly from gas boilers used for heating, probably mostly old large commerical units.
So shifting from gas boilers to heat pumps and from gas ovens and stoves to electric/indusction is also beneficial.
EVs use regenerative braking. So they hardly produce any brake particulates. And the tire particulates are heavy so they don't stay airborn for nearly as long. At low speeds, tires don't wear out as quickly.
Europe has quite a few cities where traffic is increasingly discouraged from going to the inner cities. Cities like Paris and London are much transformed from what they used to be and it shows in the health statistics.
It's not just the particulates but also nitrous oxides (nox) produced by combustion engines. Nox is correlated with lots of health issues. Take it away and you see lower rates of chronic lung issues, cancer, development issues with kids, etc.
But yes, tires are also an issue. But a fairly minor one to anything coming out of a combustion engine.
Mass transit indeed is nice in big cities. Removes the need for taking the car.
There is a generator at the end of my street in a shipping container sized metal box, it also has a mini office and loo, and is used by the construction workers digging holes in the road. It has company spiel written on the side, promoting the box's environmental credentials, including the punchline: 'Zero NOX when generator not in use'.
Might instead refer to a start-stop / battery backup kind of system, where idling-but-on doesn't burn any fuel, but sudden loads can still be serviced.
Do the numbers in that article make sense? 5.8g/km for tyre wear? Generally my tyres last maybe 25000 miles. So at that rate they would lose 230kg. Seems high.
"Non-exhaust emissions (NEE) are particles released into the air from brake wear, tyre wear, road surface wear and resuspension of road dust during on-road vehicle usage."
Regen braking means significantly less brake dust, especially at city speeds and with blended braking.
> Although…rail might solve those?
Trains still have brakes. Some can regen brake but because they usually don’t have batteries they need the rail or overhead gantry to support inputs.
But on a passenger-mile basis, I expect an electric train produces essentially no particulates compared to a car, even a light rail on tyres. I do not however have numbers.
For all that I did not care for them originally this is probably something full-height platform screen doors help with, assuming the trains themselves are also filtered that would keep the pollutants clear of drivers and users, although it does not exactly resolve the question of managing their presence in the tunnels themselves (and track / tunnel maintenance personnel should probably already be wearing respirators if not full breathing apparatus), and I could see things get pretty dire in case of breakdowns.
Impossible to retrofit, of course, but what helps more are big tunnels. Modern ~9m diameter single tunnel systems are a lot better for this than old 3.5m diameter double tunnel systems.
Tyre, no, but regen braking almost eliminates brake particles at the speeds I drive in London. But mostly I take the train. Unfortunately the highest I measured on my particulate sensor is not near the roads, but in the tube.
Electric vehicles are stills cars. But better than gasoline and especially diesel cars.
So yeah.
That said not clear to me about PM2.5 is I've never seen anything legit seeming that tries to characterize the harm based on the type/source. Though it seems agreed diesel is especially bad.
I use air purifiers mounted on my windows, running continuously except in the deep summer and deep winter. This makes my air contain 50-100x fewer particulates than the outdoor air. In contrast, the best I can achieve with floor air purifiers as people have them is a 5-10x reduction. The window purifiers also keep excess CO2 and VOCs out.
> The window purifiers also keep excess CO2 and VOCs out.
I assume you mean that the increased air-exchange (purified or not) helps CO2 that originates inside the house to leave promptly? (Equalizing it with the outdoors.)
Literally "keeping CO2 out" is a much trickier and more-expensive proposition.
Health improvements are not measurable any more if you go below 5 mcg/m2 average level of PM2.5 particulates. For 50x reduction to be beneficial, you need to live in an area where the pollution is 250 mcg/m2, which is an extreme level found only in a few unfortunate places on Earth. 5-10x reduction is reasonable almost everywhere.
I know precisely the subjective difference between a 5x reduction and a 50x reduction. Only the latter feels sufficiently good to me, and my brain operates better with it. You will know it when you experience it. Maybe it's my middle-aged brain that needs the extra support. I live in an urban area near traffic. Lately there intermittently also has been wildfire smoke coming down from Canada.
Yes, the filter absolutely has an activated carbon layer in it in addition to a HEPA layer. I understand that activated carbon doesn't last long. I have been changing the filter every two months.
Note that because this purifier is mounted at the window, it filters incoming air from outside, not the indoor VOCs that are already in the residence. The indoor VOCs will simply have to get exhausted from elsewhere due to the air pressure.
What I am suggesting is that my need for activated carbon is slightly less because I am rapidly pushing the VOCs out in the resulting exhaust.
I live in British Columbia so we have fairly good air quality. But with the yearly fires lately summer air some years is poor. So one year with the fires smoking and air quality getting poor I got an air purifier for my kids room and the living room.
It is only anecdotal but right away if felt like he had better sleeps. The smoke wasn't thick as it was from fires hundreds of miles away and it wasn't like any of us were hacking or coughing crazy but in hindsight I felt that my young son who would have been effected the most slept better and his breathing at night seemed quieter and easier.
There is a big difference between believing something is true, and demonstrating it is true and measuring the effect. One is a vibe. The other can drive policy.
Are you suggesting that it would be advantageous for humanity to evolve to live in London circa 2000?
Larry Niven played with this in one of his stories; a time traveller from the far (and highly polluted) future has to use mechanical breathing assistance, because the levels of CO2 in the air in the past weren't high enough to prompt the breathing response properly (human breathing is controlled largely by blood CO2 levels).
Asthma is so common that this is not only easy to test, but has been. That's what the article was about.
Anyway, by your own line of thinking, wouldn't sensitive lungs be an advantage? The incentive to find cleaner air is also breaking away from the pack. Since humans are social creatures, that's more likely to look like new leadership for followers who have their own reasons to break away.
Every civilization in history has started out that way. It takes more than mere brute force to beat the competition. Survival is just as much about picking your battles and working smarter.
China has 350 million electric two-wheelers, 20 million EVs. China reduced air pollution from transportation by 80% in a decade.
Delhi: 442. Lahore: 334. Beijing: 16. These are the levels of PM 2.5, one of the principle measures for air pollution, on November 19. How China cleaned up its air pollution – and what that meant for the climate: https://theconversation.com/how-china-cleaned-up-its-air-pol...
A few things standout to me from the article.
1. London when the ULEZ was brought in was already a lot less polluted than historically.Are there gains from that? London was not that bad by global standards.
2. This was followed by the benefits of COVID lockdowns (not a phrase often used!) as pollution dropped much further.
3. Is this effect even across London? Suburbs vs centre, different types of housing etc.? I grew up a the edge of London and the difference in pollution was visible (i.e. you did not need instruments to see signs of it).
4. There was also a reduction in sales of diesel cars which had been heavily encouraged (because of lower CO₂ emissions) in previous decades.
5. As the articles notes, there have been a lot of other changes at roughly the same time. It only mentions one, but there have been significant lifestyle changes, so a lot of potential confounding variables.
1. Less than historically still has a quite high baseline compared to after ULEZ - if it was more polluted, presumably the change seen here would be more dramatic.
2. Definitely kickstarted it, but we're looking at taking that impact and continuing it for some 5 years after covid ended now.
3. You can look at the ULEZ map and it really covers everything but the outer tube line suburbs [1].
5. The control group in Luton, presumably, has the same lifestyle changes - it's not that far away (about 30 miles), so it is as close as you can get to a one to one comparison, not accounting for the fact that Luton is likely to be more deprived than London (especially in the council estates, which have horrible reputations).
[1] - https://tfl.gov.uk/ruc-cdn/static/cms/images/ulezdetailedmap...
1. yes, but there was probably a bigger gain before. Confirmation would be good.
2. does the study separate impact during lockdown from after?
3. my question is whether it had the same impact everywhere. I would guess very much not.
5. the impact of those changes might not be the same from a much better baseline, nor are lifestyle changes the same in a big city and a small town.
Wouldn’t most of those effects also be in the control group too?
Much smaller place and starting from a better baseline so they would not have experienced the same changes.
Anecdata I was living very close to a busy highway, and my young daughter was wheazing when she had a cold, we had to give her medicine via a nebulizer. When we moved out to the country more, far away from any major roads, these issues all disappeared within a couple months.
Living very close to busy highways is known to generate poor air quality. I recommend anyone in those locations buy an air purifier for their kids' rooms.
I bought a couple reasonably priced HEPA purifiers and I change the filters on schedule. Replacement HEPA filters are very cheap.
Also watch out for things that we do indoors that can generate bad air quality. I had a friend who bought a VOC meter and noticed very high readings in his kid's room. He traced the source to his chemical and paint cabinet nearby, which he never considered because he couldn't smell anything. Throwing out a lot of the old containers dropped the measurements to the unmeasurable range.
HEPA filters are counterproductive in standard air purifiers. Air purifiers pump their cleaned air directly into the dirty air of the room. It doesn't matter if that cleaned air is extremely clean, because it's immediately mixed with dirty air. What actually matters is how much clean air you produce: the "clean air delivery rate" (CADR).
The more effective the filter the more it restricts airflow. If a filter is only 99% effective instead of 99.99% but allows double the airflow, it provides nearly double the CADR. To benefit from HEPA you need a clean side and dirty side, like in a clean-room setup.
https://en.wikipedia.org/wiki/Clean_air_delivery_rate
You don't need to seperate the clean and dirty air. Mixing them isn't as efficient but it should still be roughly 63% efficient (1-1/e).
A reasonable compromise is achieved by an air purifier that has the outlet on top because it’s blowing the filtered air well away from the inlet side and generally circulates the air in the room.
I used to work in the cleanest room in the state, that wasn’t a lab, back when I lived in Adelaide, and top-inlet button-outlet in a raised floor data centre is how the air handling units in the main data hall worked, so you can simulate that to a certain extent.
> The more effective the filter the more it restricts airflow.
This isn’t the whole story. Surface area and flow rate are factors.
A residential home is aiming to improve air quality, rather than grow flawless silicon ingots etc.
If you only use 99% it means there are small particles you can't catch. Being faster is meaningless if you can never clean the air.
Air purifiers are designed to run 24/7 and all they do is catch particles. Eventually all the particles will be caught. The one I got also detects if there is a lot of particles and will spin faster accordingly.
Any air purifier should be able to cycle the air in a normal room often enough that it should be quite clean in a short time.
What you wanna say is it might be more efficient with more CADR per minute with less filtration than less CADR an a higher filtration.
But a HEPA filter is better than no filter. Even if would be more effective with another.
(Also depends on size of hepa filter and room to clean. Large enough filter and small enough space and Hepa can clean all the air)
If the purifier can filter the air more quickly than air leaves the room it'll still reduce the amount of pollutants in the air. Most people aren't going to create a "clean side" and "dirty side" setup for filtering the air in a room.
I think that is what they're saying: the point is that if you're doing this, you don't want to optimize for the cleanest air leaving the filter, but more for throughput.
what a nice externality example "I recommend anyone in those locations buy an air purifier for their kids' rooms"
I drive the car, you buy the purifier.
If you’re so inclined, you can build your own air purifier with laser cut panels or 3d printed panels and use a cheap ikea air filter and standard PC fans. All the parts are readily available, and user repairable.
If you pair if with an Apollo AIR-1 you can have home assistant ramp up and down the fans with a PC fan controller based on live readings of PM2.5 in your home. I did this with the help of Claude code.
https://www.thingiverse.com/thing:6826527
https://makerworld.com/en/models/2470181-nukit-tempest-euro-...
Didn’t the Apollo 13 crew make an air scrubber out of duct tape and hope? Surely a cardboard box, a box fan and a hepa filter covered in tape gets you 90% there
if you're going to IKEA for the filters you might as well buy the whole purifier. it's cheap and it works well
I really wish the DIY folks would measure the airflow and sound levels on this sort of thing. CADR and decibels are going to vary wildly with fan choice
I came across this site which has pretty comprehensive data about PQ curves (the chart for determining CADR given filter impedance) at different noise and power levels: https://www.cybenetics.com/evaluations/fans/204/ (many other fans tested as well but I've been liking the value of P14 Pro PST)
However they look somewhat commercial and I'm not sure the funding/incentives so definitely corroborate with other sources.
It's a good start, but for VOCs and gases you'll need activated carbon. Those 2-in-1 filters do exist but cost more. And many are scams because they don't have enough volume of activated carbon.
Getting rid of the VOC source, if possible, is much easier than trying to filter it.
> Those 2-in-1 filters do exist but cost more. And many are scams because they don't have enough volume of activated carbon.
Any filter with a little bit of carbon added is going to be useless after a few days, or maybe even hours.
The only VOC filters that work have multiple pounds of carbon, with the good filters having upwards of 10-20 pounds. It also has to be replaced regularly.
I was referring to the gases from the cars on the highway more than easily removed indoor sources.
My common winix air purifier has a replaceable carbon filter.
Why would they cut corners? Activated carbon isn’t expensive.
Because it’s not obvious to most customers that a corner’s been cut. Same reason most new construction in the US sucks.
You can safely put a washer and dryer on the upper floor of a house if you add a proper floor drain, but you’re unlikely to see anyone add a floor drain in new construction because buyers aren’t looking for it. Now multiply that by everything a buyer isn’t looking for and you’re talking real money.
> You can safely put a washer and dryer on the upper floor of a house if you add a proper floor drain
European here, we've always been placing washer/dryer stacks in our bathrooms without needing floor drains. We have machines with a system called Aquastop [1] that stop the water flow if the machine detects a leak inside the system.
[1] https://de.wikipedia.org/wiki/Aquastop
You have companies choosing the component that cost 10 cents instead of 15 cents even if the 10 cents component will break 10 times faster than the more expensive one.
You simply cannot put enough activated carbon in a little foam thing that goes in front of a filter to do anything useful.
The real activated carbon filters have 10s of pounds of carbon. The little black foam thing that comes with those 2-in-1 carbon filters is useless.
And manufacturers do a sneaky swap too, my Coway 150 which is a great air filter by the way, came with a nice thick grid of hexagonal cells each filled with carbon granules - that insert alone weighs like half a kg. I ordered official filter and carbon filter replacements off their website ....got a thin carbon "foam" that weighs maybe 50g instead.
But it does cost money and so… corners are cut
The clue is in your name
Also he had the kid switch to smoking filtereds
Agreed, just buy air purifiers with HEPA filters and change them regularly. The main expense is buying one for every room, but it's one of those expenses you wish you had made sooner.
DHH is also a fan (pun not intended?): https://world.hey.com/dhh/air-purifiers-are-a-simple-answer-...
Might be better to upgrade your air handler if you're putting HEPA in every room.
NO2 is a very hazardous air pollutant which doesn’t get a ton of attention. The main sources are combustion engines and gas stoves. Asthma looks to be mostly caused by gas stoves.
I’ve got a sensor that can detect no2 and it noticeably spikes when using gas. Switched to induction after that.
>Asthma looks to be mostly caused by gas stoves.
Do you have a source for that? Because as far as I can see, asthma isn't _that_ less common in countries where gas stoves are barely used, such as germany. Still has like 60-70% of the asthma cases the US has. There's also a ton of other pollutants the US hasn't yet forbidden, but the EU has, which could also explain a lot of the difference in rates.
Don't get me wrong, it's certainly a good idea to get rid of gas stoves. I just think it's a bit much to declare them the primary cause of asthma.
This was in the news last month and might be referring to the same source
'Replacing gas stove can help asthmatics as much as some drugs, US experts find'
https://www.theguardian.com/environment/2026/jul/24/replacin...
Germany has a ton of NO2 for other reasons, for example diesel motors
I’ve often wondered about this.
Does the area immediately above where the gas stove was have an exhaust fan that vents to atmosphere?
I would have assumed a properly specced exhaust fan would capture and remove combustion products from a gas stove?
Can you smell what's being cooked on the gas stove? If so, the combustion products from the stove are also reaching your nose.
I’ve never once been in a property that had an exhaust fan sufficient. I’ve had the exhaust on full blast and the spike on the air quality sensor on another floor of the house is rapid and massive.
I suspect a sufficient ventilation would require something more like a lab fume hood that can pull a negative pressure on the area around the stove.
And from what I have seen, a good number of exhaust fans are straight up fake and just ventilate back in to the room rather than ducted outside.
> And from what I have seen, a good number of exhaust fans are straight up fake and just ventilate back in to the room rather than ducted outside.
Culinary Cargo Cult.
Doctors used to prescribe a "change of air" in the 18-19th centuries. Maybe they still should.
Sanitariums
https://en.wikipedia.org/wiki/Sanatorium
I guess the modern descendants are the health retreat, the rural airbnb, and the day spa that offers oxygen therapy.
I wanted to long for the time when people hated "Malaria" and wanted to move to "Beunos Aires". But they believed the arrows chase us at daytime and the plague engulf us at night, like in the Psalm.
https://en.wikipedia.org/wiki/Luftkurort
I don't understand why we keep on building right next to highways which are some of the worst things for our health. You don't need to live in the countryside for that. Just stay roughly 1km away from them and the situation is significantly better.
There is evidence of a lot of ugly diseases caused by this, without even mentioning the constant 40+ dB background noise.
In London that is difficult – there is not a lot of space.
Plus the idea of having everything within a 15 minute walk including access to public transport.
highway != public transport
And pollution from bus or tram is much easier to control. Looking at you petrolheads who like to "Rolling coal"
A friend of mine does research on air pollution from cars - the TL;DR is you should not live within a third of a mile of a highway. The falloff is pretty sharp, but you don't want to be in that zone.
What about biking near a highway? E.g. in Chicago the lakeshore bike trail is next to a busy 8 lane highway
I remember I’ve read somewhere that jogging is actually net harmful for health in the city due the air pollution.
Shame you cant remember the source. Ive long since wondered if its actually more deleterious for my health to cycle to work in London due to air quality. I came to the conclusion that youre damned if you do and damned if you dont in the end, as in London at least, many of the tube lines have particulates higher than is considered safe
Probably depends on the tube line; one of them, can't remember which now as I left the country in 2018, left me with black snot on each use. Cycling wasn't that bad, but neither were the other lines.
https://www.telegraph.co.uk/news/health/news/10817787/How-ch...
Generations of men have been taught that when walking with a woman on a pavement, they should always take the side closer to the road allowing her to keep further away from the traffic.
But Dr Iarla Kilbane-Dawe claimed that Londoners should avoid walking too near the kerb because on busy streets, air pollution can be up to a third higher than on the inside of the pavement.
So in effect, if you want to be the chivalrous man (which no one forces you to be) you still should choose the roadside side of the pavement.
Doesn't it depend on the mix of diesel/petrol/electric? In particular many cities ban or restrict diesel.
Tyre pollution is significant regardless of fuel source.
EV's have 100% reduction of NOx/tailpipe VOCs, 100% reduction in soot/tailpipe particulates, 70% reduction in brake pad dust (due to regenerative braking), in exchange for 25% increase in tire wear.
Vehicles are capped at emissions of 3mg/mile of particulates and 30mg/mile of VOC's. Something like 1-2mg of tire material actually becomes airborne PM10 particles every mile (and only about 10% of that for PM2.5 particles).
So, EV's really do a great job reducing emissions from 35mg/mile to <2mg/mile (PM10) or even <0.1mg/mile for PM2.5. A 95%-99.8% reduction in air pollution near highways would seem absolutely fantastic for me and my children!
https://pmc.ncbi.nlm.nih.gov/articles/PMC11636205/#:~:text=W...
Needless to say, the brake pads have never been touched and when I saw the left front one at around 110,000 to 120,000 to patch that tire, it looked like it was just installed. The regen braking almost completely eliminated the brake pad or rotor as a wear item.
Until one has a battery thermal runaway event.
Or an entire truckload of batteries catches fire.
StasheD is an engineer and firefighter, quite eye opening.
https://youtu.be/diaUMNONpvw?si=7lxYS8iJHLvCTUkt
What about the vicinity of large or uphill streets inside a city? I am curious how the data compares with highways.
Notably, most major cities have been building tons of housing (especially ‘affordable housing’) right next to highways, as it is the only areas that aren’t already built out with tons of high value houses.
Surprise surprise.
It's a dumping ground for poor people.
It’s not like they do it on purpose rubbing hands
Housing development happens at random?
Woke activists love the word "systemic" for a reason.
If a bunch of good people acting in good faith produce a result an evil mastermind would want does it matter if they are good? On many levels obviously yes, on some practical levels the system and the incentives still need to change.
My anecdote would be the revesre.
Living in the country gave me bad hay fever/asthma in the city much less asthma.
You discovered that you have an allergy.
Not exactly the same thing.
Same. I visit my family in London and my sleep improves because of no hay fever. Though then I get black boogers, horrible chalky hair, a renewed sense of misanthropy etc
You need a NMAID Non-Misanthropic Anti-Inflammatory Drug.
As long as the country doesn’t involve large scale farms because the glyphosate sprayed on them causes serious issues.
There is a chap in London who does some great work with researching and spreading awareness of air pollution:
https://clara.southlondonscientific.com/
He also runs this repo:
https://github.com/southlondonscientific/aeolus
Using scientists being "stunned" should take the same amount of relevance as someone being "slammed" in article titles.
It's a direct quote from one of the scientists:
'"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC."'
The BBC should have put it in quotes in the headline; I kept the HN title faithful to the original article.
I agree. Though they did at least put it in quotes in the first sentence, which I hope doesn't indicate how far people are generally getting through an article before commenting on it on Hacker News.
I know, generally it is not a direct quote, hence "should."
Scientists are only allowed to be stunned when results exceed 5 sigma of deviation
Or when their papers are retracted for political reasons.
To be fair, BBC is aimed at the normies, not the scientifically literate. (No hate on BBC!) Stunned probably gets more clicks than surprised.
Smokers don't magically undo the damage they did to their lungs after they stop smoking. Stunned might be hyperbole, but it is at least a little bit surprising.
> “ Smokers don't magically undo the damage they did to their lungs after they stop smoking”
Except that they do undo the damage.
“ After 15 years, your chances of getting lung cancer are almost the same as someone who has never smoked.”
https://www.nhs.uk/conditions/lung-cancer/prevention/
4x the rate is "almost the same"???
https://www.verywellhealth.com/risk-of-lung-cancer-in-former...
The lifetime risk is approximately 1.3% for women and 1.8% for men. For regular smokers: 11.2% for women and 14.8% for men. So about 15 to 30 more likely to get lung cancer. Bringing that down to 4x is close to "almost the same".
Might be that I am not reading probabilities correctly, but how do 1.3% -> 11.2% and 1.8% -> 15% become "15 to 30 times more likely"? Sounds like less then ten times?
They absolutely do! Not all the way, but if you'd have smoked a pack a day for 15 years and then have given up for the last 15, there's absolutely no way you'd be saying this!
Hey here is something for you to stun on:
https://old.reddit.com/r/OldSchoolCool/comments/1v73w9s/hydr...
"Stunned" isn't really a scientific term. It's the sort of editorializing you should expect to come from people who aren't the scientists themselves. More than hyperbole, it is classic click bait.
Also, quitting smoking definitely eases a number of symptoms, especially if you're not at the point of chronic emphysema. The reduction of inflammation triggers alone after a bit of time is fairly significant. Less coughing, less mucus buildup, etc.
But this isn't that at all. "Stunned" is used here because it's the word one of the study's authors actually used.
'"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC.'
Sounds like an announcement of the latest AI news from Wes Roth. I'm surprised the Professor wasn't "shocked"
I'd like to imagine the stunned scientist is a scientist from another field, they show some medical findings to a guy who looks at snail butts all day and he's the one "stunned" by the findings
The scientist who used the word "stunned" is one of the study's authors.
I'm obviously supportive of less pollution etc etc but looking at the actual graph results I wouldn't describe them as 'stunning', the needle barely moved. But of course, they have to have something to make headlines after spending so many million on the study and who knows how many billion on ulez. I'm not one of these anti ulez people I think it's good. But you can imagine the pressure to spin tepid results into headlines.
The entities with a ton of money tied up in the ULEZ are, perhaps with a layer or two of indirection, are likely the same ones funding this research, or if not this research then the guy across the hall in the same lab.
> strongest evidence yet that local clean air zones could help reduce some of the harm caused by pollution during childhood.
It's incredible this is even in debate. It's one of those intuitive things well known since the reduction of coal burning and smog during the industrial revolution in London?
The right (Conservative) and far right (Reform) parties both say they will abolish low-emission zones and other measures to reduce pointing traffic.
They made it into a culture war topic.
The right latches onto anything where a small minority are upset and amplify it. They are the ultimate rage baiters.
Somehow I don’t think that is the exclusive domain of the Right.
It is not, but all they have to offer.
Fact check, the conservatives want to block the expansion into outer London. Reform wants to end them all.
Bloody Sadiq Kahn and his militant sharia ulez improving the health of forriners. /s
You joke, but of course...
https://www.theguardian.com/politics/2023/aug/01/fake-tweets...
I've needed my inhaler way less since the ULEZ came in.
Visiting London used to mean blowing your nose to black snot for a week afterwards, these days living in London it's pretty good.
ULEZ massively reduced the amount of NO2, which is a trigger for asthma. It also seems to have reduced the hospital admissions for heart related emergencies.
Sources:
https://www.bbc.com/news/articles/c75q9d2pqyeo https://www.theguardian.com/environment/2026/jun/12/emergenc...
I've not lived in London for more than a decade. I always thought the black snot was from the Tube. Is it not?
Yup, especially on the older lines (Northern, Victoria, Jubilee, Bakerloo). Particulate pollution can be two orders of magnitude higher than at street level. This tends to be glossed over when trumpeting the success of ULEZ measures pushing people away from cars and onto public transport, and I say that as a non-car-owner.
People tend to walk 10-15 mins at either end when taking the tube, and will walk more through the day. My understanding is this activity is net positive despite the extra particulates while on the tube. I might be misremembering this with a study I read on cycling in road pollution though
Almost certainly some asbestos dust still in there from prior decades as well, the tube is absolutely filthy and never cleaned properly
Indeed.
https://www.theguardian.com/uk-news/2026/jul/18/london-under...
I've lived in London all my life and I only get black bogeys on days that I've been on the tube. Before COVID that was every day.
I lived on Upper Street in Angel, London by some traffic lights and there was always a layer of black dust inside. I assumed it was brake particulate.
Tire wear was probably a greater source than brake wear.
Every house inner London is covered in black soot from the days of coal fires. Have you ever seen one after it's been sandblasted?
It is, but not just from it.
Anecdotal, but similar situation here for me (I don't need an inhaler, but visiting London around 2015 meant blowing my nose to black snot for a week, and then back in 2024 it was completely fine)!
More anecdata: I've been using my inhaler more since moving to a city with worse air quality than my previous location.
People don't fire their chimneys or have garden bonfires much any more, either.
Pretty sure that's due to the tube.
What's so uniquely bad about the tube in London? Poor ventilation and brake dust?
Its the oldest metro in the world. An achieviement, yes, but in old stations ventillation is crap, materials are poisonous, etc.
Yeah, seems way better now than it was in the 90s though. They’ve improved the ventilation a lot.
I grew up in a small town in the mountains in Norway. There is a children's "hospital" there (Geilomo Barnesykehus), where kids come to live because they can't live in the cities. Kids with severe asthma, eczema and some other conditions. It started as far back as the 1930s, still unfortunately a problem so kids have to come live there away from their families.
My anecdata: I have a Japanese friend who was born in 1964. She grew up in Yokohama for the first ten years. Japan didn't pass its first (serious) environmental protection law until 1967. She said many, many of her friends had asthma. Fast forward 50 years, very few children have asthma in Yokohama.
I will never forget watching this documentary about a Canadian man, Doug Rogers, who went to Japan in 1964 to train martial arts at a dojo. This YouTube video[1], watch it from 1:00 to 1:10. The air pollution is simply stunning. It shows you just how terrible the air pollution was in Tokyo in 1964. Today, it is night and day. The same is true for most large cities in highly industrialised nations.
[1] https://www.youtube.com/watch?v=CBFx1a4L2ig
completely anecdotal. my earliest childhood memories in india were of asthma, sinusitis and constant cold. this was consistent until i was 26 and since then I've moved to the US and lived in New York with 0 days of sinusitis or breathing trouble. and i fallback to trouble breathing when i go home again.
even New York is so much more better than Bangalore or my small village in the middle of coffee farms
Bangalore has historically (over decades) been known to have a high incidence of asthma due to the high pollen in the air. It's been made worse in recent years due to pollution. The pollen is present for a significant portion of the year while other pollen regions in the world tend to have it for a smaller duration.
During my childhood, I lived across the street from a brewery. I suffered from chronic sinusitis for years, and no one understood the cause. When I moved to a different part of town, the problem immediately stopped. The same thing happened to one of my classmates who lived in the apartments next to me.
Yes, pollution has both acute and chronic effects. What you describe here is an acute effect.
I just made a comment about having good air quality but with summer fires we were getting smoke for weeks at a time so I got an air purifier. My kid wasn't struggling horribly but I did notice right away after putting one in his room that he slept better and his breathing seemed so much more relaxed at night and it just felt like it made a noticeable improvement to me.
What is more amazing to me is I thought this wouldn't be localized. I thought we have on earth and one atmosphere but clearly not? Like the standard of living can wildly change if we change our own local area. We don't need people in Montreal or Paris to come up with a plan?
So unlike greenhouse gases, which can last in the atmosphere for years, seems like NO2 and particulates only stay in the air for less than a day or a few days. This is an amazing little fact because we can start small and call for meaningful reform where we live without requiring a global coordination. Maybe there will be a global consensus later but it doesn't matter because we can start making improvements today within our own local context. The bonus is we will likely also lower our own carbon footprint as we reduce our other emissions. I think this is the "selfish" breakthrough we need to convince people.
When I say it doesn't matter, I don't mean like cross border contamination does not happen but rather that we can improve our own lives with our own action regardless of what others do.
The obvious actionable thing that you can do for your own life is to stop using or being around gasoline or petrol powered two stroke engines such as in a leaf blower. But we can do more. We can completely ban these two stroke engines from being sold at all and that will bring meaningful improvements in weeks, not years.
The problem is to make more impact, we will need to actually get people to give up or retrofit their existing equipment. We will need to educate people about the harms that these things cause and why the change is good. However, in today's siloed world, I don't think it will be easy at all. So perhaps the most difficult part ironically in a very connected and yet siloed world is the marketing of this idea and connecting the required change in behavior with the benefits.
As we saw with the leaf blower example, the costs are concentrated, yes but so are the benefits! The benefits are NOT at all diffuse because guess who benefits the most from not inhaling in gasoline fumes? The person operating the leaf blower!
The localisation of it struck me when I read an Irish EPA report on traffic-related air pollution a few years ago that recommended carrying your child if you were walking regularly near heavy traffic. The air at 0.8m (their breathing height) has 5-15% more NOx in it than the air at 2m (the height they would breath at being carried by you).
I remember reading something similar about walking on the part of the pavement furthest from the road, because being an extra meter or so away makes a big difference
A quick note for my fellow US Americans -- A British speaker calling it 'pavement' is referring to what we call the sidewalk.
Most air pollution is pretty localized. CFCs and greenhouse gases are the biggest outliers for how global their effects are.
Link to the original study below, free to access [0]. The key data appear to be this:
>At baseline, 184 (14%) of 1280 children with successful FEV1 measurement in London had a clinically low FEV1 (pre-bronchodilator FEV1 <80% of predicted value) compared with 126 (9%) of 1339 children in Luton (appendix p 8). At the end of the study, these values had dropped to 51 (9%) of 585 children in London and 41 (7%) of 606 children in Luton (appendix p 8).
So the proportion of children with low lung function dropped from 14% to 9% in London, and from 9% to 7% at the comparator site in Luton. It's not that much different, though any improvement is obviously welcome.
https://www.thelancet.com/journals/lanpub/article/PIIS2468-2...
Seems electric cars produce the same or sometimes more non combustion particulates than ICE cars, eg. bits of road and tire that are flung into the air while driving.
So EVs are better than ICE for air quality, but fewer cars even better.
I think it’s mostly break dust. Electric cars are heavier but can also hopefully mostly use regenerative breaking instead of break pads. Road vibrations (and wear?) tend to go as the fourth power of weight over the axle and so it tends to be worse for (naturally heavier) electric cars but even worse for goods vehicles.
> Initial results showed children's lungs in London were smaller in capacity than those in Luton
Sure but they had to live in Luton
Newsflash, living in a healthy environment is healthy!
Of course, but governments and corporations have consistently argued otherwise.
In the UK's far-right media culture, Khan's ULEZ is painted as fringe extremism, not as a common sense public health measure.
It was news to me that the lung damage from pollution isn't necessarily permanent in children, if a change in environment happens early enough. Up until reading this, I was under the impression it would be.
We had a lot of construction work in the neighborhood, our house covered in fine dust particles each day. My kid got asthma in the same period, keeps asking when she can stop taking the medicines, and I say "I don't know" thinking "probably never". But maybe now the construction work is over, there is hope? (And if construction starts again, we know that it is better to move, because there is hope.)
Pointless anti-intellectualism.
There is a big difference between believing something is true, and demonstrating it is true and measuring the effect. One is a vibe. The other can drive policy.
Opinion article on this by Sadiq Khan, the London mayor who introduced ULEZ:
https://www.theguardian.com/commentisfree/2026/aug/18/ulez-h...
The sad thing is... when the ULEZ went into effect, there were some wild conspiracy theories about it. Suddenly even my father was an expert and viewed it as sinister government intervention - all because of youtube crackpots. I couldn't get him to relate to my view that cleaner air must be a good thing.
I bet if some youtube weirdos pushed out videos against "big soap" for making us unnecessarily clean our hands after pooping... we'd have a growing following of angry "freedom from big soap" people.
> I bet if some youtube weirdos pushed out videos against "big soap" for making us unnecessarily clean our hands after pooping... we'd have a growing following of angry "freedom from big soap" people.
At one point during Covid, I tried (not very hard at all) to float a conspiracy that the vaccine was in fact not the poison, but the antidote. That Covid was deliberately designed by governments to filter the 'independent thinkers' (who won't take the vaccine) from the sheep (those who do take the vaccine). So by not taking the vaccine, you were giving the governments what they wanted.
This was because the conspiracy that governments were killing the loyal sheep with the vaccine, therefore only leaving the 'independent thinkers' behind, made absolutely no sense at all to me.
When I talk about health implications I often end up saying "but it's less bad than living next to a street" which statistically many things we spend time optimizing about are.
However most people live next to a busy street ...
The street isn't the problem. Cars and trucks are. If those streets were filled with people walking, cycling, etc., the health penalty of living next to one would vanish overnight.
A street full of EVs in a traffic jam is also pretty good. No exhaust pollution and low tire wear due to low speeds and low acceleration.
Ok that's not what I consider a "busy street" but I get your point, need better wording there.
Why not? A lot of streets often seem busy simply due to the incredible space inefficiency of cars. What I like to do sometimes, when I wait at a traffic light with my bicycle, is to count the actual number of cars that cross during a phase. The amount feels large, but when you count, it's often not more than the amount of cyclists that cross in the next phase, and they take up just a tiny fraction of what cars need.
Sure it absolutely makes sense. But for me and my eyes 200 people passing by are somehow still less "busy" than 25 loud and stinky cars. That's what I mean with I need better wording
Generally, the busiest streets are pedestrianised; you just can't move that volume of people in cars.
(Actually, the _very_ busiest streets are probably major bus gates (where, again, there are no cars), those can have fairly ridiculous density at peak times.
- Fuck diesel cars
[0]: https://www.zh.ch/content/dam/zhweb/bilder-dokumente/themen/...
"High diesel-family averages were approximately 1–3 g NOx/km. Most gasoline-family averages clustered around approximately 0.02–0.15 g/km."
[1]: https://publications.tno.nl/publication/34635198/KxBBl3/TNO-...
"TNO tested in-use vehicles directly at the tailpipe. Three diesels with DPFs emitted: 3.9–5.3 million particles/cm³ at warm low idle. The same report measured warm Euro 5 direct-injection gasoline cars without gasoline particulate filters at: 50,000–60,000 particles/cm³ at low idle."
[2]: https://d-nb.info/137495313X/34
"In 2017, the highest diesel was approximately 12 g black carbon/kg fuel, versus roughly 0.4 g/kg for the highest gasoline car. In 2023, the highest diesel was roughly 8 g/kg, versus approximately 0.7 g/kg gasoline."
[3]: https://trueinitiative.org/insights/true-brussels-emissions-...
"approximately 5% of measured Euro 5b/Euro 6 diesel vehicles exceeded one million particles/cm³, and this small group produced more than 90% of the particle emissions from the tested diesel group"
Isn't this common sense? What is being "stunned" !!
If you click the link at the top you'll find it goes to an article. The article will often expand upon the text in the link!!!
In this case:
"While we would expect children's lungs to grow year on year, our results indicate that the London children's lung growth had accelerated during the four years to 'catch up' with the control group in Luton to reach similar levels of lung capacity," researchers say.
"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC.
"The speed of catch up in lung capacity in the London group was surprising and impressive."
While having something done at Stanford's hospitals, at one point I was placed in a room with signs indicating it was on a heavily filtered ventilation system rated for COVID, etc. It was striking to be in an environment with air almost to clean room quality.
This is a reminder that getting an air purifier with high airflow filters (NOT HEPA!) is lifechanging in cities with high pollution levels.
I recommend getting one of these https://www.youtube.com/watch?v=sQGfO4hNb60 and just slapping a MERV 12 to 16 filter on it, you can get a whole roll off aliexpress for cheap and replace them monthly if you wanted to and it would be cheaper than 1 hepa filter replacement. They can also filter vastly more air, while you can keep hepa for 6 to 12 months MERV will filter a lot more air.
I've been meaning to do some data mining on how much PM2.5 differs with even a few hundred feet of elevation. I have a theory that even around Silicon Valley, living even up a little bit in the foothills would have you breathing massively cleaner air most of your life vs living in the pits of the valley. I see it all the time when I'm out there for recreation or just driving, the smoggy haze all over that just sits in the valley and the Bay. It's probably not too tough of a data processing challenge to compare the stats on Purple Air AQI sensors in reasonably close geo proximity vs elevation to get some statistically-significant data on this.
Who knew that populating Earth with mechanical horses that shit into the air is not such a great idea.
So punchline, probably a good idea to electrify all the cars yeah?
100%, and not just due to no emissions / minimal break dust. The noise reduction is a massive dividend. I used to live in london 10+ years ago, and when I come back I’m stunned by the noise difference, it really is so much quieter especially in central london. EVs everywhere especially replacing the horribly noisy diesel black cabs and buses. Very noticeably different and much more pleasant, and improving all the time as EV adoption continues to accelerate, hooray
Absolutely.
It's annoying though that EV's need that extra Darth Vader on wheels sound to warn pedestrians, I'd prefer them to be as quiet as possible.
You can switch it off, or make it play one of several different ridiculous sounds.
On which vehicles can the humming in reverse gear be switched off? I understand the Tesla (my car) and the BYD (expires car) can not turn that off.
London's also been putting effort into improving safe bicycle routes lately. I visit London every few weeks and if I'm going somewhere in central, I'll often just grab one of the Santander hire bikes instead of the tube. Well, most of London (looking at you, Royal Borough of Kensington and Chelsea)
Probably a much better idea first to have a decent public transport and electric car support network throughout the country first.
We don't all live in the city.
And those of us who don’t can just plug in at home.
Yes, and...
In some areas of London the ULEZ has been so successful that the measured NOx is now coming mostly from gas boilers used for heating, probably mostly old large commerical units.
So shifting from gas boilers to heat pumps and from gas ovens and stoves to electric/indusction is also beneficial.
That doesn’t solve brake and tire particles. Although…rail might solve those?
EVs use regenerative braking. So they hardly produce any brake particulates. And the tire particulates are heavy so they don't stay airborn for nearly as long. At low speeds, tires don't wear out as quickly.
Europe has quite a few cities where traffic is increasingly discouraged from going to the inner cities. Cities like Paris and London are much transformed from what they used to be and it shows in the health statistics.
It's not just the particulates but also nitrous oxides (nox) produced by combustion engines. Nox is correlated with lots of health issues. Take it away and you see lower rates of chronic lung issues, cancer, development issues with kids, etc.
But yes, tires are also an issue. But a fairly minor one to anything coming out of a combustion engine.
Mass transit indeed is nice in big cities. Removes the need for taking the car.
There is a generator at the end of my street in a shipping container sized metal box, it also has a mini office and loo, and is used by the construction workers digging holes in the road. It has company spiel written on the side, promoting the box's environmental credentials, including the punchline: 'Zero NOX when generator not in use'.
No shit Sherlock.
Might instead refer to a start-stop / battery backup kind of system, where idling-but-on doesn't burn any fuel, but sudden loads can still be serviced.
I look forward to the day coke is marketed as “zero fat!”
https://www.emissionsanalytics.com/news/pollution-tyre-wear-... Rail, bike, even busses are better. Cars are uniquely bad transportation in urban environments
Do the numbers in that article make sense? 5.8g/km for tyre wear? Generally my tyres last maybe 25000 miles. So at that rate they would lose 230kg. Seems high.
"Non-exhaust emissions (NEE) are particles released into the air from brake wear, tyre wear, road surface wear and resuspension of road dust during on-road vehicle usage."
I guess they mean total non-exhaust particulates.
They might be counting trucks?
> That doesn’t solve brake and tire particles.
Regen braking means significantly less brake dust, especially at city speeds and with blended braking.
> Although…rail might solve those?
Trains still have brakes. Some can regen brake but because they usually don’t have batteries they need the rail or overhead gantry to support inputs.
But on a passenger-mile basis, I expect an electric train produces essentially no particulates compared to a car, even a light rail on tyres. I do not however have numbers.
The usual brake on a train that can't do regenerative breaking is a big grid of resistors to dump the energy as heat.
It's much less wear and tear than friction brakes.
https://en.wikipedia.org/wiki/Dynamic_braking
And diesel hydraulic trains (and some buses) usually use these: https://en.wikipedia.org/wiki/Retarder_(mechanical_engineeri...
I believe at least subways tend to have lousy air:
https://engineering.nyu.edu/news/subway-air-pollution-dispro...
But I expect it's much better in open-air rail systems.
I was thinking open-air yes, tunnels do indeed have major issue. With pollutant concentrations, road tunnels are the same (https://www.sciencedirect.com/science/article/abs/pii/S13619...).
For all that I did not care for them originally this is probably something full-height platform screen doors help with, assuming the trains themselves are also filtered that would keep the pollutants clear of drivers and users, although it does not exactly resolve the question of managing their presence in the tunnels themselves (and track / tunnel maintenance personnel should probably already be wearing respirators if not full breathing apparatus), and I could see things get pretty dire in case of breakdowns.
Impossible to retrofit, of course, but what helps more are big tunnels. Modern ~9m diameter single tunnel systems are a lot better for this than old 3.5m diameter double tunnel systems.
Tyre, no, but regen braking almost eliminates brake particles at the speeds I drive in London. But mostly I take the train. Unfortunately the highest I measured on my particulate sensor is not near the roads, but in the tube.
Electric vehicles are stills cars. But better than gasoline and especially diesel cars.
So yeah.
That said not clear to me about PM2.5 is I've never seen anything legit seeming that tries to characterize the harm based on the type/source. Though it seems agreed diesel is especially bad.
And yet we’ve still got people cutting down the enforcement cameras with angle grinders at night
I use air purifiers mounted on my windows, running continuously except in the deep summer and deep winter. This makes my air contain 50-100x fewer particulates than the outdoor air. In contrast, the best I can achieve with floor air purifiers as people have them is a 5-10x reduction. The window purifiers also keep excess CO2 and VOCs out.
> The window purifiers also keep excess CO2 and VOCs out.
I assume you mean that the increased air-exchange (purified or not) helps CO2 that originates inside the house to leave promptly? (Equalizing it with the outdoors.)
Literally "keeping CO2 out" is a much trickier and more-expensive proposition.
You are quite correct on both counts.
Health improvements are not measurable any more if you go below 5 mcg/m2 average level of PM2.5 particulates. For 50x reduction to be beneficial, you need to live in an area where the pollution is 250 mcg/m2, which is an extreme level found only in a few unfortunate places on Earth. 5-10x reduction is reasonable almost everywhere.
I know precisely the subjective difference between a 5x reduction and a 50x reduction. Only the latter feels sufficiently good to me, and my brain operates better with it. You will know it when you experience it. Maybe it's my middle-aged brain that needs the extra support. I live in an urban area near traffic. Lately there intermittently also has been wildfire smoke coming down from Canada.
You have activated carbon to filter out the VOCs?
Yes, the filter absolutely has an activated carbon layer in it in addition to a HEPA layer. I understand that activated carbon doesn't last long. I have been changing the filter every two months.
Note that because this purifier is mounted at the window, it filters incoming air from outside, not the indoor VOCs that are already in the residence. The indoor VOCs will simply have to get exhausted from elsewhere due to the air pressure.
What I am suggesting is that my need for activated carbon is slightly less because I am rapidly pushing the VOCs out in the resulting exhaust.
cease all travel and live to 88
s/stunned/pleased/
Rtfa. "Stunned" is the actual word the scientist used.
I live in British Columbia so we have fairly good air quality. But with the yearly fires lately summer air some years is poor. So one year with the fires smoking and air quality getting poor I got an air purifier for my kids room and the living room. It is only anecdotal but right away if felt like he had better sleeps. The smoke wasn't thick as it was from fires hundreds of miles away and it wasn't like any of us were hacking or coughing crazy but in hindsight I felt that my young son who would have been effected the most slept better and his breathing at night seemed quieter and easier.
Scientists stunned healthy living is healthy?
Pointless anti-intellectualism.
There is a big difference between believing something is true, and demonstrating it is true and measuring the effect. One is a vibe. The other can drive policy.
Short-term gains are likely to produce long-term negative effects.
Hormesis and natural selection have been driving factor of evolution for a long time.
What is this, eugenics from first principles?
Are you suggesting that it would be advantageous for humanity to evolve to live in London circa 2000?
Larry Niven played with this in one of his stories; a time traveller from the far (and highly polluted) future has to use mechanical breathing assistance, because the levels of CO2 in the air in the past weren't high enough to prompt the breathing response properly (human breathing is controlled largely by blood CO2 levels).
Asthma is so common that this is not only easy to test, but has been. That's what the article was about.
Anyway, by your own line of thinking, wouldn't sensitive lungs be an advantage? The incentive to find cleaner air is also breaking away from the pack. Since humans are social creatures, that's more likely to look like new leadership for followers who have their own reasons to break away.
Every civilization in history has started out that way. It takes more than mere brute force to beat the competition. Survival is just as much about picking your battles and working smarter.