A study on the extent of global air pollution | Hacker News Reader

A study on the extent of global air pollution

scienceswitch.com

102 pointsconse_lad70 comments

This article does a couple of things that seem strange. The title’s “first ever” claim is a bit odd since the WHO has been basing their recommendations on global studies for decades. The WHO page already says “WHO data show that almost all of the global population (99%) breathe air that exceeds WHO guideline limits and contains high levels of pollutants, with low- and middle-income countries suffering from the highest exposures.” https://www.who.int/health-topics/air-pollution#tab=tab_1

Another strange bit is the quote “the WHO’s recommended safe limit of 15 μg/m³.” The WHO’s 2005 “ideal” recommendation was 10 for average annual exposure, and the recommendation in their 2021 is for 5 μg/m³. I’m not sure where the 15 came from, but the WHO has proposed 4 levels of “interim” targets for cities & counties to aim for, starting at 35 and dropping to 5.

For anyone who cares about air quality, I’d totally recommend reading the WHO’s material, there is a shorter executive summary [1], a much longer full report describing methodology [2] and a web site full of resources [3].

[1] https://apps.who.int/iris/bitstream/handle/10665/345334/9789...

[2] https://apps.who.int/iris/bitstream/handle/10665/345329/9789...

[3] https://www.who.int/health-topics/air-pollution

> a Monash University study has found that only 0.18% of the global land area and 0.001% of the global population are exposed to levels of PM2.5 - the world’s leading environmental health risk factor – below levels of safety recommended by Word Health Organization (WHO).

I can't quite suss out the details, but it seems like they're saying that only 0.18% of global land area had levels of PM2.5 lower than the WHO's recommended levels _every day_.

Most of the study seems to be looking at how those levels vary by day, but the big claim doesn't reference % of days at all, which is odd. Their bullet points are a little confusing as well:

> Despite a slight decrease in high PM2.5 exposed days globally, by 2019 more than 70% of days still had PM2.5 concentrations higher than 15 μg/m³.

Where, though? They measured different geographic areas, but this has no geographic information. That leads me to believe that the claim is that on 70% of days there was at least one geographic location with PM2.5 concentrations higher than 15 μg/m³.

> In southern Asia and eastern Asia, more than 90% of days had daily PM2.5 concentrations higher than 15 μg/m³.

This is much clearer but suggests that my interpretation of the last bullet was wrong... maybe that one meant a global average?

I dunno, maybe I should read this again after some more coffee, but it seems to be written in a confusing way that goes back and forth from global averages to local averages to number of days above a threshold to annual averages.

If you live in the US, the EPA has a website to check outside air quality

https://www.airnow.gov/

There was a recent thread[1] about air quality sensors a few months ago. From that thread there were a lot of recommendations. I ended up buying the Airthings ViewPlus[2] because it covered the widest range. If it's too pricey for you, AirGradient[3] sells a DIY "Pre-soldered" kit for cheaper that I strongly considered as well. The article in that thread was about how "Many indoor air quality sensor products are a scam," but like people mentioned in the comments, even if they are not 100% exactly accurate, you can still see that something has changed and you can crack a window, or close one if PM2.5 from outside is too high.

1. https://news.ycombinator.com/item?id=33025995

2. https://www.airthings.com/view-plus

3. https://www.airgradient.com/open-airgradient/kits/

Seems like too few categories, safe or not safe? Clearly this is a spectrum

Why? If critical levels of "unhealthy stuff" is exceeded, it's not safe. Your spectrum is on the threshold of "unhealthy stuff"

So there is a magic point, greater than zero, where it simply switches from healthy to unhealthy? That seems improbable.

Edit: Downvotes but no comments. That's a pretty low effort way of admitting your position is faith-based, not scientific.

You have a multitude of things to measure in breathing air. For each you can establish thresholds for safe levels through the scientific method with evidence. Likely there is a transition area, but also regions with a very high likelihood of being unhealthy.

If any of these measures is "in the red", your air is unhealthy.

Why not?

As with most things, even if there is no "magic point," you need to draw the line somewhere as accurately as you can, or you'll be trapped in pedantic bickering and inaction forever.

>or you'll be trapped in pedantic bickering and inaction forever.

There are lots of people and groups out there for which this is the goal.

Drawing an arbitrary line where none logically should exist is the cause of, not the solution to, pedantic bickering and inaction. You're going to get a lot more people to agree "pollution should be lower" than "this is a good amount of pollution."

Why? Here is a model that would make sense: your body is capable of clearing x ug/day and anything over that causes inflammation. Well then stay below that level and it is

This is the battered spouse argument in our relationship to our living environment. Well of course the air is unhealthy, but see, you need to understand the whole story!

Categorical thinking is not always because of a lack of nuance or of zealotry or stupidity (which are generally more modern dismissive interpretations). Delineating categories is a useful framing to firmly separate what is on the one hand good and virtuous (clean air), and on the other evil and depraved (polluted air). It's an excellent way to identify when exactly rationalization, submission or complaisance kicks in. Well, it's not as bad as it used to be. It's even worse in xyz country. It's not reflected in the average life expectancy. It's the price we pay for modern luxuries etc... etc... Having firm categories, and these will read as fearful or callous defenses.

Good categories should compel to action. In this case, what can be done to move from Box B into Box A. And then do those things (because Box B is inherently evil).

The real world is grey. For sure. And multiple opposing things can be true at once. Nonetheless, we need to cut through that, and I'm fearful we've forgotten how. The reason our cities are degraded is in large part because we have failed to think in categories, and have rationalized away (categorically) wrong habits.

No it's not, and the comparison is absurd.

With domestic violence it is trivially easy to have none at all, and there is a very distinct difference between none and some.

With air quality there is a smooth and continuous measurement for what is in the air. You will never get to zero particulates per cubic meter, you can only get under a certain level. Further, the effects of air quality are also a smooth continuous function - there isn't some distinct point where if you are below it there's no risk of health issues and immediately above it you have guaranteed serious health issues. A binary categorization is clearly inappropriate.

Binary categorization is quite appropriate, considering there are IDLH levels. And it is actually highly nonlinear for most contaminants. There's an area of none to low risk, even chronic, then an area of exponentially increasing risk, then area where the levels are known to be harmful chronically, and yet another where they're immediately dangerous.

So while not binary, the difference between dangerous and not is usually pretty sharp.

For PM 2.5, < 12 ug/m3 is considered safe, while > 35 ug/m3 is considered harmful after just few hours. For chronic exposure, mean levels of < 15 ug/m3 over 3 years is considered safe. (There is probably some level that is certain to produce silicosis in about everyone. I would have to dig on that.) That is how thin the margin is. And these are the laxer NIOSH values.

Even AQI which is weighted to be more linear and granular, easily gets pegged at moderate (risky to sensitive people) in clean seeming cities unless there's wind... (That is a level above 15 ug/m3 already by some.)

I think you have a point. If there were no people on Earth, what would the PM 2.5 look like? If it would still be too high, then it seems this measure while, baseline to know, wouldn't be practically useful. We'd have to then control naturally occurring PM2.5 in the environment.

That's not to say the obvious is not true, that Regions of China and India suffer from too much PM2.5 due to human activity and should be addressed. However, a chicken little situation is not helpful as people will tune out.

Indeed it is, you’re right. Here is the spectrum the WHO publishes: https://www.ncbi.nlm.nih.gov/books/NBK574582/table/fm-ch1.ta...

Note that the idea of a single safe “threshold” limit is based on the best available research today showing that they haven’t measured adverse health effects below 5 μg/m³ average annual exposure. The spectrum here is a spread of increased mortality that can be attributed to pollution above that limit. There’s a different threshold for a single day exposure than for average exposure. Also note that the recommendation recently came down from the 2005 recommendation of 10 μg/m³ due to more research showing adverse health effects of pollution. There might not exist any so-called “safe” limit, and speculating wildly, we might expect their recommendation to drop again in the future.

My wife has severe astma and when traveling this is something that worries me all the time. At home we have blue air machines and plants to filter the air, but astma attacks still happen (when she didn't use her medicines enough) when she travels from work to home on bad air quality days in Amsterdam. The astma medication is something that comes with a lot of trade-offs/health complications if you use it too much. Hope this will improve in future, but prevention would be even better.

I looked up the amount of people in the Netherlands that have health issues connected with air quality and it isn't negligible at all (1+ million on a 17,53 million population), but I don't understand why politically it doesn't get the attention it deserves.

Unfortunately I can't create this kind of machine (software eng, no hardware skills), but I think there is a very big market for portable masks with safe air to breath temporary when you are outside. Especially with all the research that has been done on how much air quality impacts your health.

I don't understand why politically it doesn't get the attention it deserves

Same as the obesity pandemic, the climate crisis, the biodiversity crisis: there are no clear immediate effects for the general population (consequences of that in turn lead from claims that it's fake to 'yeah sure whatever I don't care doesn't affect me' and everything in between), dealing with it will in the short run cost lots of money, not enough momentum to get anything long term going, sprinkle some lobbyism on top. Sounds cynical, I know, but: I've yet to see this proven wrong.. The wait for the tipping point has started.

I agree with you, however historically the move from leaded fuel to lead-free fuel proved that we could do it or the protection of the ozon layer (one of the few times in history that we took collectively action against something damaging humanity, but it doesn't happen often enough). Curious what would cause a tipping point for improving air quality or any of the other multiple crises you mentioned and if we could learn something from history.

The only worked because we had a ready replacement in place. (Different comparable gasoline additives, different comparable refrigerants, alternative motive gasses for pressured containers.)

And even today, leaded gas is still used for aircraft.

The problem with fossil fuels is we really do not quite have anything as energy dense and useful, not even lithium. (Which there is too little of, not to mention mining issues.)

As such, it will require a major change not just a tweak.

> Same as the obesity pandemic, the climate crisis, the biodiversity crisis

That and almost every problem is a political party's solution. Get the voter base whipped up about any attempts to do anything and get reelected for obstructing it. Rinse, repeat.

Politicians don't care about issues, they care about getting reelected; to do that they must exploit and perpetuate problems they're supposed to fix.

a wise activist once said -- it takes an immediate crisis to move the needle in public action

> portable masks with safe air to breath temporary when you are outside

With regard to PM2.5, that already exists and is called an N95 mask.

Unfortunately those masks are not protecting you against gases and vapours like sulphur dioxide, nitrogen dioxide, ozone, and carbon monoxide which do impact asthmatic people a lot or are the cause of developing asthma.

Well, a mask with an activated carbon filter actually does, to an extent, except for carbon monoxide.

(There are other more specialized filters that are more effective against SOx and NOx too, but carbon is also good against VOC.)

>Unfortunately I can't create this kind of machine (software eng, no hardware skills), but I think there is a very big market for portable masks with safe air

You may not need to DIY (much).

I recently posted my experiences and tips with the AirPro mask,[0] and the response was at least entertaining! Tl;dr it's a wearable HEPA device that pipes 99.97% filtered air into any N95 mask. Besides improved filtration, this also prevents the hot humid mask feeling that some people dislike.

You might consider adding a carbon prefilter (look for sheet filter medium and cut to size) for the HEPA unit, and pairing that with a carbon N95 mask (eg 3M 8247). This should filter several pollutants of concern you mentioned, including nitrogen oxides, sulfur oxides, and ammonia. Sadly CO is nearly impossible to filter.

For indoor filtration, you might find some MERV-13 filters[1] and make a Corsi Box[2]. No engineering skill required, just a bit of duct tape.

Maybe something here will help! Cheers and good health

[0] https://news.ycombinator.com/item?id=34378478

[1] https://news.ycombinator.com/item?id=34797981

[2] https://cleanaircrew.org/box-fan-filters/

This comment made my day! I'm going to give it a try and will convince my wife to test it to see if it helps :)

Glad to hear it. :)

A couple tips I forgot, some of which may increase the all-important "wife acceptability coefficient":

- carbon tends to get saturated pretty quick, so in regular use I would replace the (cheaper) prefilter at least weekly, mask every 2-3 weeks

- testing may show you can get away with a non-carbon N95 and just the carbon prefilter; cheaper and the look may be found more acceptable

- carbon will immediately start adsorbing pollutants from ambient air, so keep all unused carbon in a sealed jar or sealed original packaging

- have fun with it! At Starbucks and pizza places I'm either Mr Snuffleupagus or Discount Darth Vader :D

- Corsi Boxes can be loud, so I use Low if people are around (High only for unoccupied space); shrouding or draping with fluffy towels can help too (hint: not the good towels)

- if you have forced air HVAC you might start out just using a MERV-13 filter in there; I prefer Filtrete 1900, but in general anything with many pleats = low pressure drop is better; most HVAC is not rated for large pressure drops across the filter

- I've had good success making an experimental "Carbon Corsi", taping two cheap 20x20 filters together with ~2 lb of replaceable aquarium carbon in the middle (change every ~two months) and taping that on top; this filters gaseous pollutants in the home, and can further muffle the box fan

(sorry, I swear this list was two items long when I started...)

Hope she can find some relief via your mutual efforts! Severe asthma can feel almost like a prison, so it's important to be extra kind and patient. Best of luck you guys

“the lack of pollution monitoring stations globally for air pollution underscores the importance of innovative approaches such as machine learning to estimate global surface-level daily PM2.5 concentrations accurately.”

“The health impacts of exposure to PM2.5 are significant”

I think they need to elaborate on this to put the funding in greater context. Statistically significant? Significant in terms of actual impact on one’s life?

From the article: “The health impacts of exposure to PM2.5 are significant and include respiratory and cardiovascular diseases, lung cancer, and premature death.”

Yes, that’s what I quoted too. I’m drawing a distinction between what is “statistically” significant and what is pragmatically significant.

An example is the processed foods study from a few years back that showed a statistically significant increase in cancer risk. But if you look harder at the data, it increases your risk from 1.0% to 1.18%. A relative difference of 18% sounds huge, but the absolute difference is very small. That’s not really much difference in the grand scheme of mortality risk.

You can measure very small statistically significant differences with large data sets. It doesn’t necessarily mean it should drive people to change their behavior for every “significant” scientific finding.

Right, since there is no research on this topic already...

So they should quote it to put it in context. Otherwise, it comes across as click-bait and out-of-context

And how do they square the circle that with the deindustrialisation and move to central heating that those particulates production are at a century low in many western countries yet seem to be more deadly than ever.

This is what I cannot fathom.

I was born the 70's, played outside for all my childhood amidst all the leaded petrol and sulphur dioxide, I handled leaded petrol for a job at a petrol station for solid three years and I lived in dense urban town from childhood until today.

Everything seems to be way lower than it ever has been:

[1]: https://www.gov.uk/government/statistics/emissions-of-air-po...

[2]: https://www.gov.uk/government/statistics/emissions-of-air-po...

[3]: https://www.gov.uk/government/statistics/emissions-of-air-po...

[4]: https://www.gov.uk/government/statistics/emissions-of-air-po...

So why is everything framed as being more deadly now than it was given the all time lows?

Explicitly mentioned:

"Moreover, the study revealed that while daily levels of PM2.5 have reduced in Europe and North America over the past two decades..."

> So why is everything framed as being more deadly now than it was given the all time lows?

Because it's a false predicate for the war on the car and the removal of personal agency in urban areas - a war being waged at multiple levels of government in the UK in particular.

The source data is linked in the article:

https://www.thelancet.com/journals/lanplh/article/PIIS2542-5...

Their data is measuring the PM5 levels. What I’m asking about is how that difference gets translated to actual health risk. It’s related, but not in their data set (as far as I can tell on mobile).

There’s a distinction between measuring the difference in a plausible mechanism (PM5)and an outcome of interest (health). It’s easy to get caught up in the “mechanism porn” of scientific studies and extrapolate too far in terms of assumed outcomes.

Lets say I'm living in one of these areas ( and can't help it) besides wearing a kn95 when going out, is there anything that can be done?

Buy and maintain an air cleaner for your home. That's the one and only realistic change you can make.

The average home in a mildly polluted area will actually generally have clean indoor air without filtration. Even with windows open. Don't ask me how this works, but I've verified it using a PM 2.5 monitor, a laseregg 2. With indoor and outdoor measurements on the same day.

I recommend indoor filtration for other reasons (allergies, diseases, cutting down pollution from cooking). But if someone already isn't producing much cooking PM 2.5, an indoor filter won't actually cut their exposure much.

A car with good filtration and a mask outdoors would be the most effective things one could do short of moving. Note that even lower quality masks such as surgical cut air pollution a fair bit. People somehow convinced themselves they have zero impact, because they lack perfect impact.

Studies have found surgical masks generally cut over half of particles: https://smartairfilters.com/en/blog/surgical-masks-surprisin...

No one but the most concerned loonies are gonna start wearing a mask though and how do you select for a car with good filtration among the countless other decision parameters for a car?

One option, regardless of the car you choose, might be to seek out a high-efficiency aftermarket replacement when you change your cabin air filter.

I went longer in life than I should have before I even realized I should be changing mine out every 15,000 miles or so in the first place.

It really depends where you live. What's the pm 2.5 in your city? Mine isn't high enough to worry about outdoor pollution, and if it was I would move.

But people in high smog cities do wear masks. They have regular smog warnings too; people treat it like the weather. See this pre-pandemic article showing people wearing masks during a smog outbreak: https://www.ctvnews.ca/lifestyle/beijing-locals-don-colourfu...

For cars, I think the biggest factor is choosing a good filter and making sure it remains in good working order.

Use an air purifier. I have a small one from a Korean company. I run it non-stop. It's very quiet normally, but when it detects higher concentration of stuff (almost always when I open a window) it spins up for a few minutes.

When going outside? Probably very little unless you can overall reduce the pollution producing factors in your surrounding area.

As for inside your home, there's a few things but the effectiveness will depend on your situation specifically. The US EPA has a good starting point with information.

https://www.epa.gov/indoor-air-quality-iaq/indoor-air-qualit...

* Testing/replacing car air filter

* Any mask outside. Even surgical can cut more than half of pm 2.5

* A lot of people recommending indoor filters, but indoor pollution generally a lot less than outdoors except when cooking. You can verify this with a PM 2.5 monitor. I do recommend indoor filters, but if budget is limited and you're working on overall lower pm 2.5 filters, testing car and getting masks is the more effective intervention

Surgical mask source: https://smartairfilters.com/en/blog/surgical-masks-surprisin...

Best pm 2.5 monitor I found is a laseregg

> indoor pollution generally a lot less than outdoors

Why would that be? Unless you have central A/C with good filter, I don't see how indoor air would be cleaner.

Couldn't say. If I had to guess, a lot of ventilation happens through walls which act as a filter. Even window screens likely do.

Regardless of reason, my AQI will regularly be 4-13 indoors when it is 38-54 outside, even if I have windows open.

Note that this only covers PM 2.5, and not other stuff such as VOCs etc.

As with most environmental issues, the best thing anyone can do is getting political active and create changes that reduces air pollution. Problem created by people acting as a social group (i.e. densely populated cities, power plants, factories, highways and so on) do not really have solutions that individuals can easily apply.

I live in an area that has harmful amounts on PM2.5 during the winter(80ug/m3+, double that a few days of the year).

You'll need an air filter, but not just any other one - it has to be oversized for the living space and spin up at a low threshold - air filters commonly only actually start when the measurements indicate more than 25ug/m3.

Also nice if it has an ionizer - my experience is that it generally increases effectiveness even though that's not exactly its purpose.

Aside from that it's important to seal all windows properly. Even a large filter won't do much against draft.

> Also nice if it has an ionizer

I'd be concerned that the ionizers generate trace ozone. Am I wrong about this?

They do - no way around it which I would know of.

I only experienced a whiff of ozone when I returned home after two weeks, with the device on all this time.

Personally I only ever feel the irritating effect of elevated PM levels, so I keep the ionizer on.

I definitely cough much less during a cold now, having the purifier, than before purchasing it.

Vote for candidates who will do something about it.

For those looking for additional data and more comprehensive coverage on the topic I would point you to Our World In Data's entry on outdoor air pollution.

https://ourworldindata.org/outdoor-air-pollution

"Better air quality is the easiest way not to die" https://dynomight.net/air/

So give up your ICEs.

> ICEs

Internal combustion engines, for others that did not know

Or, more generically: just that C. Burning fossils for heating and especially burning wood are serious contributing factors as well, no engine involved.

Or stop reproducing so much, so there are fewer ICEs needed in a few short generations. How anyone chooses to have children these days is beyond me..

Where has the least polluted air? Is there a map?

https://www.thelancet.com/action/showPdf?pii=S2542-5196%2823...

Third page down.

https://www.iqair.com/earth?nav=

Only seventy thousand people? I don't believe you.

Just the people living in Greenland, Lapland and the Antarctic scientists probably passes 70 thousand.

Unless they include people breathing in smoke from their wood fires as they roast their wild venison or salmon.

What makes you think the people living in Greenland, and Lapland aren't doing anything with diesel engines or industry? Wikipedia says Greenland's main industries are "fish processing, and oil, gold, niobium, tantalite, uranium, iron, and diamond mining".

Good point. I thought the fresh ocean winds would dilute those, though probably most of that takes place in closed environments.

Yeah, maybe there's a confusion between percentage and fraction, and this was meant to be 0.001 (not 0.001%). But if so, the error is not the journalist's: I clicked through and the original paper also contains this improbable figure.

Reply on news.ycombinator.com