Exactly.

PM 2.5 means particulate matter 2.5µm. The weight per cubic meter doesn't tell the whole story either. From the EPA

Assuming that the particulate matter is the same density (not an invalid assumption at that particle size), a 10µm particle weighs more than 2.5µm particle which weighs more than a 0.05µm particle. Roughly, you need four 2.5µm particle to weigh the same as a single 10µm particle and you need 200 0.5µm particles to weigh as much as one 10µm particle. But, because of the process by which the particulate is formed, you have many, many more 0.5µm particles than you do 10µm particles. You don't get a 30% reduction in the number of particles that you breathe in. You might get a 30% reduction in the weight of particles but the number is far more important. If don't breathe in one 10µm particle but you breathe in 200 0.5µm particles, you aren't doing anything to protect your health.

The guy in your other link got out the big bits but those aren't the problem.

So, yes, the mask is a placebo.

Are you implying that their 15% reduction number in that is false?
If not then what would be a proper estimation for the PM2.5-PM10 range?

By the same reasoning as you do there is more 2.5µm than there is in the 10µm range so we can safely assume that a reduction of 2.5µm over a reduction of 10µm particles will decrease the number of air pollution-related death even further over the one for a reduction of 10µm particles.

Plus we can make the assumption that those masks don't stop at 2.5µm and will probably filter 10µm particles and probably some of the lower than 2.5µm particles (due to physics) which are even more harmful than the 2.5µm one.



Though there is unknowns about how much and for how long one of these masks will actually filter these particles for one individual other that the few people who tested them but my estimate of 30-50% reduction of air pollution-related death seems plausible to me.

Having no mask means that there is no way one of these physics events will happen. Having one increase the odds which means no placebo here.

No, but. A reduction of all particulate matter is going to cause a reduction of the smallest particulate as well. The WHO report is talking about reduction at the source, not reduction through filtration. Those are two distinctly different mechanisms.


By weight, there is more 10µm particles than 2.5µm particles. Again, by number, there are far more 0.05µm particles than there are either of the other sizes. Weight is a mostly meaningless measurement when it comes to particle reduction by filtration. If you go back to the production of the particulate, weight is a bit more important but the number of particles isn't unimportant.

You are worried about a big particle and a slightly less big particle. Those don't matter. Yes, some of them are going to get stuck on the fiber of the filter by the mechanisms in the illustration but look at the diffusion part of the illustration. The bulk of the smallest (and most harmful) particles are going to pass right by the filter and never get stuck to it. A few will but the number (and weight) is going to be trivial. They are going to be like the dust passing through a screen door analogy. Most are going to pass right through.

No. The reduction of air pollution-related deaths depends on reducing the particulate at the source...which the US and most of Europe has done through regulation. Trying to reduce the very smallest and most hazardous particulate at the user end is a useless exercise. Dust masks can prevent you from inhaling large particles...I use them regularly at work and at home...but they are totally ineffective on the small stuff. Having a dust mask with even a 0.3µm filtering capacity will have only a minor impact on the number of particles that you inhale that are smaller than 0.3µm in size...which is the bulk of the particles.

Something that has no impact but is used for peace of mind is the very definition of "placebo".

I know the difference between the 2. But via filtration through a mask there is still reduction of particles one breath.
If we were living in Beijin type of air reducing air pollution during a ride would be probably meaningless but we aren't.

WHO tells this
WHO | Ambient (outdoor) air quality and health
The guy from one study tell this
My Personal Fit Testing: Here?s the Best and Worst Pollution Mask For Me » MyHealth Beijing

Then again by your reasoning you're dismissing the result of WHO.
They talked about "large" PM10 particles and did find a positive impact on people whatever the situation with smaller particles is. So whatever how dangerous "smaller" particles are results about large particles remains and 15% reduction of air pollution-related death isn't a placebo.
Now because of so many unknowns, the problem lies in what gain to expect from wearing a mask during a ride.

Raising engine efficiency and emissions standards for everything from that kerosene burner in the street vendor's food cart to mining trucks and locomotives and boilers/furnaces could make a drastic drop in noxious pollutants.

People are complaining about not enough jobs, and we have the tech to do it........ i see a solution and a problem that could connect to improve things.... but that takes money and no one seems able to admit that we need to raise taxes a lot on a bunch of things to get the **** done that needs to be. Stuff is falling the hell apart as well.... Remember penn central and their deferred maintenance? They went bankrupt.

- Andy

Except the coal burning electric generating plants create more particulate pollution than gas powered cars adn trucks

[MENTION=324342]erig007[/MENTION], why do you suppose the air is so full of carbon inside the subway tunnels? Maybe it's brake dust? I do notice a sooty layer on everything. The train motors are electric, so they're not spewing soot. Other factors are that the tunnels are below the ground, so gravity brings dirt in. There are too few methods for the dirt to leave, and ventilation is insufficient to clear it.

I think [MENTION=112025]wolfchild[/MENTION] is right. Best not to worry about it unless you know it's a problem. And if it is a problem for you, I think the only solution is to move to a much cleaner place.

35 years ago I read that the benefit of exercising outside outweighs the detriments of air pollution. Of course, this can't be true in all places, but I suspect I'm healthier than lots of other New Yorkers.

Sorry but you don't seem to understand the difference between removing the particulate at the source and trying to filter it. One can work...removal a the source...and one is ineffective. You are reducing the number of particles you breathe by using a dust mask but not the ones that matter. They pour right through and the number isn't significantly reduced. I won't dispute that the guy in Beijing is reducing the mass per volume of particles above 2.5µm. He's probably reducing the even smaller particles...down to 0.3µm. But if the larger number of particles is in a range that is even smaller and the smaller particles can do more damage, then breathing less weight of larger particles isn't a reduction in number of harmful particles which is a more important metric.

No, I'm dismissing your interpretation of the WHO results.

Yes, they talked about reducing the 10µm particles but they aren't just reducing those particles. The 10µm particles are agglomerated 0.05µm particles. Reducing particulate matter overall will result in a decrease in the number of smaller particles and a reduction in pollution related deaths. It's still about reducing the overall particles and not about trying to filter out a specific size range.

Think of it this way: If dust masks worked to reduce pollution-related death, why not just issue everyone a dust mask and not worry about reducing the particulate load or the pollution? It would be easier and cheaper. Unfortunately, dust masks just aren't up to the job. Reducing particulate at the source is far more effective.

Based on the size distribution of the particulate and the efficiency of the mask, the answer is to expect very little.

That's essentially what the WHO is saying. Reduce at the source, not at the end user.

The carbon could be coming from a number of different sources. Carbon black at the surface is oxidized quickly to carbon dioxide...you don't see large drifts of tire dust along the roadways...but that is largely due to sunlight and oxygen. But without sunlight, the reaction could be much slower.

And the tunnels in the subway are basically air pumps. The trains are the plunger. They could easily draw air from the surface that is ladened with tire dust, brake dust, dirt and other dark materials. Once out of the sun, the oxidation reactions slow down. The trains themselves have brakes, as you've pointed out, which could contribute. But the rails and the wheels also wear and that dust is going to appear black as well. Just because it is black doesn't mean it is carbon.

Very interesting stuff, [MENTION=21724]cyccommute[/MENTION]. Thank you. What kind of scientist are you? It's great to have you.

I'm not worrying about that. Been wearing a mask for years so i have pretty much settled on this. I learned that way that my mask doesn't protect me against everything since i can smell them through the mask, especially car fumes. But when you don't smell rosted chicken, smoked meat or fresh croissant while passing by you know that it works for some at least. (filter everything that it isn't supposed to and the opposite )

Will upgrade my mask and be done with it (until someone brings the subject back )

I wonder which would be more enjoyable... riding to work with a mask, or reading every article and study linked in this thread.

Don't worry you won't find any definitive answer to your questions here so don't set your expectations too high

To sum up, there is pretty much 2 sides here:

1) there's nothing we can do, masks don't work so don't wear it
2) there might be something we can do masks might partially works so wear it for lack of better

this effort is now live:

What's in the Air as You Cycle City Streets?

From our local advocacy board:
Hi all,

The Columbia School of Public Health in collaboration with WNYC is doing a study of how much air pollution bike commuters encounter on their ride to work. It sounds like the study requires cyclists to wear some air monitoring equipment while riding. If you're interested in volunteering for the study or just finding out more info, the preliminary questionnaire is here: Columbia Bike Study.





sign up to be a part of the study. bikes + science = fun!

I took this picture in Busan, South Korea. I seriously wondered what it was like riding with a mask, but don't want to try it.

Some times I wear a mask at work. The kind that fit fairly tight and you feel like an asthmatic because you have to breath hard to get the air in. The air would have to be a lot worse around here before I'll wear a mask while riding.

Good discussion on particle size. Never thought about it before.

Um, Tesla. Focus Electric. Leaf. Smart electric. Chevy Spark. BMW i3. Rav 4 EV.

https://en.wikipedia.org/wiki/List_o...ctric_vehicles

"primary research is about the health effects of air pollution in low-income settings. He’s been looking at how much pollution, for instance, women inhale while"

That piece reminds me of the old story of a press release about a asteroid hitting Earth. "Earth to be destroyed.... women and poor will suffer most"

My grandfather died in his late 80's.... more than 40 years ago. Never once did he breath air as fresh and clean as it is (in the same places where he lived, and breathed,) as it is today. Clean air is all good! Hyper vigilance about environmental concerns.... is a disorder.

i've been using airnow.gov to tell me the quality of the air and it seems OK around here (NYC)

i only notice how noxious the fumes are when we are in a car in the tunnel, the air filter just brings in that bad air into the car. while cycling, i notice it at times, but i've heard from others who ride thru chinatown that it is superbly bad.

this came out last month: The air in NYC lowers kids? IQs | New York Post

NYC air according to this Columbia study affects kids IQs but the sample size is super small 276 kids and they only looked at minority kids. the poorest kids are most affected. of course i'm more inclined to think it's b/c they are poor.