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The health benefits of better air (dynomight.net)
693 points by spekcular on April 28, 2021 | hide | past | favorite | 455 comments

This article seems to make fantastic jumps from the believable -- mortality from overall air pollution (e.g. in Delhi) to the frankly unbelievable -- your ultrasonic humidifier supposedly reducing your life by nearly an hour each night, or that a daily commute between Newark and NYC takes half a year off your life.

According to this logic, anyone who works in the subway should be dying, what, 10 years earlier? Which is obviously not happening.

Similarly, it seems impossible to believe that the minerals in the air from humidifiers are equivalently dangerous to factory pollution or cigarette smoke. Different categories of particles are going to affect the body differently, no? I mean, our body requires minerals -- we're drinking them in our water all day long -- while certain factories may be belching out straight-up poison.

These statistics are just not passing the smell test. They seem to be extrapolations of extrapolations of extrapolations. This article's conclusions don't seem even remotely convincing.

When it comes to ultrasonic humidifiers, they do generate a lot of PM 2.5, see:


It is NOT certain that these particles are as bad as ones from dust or combustion. All in all, when small droplets evaporate, what remains is water-soluble salts, rather than anything more reactive or harder to remove, see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3922954/ as mentioned in https://learn.kaiterra.com/en/air-academy/humidifiers-cause-...:

"In a study on mice, researchers discovered that inhaling the dust from ultrasonic purifiers produces a cellular response, but this response lacks the inflammation and damage associated with other forms of particulate matter."

Myself, I got shocked when my air purifier suddenly started showing a huge amount of pollution (and yes, my eyes turned red). Only afterwards, I checked it was exactly because of my freshly-bought ultrasonic air purifier. Now I have an evaporative one - not as fast, not as spectacular, but better.

That's why you gotta use them with reverse osmosis filtered water. And not one that remineralizes, you can do that later on your own. I have a ultrasonic humidifier, reverse osmosis water filter and air quality sensor, it's all good.

I use distilled water

is there a downside to just using an evaporative humidifier?

They have mold/bacterial growth problems (and use more electricity).

But both types have easy solutions to their respective problems:

- Use distilled water in the ultrasonic.

- Regularly clean/replace wick in your evaporative (or use a water stabilization agent).

Even the article at the top says they measured "0" particles when distilled water was used.

Until reading this thread I thought using distilled water in them was common knowledge. I believe that is what the manual with mine even said.

Ultrasonic one is my first, only started paying attention to all this stuff because of 2020 and went all in, just trying to make my home a less crummy place.

Watch this https://www.youtube.com/watch?v=oHeehYYgl28

Optional follow-ups:



I literally just have some planting trays with a half-inch of gravel that I pour water into every couple of days.

Works wonders, is cheap, and easy to clean. Evaporation happens for free if you let it.

Maybe works for one small location, but that doesn't put nearly enough water in the air for common humidifier use cases of a gallon a day or more.

This seems crazy to me. I have to dehumidify my home to keep it at 35%. Humidity is a constant battle. I couldn’t imagine paying to dump water in my air and promote mold.

This is very climate dependent. New Orleans or Miami will have much more natural humidity than Boulder or even Boston in the winter.

Dry mucus membranes makes you more susceptible to a number of respiratory problems. If you have mold, everyone does to some extent, drying it out will just make the health problems worse as it aerosolizes the mold. Mold aside, for optimal health a level between 40-60% is advised. Allergy sufferers are especially sensitive to this.

The recommended humidity level is 40-60%.

The power draw at the humidifier will be larger, but the net power cost is about the same assuming a constant indoor air temperature. I always use filtered water for the US humidifier, but I'm reconsidering it now.

I’m curious whether you’d get the same effect from living/working near a waterfall / other natural source of vaporized water droplets.

Do the hospitality staff at Niagara Falls get sick more often than other people in hospitality?

Are these humidifier particles bad at all? What does “cellular response” mean? Typically combustion particles are bad because they contain carcinogens and PM2.5 can deposit deep in the lungs.

This seems like a “PM2.5 bad no matter the source” theory which isn’t supported at all.

> Are these humidifier particles bad at all?

It's limescale, you don't want it in you lungs. Kidney stones also have some relation to it, probably not exactly caused by hard water, but they get their building material from somewhere.

Technology Connections did a video on humidifiers, and if I remember correctly the evaporative ones weren't actually slower than the ultrasonic ones: https://www.youtube.com/watch?v=oHeehYYgl28&ab_channel=Techn...

this page from the same site as the OP has links to more studies: https://dynomight.net/humidifiers/

Extinguish candles with a lid.

If you are worrying about the method by which you extinguish a candle, worrying is what's going to shorten your life, not the candle.

I don’t think it’s generating anxiety, just creating a habit. Like washing your hands with soap after you go to the bathroom. Once upon a time that sentence might generate the response “if you’re worrying about how you wash your hands, then the worrying is what’s going to kill you!” (in actuality it was worse, the suggestion that a surgeon should wash his hands before surgery was considered offensive). But today it’s pretty automatic, not some laborious mental checklist. And if you’re in a situation without soap, generally you don’t freak out, you do your best with just water and move on.

Anyone whose health can be reasonably influenced by how you put out a candle has not been born yet. Everyone else has to deal with jobs and living circumstances that requires one to be inside all day, work strange hours, be outside in the sun all day, inhale fine dust from any kind of road nearby. There is a near endless list of similar/worse risk factors at play in one's life. Even though these risks might be provable in their damage to your functioning and there might be reasonable solutions to them, implementing them will still be insignificant. Just like how you should avoid apples because at least apples have killed people.

I have a cheap pm10 meter and ran it continuously for a few weeks. Next too cooking meat the other activity that stood out was blowing out the birthday candles. The pm10 rose to 300 and only was backs to healthy levels (below 50) several hours later. I was as surprised as you are. Next time I'll definitely open a window

Not all particles are equally toxic. If I had to guess, the smoke from a recently-extinguished candle is probably condensed wax vapor rather than PAHs and heavy metals.

I don't think condensed wax vapor has looks like the dark smoke that comes off a recently extinguished candle. I'm pretty sure it's carbon compounds from the wick.

The black smoke is soot from partially burned wax and it's definitely carcinogenic.

Condensed wax vapor can’t be good for your lungs when inhaled

Where did you get a cheap meter and what do you consider cheap :D?

It's a pms5003 which I bought for €12 from aliexpress

How often do you blow out birthday candles?

At least once a year

You're lucky not born on 29th February.

The absolute values measured are not that high luckily. In the Netherlands at New years pm10 of greater than 1000 can be observed. I believe my outdoor sensor peaked at 900 in the first minutes of 2020. Glad fireworks were banned this year

My first thought on the candles was: If you're worried about paritculate emissions and air quality in your flat then maybe just don't burn anything in your flat.

I haven't researched that, but it always seemed entirely obvious to me that candles aren't exactly healthy in terms of air quality.

One big thing is natural gas combustion producing nitrogen oxides. Gas burners used for cooking make a LOT of it, right inside the home.

That is also one of the arguments for choosing induction over gas, since it removes combustion from the kitchen.

I think my follow on question would be which is better- a scented candle or a scented plug in like an Air Wick or Glade? Or are they similar and the only good choice is to have no perfumes floating in the air? I’ll gladly switch systems if there is a difference but I’d like to have something to make my house smell better.

Depends on your risk tolerance.

Candle emissions have a low but known impact on your health. Plug in air fresheners don't have a known impact but they have god knows what chemicals in them. Maybe you'll get cancer at 60, maybe it would take three lifetimes of exposure to have any effect.

I genuinely can't be convinced there are people alive today that the risk of one scented candle in the home and/or plug in air fresheners are higher than the background danger of auto, industry, and just general pollution. This seems like an anxiety in search of a problem, or am I very underestimating it?

It just seems like the road in front of my house is probably more of a problem than my vanilla candle.

I once forgot to extinguish a candle before going to bed, it burned down, and produced a massive amount of soot. Their was a stripe of black suit on the wall where the candle was standing, a black spot on the ceiling, and my upper lip and nostrils were black from soot.

I'm not sure what effect on my health a one time event like this has, but if I can avoid it I will.

I can't do anything about the pollution outside.

The thing is that wind and sheer volume of air tend to mitigate the pollution but in the home the air can stay static.

I wonder if people thought the same about radioactive substances?

There's a large body of emerging science that points to inhaled particulates reducing health and lifespan.

Thank you. That is such a great one liner that I wrote this down in my quote collection.

I think the particular bit about the subway may be informed by very recent news that the air pollution in the New York subway stations is far in excess of what anyone had inspected.


As for actual subway workers… I mean it’s not exactly a coal mine, but I would be pretty surprised if their mortality wasn’t at least somewhat measurably lower than, say, that of shepherds.

Just to point out how why this is a fairly nuanced topic, a shepherd may be breathing clean air but they're also exposed to UV radiation all day. They may have a higher morbidity due to increased skin cancer rates.

I'm no way an expert on the matter but by pure logic it's still amazes me how we survived (and evolved!) as a species for thousand of years without almost no shelter from direct sunlight and yet now (too much) sunlight exposure is seen as a cause of death. I know we lost almost all the body hair we used to have but still, we usually wear clothes when under the sun.

According to my naive knowledge:

1. We have more ozone holes now.

2. We weren't constantly in direct contact with sunlight. If you move past very early stages, we had shelter in forests, caves, tents, igloos.

3. When we were in direct contact with sunlight, we had a darker skin, which is more resilient to that.

Correct me if I'm wrong.

We have more ozone holes now.

The global ban on CFCs (https://en.wikipedia.org/wiki/Montreal_Protocol) is working, and although there are still big holes that open and close every year we're on the way to getting back to pre-1980 levels of holes by 2060. https://public.wmo.int/en/media/news/record-breaking-2020-oz...

Maybe, if China would curtail their CFC usage perhaps.

...A recently reported slowdown in the decline of the atmospheric concentration of CFC-11 after 2012, however, suggests that global emissions have increased...

We show that emissions from eastern mainland China are 7.0 ± 3.0 (±1 standard deviation) gigagrams per year higher in 2014–2017 than in 2008–2012, and that the increase in emissions arises primarily around the northeastern provinces of Shandong and Hebei. This increase accounts for a substantial fraction (at least 40 to 60 per cent) of the global rise in CFC-11 emissions.


Still, the Montreal Protocol is a good example of what can be achieved when we finally reach an imminent crisis.

That's from 2019, they have since reduced the leaks, this from 2021: https://www.nature.com/articles/s41586-021-03277-w

Great news, thanks for the update.

Moving to the country and being outside for 8+ hours of the day finally made it clear that cowboy hats, sombreros, etc. don't have wide brims just for fashion.

This was my thought. Traditional clothing for people who live and work outdoors in sunny climates generally does not feature a lot of exposed skin. I'm pretty sure that the "shorts and a t-shirt" summer wear is a fairly modern phenomenon.

Nobody counting skin cancer deaths and saying "this is completely avoidable and dying at that age is abnormal" back then either...

Evolution (and survival) only cares about if you survive to reproduce. So human evolution (and survival) matters only until 14-40, and humans aren't dying of skin cancer at exceedingly large numbers at those ages.

If we pushed back the reproductive age we'd eventually evolve to live longer (though would have more people dying without reproducing first). This experiment has been successfully shown in fruit flies.

> So human evolution (and survival) matters only until 14-40

Not necessarily. I'd imagine it helps the survival chances of your grandchildren if you're around when they're growing up (though it probably mattered less back when children were raised by communities than in the nuclear families we have nowadays).

Sure, it would have helped homo sapiens even more if more of their children had lived to childbearing ages (if, say, they'd discovered antibiotics a few millenia earlier or evolved more natural immunities). But the infant survival rates back then were enough to ensure the species survived, just like the smaller fraction of the population struck down by skin cancer every year wasn't enough to put evolutionary pressure on us to develop resistance to it or develop sunlight avoidance traits. Evolution doesn't guarantee that every possible beneficial adaptation takes place.

> I'd imagine it helps the survival chances of your grandchildren if you're around when they're growing up

Keeping toddlers from walking off a cliff (and the other things unsupervised toddlers will do to kill themselves) is probably why he said 14-40 and not 14-30.

> human evolution (and survival) matters only until 14-40

I just don't think that's true. I think grand parents being around was important for human survival.

If it wasn't, if all that mattered was having the most kids, then why would women go through menopause? Wouldn't it be better if women continued having children until they die?

I think it makes sense that young people have kids (the sooner the better, faster evolution and less chance of DNA degradation)

Then they should live as long as possible to help raise their grandkids to ensure their genes survive.

> If it wasn't, if all that mattered was having the most kids, then why would women go through menopause? Wouldn't it be better if women continued having children until they die?

Given that the risk of birth defects goes up significantly the older a woman is, menopause is probably evolutionarily advantageous.

I may be overly cautious given where I live has an 11+/Extreme UV rating all year round.

Though I do want to point out that clothing doesn't protect against UV as much as you might think, and a sunburn or lack thereof doesn't tell you all that much about your UV exposure for the day. You could have exceeded your healthy exposure for the day without getting a sunburn.

Unless that skin cancer thing is also actually overblown… https://elemental.medium.com/what-if-avoiding-the-sun-is-bad...

As the parent said, plenty of nuance to go around.

If the shepherd has kids before dying (of skin cancer or something else), it doesn't really make a difference for the survival of the species...

Skin cancer probably plays no role for your ability to reproduce. By the time you die from skin cancer you already had children and probably even grandchildren.

The longer you live as a male the more children you can have. Also grandparents helping raise grandkids is a factor in their survival in the village ..

We also used to be black. Humans now move to places for which they do not have a suitable skin colour, like Australia.

Shepherds (like all folks) wear and wore clothes, long sleeves and often hats also in the summer. Also if skin is exposed to sun regularly, often, its much less sensitive compared to usual office worker seeing almost no sunlight and then having 2 weeks of mega exposure and sunburns on vacation.

The last time I looked in to this, enough sun exposure to tan is also enough sun exposure for folk of northern European discent to badly increase skin cancer risks.

This is why tanning studios have been banned in Australia.

Why would sunlight cause us to lose hair but not other animals?

I don't see how sunlight would cause us to lose any animals, unless perhaps it was too bright.

Wide brim hat and long sleeves.

comparing average lifespan of 30 to 80?

That's actually a valid point, thanks. Although I don't know what's the age distribution for skin cancers.

Besides melanomas which are relatively rare, most skin cancers actually carry a net mortality benefit because of the association with being outside.

That's super interesting!

I don't know about that. My memory of shepherds from when I was a kid in my grandparents' village was of a guy being covered head to toe in what looked like terribly hot clothing for the summer. And this wasn't some high-altitude village, either.

I figure I was getting much more sun exposure as a kid running around in t-shirt and shorts then the local shepherds did.

I'm sure their skin cancer morbidity is higher but the studies I've seen seem to show that sun exposure overall correlates with lower mortality and morbidity overall. There may be confounders like exercise at play but shepherds are probably getting more than most subway workers.

I put together a monster air quality monitor with just about every sensor I could cram into it. Dust sensors, geiger counters, the whole works.

One of the biggest problems I found was indoor CO2 levels. High CO2 levels (much less than dangerous CO2 levels) make you groggy, sleepy, and can induce headaches. I now get notifications to open my windows when CO2 levels pass a certain threshold.


Having good data is the first step towards making a change.

I like that the air quality monitor enables you to figure out how much the window has to be opened and also when.

That's far more useful than the blanket advice of opening windows daily.

Is it possible to buy one of these from you?

> According to this logic, anyone who works in the subway should be dying, what, 10 years earlier?

Just two more nuances:

1) The article is measuring loss in "DALYs" = disability-adjusted life years. 10 DALYs lost may not mean dying 10 years earlier, but could also mean suffering from Alzheimer's for 16 years (Alzheimer's has a weight of 0.66 [1]), or any combination thereof (e.g. 10 years of Alzheimer's + dying 3.3 years earlier).

2) The cited number is for the "worst offender" on the NYC metro. The pollution levels on the London underground are less than a 10th of that.

[1] https://en.wikipedia.org/wiki/Disability-adjusted_life_year

Statistical evidence for high BMI's effect on quality of life and morbidity is more compelling, at least in the developed world. Author's thesis does stand insofar as AQ often being overlooked as a causative agent behind cardiovascular disease.

BMI is known as a very bad measure

BMI is known to be a bad measure for outliers (e.g. bodybuilders) and just a ballpark rather than exact but for most people there's a pretty decent correlation between BMI and body fat percentage or whatever you prefer.

BMI is a fairly decent measure for folks who don't work out or otherwise build excess muscle. And since that's _most_ Americans, BMI is a good starting point to use when judging health fitness.

So what is a better measure ?

BFP is the real deal: https://en.wikipedia.org/wiki/Body_fat_percentage


(however the statistics on BMI vs mortality as still completely valid)

Great now let's figure out how to measure BFP across the entire population the way we can with BMI. Every guide i've seen either uses expensive displacement equipment or trained professionals with calipers. That doesn't scale nearly as well as a height / weight calculation

> Great now let's figure out how to measure BFP across the entire population the way we can with BMI

I never said that. I said the opposite.

Waistline to height ratio measures unhealthy weight better than BMI.

For anyone who isn't a bodybuilder and is between 5'0 and 6'3 BMI is a pretty damn good estimate.

Use height to the 2.5th power as the denominator rather than height squared.

> anyone who works in the subway should be dying, what, 10 years earlier?

From my ad-hoc survey of subway driver friends, this seems about true... Most die in their late 60's in a country where most people make it to 70/80.

Obviously the fact their job involves sitting in a chair all day doesn't help things...

This. (Warning: light-weight argument incoming, but it’s intriguing) Is anyone seriously looking into this? How do we know that (for example) subway workers don’t have shorter lifespans that can’t be accounted for any other way? Just taking a superficial, devils-advocate stance makes me wonder what other broad correlations may exist that aren’t known just because they’re not being investigated rigorously? In some ways this also intersects with the bias against publishing negative results - what if a good study of this has been done but wasn’t published because it wasn’t headline-grabbing?

Is there a fundamental reason why the subway must be like that? I assume it's not as bad in say Hong Kong? Copenhagen metro for example is automated and there's a wall and automatic doors separating the tracks from the platform. I assume it's quite clean.

Subways are dusty because they use mechanical brakes that produce metal dust particles.

For $50 per carriage, dust collecting sponges, fans or filters could be fitted, but train companies don't care. By doing anything about the dust they might be opening themselves up to lawsuits claiming they didn't do enough about a risk they knew about... There are also political issues - often the train company bought the trains 50 years ago and will pay extortionate prices to the original manufacturer for any modifications, and if they make modifications themselves the manufacturer will drop all support.

Many modern trains are starting to have electric braking, and that produces far less dust.

You say “train companies” as if every major subway/metro outside of Japan wasn’t nationalized in the early 20th century.

Same applies even moreso when it's government run...

> Is there a fundamental reason why the subway must be like that?

1) Dust from brakes, as noted by other comments.

2) Tunnels, and stations in underground spaces, therefor hard to ventilate.

> I assume it's not as bad in say Hong Kong?

No idea, but air quality in the London underground is very bad indeed. I mean you can sometimes see a visible brown haze looking down the length of the platform.


Having lived in Manhattan for 7 years, and Hong Kong for 9, I'm pretty sure the air quality inside the Hong Kong MTR is better than the NYC subway. Air in the stations in Hong Kong is air conditioned and filtered. Not that feeling is the best measure, but the feeling of the air in a lot of the NYC stations is just not great.

Outdoor air quality in Hong Kong was pretty rough a few years on either side of 2014, but it has either gotten better lately or I've stopped noticing the bad days.

I was surprised about the actual driving too. Vancouver's Skytrain is automated and largely outdoors, with the exception of occasionally needing to take a train over manually

I agree with what you are saying, but there is just a small technicality I'd like to correct.

> ...I mean, our body requires minerals -- we're drinking them in our water all day long

Regardless of the minerals in question here, route-of-delivery is a big deal in toxicology, so the line of thinking here is a bit flawed.

> These statistics are just not passing the smell test.

These numbers are derived from estimations, for sure. But they are sophisticated estimations and serve to rank other health risks in life. In rich countries we usually obsesses about things like pesticides in food or „small particulate matter“ to an extent that it is absurd. Air quality is a real threat in many countries but not anymore in the US or most of Europe for sure.

As the article shows obesity is the killer number 1 in the US. A healthy diet is something which is totally under our control. And for sure smoke generated at a BBQ for example is not very healthy and can be avoided by using a gas grill.

These are things usually ignored and thus underestimated in our health obsession.

“Air quality is a real threat in many countries but not anymore in the US”

Couldn’t be more wrong.

As the author casually admits, we know nothing without experiments. End of story.

What makes your statement so wrong is that it takes decades for the consequences to show up, if they are measurable at all, in non experimental studies. That is exactly the same reason that cigarettes were considered safe for so long. Health consequences take decades to show up and without experiments all we get are loose correlations. Air quality in many places in America is getting worse, the size of the population in these areas is massive. To declare to potential health consequences 60 years in the future without any solid experimental evidence is the same as the doctors of the 50’s telling patients to smoke up, there’s no evidence cigarettes are bad. Exactly the same.

> What makes your statement so wrong is that it takes decades for the consequences to show up, if they are measurable at all, in non experimental studies.

So, you're telling me the air quality is getting worse despite this trend not being observed, yet? There is a logical fallacy somewhere. Furthermore, the link between lung cancer and cigarette smoking was well observed already in the 50s but the tobacco industry naturally downplayed the risks.

BTW: It is an established fact that air quality in the cities of 19th century was way worse -- mainly due to the fact that people cooked and heated their places with open fires and coal. For some insight on the UK: https://theconversation.com/air-pollution-in-victorian-era-b...

Define “air quality” as a single metric is crude at best, but arguably dishonest. The nature of pollution and the pollutants themselves have changed have they not?

Edit: To illustrate the point, assume that getting regular physical is more important now than 100 years ago, due to on average more sedentary contemporary lifestyles. Assume heavy air pollution decreases outdoor activity, which seems plausible if not certain. How long would it take for a body of scientific literature to develop to document the problem? Given measurement problems and the difficulty of doing simulation heavy research, we might never be able to prove such a linkage exists, even if it did.

> According to this logic, anyone who works in the subway should be dying, what, 10 years earlier? Which is obviously not happening.

I don't think you're being honest here, it obviously isn't try to make the point that each commute = 1 year, that's why it's in the "lifestyle" category and not in the "single event" one

> it obviously isn't try to make the point that each commute = 1 year

They aren't saying one commute takes a year off the life. They're saying that people who's job is riding the public commute infrastructure spend roughly 20 times as much time breathing the air in the commuter infrastructure as people who commute to/from work, so if the effect is linear... that's roughly a 10 year reduction in lifespan.

Or, are you trying to say that some underlying common factor between commuting and home/office air quality is present, and so the commute is just a proxy for that common factor? If that's the case, if that common factor is identifiable, it should be named. If that common factor isn't identifiable, how are we confident in attributing it to air quality?

Or, are you claiming that the air quality in the commute infrastructure is the culprit, but the effect is dramatically sublinear?

> or that a daily commute between Newark and NYC takes half a year off your life.

As compared to an "average" US city taking off a quarter-year. I think the commuting thing is a red herring, and they just mean living/working in the NYC metro area, which as a densely populated area likely has slightly worse air than an average US location.

>or that a daily commute between Newark and NYC takes half a year off your life.

>According to this logic, anyone who works in the subway should be dying, what, 10 years earlier?

I don't think that's what they mean. I think it's a lifetime NYC commuter on average should live half a year less than someone out in the country.

> According to this logic, anyone who works in the subway should be dying, what, 10 years earlier? Which is obviously not happening.

Are you sure this isn't happening? I could easily imagine people working in dusty places for example dying earlier due to health related issues that could be traced back to the lifestyle.

Yeah, it is not at all obvious to me that this isn't happening. Is anyone even collecting the data you would need to tell whether or not it's happening? I'm sure the transit authorities would rather not know.

Oh I read their allegedly "humidifiers kill" snippet, so tl;dr:

> but ultrasonic humidifiers produce huge numbers of particles. They turn any minerals in the water become airborne particles. got the following steady-state increases over background levels.

> Mineral water: ~265

> Tap water (Seoul): ~260

> Purified water: ~50

> Distilled water: ~0

So what you mean is that if I follow the instructions on the manual and use distilled (or at least purified water) for mineral and biological reasons, the issue is smaller to non-existent?

Get a TDS meter and measure PPM in your water. Reverse osmosis filtered water will do, just activated carbon filtered water will not.

You can't readily buy DI water, but you can buy distilled water. The two are entirely different purity levels.

Reverse osmosis filtered water is mainly what I have in mind, companies sell that. 6-14 PPM is what I measured personally and I think it falls into this category.

That's some crappy RO water. My home system takes 45 ppm water and reduces it to <2 ppm (~500 kΩ). For all intents and purposes, it's not conductive on its own.

Distilled water is made by steam condensation, and nearly ultra-pure but still contains dissolved gases.

DI water should be made from some distilled water to be the highest possible purity, but it's usually made from RO or simply filtered tap water.

There are some things DI can do that steam distillation can't, and vice-versa. The two processes are entirely different and NOT interchangeable.

Ok, I modified my original comment.

> My home system takes 45 ppm water and reduces it to <2 ppm

My tap water is around 227 and filter is just recently installed, there's still some air in the system. I don't think it will go that low ever, but it's good enough for me. I plan to remineralize it a bit for drinking anyway, so it's all a bit moot.

Filters and RO systems rarely remove dissolved gases. Try making ice from RO water vs. lab DI water.

I don't need it to remove air from water, I need it to stop mixing air that was in the empty spaces around filters when they were installed into said water. Tap water doesn't have much air in it I don't think, it will sort itself out eventually. Right now I have very small air bubbles that are still visible when filling up a glass, they are created when air and water pass through RO membrane. After you let it sit for a while PPM number drops.

> According to this logic, anyone who works in the subway should be dying, what, 10 years earlier? Which is obviously not happening.

On the contrary, that sounds extremely credible.

If you divide life expectancy stats just by gender and race, you already see more than 10 years difference.

> According to this logic, anyone who works in the subway should be dying, what, 10 years earlier? Which is obviously not happening.

Why is this obvious?

Because you would see all the time commercials on tv letting you know that if you, or a late loved one, worked in the subway you may be entitled to financial compensation.

No. Just no. That's not how science works.

Not unless data has first been collected and analyzed. There was a long period of time between people suspecting cigarettes were unhealthy and actual data showing it

> According to this logic, anyone who works in the subway should be dying, what, 10 years earlier? Which is obviously not happening.

We know this?

I find it hugely suspicious that huge claims are made but the methodology behind the numbers presented in the first figure is not explained at all.

Further down, correlation plots are shown but no analysis of potential confounders that could affect life expectancy as well, like access to medical care, education, wealth.

People are dying from air pollution it's just that we like to ignore it because what are you realistically going to do about it... Move to your villa in the countryside? Thankfully as a human being I'm perfectly able to ignore and suppress inconvenient information.

"According to this logic, anyone who works in the subway should be dying, what, 10 years earlier? Which is obviously not happening." And you know this how?, Where YOUR numbers and conclusions come from?

As for humidifiers, specifically ultrasonic ones - we bought one for our baby, but immediately with it also the best water purifier we could find (Zero water) that produces demineralized water practically absent from other molecules than H2O. There is no dust the next morning on the floor (or anywhere), there is no buildup of calc in the machine.

I do believe that breathing that fine dust isn't very healthy long term, but that article outright lies about using it = taking 50 minutes out of every 1440 minutes of everybody's lives.

We would see this effect in dusty (ie Saharan) regions already, there are hundreds of millions of people living in those conditions. What is dust if not small particles of stones and organic compounds flying around.

> produces demineralized water practically absent from other molecules

This is plain false.

And in NYC and the US in general having better health care especially for poorer workers will have much more of an effect.

Completely untrue. The US spends the most per capita and gets worse outcomes than other countries. This fact was even highlighted in Michael Moore's Where To Invade Next?

Worse than many countries, but certainly not worse than India or Indonesia that the US was being compared to in this article.

I said "Better" not throw more $ at the current omnishambles

do you know of mortality statistics specifically for subway workers? Because it may very well surprise you and it can't be grounds for dismissing the hypothesis.

I wonder what the PM2.5 meter would say about fog or mist.

a bit off topic, but i can logically guarantee you that smoking takes at least 5 minutes off your life. It takes that long to smoke a cigarette...

You have to put things into perspective, why should you care less about living now then in 40 years in the future? Chances are your quality of life will only get worse etc.

> Chances are your quality of life will only get worse etc.

The quality of your end of life gets (on average) much worse if you smoke.

Not only do you die 5 minutes earlier, but you also spend more additional time with disease impacting your quality of life, such as COPD.

Not if smokers multitask, like making your contact cleaner solution in the factory or making your delivery food.

IMO, all cigarettes should have cyanide added to them to reduce the costs to society by speeding-up the slow suicide and excess harm to others.

should all diesel cars have lead fumes pumped into the cockpit? Should all alcoholic drinks contain methanol?

Frivolous response.

Diesel vehicles are extremely hazardous causing great harm to millions but go under regulated because of money. ICEs should die.

Alcoholic drinks don't directly harm anyone else in their consumption and the QALY/micromorts involved are small.

Do you have any other rude, unscientific arguments?

no need to label other people's comments as rude.

Also, the suggestion to make products more deadly so that they are used less seems like bad policy. Reduction of harms usually does not mean killing the patient.

Thank you for this extensive resource on air quality. Yes, it needs to get more attention as it is one of the main drivers of mortality of environmental risks.

One thing one has to bear in mind is that often when you optmize your home for low PM (e.g. with air purifiers and fixing of air leackage) your CO2 will get very high causing headaches and reduce cognitive performance.

So it always makes sense for indoor air quality monitoring to measure PM and CO2 in parallel.

We have open source, open hardware build instructions for a very reliable Air quality sensor that can be used to measure PM2.5 and also CO2 [1]. It is very accurate for the fraction of the costs of commercial sensors. You can build it for less than USD 20 (or with CO2 for less than USD 50) and send the data to our cloud server or any other backend.

I am more than happy to send you some free PCBs (you just paypal me the cost of the postage) and you can build your own sensor and log the data. Contact me if you are interested.

[1] https://www.airgradient.com/diy/

I have an AirVisual Pro, which is quite expensive, but my half finished air quality monitor project had been on the bench for much too long.

I have windows open all the time, air conditioning on too often, and dehumidifiers and HEPA filters as well. It is not efficient or particularly environmentally friendly... but I want a CO2 level < 800 ppm and a PM2.5 level under 10... so here we are.

My next half baked idea is figuring out a way to have a sealed home and an appliance (or messy bench-top device) to remove CO2 from the room continuously and exhale outside -- current ideas revolve around using a carbonate (lithium? sodium?) in water in an electrolysis cell and an aquarium bubbler to collect CO2 and expel it outside. The best I've been able to accomplish so far is baking CO2 out of baking soda (sodium bicarbonate) and sealing it in about a cubic foot container and achieving ~300 ppm CO2 (lower than outside which is ~400-450).

> and an appliance (or messy bench-top device) to remove CO2 from the room continuously and exhale outside

There are these things called "plants"...


From my armchair-research, there are scale challenges with plants.

Algae is commonly the go-to for CO2 scrubbing for it's relative efficiencies. Algae might scrub 1-3 grams of CO2 per liter per day (https://www.osti.gov/servlets/purl/1485133).

Humans exhale approximately 1kg CO2 per day.

I consider 300-1000 L of algae scrubber tanks per person a lot of volume.

The study you linked did not measure CO2.

Bubbling air through quicklime slush is an easy way of removing CO2. You can turn the calcium carbonate that forms back into quicklime by applying heat.

But it's probably better if you invested into a counterflow heat exchanger for ventilating your home. You can recover a large part of the heating/cooling energy.

The question is how much CO2 can I fix with a reasonably sized apparatus and really I would prefer a continuous system (which is why electrolysis) rather than a batch system.

Also I would prefer levels lower than outside, obviously air exchangers will necessarily be worse than just being outside.

You might try using oxygen conentrator with high throughput to concentrate oxygen from outside and pump it into your home.

With small device I could drop CO2 levels to zero in volume of a gargabe bag in few minutes.

But that would give you oxygen rich atmosphere. You'd probably want to add some inert gas to that. Nitrogen preferably. Are there nitrogen concentrators?

Also all of that is probably really dangerous because human body doesn't detect oxygen level, just CO2 level. So you might easily pass out and suffocate without any warning if your oxygen supply unit get damaged but your nitrogen supply unit doesn't.

We are still talking about home... on planet Earth, right?

Of course. :-) The whole idea is based onthat ouside of the fact that there's plenty of oxygen for the concentrator to concentrate.

I'd assume that some chemist or other has already published a paper about that. But you could probably figure it out yourself experimentally by weighing quicklime, letting it react and weighing it again. Start a youtube channel to finance the project :)

Well I've gotten as far as purchasing 20 pounds of baking soda... my experiments thus far haven't been able to remove a detectable amount of CO2 from a room.

My literature searches haven't had much success thus far, lacking a chemistry degree hasn't helped. I have found some things but not enough to come to any sort of engineering designs. I'm assuming it's one of those things that's almost too simple for anyone to have bothered writing a paper about unless they had the exact sort of ideas I did. (OR they're using terms that I haven't been able to come up with yet)

Try buying 20 lbs of calcium hydroxide, it is sometimes used for soap making iirc, so it should be available on amazon. Bubbling air through a concentrated solution should do something. At least at the CO2 concentrations of exhaled air you get visible amounts of insoluble carbonate: https://www.youtube.com/watch?v=Vl9A8Iyc_LY

Really prefer co2 levels lower than outside? What's your outside environment?

Before the industrial revolution the CO2 levels outside were around 250ppm or at least less than 300.

Current levels outside as measured by my device just now are about 450ppm.

My measurement is also about 450ppm and it's fine for me. How do you discovered lower level is better for you?

I don't know for sure, but there are certain things I notice which I think may have been improved when I started keeping track of CO2 and keeping my windows open. (I don't spend most of my time outside and I certainly don't sleep outside; outside levels might be 450 but inside levels even with my mitigations are usually around 700)

Like so many things I think it is a small effect; it's not like I can go anywhere for a week to experience 300ppm air.

I haven't gone to the levels of designing experiments and data tracking on myself. The fact that I've lived with allergies and a broken nose most of my life probably hasn't helped my personal respiration characteristics.

> by applying heat

More heat than is common for home appliances I know! A commonly referenced stat is 825 C. There's really a gradient: https://en.m.wikipedia.org/wiki/Calcium_carbonate#Calcinatio...

Ah yes, with "heat" I meant a nice fire.

You are describing an anaesthesia circle breathing system, otherwise known as a rebreather scuba set. :-)

You would need to consider the occupant oxygen consumption. A typical human respiratory quotient is 0.8 (0.8 mole of CO2 produced for every 1 mole of O2 consumed). You’ll get a net inward movement of gas into house all things being considered.

Anyway, don’t do if. If you do it ‘right’ the argon will slowly build up and you’ll asphyxiate. Thankfully achieving that level of seal is very difficult.

If you are really worried about PM2.5, just wear a PAPR.

Oh I'm not interested in hermetically sealing my apartment, there are no worries of normally constructed buildings being able to withstand a meaningful difference in oxygen pressure between inside and outside. CO2 pressure though can easily be increased by a large factor (5x is easy) and maintained with humans inside and closed doors and windows.

PM2.5 is easy to maintain with HEPA filters.

CO2 is not easy to maintain without forced ventilation, and really I would like to try inside levels lower than outside levels. (say 300 ppm)

I’m intrigued by the idea of chemically scrubbing co2 at home as well. Hepa filters are easier to use than I’d expected. The next big step is co2 reduction.

Maybe get in touch

Don’t those requirements conflict? Maintaining a partial pressure difference between inside and out for CO2 but simultaneously preventing a partial pressure difference in O2? I guess with a large enough scrubber running constantly it might work but it will be highly inefficient - a bit like running AC at full blast with open windows.

They do to a degree but overall composition of the atmosphere has so much oxygen and so little co2 that the dynamics are quite different.

There’s something like 50x as much oxygen in the atmosphere as co2 so a relative change of 1% nominal value will correct itself fifty times faster for oxygen than for co2 between outside and inside (ok a wild simplification, but still)

The result is that without really intense sealing it’s basically impossible to make a difference in indoor oxygen levels whereas with even a cracked window i can maintain co2 levels two to three times outdoor concentrations in my apartment.

Running a co2 fixer with the place shut up would be more like... running the air conditioner full blast with the place shut up. Yes there would be losses but they would be relatively contained.

Typical Passivhaus-Buildings are very airtight and feature air exchange systems often even with HEPA-Filters. That should do the trick.

Could you get a few more plants around the house? Plants can remove things like benzene, formaldehyde, xylene, and toluene. Maybe not the fastest but certainly don't cost much once you have them.

Unfortunately this myth, which I also once believed, has been debunked. You just need waaaay too many plants to actually have an effect. The tests the myth were based on all assumed a closed system, which just isn't realistic.

From one randomly googled article on the myth of house plants cleaning the air:

"To remove toxins, you would need at least 10 plants per square foot."

To remove how many "toxins" exactly? Like, let's say I actually have a shitload of plants, like my ceiling is just lined with peace lilies. Presumably there is some % of something being removed, I'd be curious to hear what that is.

Well "toxins" is ill defined.

But CO2... to simplify imagine being a vegetarian, how much plant matter would you eat in a day? How much plant matter grew in one day in your houseplants? The only way plants are going to fix carbon is by adding it to their own mass. Just think about a conservation of carbon atoms. There's no way any plants in your apartment are going to make a dent in the carbon cycle of your personal environment.

There are arguments to be made for lots of things sticking to or getting sucked into the leaves of plants... maybe if there were a whole lot of plants a meaningful amount of VOCs or other pollutants could be removed... maybe.

If you think about it you have to grow an amount of plant matter comparable to the amount of food you eat in order to maintain levels (considerably less of course because a lot of carbon goes down the toilet, but still a fixed fraction, this would take full sun an a considerable area, like a fraction of an acre)

That's weird. I can easily get CO2 levels way below 800 with windows closed, just not completely sealed.

And then air purifier can keep PM2.5 levels below 10 on the lowest setting while outside is above 30

What kind of home do you live in? I think a lot of the new construction is sealed very well and there are few leaks besides the actual interfaces.

Block of flats. Apartment is fairly well sealed. If I seal the windows I can drive up CO2 levels to 1500. I have plastic windows with seals that have "unsealed" mode. In this mode window is just barely opened. Like 1mm gap between a window and a frame.

And one window cracked like that is enough to drop CO2 levels below 800 while there's one person in the apartment.

note that the effects of periodically higher co2 concentrations on overall health is inconclusive at best (life evolved with significant co2 around). particulate matter and atmospheric pollutants (like voc’s), however, are most assuredly detrimental to our health, so it makes sense to act mainly on the latter (with air filters/purifiers) over the former.

I've worked in offices where the CO2 levels regularly spiked to levels not seen since... pants first started colonizing the land.

It's been, what, 30? 50? million years since atmospheric CO2 levels matched current outdoor levels, much less what happens inside.

the point is that humans (and life in general) have entirely evolved with varying levels of co2, so the excess levels found in a fairly closed room is unlikely to be a really serious risk (vs. a sealed room with much higher concentrations, where it's obviously a serious asphyxiation risk). this risk, according to research, is currently inconclusive at best.

the concentrations and types of particulate matter, however, is unprecedented, and as such, presents a higher inate risk, something that scientific research is really only starting to grapple with but so far is showing to be likely a serious risk to many (most?) species on earth.

with that said, i'm not trying to discourage your project in any way, just saying that for most people, addressing particulate (plus voc) risk is likely going to be the overwhelming majority of the benefits to be found in relation to indoor air quality. reducing co2 could be worthwhile if you have an especially airtight room/house, but nearly no houses are that airtight (passiv houses are meant to be so, however).

What kind of pants are best for removing CO2?

The kind with lots of chlorophyll... all the rage with the kids these days (sigh... plants... plants)

What about acetone or ethanol or whatever else we exhale that builds up?

shrug big effects first.

You might be interested in this paywalled paper (or similar ones): https://pubs.acs.org/doi/10.1021/acs.iecr.0c02255

I've seen a study or two that claim that the bulk of some PM, like brake dust for example, is much smaller than 2.5um. Having exposure to the industry, do you have hopes for sensors that can identify smaller particles than .3um (that's the smallest Purple Air goes).

In practice, how does one try to achieve a balance between CO2 and PM? Do you open the windows for a while when CO2 is up and PM is down, and then close them and run your purifiers when CO2 starts to go back down? Is it possible to keep both low with HEPA filters on the windows?

A solution that one of our customers uses (Prem Tinsulanonda International School) is the installation of a positive pressure system. They are able to achieve near zero AQI in their classrooms when you have more than 300 US AQI outside.

You can read more on it on the See the Air Blog: https://seetheair.wordpress.com/2021/04/26/thailand-school-s...

I keep my HEPA filters on with the windows always open.

If the air quality is decent outside, it is easy to maintain a PM2.5 rating of near <10 like this.

In California fire season I have a box fan on high in the window pushing air in (and sealing the areas around the window) through an MPR 2800 furnace filter (which is better than the 99.97% rated hepa filters, would be marked as a ULPA filter I believe in different contexts) with this I can maintain the ~0 PM2.5 rating inside even when the AQI outside is >300 while keeping CO2 in check.

It's been quite surprising how easily the CO2 spikes with closed windows and doors in the bedroom with just one person... I essentially always have a window in each room open several inches, cracked isn't enough, usually with at least one fan pushing air through a window.

The best case solution would be a passive house with MVHR (Mechanical Ventilation with Heat Recovery) and incoming air filtration. This means your home has a steady flow of fresh, low-CO2 air that is filtered for pollen and other particles (depending on the air filter chosen).

Another solution is to install a positive pressure system with high performance HEPA filters. This is especially recommended if you live in areas with very high air pollution.

Positive pressure systems can virtually achieve zero AQI inside even on the worst polluted days. You can read more here: [1] https://www.airgradient.com/blog/2020/01/08/positive-pressur... [2] https://seetheair.wordpress.com/2021/04/26/thailand-school-s...

This. Architects now include heat exchangers in houses, so air is renewed at basically the same temperature, ensuring ideal comfort for low CO2.

co2 and pm should both go down with windows open.

i put my air purifiers on low when the windows are open to deal with the particles i throw up by moving around and doing stuff indoors. with the windows closed (usually only at night), i put the air purifiers on medium/high.

> co2 and pm should both go down with windows open.

Very much depends on where you live. I have a few DIY air quality stations with data being piped to Grafana. I just looked at the latest data, the average outside PM level for the past 5 months has been around 100 µg/m³, while inside it's around 10 µg/m³.

This spring happens to be pretty windy and this skews the outside levels down, otherwise the ratio would be much worse.

Don't think this would be true in any city in Asia or for city centers around the world.

i live in LA on a relatively busy neighborhood street and according to my air quality meter, it’s true. concentrations go down during the day (windows open) and up at night (windows closed).

edit: i mentioned the road to note that outdoor pollution is higher during the day, yet opening the windows despite that lowers overall particulate levels indoors. it may be different in indian cities or cities like beijing with much higher pollution levels.

I have noticed every time I open my windows, the no2 levels reported on my Dyson filter spike. Not sure what to make of it but it’s interesting.

nox is a combustion byproduct so probably that?

Yeah I would assume it was coming mostly from nearby cars.

The crazy thing is there are no nearby cars. There is a highway about 1.5km away which I assume it must all blow from. There is nothing else within 1.5km

That's a great resource, thank you. As a tinkerer who is already quite far down the ESP8266 rabbit hole, are you able to tell me if your software distribution has any particular "special sauce" around the interpretation of the data from these sensors? Or is it predominantly glue between the sensors and the OLED display / your cloud service?

I am interested in replicating your hardware stack but implementing the software stack using the esphome framework which supports all of the components used in your DIY solution.





There is no secret sauce needed. The Plantower sensors tell you the PM2.5 in micrograms directly and we just display it to the OLED display or send it to a server. It is all open source so you can check the code.


Thank you for all of you interested in getting the PCBs. To send me a message please go to https://www.airgradient.com/diy/ and send me a message with the orange chat button. Thanks!

There was a bit of interest last time I remember you posting on here as well - have you thought about putting up a batch on something like crowd supply? I think it would sell well enough to make it worth your time, and fire season is coming up again soon.

Yes that might be a good idea but I am very happy that so many people are interested in building one and that we can increase the awareness on air quality so I am happy to do the work ;)

Yeah, this is an interesting enough problem to me that I recently started researching how to build an arduino version of what this person is offering - in my head, I basically reinvented the product they're offering, without all of the nasty bits of actually having any idea how it works. I would definitely pay a reasonable amount of money for a set of sensors that Just Worked that would collect data in my house.

I understand how fixing leakages, or more generally, not properly ventilating your place, would increase CO₂ levels, but where do air purifiers come into the picture? Is it just because someone who has an air purifier is also more likely to not ventilate (to keep PM2.5 down?), or are air purifiers themselves somehow bad for CO₂ levels?

I can't guess why they would be, and searching around a bit doesn't seem to suggest that's the case either.

How should someone contact you? I looked into setting up something on an Arduino last year, and the CO2 sensor I ended up purchasing was not very good, so it's cool to see someone thinking about this problem domain.

We use the Senseair S8 CO2 sensor which is very accurate and of high quality. Some of the TVOC sensors give an estimated CO2 level (eCO2) which is not recommended because these values are not very accurate.

To send me a message please go to https://www.airgradient.com/diy/ and send me a message with the orange chat button. Thanks!

FWIW I've been pretty happy with Senseair S8 0053 for my DIY stations. They're relatively expensive though.

Not affiliated in any way.

Yes the Senseair S8 is very good. Only problem is that the automatic baseline calibration sometimes needs 7-10 days to kick in. But you can also do a manual calibration.

I'm definitely interested to build one of these. Located in Vancouver Canada. Maybe you can mention in a reply to your own post how people can contact you (if you can't still edit your post)?

What is your PayPal?

I see the aliexpress link to the PM sensor doesn't work (at least not in the US); where else do you recommend buying one?

Yes, sometimes some components are not available for all countries. Just search for the same sensor on aliexpress. There are many vendors for the same sensor. Some will ship to the US.

Search for SDS011 on aliexpress, the USB version. It's good and not too expensive.

I am interested. Do you ship to Canada (happy to pay the difference/wait for you to figure out the postage rate)?

Also in Canada and interested in getting some PCBs. Not sure if OP is selling if not i would be into splitting the cost of getting a batch made if its economical

Yes, we will ship worldwide. Please send me a message from our website and the number of PCBs you would like to get and I will check the postage.

I too am interested but I'm from Chile.

(replying to you to not pollute parent level replies)

Please send me a message through the orange contact button on the webpage.

Does the Senseair S8 actually measure co2, or is it inferred via VOC levels?

I don't know the answer to that specific question, but I do know it's an NDIR sensor. The Wikipedia page on that sensor type likely answers your question—


I am extremely interested. Willing to pay you the cost of the PCBs too.

just fyi, the contact us for details button is not working for me.

4(index):14 Uncaught ReferenceError: zE is not defined at openWidget ((index):14) at HTMLDivElement.onclick ((index):308)

I'd be very interested in this, please email me your PayPal!

Can it be powered by a battery, to be portable?

You can just power it with the USB cable from a power bank.

The biggest pitfall I see with this is we’re extrapolating from large doses of air pollution to very tiny ones.

Clearly we have enough evidence to say that smoking a pack a day or living in a smog-filled city will cut years off your life. But we would need truly gigantic samples to show that blowing birthday candles or broiling fish once a week will cut weeks off your life.

Instead these conclusions are being derived on linear extrapolations from large air particulate doses. Yet many things in biology follow the principal of hormesis, where a small dose or a toxin may be harmless or even helpful.

Similar models have been used for years and are still the gold standard when predicting the health effects of radiation exposure. Yet mountains of evidence show that radiation workers, who are regularly exposed to small dosages of otherwise harmful regulation do not have anywhere near the cancer rates we’d expect from the linear extrapolation models.

Sorry for the pendantry: it sounds like you mean linear interpolation, rather than extrapolation. Extrapolation is where you project outside the range of previously collected data, and is particularly likely to result in false conclusions. Interpolation is where you estimate a value inside the range of collected data from points around it, and is usually a lot less dangerous. But I agree with your point that, in this case, it does seem pretty baseless.

But the article is extrapolating, not interpolating.

Extrapolation is when you're extending to outside of the measured data range. In this case, the measurements were all of large values, and it's extrapolating (linearly) to small values. Just because the values being extrapolated to are smaller, rather than larger, doesn't make it interpolation.

Which is precisely why this has the risk of false conclusions, like you say.

Could you give some citations for studies on radiation workers? The permissible doses in most countries are extremely low and there are not that many people working in the industry. This makes me wonder they manage to achieve statistically significant results.

Everything is a poison, only dosage takes that characteristic away.

EVs reduce tailpipe exhaust near roads but it's worth noting that brake abrasion dust isn't going away anytime soon and it's considered very bad to breathe, possibly in the same league as diesel emission particles.[1] I guess regenerative braking on an EV reduces this somewhat.

Tire dust is also concerning.[2]

[1] https://academic.oup.com/metallomics/article/12/3/371/595624...

[2] https://pubmed.ncbi.nlm.nih.gov/22642836/

Most EVs indeed use regenerative braking. Which means your brake pads last a lot longer as you barely use them. Tire particles are a bigger problem. Just think of the mass of tires that you erode away before you replace them (routinely) and compare that to the brake pads you replace much less often. And it's not just the tires that erode but also the road. Asphalt particles are nasty as well. Though most of that dust is quite coarse and doesn't stay in the air as long. But then, tire and road dust is apparently the biggest source of microplastics in our oceans. It washes away, enters our sewers, rivers, and eventually the oceans. It's bad for different reasons as well.

EVs might as well be replaced with rail cars. In which case, it would be better to have local and national trams rather than single-occupant vehicles.

It also would be cheaper to have carbon-captured concrete bicycle and walking paths rather than asphalt highways or roads.

Single-occupancy vehicles need to go away.

Anecdotal, but since recently getting a plug-in hybrid I've only been using regenerative braking except for the most abrupt stops. Whenever you approach a red light or junction it's not hard to stay within the regen braking zone.

I’ve always made it a game to see how little I can use my brakes, whether in bumper-to-bumper traffic or more wide open suburban roads. I never understand why people need to race up to red lights just to do a hard brake. I take solace thinking they probably replace their brakes 20% more frequently.

I did that too and my brakes rusted from lack of use. Ended up having to get towed for an expensive repair..

Yes, I have owned a Prius and Corolla Hybrid and on both vehicles the front rotors always go very rusty because I only ever press the brake down enough to activate the regenerative braking (for better fuel economy). The regenerative braking power of these vehicles is about 20-30kW.

And as a side effect, I haven't needed to replace the brake pads for about 150,000 kms on the Prius. Actually the mechanic told me that they look brand new. I haven't experienced any problems from the rust yet. The front rotor on the Corolla (2020) seems to be a much better, newer design, and doesn't rust nearly as much as the Prius (2014).

endnote. For anyone considering the new Corolla Hybrid ... I rate it very highly as perhaps the best car ever designed.

That’s a bummer to hear, and I saw other folks mentioning that on this thread too. Could you describe the climate in which you’re located? Maybe a humid, salty coastal climate will affect that differently than a dry, dusty climate.

Nordic, inland. Plenty of salt on the roads throughout the winter.

EVs drastically reduce brake dust.

Probably not in the city, regenerative breaking doesn't fit most scenarios, especially seeing how people tend to drive high torque vehicles.

I drive a 12yo hybrid and my annecdotal experience suggests that isn't correct.

I drive mainly around the city and had to replace brake pads recently as they became rusty (salt during winter). The pads had been on for 80,000km and were less than half worn. On regular ICE cars (which have bigger brake pads) you'd usually have to replace them well before that point as they'd be worn down. I'd imagine they last even longer on newer hybrid and EVs.

What? I am driving EVs multiple times a week in a European city and regenerative breaking is always happening at every brake action until mechanical brakes kick in.

That must reduce appliance of mechanical brakes at least by half.

You can turn regen braking off, but why would you unless maybe the EV model feels like shit when switching between regenerative and mechanical brakes.

Most definitely in the city. Regen handles the vast majority of braking for me. Depends on how strong the regen is in your vehicle I guess, but it's definitely possible to make it strong enough.

Brake dust is a bad example for EVs that make use of recuperation.

But tire abrasion is arguably worse for EVs due to the higher initial torque. Does anybody know if there is any difference between EVs and ICEs?

Another reason why we should not be making this big push for EVs but instead try to shift our infrastructure away from personal vehicles and towards mass transit and micromobility.

EVs will still make this picture look the same and are thus inherently an inefficient form of transport:


A lot of people don't know how to use engine braking, I guess teaching them that is going to significantly increased your brake pad life on existing vehicles in circulation.

Remember there are 3 brakes in your car, handbrake, foot brake and engine braking.

Foot brake and handbrake are effectively the same thing because they operate on shared friction components using mechanical wires instead of hydraulic lines. There maybe a different mechanism but it ultimately uses the same drum or disc.

Engine braking (jake braking) by trucks is illegal by statue in many cities and towns because it's very loud. Also, engine braking is riskier in terms of costs (stresses to drivetrain, torque converter, transmission, engine) than brake pads, so people aren't going to do it. Furthermore, they rarely have the skills or transmission to be able to do it conveniently. In addition, if it were more efficient or safer, it would likely be a feature, but I've never seen it in a standard transmission passenger vehicle.

I'm completely not a car mechanic, so the following is essentially a question phrased as a statement. But I'm a bit skeptical about this idea.

I assume you mean the engine break in a manual tranmission car (AKA stick shift in the US). But that relies on your clutch, which is still a friction based mechanism. Admittedly if you're breaking you're probably going to change gear either way, but the amount of friction depends on the difference in revs between the two parts coming into contact, which is presumably going to be larger if you're using it to engine break. So it seems to me that you're reducing wear on your brake pad but just switching that to increase wear on your clutch - with similar effects on air quality.

The clutch is only actuated when changing between gears. Engine braking happens when in gear, and at that point the clutch plates are compressed together and spin as one unit - no dust being generated. Any significant slipping of the clutch would make it burn up very quickly, since cars use dry clutches which cool down by radiating heat into the air.

Engine braking happens because engines have very high internal resistance - with motorcycles for example, there's no parking brake, you just leave it in 1st gear and it will not roll. So when you're not on the throttle, the inertia of the wheels/drivetrain will keep the car moving and the engine RPMs from dropping to idle instantly, but over time the engine will drain that inertial energy and slow down the car.

Also, engine braking is pretty weak on modern manual cars AFAIK. At least in my Honda Civic it basically doesn't engine brake, compared to my motorcycle. The effect is there but very minor.

Interesting, thanks!

No, it isn’t actually the clutch doing most of the braking, it’s the inherent friction of the engine moving without combustion

Actually EVs are much worse than ICEs for tire dust and road abrasion, as they tend to be much heavier than an equivalent ICE car, with much more torque.

One of the problems with EV’s is that the brake discs are rusting because they almost never gets used.

I don't think that really happens because breaks are used every time you stop. You can't regeratively break to 0.

Depends on how much your drive. Drive only now and then and brake only the bare minimum, you can get really rusty brakes. I ended up having to get towed with brakes being seized due to rust and lack of use.

I didn't notice any more rusting with a hybrid with regerative breaking than I did with normal car.

Rusting is for me more associated with the weather and lack of use of the whole car than with how much do you use breaks when you use the car.

Well yes, weather will cause rust. Good use of brakes can clean it up and keep the mechanism from seizing. Lack of braking = lack of use as far as the brakes are concerned.

I could run my errands without braking at all (except when stopping at a parking lot). Anticipate lights and traffic flow, downshift to slow down.. that's how I used to drive. At home I could even park without braking to slow down, thanks to a small incline at my parking spot.

My previous car, which had automatic transmission, didn't have really show any issues with rust because I actually had to brake when driving around town. Same weather, same locale.


It's a real problem. Your brakes can get totally stuck (been there), also you can fail the car's inspection with rusty brakes.

Yes, problem. Because the end it sheds more particulate matter when it is used. So the savings might not be as high as imagined.

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