8 ms·

Anyone living near a busy road is swimming in particulate matter on the micrometre and nanometre scale, and particles on that scale bypass the normal defences,

• sandworm101 7y ago
  And what many overlook is many of these particles have nothing to do with emissions. Brake pads and tires turn to dust. So too bits of the road surface are slowly converted to fine particulates. Converting everyone to autodrive teslas powered by fusion reactors wont stop rubber from meeting asphalt. (Switching to manual transmissions would probably reduce the brake dust. Id like to see if european roads suffer as much. Between automatic transmissions, weight, and some traction control schemes, NA cars chew through brake pads.)
  • mrob 7y ago
    Switching to electric vehicles would reduce brake dust even more, because they use regenerative breaking to avoid using the break pads when possible.
    • murkt 7y ago
      Additionally, roads can be designed in a way that calms vehicle movement instead of accelerate-brake cycle. For example, narrower roads with curves instead of wide straight roads with speed bumps near pedestrian crossings.
      • sandworm101 7y ago
        Curves are just accelleration in a different direction. Tires would degrade just as quickly.
      • thrwaway69 7y ago
        Wouldn't that cause friction too? I feel like it might even increase braking more if it's a busy road and people want to move faster.
    • Scoundreller 7y ago
      At least newer automatics finally do engine braking as well.
      • Jamwinner 7y ago
        As well as all cars with manual transmissions.
        • sandworm101 7y ago
          "Engine braking" isn't just letting the engine spin down at 0 throttle. Propper engine braking, aka "Jake brake", is letting the engine spin at 100% throttle but zero fuel input (and some valve trickery). This lets air in to be compressed, releasing it before the down stroke of the piston. No car does that. It is a separate installed system on trucks. It can be almost as powerful as the engine. In a car, it could handle all but emergency braking. https://en.m.wikipedia.org/wiki/Compression_release_engine_brake https://en.m.wikipedia.org/wiki/Compression_release_engine_b... When you hear a truck making popping noises like a machine gun, that's the Jake brake in action.
          • hamandcheese 7y ago
            > Engine braking occurs when the retarding forces within an engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes. > The term is often confused with several other types of braking, most notably compression-release braking or "jake braking" which uses a different mechanism. https://en.m.wikipedia.org/wiki/Engine_braking https://en.m.wikipedia.org/wiki/Engine_braking
            • sandworm101 7y ago
              But when you see a sign saying "no engine braking" it refers to the jake brake, not down-shifting in a car. (It's a long trademark story over the use of "jake")
          • saiya-jin 7y ago
    • woodpanel 7y ago
      while switching to electric vehicles likely reduces break dust, such switch would simultaneously increase dust from tires, since increased acceleration. The latter being already 80% of urban "particulate matter" pollution.
      • iguy 7y ago
        And weight, presumably heavy vehicles wear through more rubber, and batteries are heavy.
        • brownbat 7y ago
          Weight. This is so much about vehicle weight. I think the heavier EVs hit a crossover point because of regenerative braking, but weight does set them back, that's one of the whole points of this study: https://www.sciencedirect.com/science/article/abs/pii/S135223101630187X https://www.sciencedirect.com/science/article/abs/pii/S13522... This is a curve though. We could almost simplify the problem and only look at what heavy trucks generate and ignore all the cars completely, it'd be a non-crazy approximation.
      • DenisM 7y ago
        I don’t think Nissan Leaf is particularly good at neck-breaking acceleration, and it probably outnumbers the drag-racing Teslas. Even then, a Tesla isn’t particularly speedy in traffic.
        • Geeflow 7y ago
          I often drive a Renault Zoe which also isn't a sports car. I frequently leave sports cars behind at the traffic light. From 0-30 kph even the small/cheap electric cars are sport cars. And it is terribly tempting to develop a pedal-to-the-metal habit. So I assume tire dust will increase significantly in the cities.
          • sandworm101 7y ago
            Rate of acceleration isnt the issue. You may make more dust per second but so long as you are getting to the same end speed, and not spinning tires, the total amount of acceleration is the same. In my experience, over braking is the greater problem. Front tires degrade more quickly than rears. The average driver brakes far harder than they accelerate.
    • dsfyu404ed 7y ago
      A set of pads typically lasts about as long as a set of tires (at the very least they're within a factor of two of each other). Compare relative volumes of materials. Brake dust is always going to be a much smaller source of particulate matter in the air than tire dust. FWIW if the fumes/particulate from burning them are any indication tires are probably way nastier than brakes.
      • samatman 7y ago
        First paragraph is perfectly reasonable. Second paragraph, though: I've never been around a brake pad fire, but I'd rather breathe vulcanized rubber than "metal shavings of copper, steel, graphite, and brass bonded with resin": https://www.yourmechanic.com/article/what-are-brake-pads-made-of https://www.yourmechanic.com/article/what-are-brake-pads-mad...
        • dsfyu404ed 7y ago
          In my non-chemist, non-doctor opinion the circumstantial evidence points to brake dust being way less bad than tire dust. Being inert in the presence of most common substances tends to correlate well with low toxicity. It's the stuff that chemically reacts to all sorts of things that tends to be the most poisonous. Tires break down over time under "normal earthly conditions" which includes a lot of the same temperatures and molecules that are found inside the human body. To me this is a massive red flag for toxicity. High temperature tends to make things react more readily. Most of the stuff in brakes has to be really stable at high temperatures and being stable at high temperatures tends to correlate well with being chemically inert. The most reactive stuff in brakes are the long complex molecules used to bind it all together. These sorts of molecules are similiar to the molecules used in tires and all sorts of other plastic like things. So all else being equal tires probably have more of the chemically interesting things that cause problems in the human body. Burning brakes smells way better than burning tires which seems to confirm this (remember, your nose has millions of years of incremental improvement when it comes to indicating what is and isn't suitable to ingest). And before anyone thinks they're gonna get some easy internet points by saying "but asbestos", the amount of asbestos in brake pads is nonzero (to account for the sketchy unbranded stuff that may or may not use it) but still tiny enough that people working in proximity to it have mostly stopped dropping dead at 60 thanks to lung cancer so I think that however much asbestos is in brake pads it's low enough to not be an issue from a public health POV. TL;DR I'll take my chances with brakes over tires.
  • scythe 7y ago
    From slide 17 here you can see that the switch from fuelled to electric vehicles is expected to decrease particulates by 60-80% from 2000 to 2040: https://www.epa.gov/sites/production/files/2015-09/documents/sbai_pres.pdf https://www.epa.gov/sites/production/files/2015-09/documents... This doesn’t seem like a trivial improvement. Particulates are not the only toxic component of exhaust either; electric cars should produce no NOx, CO or O3 which is a big improvement. It’s also worth noting that brake wear particulates haven’t been a target because historically exhaust-related emissions were so much larger. If we haven’t really tried to fix it, who’s to say we can’t?
    • iguy 7y ago
      Thanks, and good point. It might not be very hard to reduce brake dust dramatically, just put a vacuum cleaner in your frunk right?
  • derefr 7y ago
    Tangential question: do trains produce fine particulates where their wheels meet the rail? I.e. is it bad to live near a train (or subway!) line?
    • sandworm101 7y ago
      Yes but far fewer. The metal turns to dust, but orders of magnitude less quickly than rubber/pads/road surface. The stuff carried by the trains is probably more dangerous than the train itself.
    • johnwalkr 7y ago
      Trains do use brake shoes on the wheels, and in some cases disc brakes. All trains have mechanical braking capability, as far as I know. Many also have electric braking, especially passenger trains with frequent stops, which is either regenerative or dissipated as heat via resistors. Freight trains tend to use mechanical breaking, but have infrequent stops and can plan a long slow-down. In any case, the braking force has to be transmitted somehow to the wheels before it is transmitted to the rails. There is only rarely wheel on rail sliding outside of emergency situations. But, particulates of steel on steel sliding should be relatively benign. A good train system is better utilized compared to cars as well. All this is to say that yes, there are fine particulates from trains, but it should normally be much less than from living near a highway.
    • rezgi 7y ago
      I remember from my days working for London Underground Ltd that whenever I'd blow my nose after a shift, my snot would have a concerning amount of black matter in it. The days I was off and not entering the subway, my snot didn't have this black particulate matter. I like to think it was my nose doing its job and keeping all that from entering my lungs, but I'll never know.
  • Nasrudith 7y ago
    Dumb question - how well would an attempt to suck in the particles work putting aside the obvious impracticality? There are currently tons of reasons not to do it today but could it theoretically be solved via clean and cheap energy to make the efficiency loss not a foregone self defeating act.
  • joncrane 7y ago
    You're asking people to use a much more expensive part (transmission) to reduce their speed. The days of using the transmission to slow down are over. Brakes are better and more reliable (and cheaper) than ever.
• Spooky23 7y ago
  I live in a side street about 100 yards from a major avenue in my city. You can see on our front porch the impact of particulates... it’s covered in gross sticky dust once we do our spring cleaning.
  • wkearney99 7y ago
    Likewise being under a flight path to a major airport. The white deck on our boat at a marina on the approach to BWI gets all kinds of particulates on it from the exhaust of planes passing overhead.
• KallDrexx 7y ago
  I'm curious how different living next to a highway is to living in a dense urban city though (like NYC) and if it's different why? In either case you have a lot of car traffic (probably closer to your place of residence than people that live close to a highway) Not to mention if you live in a dense urban city then you will spend more time walking directly next to traffic.
  • deleted 7y ago
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  • lotsofpulp 7y ago
    I'm sure the underground trains also cause plenty of particulates each time they brake to stop at a station.
  • zzzeek 7y ago
    the one thing that strikes me as different, having lived in manhattan / queens / brooklyn for 25 years, is that by a highway there is high speed traffic, which is extremely loud and sudden, and a lot of it is heavy commercial traffic, heavier than what is feasible within an urban environment. the next time you're at a rest stop off of I95 just stand outside and listen to the noise of huge trucks blowing by at 80mph. I think those sudden blasts of sound and vibration are well above and beyond the stress when you're in a dense urban environment. City traffic, especially if you're on a side street as is more common for residential, you're looking at 10-20mph traffic for the most part and without 18-wheelers going by most of the time. There is also the issue of subway noise, which is more like a constant stream of periodic vibrations. that is probably not good for one's nerves either but it is fairly subtle. The most stressful thing about urban living for me was the constant light, ugly sodium colored light at all times, flashing lights, emergency lights, etc. I now live in a rural area and I will bundle up and sit outside on my deck at 1 am in 20 degree weather just to enjoy the darkness. There was never total or near total darkness in the city at any time, not even indoors unless you have blackout shades which we did not. the worst of all worlds are those folks living in those apartments that overlook the BQE and stuff like that. They look like expensive places and I think whoever is choosing to live there is completely crazy, they get the most particulate matter (except that their windows are probably sealed shut, which is bad in itself), the most noise, the most light, etc.
• graeme 7y ago
  If the pm 2.5 is low, are the nanoparticles also low? I live near a semi busy urban road, but there’s a wall of buildings + an alley between me and it. Pm 2.5 is very low at my place, and so is noise. Never thought about the nanoparticles pm 2.5 doesn’t measure, but am assuming it’s similar.
  • 0x38B 7y ago
    According to this article[1], nanoparticles drop off quickly compared to larger particles: "However, the highest averages were recorded inside the cars and buses: the closer to the source of the pollution, the exhaust pipes spewing out the fumes, the higher the total number of nanoparticles. The difference between walking by the kerbside of the road, and by the building side, on the same pavement – just a few short steps – was an average of 82,000 particles versus 69,000. The same readings registered no change in PM2.5." 1: https://www.bbc.com/future/article/20191113-the-toxic-killers-in-our-air-too-small-to-see https://www.bbc.com/future/article/20191113-the-toxic-killer... HN discussion: https://news.ycombinator.com/item?id=21552934 https://news.ycombinator.com/item?id=21552934
• papito 7y ago
  Quality of air definitely matters, but I wonder what actually has more negative effect - poor ppm levels or the stress from the noise. People think that's not a big deal and you just get used to it, but the truth is, your brain is ALWAYS processing that noise in the background as a source of potential danger, taking a long-term tall on your mental state. I work in an office with poor CO2 PPM levels, and constant noise. I've started enjoying working from home, even though I used to absolutely hate doing that.
  • deleted 7y ago
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  • drcross 7y ago
    The depth and breadth of neurological issues could not possibly be explained simply by noise. Humans lived in close quarters for most of our existence which would have included a lot of elevated noise levels.
    • mmhsieh 7y ago
      there might be a different set of neurological effects caused difference between the noise spectra of natural sources, to include human generated noise, and the unnatural sources like car traffic. the color spectrum of natural scenes has been found to have different impacts than that of manmade urban scenes.
  • Reason077 7y ago
    Yes, I wonder about the noise issue too. In my personal experience, living near a busy road had a huge effect on sleep quality which in turn increases stress levels and reduces wellbeing.