Category Archives: Hall of Fame

Here is my personal selection of my favorite articles.

Digital Media and Children: Not All Screens Are Equal


I knew it was inevitable, but I was hoping to delay it a bit longer: my son Alex has discovered the digital world. Almost two years old, he’s increasingly fascinated with mommy and daddy’s smartphones, tablets, and laptop computers. As I help him drag Curious George toys on an iPad app to complete a puzzle, I feel a pang of guilt knowing I’m breaking a taboo to have no screen time of any type for any child under two (and two hours maximum total screen time for older children), policies long recommended by the American Academy of Pediatrics (AAP) and the Obama administration, among others.

Am I already ruining his chances to go Ivy League?

This hard and fast two-hour policy, beaten into parents’ brains by their pediatricians, troubles me and many others partly because it was last updated in 2011 before the astounding boom of tablets, smartphones and touch screens among both kids and adults. The policy warnings had focused very reasonably on TV and its clear long-term harms to healthy development in kids under two—especially harmful when passively watching non-interactive, non-educational TV.

But such traditional passive TV watching, while still the dominant form of media consumption for most children, is rapidly becoming meaningless for many. Clearly, an interactive video game that parents and toddlers are playing together or watching family vacation videos on a smartphone can have huge value compared to zombie-like staring at an episode of Spongebob or China’s popular Pleasant Goat (喜羊羊) cartoons—these kinds of shows are shown in studies to harm a young child’s executive functioning, a prefrontal brain skill set including memory, attention, and setting goals.

Not all screens are equal, and guidelines need to be updated to reflect these differences.

The policy also doesn’t reflect the reality on the ground: a recent survey of parents by Common Sense Media shows that toddlers under two are spending almost one hour a day using screen media anyway. This is why, in my own efforts to offer better advice to my patients as well as myself and my wife, I set out to find the most recent research that focuses on digital media with young children.

Teachers are an obvious source to assess what’s working for children’s education. In a Joan Ganz Cooney Center 2013 survey of 694 American teachers of kindergarten to eighth grade, most teachers (74%) reported they were already using digital games as part of their classroom teaching. A great majority (78%) thought that digital games were improving student mastery of basic curriculum (especially math), and 71% agreed that they helped with extra-curricular skills such as critical thinking, collaboration and communicating. Only 21% thought that digital games in classrooms led to behavioral issues.

We often, and by default, assume that video games are inherently antisocial and couldn’t truly be healthy for our society. But much research has shown that many of these games are quite the opposite, actually helping to foster social skills such as empathy, caring, and sharing. I encountered the term “prosocial” quite often in the new research, and I think it’s a powerfully evocative word to help understand digital media’s positive potential.

An impressive study published last August in Pediatrics, surveyed 5,000 children ages 10 to 15 and found that those who played video games up to one hour a day had higher levels of life satisfaction, prosocial behavior, and behavioral control compared to those who played no games. The study also showed that playing too much (more than three hours a day) had the opposite effects. Another main point was that both positive and negative effects were actually quite small.

It’s also helpful, and important, to distinguish between types of screen time. Passive TV watching is clearly the worst type of screen time. An excellent review published last year in British Medical Journal surveyed 11,000 mothers in the UK and compared whether TV and electronic game use in five-year-old children led to behavioral issues when they reached seven. They found that excessive TV (or DVD) watching (over three hours) led to worsening social behavior, conduct, and hyperactivity, compared to light TV watching, under one hour a day. And light video game playing also showed improved social behavior compared to no playing.

I still generally agree with most of the AAP’s family media plan advice, especially no TV ever in bedrooms and no screens at certain times of the day, including during meals, and screen time limits depending on age. With children under two, I definitely believe that screen time should never be spent alone: kids always benefit more from any activity when parents are playing along.

Even more practical advice about which digital media may be helpful or not is in the outstanding website from non-profit Common Sense Media. The site has a handy list of best apps for preschoolers, along with very practical ratings including quality, learning potential, positive role models, ease of play, and consumerism. This is where I discovered highly rated apps like Busy Shapes, which I’ve played with Alex and has positive developmental benefit—but still probably isn’t nearly as beneficial as an old fashioned wooden puzzle set. I tried the e-book version of Dr Seuss’ My ABC Book, but he ignored the lovely rhymes and kept tapping to hear the noises (some, but not all, research does show that e-books are often inferior—as children who focus on the distracting technology absorb and understand less of the story).

For all the redeeming qualities of interactive screen time, however, what is clear to me after all my research is that even a highly-rated app or video games could never be as stimulating or educational as actual 3D games. Stacking, matching, reading books—all of these flat 2D-screens just can’t compare to a pile of crayons, wooden blocks and Legos. But I’ve also decided that Alex, at 21 months, can continue to dabble in some digital media. My wife and I haven’t watched traditional TV in many years and only use it for DVD or ad-free TV shows, and we always keep the kids away from this passive exposure. In all cases, we still limit total time to far below one hour a day, and almost none of it is ever unsupervised.

I think we’re doing a pretty good job in this new digital world. Screens are an ever-rapidly essential and inescapable part of modern and future life, and with a bit of evidence-based guidance, our kids will be just fine.


© 2014 Richard Saint Cyr, as first published on Quartz

The Science of Air Purifiers and Better Health: Is There Any?

happy kid in the field

What’s the hottest gift this Chinese new year? Perhaps instead of moon cakes and red envelopes, you could give “the gift that keeps on giving”: an indoor air purifier. They certainly are all the rage in China since last year, with skyrocketing sales and sold-out inventories after the trio of highly publicized airpocalyptic crises. I think this is a good turn of events: plenty of independent testing, including mine, has documented that a good air purifier can dramatically improve your indoor PM2.5 by 80% or more. But is there any good data that proves that this actually makes you healthier? It seems logical, of course, that decreasing exposure to pollution would decrease harmful health effects. But medical history is filled with tales of common sense and tradition that later turn out to be worthless or harmful — like bloodletting, or the more modern tradition of multivitamins. A big percentage of people reading this article take a daily multivitamin, assuming it’s “healthier” to do so, but the best evidence shows they are worthless, and possibly harmful. Could air purifiers be the same?

In theory and in testing, a good purifier should improve a room’s pollution levels more than 80%; this 80% reduction is also what the private Association of Home Appliance Manufacturers (AHAM) uses in their clean air delivery rate (CADR) tests, which are widely cited in comparison charts of air purifiers. So let’s say you’ve installed a top-of-the-line purifier in your living room, feeling quite safe and cozy. But how much of your time is actually in that filtered room? Or maybe the purifier is too small for that room size, or the filters are old, or the fan speed is too low, or the windows are open? Even this commonly cited CADR test is just a lab test for only 20 minutes — what about in the real world? I want to take this conversation to the next level, seeking out proof that your health will improve when using these machines. I want to be able to tell my patients and readers that there are published research studies which followed people over many months or even years, compared them to a control group not using air purifiers, and measured their health to see if there was any improvement in heart and lung disease, cancers and death rates. Are there any such studies?

I searched the Pubmed scientific database to find the best studies, and I was disappointed but not surprised to find very little strong data. A properly designed research project like this would be very difficult and expensive. But there are a few attempts, especially studies looking at using HEPA filters to help children with asthma. One was a systematic review published in 2002, which found that air filters helped to improve asthma symptoms — but the effect was small, and there was wide variation between studies which made conclusive assessments difficult. A more recent, very well designed study published in Pediatrics in 2011 followed two hundred children with asthma who also were exposed to secondhand smoke at home, and gave half of the kids a true HEPA purifier and the other half a fake purifier for their bedrooms. After a year, the HEPA group of children had less doctor visits for asthma flares, which possibly — but not conclusively — could be due to the 25% decrease in PM2.5 in their homes.

Other studies have focused on allergies, including an interesting study from 2008 which assessed children with documented pet allergies, following them over a year and recording lung function and blood markers. After a year, those who used HEPA air purifiers showed no clear difference in lung function, use of allergy medicines, or blood markers of allergies. Another study back in 1990 was a bit more impressive, showing not only a 70% reduction in indoor PM0.3 but also improved patient symptoms of allergies.

All of these hint at health benefits, but they still dance around the edges of what I want to know for us in China and the developing world. In the USA, most of the air purifier marketing and testing focuses on allergies and asthma. But here in the developing countries, the air pollution is much more severe and thus the health risks are far more serious. We are worried about pollution’s long-term risks of death, heart and lung disease and cancer. These studies I just mentioned still aren’t answering that deeper question: can long-term use of indoor air purifiers prevent death, heart and lung disease, and cancer?

Happy Family Riding Bicycle With Cloud Background

The best study I found was published in January 2013 in Indoor Air. It was very well designed for this complicated type of study, being a randomized double-blind crossover study of 20 homes over three weeks, using an air purifier or a placebo purifier. Their main goal in this remote First Nations community in Canada was to assess whether air purifiers could improve cardiorespiratory health. As their abstract says,

“…each home received an electrostatic air filter and a placebo filter for 1 week in random order, and lung function, blood pressure, and endothelial function measures were collected at the beginning and end of each week… On average, air filter use was associated with a 217-ml increase in forced expiratory volume in 1 second, a 7.9-mm Hg decrease in systolic blood pressure, and a 4.5-mm Hg decrease in diastolic blood pressure. Consistent inverse associations were also observed between indoor PM2.5 and lung function. In general, our findings suggest that reducing indoor PM2.5 may contribute to improved lung function in First Nations communities.”

This same Canadian research team had earlierpublished a similar study, testing 45 non-smokers for 7 days in 20 homes that used wood stoves, comparing health effects with or without HEPA purifiers. The people using the filters showed improved endothelial function and biomarkers of inflammation such as CRP. As most pollution researchers now see pollution as a pro-inflammatory disease, testing for such biomarkers could indeed be an accurate surrogate for later health problems. This approach is also being used in studies of air pollution masks, which I recently reviewed.

My take from these studies? Firstly, they all confirm what we already know: air purifiers can reduce the levels of indoor PM2.5, but with a wide range of effectiveness. Secondly are the more important results looking at health markers. I think the most encouraging finding was the First Nation study showing improvement in lung function, even in such a short amount of time (less than a month). Their data was a bit less convincing on blood pressure improvements, but perhaps a larger study would help confirm their initial findings of a slight improvement.

None of these studies are slam-dunk proof for me, but I honestly don’t know whether we ever will get many more well designed studies like these, unless governmental researchers or Gates-type philanthropists fund them. But until better studies come along, we must rely on what we do know:

  • Air pollution contains many chemicals, but PM2.5 is considered to be the most harmful to health.
  • There is no such thing as a “safe” level of  PM2.5. Lower is always better.
  • Worsening PM2.5 causes deaths from all causes, especially heart and lung diseases and cancers. Many studies have shown this, including this 2013 meta-analysis of the population in China.
  • On the brighter side, long-term improvements in PM2.5 do help to decrease mortality. The best study was a huge epidemiological analysis of entire populations in American cities as the air improved from the 1970’s to 1990’s. Lifespans improved for everyone, for a multitude of reasons, and they estimate that 15% of the improved life expectancy was due to cleaner air.
  • Shorter studies have also shown improvements in health from better outdoor air pollution. The best designed study I’ve seen on this happened right here in Beijing, during the 2008 Olympics. A team of researchers followed 125 healthy young doctors before, during and after the Olympics, and found improved blood pressure, heart rate and other biomarkers of inflammation during those lovely days of improved air pollution. Another encouraging study followed pregnant women and their babies in Tongliang, China both before and after a heavily polluting coal-fired power plant was forced to shut down in 2004, and found improved neurodevelopmental scores in newborns at age 2 years.

Is all of this enough to convince you to use an indoor purifier? For me, I was already convinced years ago — it’s not just common sense, it actually makes biochemical sense and also perfectly fits with the precautionary principle: “When an activity raises threats of harm to the environment or human health, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically.”

Make Your Own Air Purifier For 200 RMB? Really? Really.

DIY air purifier filter PM2.5 china
Kids, DO try this at home!

Last January we had the airpocalypse, and this January — hell hath frozen over. Because a bright-eyed Fulbright scholar and his disciples are spreading across China, preaching in their revival tents to swooning crowds that “you — yes, YOU, ma’am, in the corner!” (rising applause) “Yes, I swear to you right now that you can make your own air purifier for under 200 RMB — and get the same results as your fancy-schmancy, Perrier-sipping import! Can I hear a yee-haw!” (wild clapping).

I refer to Thomas Talhelm’s evangelistic, data-filled blog and his company spinoff, Smart Air Filters, offering frequent DIY workshops on just this subject, as well as selling their own two models. And yes, the cheaper one is really only 200 RMB. Crazy, no? Like a fox, maybe. Because Thomas’ scrupulous data, far geekier than anything I’ve written (that’s a compliment), does indeed show quite impressive PM2.5 reduction with these machines, even when directly compared to some famous models we all know about.

Thomas actually was inspired to do his own testing from all of my own tests and blog posts, and we’ve been emailing back and forth since last summer, comparing notes. As I mentioned last week in my Philips review, I’m quite a fan of his goal to find affordable protection for the masses against indoor air pollution. And his message has spread quickly, with many news groups covering the story. Many of my readers have asked me to review his machines, and I recently got to test both his Original and Cannon. So how did they do? Is he a prophet or a charlatan?

Let’s cut to the chase: a true HEPA filter and a strong fan indeed are all you need to eliminate bad particles in the air. Almost every top air purifier machine out there, no matter how fancy, is still built around those two pieces: a HEPA filter rated to eliminate 99% of particles larger than PM0.3, and a fan blowing air through it at a proper flow rate. No other features really matter as much as this, at least here in China. If you have a car, a HEPA filter can go into your exhaust system and clean your air; if your home or office has an HVAC system, installing a top-rated HEPA filter is incredibly effective, and much cheaper than a floor machine.

So yes, it makes perfect sense that a do-it-yourself combo could work — and it does. I tested the smaller Original model in my three small rooms, 10-13 square meters in size, overnight with the doors closed. And this little guy did about as well as any other machine I’ve tested: PM1 levels were 91% lower than the outdoor air, and PM5 levels were 95% better. This was on its lowest speed setting, which was tolerably loud but certainly noisier than my usual Blueair settings at night. In my most recent testing of Blueair, IQAir and Airgle, I got bedroom results of 88-90%. For small rooms, this little HEPA filter was at least as efficient as all of the big boys.

Thomas tests his machines a bit differently than I do, comparing them to the same room before and after, and he also measures PM0.5 and 2.5, whereas my Dylos machine measures PM1 and 5. He also mostly tests on highest fan speed, which I find impractical and too noisy for a real world scenario. But even with these differences, we still got about the same results: effectiveness always at least in the high 80%, which also at the very least was a strong match to the bigger machines — sometimes better.

So our data does match, and again why wouldn’t it? He’s using a real HEPA filter and a fan with a flow rate that works. I think their smaller Original model is especially a reasonable option for students and people with limited income to use in their bedrooms. It certainly is far, far better than having nothing at all, when the AQI outside is crazy bad.

DIY air purifier Blueair Philips Thomas Talhelm PM2.5His newer machine, the 450 RMB Cannon, was designed for bigger rooms, and I think that also could work well in theory, since it’s the same HEPA filter on a stronger fan. I wish I could share hard data with you, but honestly I didn’t get a lot of data points on this machine, mostly because it was just so darn noisy that I didn’t want to test it any more in my living room. Even at the lowest setting overnight, it was much louder than normal background decibels from my current IQAirs. For me at least, that’s a non-starter as an option. Thomas openly admits that the Cannon is a bit loud, but it still is effective even on low settings (see the graphic to the right).

But let’s not get bogged down in the details of these two models. These are early, first generation attempts, and besides, it’s distracting from his and my main message: everyone everywhere should always try to limit their exposure to pollution, and a DIY HEPA filter and fan combo are a heck of a lot better than nothing at all.

I assume the PR teams at the famous air purifier headquarters are now champing at the bit to correct me, aghast that I would gloss over their superior technology. And of course that’s partly true, as some top end filters do indeed claim to filter down to PM0.003, a hundred times smaller than a normal HEPA. Not to mention the other filters for VOCs and other chemicals besides PM. And maybe that does matter in a place as polluted as China — but I haven’t seen any data or medical resource claiming any specific advantage in targeting those ultrafine particles. Perhaps in the next couple years, with better research, we may learn that spending that extra $$ on the top end models may prove more beneficial to your health.

Until then, I say to the hundreds of thousands of people who’ve bought air purifiers: keep up the good work. But for the hundreds of millions of unprotected people across the developing world, anxiously awaiting the next inevitable airpocalypse — go get a HEPA filter and stick it to a fan. And buy yourself a particle monitor, test your machine, and blog about it. Viva la consumer revolution!

Air Purifiers For The Other 99% — How About Philips?

UPDATE, March 2015: Please check out my 2014 review of the science behind air purifiers; my 2015 tests of air purifiers under 1,000 RMB plus my 2014 review of two dozen top air purifier models in China.


I’ve blogged a lot about testing my air purifiers at home, a quartet of machines (three IQAirs and one Blueair) working in symphonic harmony to create indoor air 80% cleaner than the outside air pollution — 24 hours a day, every day. I find this 80% to be very reassuring, especially for my newborn son, who will be spending almost 100% of the first years of his life inside our home. Air purifiers in China are a no-brainer, must-have item! I would be even more cheerful if one more criteria could be improved — the cost.

philips AC4072 air purifier HEPA pollution ChinaEach time I pay for replacement filters, I get really ticked off that I’m paying so much money — and so much more than I would than if I lived in the USA or Europe, ordering exactly the same filter. It’s simply infuriating that a replacement filter in China could cost more than an entirely new machine in America! In the respected Consumer Reports list of top air purifiers, the highest rated machine is only 2,118 RMB (~350 USD,  the Whirlpool APS 1030K). Even the Chinese press has started to cover the extortionate prices of some air purifiers, especially the replacement filters.

I actually feel partly responsible for this, as many thousands of readers have bought machines based on my recommendations. Here in our expat bubble world, sheltered underneath our shiny pollution domes, we all keep self-promoting the same heavily advertised imported brands, creating a self-reinforcing illusion of brand superiority. Meanwhile, the other 99% of people in China couldn’t possibly afford almost any machine I’ve recommended. So while I appreciate my current machines, and while they truly are highly rated from many independent sources, they are far from the only viable options out there — and definitely not the best value for anyone with limited income.

I can’t say I’ve found the perfect solution quite yet — perhaps the team at Smart Air Filters could help fill that gap — but I may have finally found a decent value. It’s the Philips range of air purifiers, especially the AC4072, which I recently gave to my in-laws as a Christmas gift (only in China would that be a hot gift!). I chose this because it ranked very well on the test results last year from the Shanghai Consumer Rights Protection Commission, where its sister model, the Philips AC4074, filtered 96% of PM2.5 and 53% of formaldehyde — using the same HEPA filter as the cheaper AC4072. Plus, my new comrade-in-arms in geeky air pollution testing, Thomas Talhelm, recently published his own data comparing his DIY filters against this Philips as well as the Blueair 203 — and the Philips was as good or better than the Blueair, eliminating 93-96% of PM0.5-2.5 on high speed overnight in a small bedroom. Thomas and I are on similar missions to share data with the world, and he’s even more focused on finding value — a very important and noble goal. The AC4072 is currently 2,900 RMB direct from Amazon China, compared to my Blueair 503’s price of 5300 RMB, my IQAir Pro 150 price of 9,000 RMB and my Pro 250 price of 11-15,000 RMB (depending on voltage and import status). 

For my own tests, I did my usual routine: I compared real-world situations, not just blasting them on high speed all night, which I feel is an impractical and loud scenario that no one does in real life. In real life, we want the most effective machine at a reasonably quiet level. I want to know:

  • How much better is the air when I’m sleeping?
  • How much better is the air in my big living room, and the rest of my house, during the day?

I always compare my indoor pollution to the outside air at that time, because again my most crucial question is “how much better is my air inside, compared to outdoor air?” As I mentioned before, my current system is 80% better. Can the cheaper and smaller Philips keep up the same good results as these famous flagship models?

Envelope, Please…

I was very pleased with the results. In my 13 square meter bedroom, overnight with the doors closed, the Philips AC4072 on a lower setting filtered out 87% of PM1 and 98% of PM5, when compared to the outside air. I usually have the Blueair there, and while the AC4072 wasn’t as wonderfully quiet, it was very reasonable white noise and still performed at least as well as Blueair and others in previous tests. During my last testing of Blueair, IQAir and Airgle in my bedroom, their combined effectiveness overnight was 90%, so the Philips data is right in line with that.

In my 30 square meter  living room, it filtered 84% of PM1 and 96% of PM5, again compared to the air right outside my window. These numbers are very comparable to previous data, which again is impressive given the clearly smaller size and price. In last summer’s test, the living room average was 85%, so yet again the Philips is exactly in line with that data.

My Bottom Line

Despite the clearly smaller HEPA filters and unit size, the Philips AC4072 performed equally as well as all other units I’ve previously tested. Plus, it was generally quiet at most settings, and their automatic mode was quite useful for the front room. And it doesn’t hurt to be a bit sleek and stylish, occupying less than half the floor space of my other units. Regarding value, it’s half to a third the price of my current machines (same goes for the filter replacements).

That’s good news for me, and for the tens of millions of others across China who are looking for quality performance with value for money. Even this AC4072 is probably overkill in smaller bedrooms, and maybe their cheaper AC4025 or AC4012 would be fine. Besides Philips, I’m sure that quite a few models from the other major brands also would be just fine, many with prices far below the famous foreign brands. Daikin, Sharp, Panasonic, Whirlpool, Westinghouse, Honeywell, Yadu … as the DIY folks are starting to prove, all you really need is a good HEPA filter and a good fan. 

Do Pollution Masks Really Work?

Do pollution masks actually help to protect you? This winter has already seen harsh pollution spikes first in Harbin, and recently in Shanghai and eastern China. By coincidence I had been taking the train from Shanghai to Beijing during one of those days, and I sat mesmerized as we barreled through endless vistas of ghostly cities disappearing into the shroud.

Double Protected -- Totobobo mask and bike helmet
Double Protected — Totobobo mask and bike helmet

Such events, along with Beijing’s own “airpocalypse” last January, have dramatically increased public awareness and discussion about air pollution in China. Online stores are flooded with anti-pollution products; chat rooms and coffee shop conversations are filled with personal comments about their adventures with masks. Even in convenience stores such as 7-11 you can now find a big display of pollution masks stamped with N95, 99% or something similarly impressive on their labels. Let’s step back from this marketing hype — is there any evidence that any of these masks really do any good? This question is deadly relevant to me and my family, as well as to the hundreds of patients and readers who have asked me this question over the years.

What is my answer? I usually tell them, as I now tell you: yes, there is evidence of benefit — sort of.

There’s no medical doubt that smaller particles — the ones smaller than 2.5 microns (called PM2.5) — cause major inflammatory damage that leads to heart disease, lung disease and cancers. Quite a few studies have also shown encouraging results that lowering an area’s air pollution improves the health of the community, lowering ER visits and overall mortality. Lower your exposure, improve your health: yes, this seems obvious, but research is filled with assumptions that were proven wrong. Not in this case.

Let’s return to the masks. Construction sites all over the world can be filled with dust, heavy metals, and dangerous gases. These workers, for decades, have relied on protective masks made by companies such as 3M, with proven test results from independent labs that they reduce inhaled exposure by at least 95%. This is exactly what N95 means, a term we see often: an N95 mask, if officially certified by the National Institute for Occupational Safety and Health (NIOSH) in the USA, has passed the fit-test results on a human face. During this test, a person is wearing the mask for about 15 minutes, moving around in many positions, with the mask attached to special machines that record the concentration inside and outside the mask. If the air inside the mask is more than 95% reduced in particles, that mask passes the N95 test. Quite a few masks have this certification, and it’s for this exact reason that I am sure that these same masks can dramatically decrease all of our exposure to air pollution’s most dangerous particles, those PM0.3-PM2.5.

The main problem is jumping to the next level of assumptions — that by wearing the masks, you can improve your health. Yes, again this seems logical, but to date no studies have been done which follow such mask-wearers over months and years, testing their health and looking for improvements. Most likely these tests may never be done, unless a governmental agency such as the NIH pays for it. So in the face of lack of terrific data, the best data we have are a pair of short term studies from the same team of researchers, using subjects walking around the streets right here in Beijing. These researchers, from Cambridge as well as Beijing, first tested s couple dozen healthy young subjects and had them walk around the side streets around Second Ring Road, one of our many notoriously congested highways. When they wore a mask (the 3M 8812 model), they had a large improvement in blood pressure, 7 points on the scale.

But their follow up study, published last year in Environmental Health Perspectives, was much more relevant for me, as a family doctor. This time they tested people who already had heart disease — stable, but on medicines. Almost 100 people were tested this time, both with and without the same 3M mask for more than 24 hours. With the mask on, they showed improvement in heart rate variability, blood pressure, and stress markers for ischemia. All of these are considered risk factors for heart disease problems such as heart attacks and strokes, so any improvement in this objective data could have a major positive impact.

Why is this so important? Because air pollution doesn’t just cause lung problems, it causes heart attacks and chest pain, and strokes. And besides small children, I’m most worried about older people with heart disease, and this study proves that wearing a mask on those super bad pollution days just may save their life, preventing a heart attack.

These studies do have their flaws, especially their admitted fact that the control group wasn’t wearing a “placebo” mask, and perhaps the reported benefits are partly psychological as the subjects maybe were more relaxed while wearing the mask. But these are the best studies we have so far on the subject of masks, and I certainly am not going to wait around for better designed studies. I’m quite convinced that the underlying principle  is quite robust and well proven: that decreasing exposure to air pollution improves your health. And we already know, from decades of construction work use, that N95-rated masks are designed exactly to decrease PM2.5 exposure, and that this PM2.5 is currently considered the most dangerous of the many harmful chemicals in the air.

What more does one need to know?