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Comment by hammock | Hacker News Reader

I wanted to find an account of what the biggest sources of PM2.5 are in the US. This article discusses traffic fumes (24% of PM2.5), but I was surprised to learn that by far, the largest source of PM2.5 - 45% - is “unspecified sources of human origin.”

Where does that stuff come from? Well, it’s created in the atmosphere via secondary reactions between agricultural NH3 emissions, SO2 and NOx emissions from shipping and industrial activities and power generation, and NMVOCs from industrial processes and consumption of solvents.[1]

Those reactions seem like an interesting area of study and those chemicals involved are far less-often discussed as sources of air pollution even though they seem to combine to form the biggest source

[1]https://www.sciencedirect.com/science/article/pii/S135223101...

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The other thing people don’t often talk of is PM2.5 inside their home while cooking. Lot of people have poor ventilation or insufficient air movement capacity in their kitchens.

From the food, or the fuel?

A lot of it is from the natural gas combustion, but the food itself also contributes. The day I got an air quality sensor (to assess risk from wildfire smoke), I realized that my kitchen is basically an asthma factory for the kids. (I haven't actually assessed the risk from that, as its different from wildfires smoke, but j just keep the kids out of the kitchen now until the air clears)

I have some air filters with air quality sensors on them, and we have an electric range so there's no natural gas combustion happening. Often when cooking (pan frying especially), those sensors will max out and send the air filters into turbo mode for a good while.

Yes, hot oils trigger the formaldehyde sensor every time for me. For doing wok frying, I got an outdoor propane burner so that it's far more dilute, and that delicious cancer-causing wok hei is delivered only to our stomachs rather than lungs and stomachs. The outdoor wok burner is also far superior to any indoor residential gas stove too for this purpose.

The actors at Conner Prairie, an 1836 "living museum" in central Indiana, explain that some of the nicer houses have a separate out-building just for cooking, to keep the heat away from the main living space, and reduce the risk of burning down the whole house too. Maybe we'll move back to that design, to keep the pollution in the main space down.

combustion (burning) byproducts are the primary harmful particulate matter created by cooking, whether that be from gas or food. like most issues, incidental contact isn't enough to worry about, but if you're a cook (commercial or home), then you're likely getting meaningful exposure. it's not an issue for kids unless they're doing the cooking every day. the range hood should either be vented to the outside or sufficiently filtered (or both), but most filters are inadequate, so venting to the outside is the more foolproof strategy.

but this is likely a very small factor for nearly all people. cars (oil) and electricity generation (coal and gas) create most of the harmful particulate matter in the air (and water and ground), so that's where we should focus our anti-pollution efforts first and foremost.

Getting an air quality monitor during covid really blew my mind when I saw the amount cooking pollution and how long it can linger. No one should be cooking inside without a vent running or a window open.

> No one should be cooking inside without a vent running or a window open.

...or perhaps, it doesn't matter that much in the grand scheme of things, and you're worried about it because you bought a measurement device and started measuring something you hadn't measured before.

This isn't a minor point. It's a recurring theme in biological and medical science where researchers start to measure things for the first time, discover a previously unknown level, declare it significant or "alarming", and ignore that there's no causative link to any known harm.

When you measure things, you find things, but most things you find are uninteresting.

Except here there is a causative link of combustion byproducts of that size causing real harm. I've also lived in lots of apartments that don't have external-venting range hoods, so all that PM you generate while cooking is just in your living space until you filter it or breathe it. Introducing a PM counter, better filters, and enhanced ventilation practices (such as running the upstairs bathroom fan while cooking) dramatically reduced the eye irritation and stuffy nose I tended to wake up with.

For what it's worth, the same particulate counter will also spike off the charts when anyone takes a shower, but as far as we can tell those salt pm's aren't dangerous.

No, here is a link between car fumes and lung cancer in mice. Unless you routinely have a car running in your kitchen while cooking (for mice), it's not related.

PM2.5 particles are not all the same, nor are periodic exposure levels in a household kitchen in any way comparable to those used in a laboratory animal study.

> For what it's worth, the same particulate counter will also spike off the charts when anyone takes a shower, but as far as we can tell those salt pm's aren't dangerous.

Yes, exactly. You are perfectly illustrating my point. You have just as much evidence for this claim as for the kitchen one (i.e. none), but you assume one is fine and the other is not.

You're not wrong... but running a vent or opening a window while you're cooking to mitigate PM2.5 exposure, which we know can be carcinogenic, seems like incredibly minimal intervention. I'd rather change my behavior slightly than wait for more conclusive data in this specific case.

Yes, of course. I'm not reacting to the idea, so much as the "everyone MUST do this" implication.

It's probably not a bad idea to open a window or run a vent (depends on where you live, I guess), but I wouldn't panic or deploy a particle meter, or stop cooking if I couldn't do it, either.

Unfortunately, this is not simple to rectify. My previous house was expensive and difficult to retrofit to have an externally vented range hood, and I'm renting now, where basically nothing has externally vented range hoods, and looking to buy a place that does. This is a hard non-negotiable requirement for my next house, but the pickings are very slim. This is a severe issue (in the US anyway), and it's difficult to retrofit for most kitchens since most houses in the US are designed with the stove on the interior wall rather than the exterior wall.

Cooking fumes are the primary pollutant in my life, and honestly is one that I struggle with since I have severe asthma but love to cook. I do what I can, but this is something I wish was taken more seriously in society because there's a huge economic hill to climb to solve it yourself vs having to deal with what's available on market.

I mean, one solution would be to minimize or eliminate the ignition of fossil fuels in the kitchen itself. Electric and induction stoves exist.

While it's true that gas stoves are a significant source of kitchen fumes, they are not the only source, just the act of cooking food produces fumes. As an example, when searing meats, significant amounts of fumes are released, as is also the case when bringing anything beyond the boiling point, steam is given off, and steam can contain other particulates. Just using an electric stove (which I use currently in my rental) alone does not solve the issue, and is not even that large of a reduction. Most of the fumes from cooking are from the act of cooking, not from the heat source.

I have an induction cook plate and the AQI indoors still goes in the hundreds when cooking on it. It takes about fifteen to thirty minutes of the air purifiers running at full blast to get down to single digits AQI.

The last place I lived-in had a hood over the electric stove/oven. The exhaust-port included a steel-mesh grease-filter before the fan. Then the exhaust entered a zinc-coated-tin (?) duct about 6 inches in diameter and 10 feet long. It travelled straight above a row of cupboards to a side-wall and to the outdoors ... exiting through a louvered vent.

I suspect such a setup doesn't have to cost much. In return I enjoyed many years of cooking, summer and winter, without mostly without the odors & humidity.

I missed it as soon as I moved here ... although the vent is up-through-the-roof vertical, it's very ineffective ... and I can no longer cook most things I once took for granted.

The typical American kitchen doesn't exhaust cooking fumes out of the house - the rangehood (typically part of the microwave) just sucks the fumes up and blows them over the head of the cooker, distributing food particles and steam around the entire house (perfect for mold growth!).

It blew my mind seeing this as an Australian, where externally venting fans are standard.

You're not quite wrong nor quite right.... I've lived in the USA all my life, in perhaps 20 or so different houses or apartments over the years, in half a dozen states through both the northeast and midsouth and in my experience.... both ways are common in the USA, unfortunately. I'm not sure why, but I agree kitchen vent fans that don't actually vent outside are terrible

And I've seen them which vent into the wall!

Oh god, that's the scariest one. Sure to be full of mold!

I wonder how important the raw amount of emissions is. Density should decrease at a cubic rate of distance, so being close to a small source of emissions might be worse than being somewhat far from a heavier source.

See for yourself.

Propublica plotted a "cancer map" of elevated cancer risks, and you can see how it drops off as you go away from certain points.

https://projects.propublica.org/toxmap/

Interesting. One question totally non-sequiter to the toxicity conversation, but why do people that use maps orient the image in a direction other than North being up so that they have to add a label to the image indicating the direction of North?

For local navigation (e.g. your phone screen, laying a map on a table, etc) it's generally considered best practice to orient the map so that North is North. For abstract purposes North is up is the standard. I can't think of a good reason to do otherwise unless you're trying to illustrate a point specifically about local navigation (e.g. orienting a map so that the headwaters of a navigable river are at the top).

It's pretty hard to separate correlation from causation. There's way more sources of carcinogens than just car generated pollution. And lots of them will tend to correlate with poverty/working class which will tend to correlate with living next to highways.

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