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Car exhaust filters fail to clean up ‘ultrafine’ air pollution
- fooker 4y agoThere’s always a <strike>bigger</strike> smaller <strike>fish</strike> particle.
- bawolff 4y agoFrom my understanding, medium sized particles are actually the most expensive to filter
- fooker 4y agoWhat's the intuition behind this?
- LaputanMachine 4y agoMultiple physical effects are responsible for filtering. Each of them works best at certain particle diameters. The combined efficiency of all effects happens to have a minimum at 0.3 microns. [1] This is called the "Most Penetrating Particle Size" (MPPS). For very small particle sizes, filtering mostly works by diffusion (quoting from [2]): >[Diffusion] is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 μm in diameter. The small particles are effectively blown or bounced around and collide with the filter media fibers. This behavior is similar to Brownian motion and raises the probability that a particle will be stopped [...] [1]: https://en.wikipedia.org/wiki/HEPA#/media/File:Filteration_Collection_Mechanisms-en.svg https://en.wikipedia.org/wiki/HEPA#/media/File:Filteration_C... [2]: https://en.wikipedia.org/wiki/HEPA#Mechanism https://en.wikipedia.org/wiki/HEPA#Mechanism
- schiffern 4y agoIn the paper[0] they define "ultrafine emissions" as <0.1 microns. "Diesel Oxidation Catalyst (DOC) and Diesel Particle Filter (DPF) has been very effective in controlling the emissions of solid particles and hence BC, but that there has been little change in the liquid mode (<30 nm) particles, and that concentrations of ultrafine particles (<100 nm) still well exceed the threshold for “high” concentrations (>10e4 cm^−3 /24-hour mean) defined by WHO. BC declined by 81% between 2014 and 2021, but the ultrafine particle (<100 nm) count declined by only 26%. Looks like DPF/DOC filters use mainly interception, but they're not terribly effective at filtering via the diffusion mechanism. [0] https://www.sciencedirect.com/science/article/pii/S0160412023001617 https://www.sciencedirect.com/science/article/pii/S016041202...
- jodrellblank 4y agoSee: https://dynomight.net/ikea-purifier/ https://dynomight.net/ikea-purifier/ Scroll down to “The physics of air purifiers seem simple.” for the relevant bit.
- maxbond 4y agoY̵o̵u̵ ̵c̵a̵n̵ ̵a̵l̵s̵o̵ ̵u̵s̵e̵ ̵U̵n̵i̵c̵o̵d̵e̵ ̵s̵t̵r̵i̵k̵e̵t̵h̵r̵o̵u̵g̵h̵ ̵c̵h̵a̵r̵a̵c̵t̵e̵r̵s̵
- fooker 4y agoIt's discouraged here for the sake of accessibility. Screen readers and translators don't do well with these characters.
- maxbond 4y agoInteresting. Thanks.
- moffkalast 4y agoAs a test I've pasted that into ChatGPT asking it to edit it so it uses corresponding letters from the ASCII table and it removed the strikethrough flawlessly. Probably won't be an issue for those screen readers for much longer.
- fooker 4y agoWow, amazing!
- deleted 4y ago[deleted]
- xenonite 4y agoLink to the study: Seny Damayanti, Roy M. Harrison, Francis Pope, David C.S. Beddows, Limited impact of diesel particle filters on road traffic emissions of ultrafine particles, Environment International 174, 2023, https://doi.org/10.1016/j.envint.2023.107888 https://doi.org/10.1016/j.envint.2023.107888.
- xvilka 4y agoAmong solutions article doesn't propose making better filters. It can happen and mandated much faster than waiting everyone switching to EV.
- throwaway290 4y ago<strike>China</strike> EV manufacturers gotta make money.
- deleted 4y ago[deleted]
- nuccy 4y agoPeople seem to miss that better filters it is not just about higher price, but also higher CO2 emissions - filters decrease efficiency of the engine since they take energy to operate, moreover the energy consumption increases nonlinearly with decrease of particulates size. There's definitely a point where better filters don't make sense any more purelly from CO2 emissions perspective.
- Gordonjcp 4y agoYou could just use cleaner fuel. You don't get anything like as much CO, NOx, SOx, or particulates if you run a petrol engine on propane. You don't even need a catalytic converter, although it helps with the microscopic amounts of NOx that does get formed.
- doubled112 4y agoThey made propane cars. What happened to them? I know a guy who had one and his verdict was never again. The valve would freeze on a cold enough day and you couldn’t get it started. He even had it freeze while he drove it. These don’t seem like impossible issues to solve though.
- gambiting 4y agoWhat do you mean? Where I'm from LPG cars are extremely popular(13.4% of all cars on the road[0]), the winters are very harsh(-20C and less isn't uncommon), and all these LPG cars drive just fine. I used to have one myself, in winter you basically had to start it on petrol but you could switch to LPG 10 seconds later and it was fine. [0] https://motoryzacja.interia.pl/wiadomosci/ciekawostki/news-polska-gazem-stojaca-ile-aut-jezdzi-u-nas-na-lpg,nId,5953089 https://motoryzacja.interia.pl/wiadomosci/ciekawostki/news-p...
- _dain_ 4y agoOn a related note, I cycle a lot, and I wondered if the health benefits of doing so were outweighed by all the particle pollution I had to be breathing in from motor traffic. But apparently the air quality is even worse inside cars compared to outside: https://www.sciencedirect.com/science/article/abs/pii/S004896971400713X https://www.sciencedirect.com/science/article/abs/pii/S00489... Plus the upholstery is probably outgassing all kinds of nasty plastic shit ... "new car smell" = cancer.
- throwaway290 4y agoDepending on where you live may want to pay attention about general pollution. I often look at it before deciding to cycle or walk a lot, on days AQI goes up I can be occasionally coughing even without lots of physical activity
- nannal 4y agoWith our air quality sensor, we've noticed that there are good and bad days for air quality regardless of any other apparent factor. We've been thinking about making the sensor portable so it can alert when it's time to mask up because its often hard to be sure if you're not being unnecessarily exposed.
- maxbond 4y agoRecently I went for a walk at night. It was a bit hazy in car headlights and such but foolishly I didn't think much of it. When I got home I happened to turn on a flashlight & I realized the air was full of ~1mm ash particles, I believe from a prescribed burn nearby. The few days after that I had shortness of breath and trouble concentrating. It was pretty alarming. Not wearing a mask, which I had with me, was a big mistake. I think your suggestion is excellent.
- throwaway290 4y agoIt seems like you don't check AQI alerts in your area, so you probably did not shut your windows/doors in advance or run air filter indoors, so the exposure you get on a single walk is not as big as what accumulated in your home. That stuff you breathe day in day out and in your sleep. So portable monitor in my view is overkill, I just check AQI in the area and close windows and run air filter indoors and don't cycle when it's bad. But if it's a really convenient monitor I'd not mind it! In my experience accurate monitors are not small and not cheap though...
- moffkalast 4y agoAh yes let's avoid the real issue of car tyres producing 2000x the particle pollution per distance travelled compared to already insanely filtered exhaust and distract ourselves with tiny improvements that make no difference. ICE emissions will be irrelevant in 10 years when they're all but banned anyway, and rubber tyres will still be the only way to drive on the road. In fact it'll be way worse with the average EV being heavier and emitting more due to more tyre wear.
- Neil44 4y agoIt’s hard to really quantify how big of an issue this is in my head, I mean a set of tyres will do 20,000+ miles and only loose a small percentage of their mass while doing so. How much damage is really being done? How much scope for improvement is there?
- marginalia_nu 4y agoDepends on the sort of tires. For examples, studded snow tires can tear up the road surface quite significantly, tend to kick up a lot of sharp fine dust. It's such a big problem they're often banned parts of the year in some regions where they're typically used. Here's some science: https://www.ivl.se/download/18.1ee76657178f8586dfc89b/1619514960917/B1830.pdf https://www.ivl.se/download/18.1ee76657178f8586dfc89b/161951... It seems to largely suggest that GP is correct (see the figure in 5.3.8 for example), with the caveat that this is mainly a problem in colder regions of the world.
- chongli 4y agoThe road itself gets torn to pieces as well. Furthermore, tire and road wear scales with the 4th power of the vehicle mass. Heavy trucks and buses cause far more damage than cars. But all that damage leaves dust all over the road which cars will scatter all over the place. Lastly, as pointed out above, EVs weigh a lot more, so the damage they cause will go up a lot, thanks to that 4th power scaling.
- ChuckNorris89 4y ago>ICE emissions will be irrelevant in 10 years when they're all but banned anyway Dream on. Germany and EU had to pull back from the ICE ban of 2035. Banning ICE by then is unrealistic considering the way things work right now. The frog needs to be boiled slowly.
- wouldbecouldbe 4y agoI live on a relatively busy road in the city, cars drive around 30km/h. Doesn't feel like a big road, but lot of cars during the weekdays. After cleaning, the white elements balcony turns black every 1.5 - 2 weeks. Dont know what it is, some people say tires. Whatever it is, it's a lot and living in cities like this have already shown a lower life expectancy of around 5 years.
- inconceivable 4y agoit's tires and brake dust.
- 1970-01-01 4y agoIn a city, its simply a combination of everything. Tires and brake dust are a small part of overall vehicle emissions. Local industry, and whatever else is on fire, are also big contributors to air pollution.
- porkbeer 4y agoTires and brake dust are an overwhelming majority of vehicle emissions however. When I see people this confidently wrong I always wonder if its a language model now.
- 1970-01-01 4y ago"Large trucks are biggest culprits of near-road air pollution" So black carbon from diesel truck exhaust (and buses) pollute a lot more than a lot of you think. They call it a 'soup' of pollution of both exhaust and tires. But you should continue to be skeptical of AI driven thought-content :) Sources: https://www.sciencedaily.com/releases/2018/09/180910111237.htm https://www.sciencedaily.com/releases/2018/09/180910111237.h... https://news.engineering.utoronto.ca/national-air-pollution-report-calls-out-rush-hour-traffic-diesel-truck-emissions-as-major-areas-of-concern/ https://news.engineering.utoronto.ca/national-air-pollution-... https://www.socaar.utoronto.ca/wp-content/uploads/2019/12/NearRoadAirPollution.pdf https://www.socaar.utoronto.ca/wp-content/uploads/2019/12/Ne...
- user3939382 4y agoWhat about brake dust? In Manhattan I’d shower, take the train to work, immediately go wipe my face in the bathroom with a damp paper towel and the paper would have black smudges all over it. Imagine the long term health implications scaled up to the whole population.
- mhb 4y ago> Imagine the long term health implications scaled up to the whole population. Compared to what?
- mort96 4y agoCompared to not having the fine particulate matter in our lungs for our whole lives probably?
- mhb 4y agoVery good. And what about in the real world where there might just be some benefit that offsets this cost?
- user3939382 4y agoThe benefit that offsets so much pollution your face goes from clean to dirty from 15 minutes of walking around? Maybe in the “real world” we should discuss solutions rather than conjure up excuses to accept major problems.
- mort96 4y agoWhat are you on about? Before we can even start discussing any sort of cost/benefit analysis, we need to know what the costs are and what the benefits are, no? You seem to be offended by the idea of even inquiring about the costs, which is what the "Imagine the long term health implications" comment is trying to discuss. Are you trying to say that you have already done this cost/benefit calculation and decided that there is nothing which can be done to improve the situation? If not, what are you trying to say?
- ck2 4y agoI'm convinced half of all those massive do-nothing pickups these days have hacks on their emission controls to save a few dollars per tank because to hell with pedestrians/cyclists. It's like barely visible rolling coal and it's non-stop every time the truck is driven. Just one mechanic sold thousands and since it's software you can be sure it's copied and used by anyone wanting to make a few dollars on the side https://jalopnik.com/a-mechanic-pleads-guilty-to-selling-thousands-of-device-1849114964 https://jalopnik.com/a-mechanic-pleads-guilty-to-selling-tho... Since many states do not have inspection, once turned off it may be for the life of the truck.
- okokwhatever 4y ago- What could we demonize this month? - Mobility is so trendy, What about car tires? -Oh, it looks cool to me, lets do it! Let's mandate the people to walk and in a couple of months we can demonize sneakers too!
- totalZero 4y agoThe article makes no case about car tires and specifically addresses the limitations of certain filters used on diesel engine exhaust. If you can't get behind cleaner transportation technology, try not to stand in its way.