Super short workouts can be surprisingly effective

Sol Cotti for The Washington Post

It sounds like one of those outrageous infomercial claims — get fitter and healthier from as little as one minute of exercise. But In this case, the assertion isn’t too good to be true. There’s now a strong body of research showing that even workouts of 10 minutes or less can produce real and meaningful results, says Jenna Gillen, an exercise physiologist at the University of Toronto. Gillen’s work has shown that even a one-minute bout of exercise, done right, can improve your fitness and health.

Of course, there’s a caveat: to get results from such short workouts, you have to be willing to push yourself hard, Gillen says. Numerous studies have shown that intense interval training protocols can get results from relatively short workouts. Gillen and her colleagues at McMaster University wanted to know just how short that workout can be.

The answer, from a study they did in 2016, was: one minute of intense exercise in a workout lasting 10 minutes total (including the warm-up and cool down), three times per week.

Even a little exercise can mean big improvements in your health

Gillen’s team randomly assigned participants to three groups. One pedaled an exercise bike at a moderate level of effort for 45 minutes, three times per week. A second group did thrice-weekly the 10-minute workouts that included three segments of 20 seconds of all-out sprint cycling, for a total of one high-intensity minute each workout. (The rest of the time was easy spinning.) A third group served as a control and did nothing.

After 12 weeks, both exercise groups had improved their insulin resistance and also increased their fitness (as measured by their capacity to use oxygen during exercise) by about 19 percent. The gains were similar between the groups, even though the group doing short workouts with high-intensity intervals had spent only about 22 percent as much exercise as the group doing traditional longer workouts.

Similarly, a 2020 study by researchers at the University Hospital Erlangen in Germany put 65 sedentary, obese volunteers on an exercise program consisting of warming up on an exercise bike for two minutes, then doing five one-minute bouts at 80 to 95 percent of their maximum heart rate, with one-minute easy pedaling recovery periods in between. With the three-minute cooldown, the total workout time was 14 minutes, and these workouts were performed twice a week for 12 weeks. Participants in this simple 28-minute-per-week program improved their VO2max scores (a measure of cardiovascular fitness), and they also reduced their blood pressure and waist circumferences.

Explaining insulin resistance and how to reverse it

The improvements in cardiorespiratory fitness seen in these studies are a strong predictor of reduced morbidity and mortality risk, and are especially important for people at risk of developing diabetes, or other metabolic conditions, says Louise de Lannoy, an exercise physiologist at Children’s Hospital of Eastern Ontario Research Institute.

Still, the intensity required to achieve the benefits of short workouts does take some gusto.

“Especially for someone who’s been sedentary, getting up to that maximal effort can be very challenging,” de Lannoy says. This level of intensity feels all out — you’re going as hard as you possibly can. “But it also can be fun. It’s quick, a little bit of pain; you get a rest and do it again,” de Lannoy says.

Another 2020 study confirmed that some people do find these hard interval exercise programs enjoyable enough to continue. Exercise scientist Matthew Stork of the University of British Columbia and his colleagues brought a group of previously sedentary adults into the lab to do short workouts with high-intensity one-minute intervals on an exercise bike. Participants reported that the high-intensity bouts were hard, but some of them enjoyed them enough that they continued to do them after the study.

No coach, no problem: How to succeed at HIIT workouts on your own

“I’ve tried these workouts myself, and it takes a lot of self-coaching yourself to get up to 90 percent of your max,” de Lannoy says. That said, if you do a workout with repeated hard intervals and a short rest period, they’re likely to get harder as you go, so even if your first interval is only 60 percent of your max, by the third or fourth one you might be closer to 90 percent, she says. If you don’t have an exercise bike, briskly climbing some stairs is another good way to get your heart rate up quickly.

“A good rule of thumb is to build over time,” de Lannoy says. “You might start at 60 to 70 percent of your heart rate max, and try to increase that over time and build toward 90 percent.”

Short workouts can build muscle

Cardio workouts aren’t the only ones going shorter. Studies also show that you can make big strength gains from brief resistance training workouts.

A 2019 study published in the journal Medicine & Science in Sports & Exercise investigated the correlation between the number of sets of exercises performed and strength gains.

Participants in the study did a similar routine of seven strength-training exercises three times a week. One group did five sets of exercises each session, another group did three sets, and the third group did only a single set of exercises per workout. By the end of the eight-week program, all groups had achieved similar improvements in muscle strength and endurance. Doing three or five sets per workout increased the amount of time people were exercising, but it didn’t result in bigger gains. (The group that did the longer workouts did make bigger increases in muscle size in thigh muscles and elbow flexors, however.)

How short bursts of high-intensity exercise could keep you (relatively) fit

There is often skepticism around the idea of short workouts because they have been portrayed as gimmicky, says James Steele, associate professor of sport and exercise science at Solent University in England and principal investigator at the London-based UKActive Research Institute. But he says that if you’re aiming to get stronger, you do not necessarily need to spend lots of time in the gym or do a lot of reps. Instead, what’s important is doing the exercise until you attain “momentary muscular failure” — the point at which you can’t complete another rep. Steele was part of a research team that published evidence-based resistance training recommendations calling for a single set of eight to 12 repetitions to momentary muscular failure.

The Dutch company Fit20 runs franchise fitness studios that specialize in this “minimal effective dose” approach to workouts. It has a data set of almost 15,000 people who had participated in their program over a seven-year period, and Steele’s team recently used it to model people’s strength progression over time. The team found that Fit20 members were making substantial strength gains (on the order of 30 to 50 percent gains over the first year), despite doing a minimal amount of training: a single set of four to six repetitions of six exercises once per week.

The study shows that you can make meaningful improvements in your muscle strength in just one short workout a week, but Steele says he recommends that people aim for twice a week so that if they miss a session, they remain on track.

The minimal effective dose approach isn’t just for average folks. Studies done by Patroklos Androulakis-Korakakis, a researcher at Solent University and a coach at StrongerByScience.com, a program offering science-backed strength training, show that it works for highly trained athletes, too. He conducted studies on serious powerlifters and found that they also make substantial strength gains while following a minimal effective dose plan.

Remarkably, the powerlifters in Androulakis-Korakakis’s studies who trained with a minimum dose approach ended up experiencing very little soreness. “They had very low soreness scores, one or less on a scale of one to five,” he says.

Androulakis-Korakakis says his research suggests that “Hey, you could be doing much less than you’re currently doing and see great results.” A minimalist approach might not give the absolute best results, but it gives a lot more bang for the buck, especially when you consider the trade-offs of time and recovery, he says.

Try intermittent workouts. You might even get more out of them.

Turning to shorter workouts is not just a way to save time. It also can help you continue to make fitness gains even when life gets in the way.

“Let’s say you have exams coming up or your job is picking up and you only have a couple of hours per week” to exercise, Androulakis-Korakakis says. Instead of feeling like your strength and muscle mass will suffer, turning to a minimum dose approach can help you continue building your fitness.

“It’s hard to argue that you don’t have 10 or 15 minutes that you can find. That’s just not checking your email one more time or getting off social media,” de Lannoy says.

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Why Time Goes By Faster As We Age

Actual time and our mental time are very different things.
Copyright 2020 Clifford N. Lazarus, Ph.D. 

Posted November 29, 2020 Reviewed by Devon Frye

Source: VGstockstudio/Shutterstock

Time is an amazing and fascinating phenomenon. It is believed to be a fundamental quality of the universe that, along with the three known spatial dimensions (length, width, and height), makes up what Einstein famously described as spacetime. What’s more, Einstein proved that time is relative and actually slows down due to gravity and acceleration. Hence time is relative, depending on its observer, rather than an immutably fixed constant everywhere in the universe.

But beyond the theoretical and practical applications of Einstein‘s theories of relativity, almost every human knows intuitively that time is relative—because it seems to pass much faster the older we get. Hence, how a clock measures time and how we as humans perceive it are quite different. This speeding up of subjective time with advancing age is well documented, but there is no consensus on the cause.

A typical explanation that might explain some of this perception is the simple fact that for a 10-year-old, one year represents 10 percent of their entire life and even 15 to 20 percent of their conscious memory. But one year for a 50-year-old represents less than 2 percent of their recallable life. Thus those long days in school and almost endless summers of grade schooler’s childhoods, and the rapidly fleeting days, weeks, and months that most adults experience.

Another intriguing hypothesis stems from the fact that young children have faster heart rates and faster breathing rates than adults. It is likely, therefore, that their brains’ electrophysical undulations and rhythms occur faster as well. Just like the heart’s pacemaker slows the heart’s rhythm as children age, it is possible the brain has a pacemaker as well that slows as people age, and this “neuralmetronome” provides an internal sense of the passage of time.

Indeed, if you ask a young child to sit quietly, close their eyes, and state when a minute has passed, most children will report a minute has elapsed in 40 seconds or less. Run the same experiment with adults and seniors, and they will likely report a minute has passed in 60 to 70 seconds. Hence, children's brains "beat" faster than adult brains, thus allowing them to have more conscious experiences in a given unit of objective time. This, in turn, leads to the subjective passage of time moving more slowly for children than it does for adults.

A fascinating explanation that extends this neural pacemaker theory has recently been posited by Professor Adrian Bejan. He presents an argument based on the physics of neural signal processing (Bejan, 2019). Bejan hypothesizes that, over time, the rate at which we process visual information slows down, and this is what makes time “speed up” as we grow older.

This is because objectively measurable “clock time” and purely subjective “mind time” are not the same. Unlike the number of a cesium atom’s vibrations (the current agreed-upon definition of one second), mental time—memory—is never veridical and universally agreed on. It is a reconstructive process that involves a great deal of mental imagery (i.e., A. A. Lazarus, 1978). Bejan believes time as we experience it represents perceived changes in visual stimuli. We know something happened because we see change. And things always change in one direction; from cause to effect. We will never see a broken glass reassemble itself and jump onto a table from which it fell.

In this way, our experience of time is always a backward-looking process, reliant on memory and is thus relative, but not only in the way Einstein meant it. Of course, memory is much more than just a sequence of images, there are other sensory dimensions to it as well. But our predominant sense is vision and therefore a great deal of our memory is visual.

We can think of a camera, film, projector, and movie as metaphors to represent a central part of visual memory and its relationship to time.

Like frames in a movie, the more frames one sees in a second the slower the image appears to pass. The fewer frames one sees per second the faster the image seems to move. In other words, slow motion reveals many more frames per second than normal motion or fast motion. Bejan asserts that as we age our brain’s neuro visual memory formation equipment slows and lays down fewer “frames-per-second.” That is, more actual time passes between the perception of each new mental image. Children perceive and lay down more memory frames or mental images per unit of time than adults, so when they remember events—that is, the passage of time—they recall more visual data.

This is what causes the perception of time passing more rapidly as we age. When we are young, each second of actual time is packed with many more mental images relative to our older selves. Like a slow-motion camera that captures many more frames per second than a regular speed one, and time appears to pass more slowly when the film is played.

The root cause of this subjective, temporal gearshift, Bejan argues, is that the size and complexity of our brain's neural networks increase as we mature and continue to age. This means electrochemical signals must traverse greater distances and span more pathways thus slowing signal processing. Moreover, aging causes nerves to accumulate damage that creates greater resistance to the flow of signals, further slowing processing time.

As Bejan puts it: “People are often amazed at how much they remember from days that seemed to last forever in their youth. It’s not that their experiences were much deeper or more meaningful, it’s just that they were being processed in rapid-fire.”

Of course, the phenomenon of time passing faster as we age is but one of the brain's unknown, and possibly unknowable, mysteries. Classical physics has incorporated and moved beyond the seismic contributions of Einstein into the realm of quantum mechanics. Similarly, it is probable that to glean the intricate and multi-dimensional workings of the mind, a quantum theory of consciousness might be needed.

Remember: Think well, act well, feel well, be well!

This post is for informational purposes only. It is not intended to be a substitute for help from a qualified health professional. The advertisements in this post do not necessarily reflect my opinions nor are they endorsed by me.

In 1922, author W.L. George imagined what life would be like in 2022. He came pretty darn close.

In 1922, author W.L. George imagined what life would be like in 2022. He came pretty darn close.
John Kelly

The Washington Post, March 8 2022

The British Airways livery on the tail fins of passenger aircraft at London's Heathrow Airport last month. W.L. George wrote in 1922: "It could take as little as eight hours" to fly between New York and London in 2022. (Chris J. Ratcliffe/Bloomberg)


As I gazed at the blurry scan of the 100-year-old newspaper page on my computer, I started to wonder if what I saw was some kind of joke: a hack of the newspaper archives or a mind game from a puckish time traveler.


“Novelist Visions World of Year 2022,” read the headline on the May 7, 1922, article in the Memphis Commercial Appeal. It was above the sort of story editors like to assign and readers like to read: predictions of the future.


But this one was … different. English writer W.L. George had gotten nearly all of it right, from how long it would take an airplane to fly between New York and London in 2022 (“It could take as little as eight hours,” George wrote), to decreasing reliance on coal as a fuel (“a great deal of power will be obtained from radium … while it may also be that atomic energy will be harnessed”); from legalized birth control to motion pictures that had sound — and color!


“When one can not prophesy, one may guess,” George wrote, “especially if one is sure of being out of the way when the reckoning comes. Therefore it is without anxiety that I suggest a picture of this world a hundred years hence.”


George was 40 when he wrote his futurecast. I’d never heard of him before. He published more than two dozen books but didn’t attain the lasting fame of H.G. Wells or George Bernard Shaw. He died in 1926, just four years after his predictions were published.


Silver Spring reader Michael Ravnitzky pointed me toward George’s 1922 essay, originally published by the New York Herald. It appeared in newspapers across the country, sometimes illustrated with drawings possibly meant to convey the outlandishness of the prediction: a female politician orating in Congress, for example.


George felt the world wouldn’t change as much between 1922 and 2022 as it had between 1822 and 1922. “[The] world today would surprise President Jefferson much more, I suspect, than the world of 2022 would surprise the little girl who sells candies at Grand Central Station. For Jefferson knew nothing of railroads, telephones, automobiles, aeroplanes, gramophones, movies, radium, etc.”


He began with technology. Planes would replace both steamships and long-distance trains. Trucks would probably replace freight trains. Communications technologies such as the telephone would go “wireless.” Wrote George: “the people of the year 2022 will probably never see a wire outlined against the sky.”


Improvements in the movies — in “natural colors,” with actors speaking “with ordinary voices” — would threaten stage plays.


George wasn’t right about everything. He thought most people in 2022 would opt for “synthetic” food in the form of pills. And he believed houses would be easier to clean, not because of robotic vacuum cleaners, but because of reduced coal smoke.


Also, he wrote, the floors and walls will be made of compressed papier-mâché, bound with brass or taping along the edge.


Rather than scrub the floor or wall, homeowners of the future would simply unscrew the brass and peel off the dirty paper, revealing the clean layer below.


George expected the family to change, with the state taking on many aspects of child-rearing. An avowed feminist, George said societal improvement would be dependent on how women were treated.


“It is practically certain that in 2022 nearly all women will have discarded that idea that they are primarily ‘makers of men,’” he wrote. “Most fit women will then be following an individual career. … The year 2022 will probably see a large number of women in Congress, a great many on the judicial bench, many in civil service posts and perhaps some in the President’s Cabinet.”


But progress would be slow, he cautioned, writing “a brief hundred years will not wipe out the effects on women of 30,000 years of slavery.”


Nations would still go to war, but maybe less frequently and in a more limited fashion.


“I suspect that those wars to come will be made horrible beyond my conception by new poison gases, inextinguishable flames and lightproof smoke clouds,” he wrote. “In those wars, the airplane bomb will seem as out of date as is today the hatchet.”


If George was wrong in places, it was, I think because he was too optimistic. He believed the United States would be more “settled” in 2022. The zeal that drove the pioneers across the continent would be exhausted. Instead of scrapping for wealth, Americans would put that energy toward producing art and literature.


He predicted “a great liberalism of mind” and a sort of national homogeneity. “The American from Key West and American from Seattle will be much the same kind of man,” he wrote.


There was a tinge of nostalgia in George’s prose, a nostalgia for a future he would not know. “The sad thing about discovery,” he wrote, “is that it works toward its own extinction and that the more we discover the less there is left.”


I’m happy to have discovered W.L. George.

Are ice-cold showers good for you? I tried it for two months.

Matt Fuchs

Washington Post

Yet I kept hearing wellness pundits rave about “cold immersion.” They made it sound fairly simple. You pop into a really cold lake, ice bath or shower; stay there for some extended period of time; reemerge, shivering and bluish; and magically reap a wide range of supposed health benefits, such as more energy, better metabolic health and happier moods. Cold showers seemed slightly better than submerging myself in ice, and the concept was intriguing, if not exactly tempting.

But I became more interested in trying it this past winter. I’d begun to feel vaguely depressed, with the sunless skies, the pandemic marching on like an evil Energizer Bunny, and my occasional overwhelm from adjusting to a new career path — all while trying to cut back on my coffee addiction. I needed a boost.

Before I tried to conquer my fear of chilly water, I spoke with experts to see if it was worth it. One of them was David Sinclair, a Harvard biologist and leading researcher of longevity whose “metabolic winter” hypothesis would explain why cold immersion supports long-term health. His hypothesis, he said, is based on the fact that, for tens of thousands of years “our status quo was being cold.” That was because our ancestors lived outdoors in seasonally cold temperatures, endured the ice age and migrated to colder climates. Human metabolism, therefore, was designed to adapt to uncomfortable weather (hot temperatures may have had the same effect). But these days we live almost entirely in climate-controlled luxury. The new status quo derails our health because it eliminates the biological challenges our bodies had adapted to.

Sinclair’s hypothesis draws from a principle, well accepted by biologists, called hormesis: Some amount of pain is good for us. In addition to cold-water immersion, other examples of hormesis include exercise and dietary fasts.

Another expert I spoke to, Anna Lembke, a Stanford professor and psychiatrist, prescribes various forms of hormesis including cold-water immersion instead of pills to some of her patients suffering from addictions. “It helps them tolerate withdrawal,” she told me. “The body responds to cold water by up-regulating feel-good molecules like dopamine, serotonin and norepinephrine, as a way to compensate.”

These theories sounded plausible. Missing my usual caffeine bump and feeling especially lethargic one cloudy afternoon, I turned my shower handle to its coldest setting, took a deep breath, and stepped in.

I gasped. Then I screamed and quickly stepped out.

“Are you okay?” my 6-year-old asked from the hallway.

“I don’t know,” I said, before reassuring him — and myself — that it was just cold water.

Take two: I turned the handle to a saner, more inviting temperature, and got back in the shower. For about six minutes, I brought the pain gradually, turning the handle in increments, allowing my body to adjust. That is, until the handle would turn no longer, and the showerhead unleashed its deepest chill. I screamed again and reached out for the handle like a drowning man grabbing a rope, shutting off the water.

Never again, went the refrain in my head. But as I got dressed, cranked up the heat in my house and stood next to my space heater, a profound sense of relief spread through me, a rebound effect that lasted several hours.

Save your skin: How you shower matters more than when, dermatologists say

Even so, I remained skeptical. I’d just finished reading “Suggestible You,” Erik Vance’s book about the placebo effect. Beyond theoretical explanations and my own subjective take, what did scientific experiments actually reveal about the benefits of cold water?

I talked with Heather Massey, a physiologist in the Extreme Environments Research Group at the University of Portsmouth in Hampshire, England. Research on cold immersion is “an emerging field,” she said. “There’s a desperate need for more studies” and funding to do them.

A handful of studies do show a link between cold exposure and upticks in various brain chemicals associated with well-being. For example, one study found that immersion in cold water — 57 degrees, to be exact — raised people’s blood levels of the neurotransmitters noradrenaline (by 530 percent) and dopamine (by 250 percent).

Some research suggests that noradrenaline helps counter anxiety and depression, and dopamine plays a key role in feelings of motivation and reward. Other research indicates that higher levels of noradrenaline could reduce inflammation.

Sinclair mentioned to me that enduring cold temperatures may also increase so-called “brown fat,” which is associated with lower body fat percentage. Notably, this research involved cold air, not water. Other studies suggest that cold water immersion can buffer the immune system.

The anecdotal evidence, however, has been enough for some scientists to take the plunge themselves. Massey swims outdoors in cold-weather months. Before the pandemic, Sinclair dunked himself regularly in 39-degree water for five minutes at his gym. Kenneth Kishida, a Wake Forest neuroscientist and dopamine researcher, told me that he likes to take rugged camping trips in state parks, subjecting himself to frigid showers and other hormetic stressors. He returns from these trips in higher spirits.

Wendy Suzuki, an NYU neuroscientist, takes cold showers every morning. “I can tell the difference when I forget to do it,” she told me. “It’s just generally activating. I feel so alive.”

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I’ve gotten into a rhythm of taking cold showers two or three times per week, usually after lunch. At first, I couldn’t stand the shock of the coldest temperature — 48 degrees, according to my thermometer — for more than a few seconds. With more of these showers, though, my endurance has improved; I can now persist through the worst pain for several minutes.

“That tracks with the research,” Massey told me. “Cold shock” is the body’s natural response to sudden cooling of the skin, involving faster breathing and heartbeat, she said. But as you expose yourself more, these defense mechanisms start to relax, research suggests. “You can extend your time in the water because you have far less discomfort,” said Massey.

Recently, my thoughts have even drifted to random subjects, as they do during warm showers, rather than obsessing over the pain. But I last longest when focusing on the boost I’ll get afterward — a strategy backed by research. Plus, longer cold exposure seems to intensify the benefits.

I asked my wife if she’s noticed any changes in my mood lately. “Possibly,” she replied, very diplomatically. Hoping for a more definitive answer, I asked my 6-year-old the same question. “Not really,” he said. But then he added, “I have noticed, when I look over at you, sometimes you’re just smiling at me.”

I shouldn’t need cold showers to make that happen. But if they do the trick, the pain is worth it.

Matt Fuchs lives in Silver Spring, Md. In addition to writing about health and technology, he is editor in chief of Leaps.org, a journalistic platform that covers health innovations. Follow him on Twitter.

Are “safe” levels of air pollution really safe? • Current evidence, and what to do about it (6M Read)

Peter Attia, MD
March 12, 2022

In last week’s newsletter, I discussed various factors which might contribute to the alarming (and potentially rising) incidence of lung cancer among non-smokers. As a follow-up, I’d like to zoom in on one factor in particular which deserves special attention: air quality.
The current state of air quality

Over the last several decades, air quality studies have convincingly demonstrated that air pollutants are associated with numerous morbidities and early mortality. Extensive evidence shows that long-term exposure to airborne fine particles is strongly associated with negative effects on the respiratory system (chronic obstructive pulmonary disease, ischemic heart disease, and lung cancer), the central nervous system (oxidative stress and neuroinflammation leading to stroke, dementia, and neurodevelopmental disorders), and development (preterm delivery, low birth weight, and birth defects). This may not come as a surprise if your mind conjures images of densely populated city centers awash in traffic and smog. For instance, Delhi has one of the highest levels of air pollution in the world with a PM2.5 of 121 µg/m3 and is estimated to have the highest premature mortalities associated with airborne particulates. (PM2.5 refers to air particulate matter equal to or smaller than 2.5 µm – sizes small enough to penetrate deeply into lung tissue.) Compare this to guidelines set by the U.S. Environmental Protection Agency (EPA), which recommends maximal annual average PM2.5 concentrations of 12 µg/m3 to minimize the risk of health effects associated with long-term exposures.

Delhi is an extreme case. In the U.S., according to the EPA’s Air Quality Trends report surveying 206 cities across the nation, the average mean PM2.5 was 13.06 µg/m3 in 2000, 9.87 µg/m3 in 2010, and 7.96 µg/m3 in 2020 – a reduction of PM2.5 air pollutants by approximately 20-25% every decade. It’s clear that PM2.5 concentrations are now at their lowest national averages in recent records – even in dense metropolitan areas like New York City and Los Angeles, levels are well below the safe limit recommended by the EPA. But what isn’t clear is just how “safe” these limits actually are.

The average person will find it near impossible to avoid some level of exposure to fine particle air pollutants, which originate from a number of indoor and outdoor sources. Outside, fine particles predominantly come from motor vehicle exhaust, burning of fuels such as wood or coal, natural forest fires, and reactions from power plants. Inside, fine particles are produced by cooking, tobacco smoke, burning candles, and lighting fireplaces. Even at low levels, might these pollutants increase risk of pollution-related disease? And should we do anything about it?
Investigating the effects of air pollution

Trying to understand the effect of low air pollution on human health is a challenge. While it might be possible to determine the acute effects of high levels of pollutants by using short exposures in controlled test environments, assessing the health effects of long-term exposure at low concentrations does not afford such opportunities for controlled study environments. By necessity, study cohorts would need to be constantly exposed to very distinct environments in order to breathe distinct air, thus opening the door for a host of systemic differences in culture, diet, occupation, age, and climate, to name only a select few. Randomization and subject blinding are impossible. Thus, our primary data on this subject come from epidemiological studies involving an endless list of potential (and inherent) confounds.

As an example, a recently published epidemiological cohort study provided data collected from seven European countries between 2000-2017 as part of the “Effects of Low-Level Air Pollution: A Study in Europe” (ELAPSE) project. This enormous dataset included over 28 million subjects ages 30+, and investigators analyzed these data to assess the relationship between long-term exposure of low-level pollution and deaths from cardiovascular disease, non-malignant respiratory disease, lung cancer, and overall non-accidental causes. Concentrations of PM2.5 were estimated from linear regression models across multiple locations in western Europe in 2010. Analysis of the seven cohorts revealed a positive association between overall non-accidental mortality and PM2.5 concentration. Further, out of the total cohort, 4 million subjects were exposed to particulate matter below the EPA PM2.5 guideline value of 12 µg/m3, and within this subset, the calculated hazard ratio of pollution exposure was 1.095 per 5 µg/m3 increment. Meaning, there is a concentration-response even at low levels below clean air guidelines, so air pollutants still pose a greater risk for early mortality.
So is this epidemiological data reliable?

Even with millions of participants, the cohort study found only a slightly increased risk of mortality associated with low levels of PM2.5 air pollution. The authors state that they did not have data on smoking status or body mass index (BMI), both of which could constitute significant covariates or might reveal a “healthy user bias.” With all the confounding factors that may not be accounted for, it’s hard to put much faith in the small difference in risk identified by this analysis. However, it is important to recognize that this is just the latest in a long line of studies over many years that have shown similar outcomes: long-term exposure to low-level air pollution is hazardous to health. Despite individual study flaws and the potential for publication biases, the remarkable consistency and apparent dose-dependency of these effects across a large body of literature adds some credence to these conclusions.

Additional support for this conclusion comes from mechanistic studies conducted in Vitro and using animal models. Mice exposed to PM2.5 at 100 μg/day for 4 weeks exhibited marked lung inflammation and early stages of fibrosis compared with controls. As part of the same study, the investigators also conducted in vitro experiments using a line of lung epithelial cells to demonstrate that PM2.5 treatment induces 2.5-fold increased expression of TGF-β, a potent driver of fibrosis. Other work in mice has demonstrated neural inflammation and cognitive decline following PM2.5 exposure, in addition to pulmonary inflammation. Exposure of pregnant female mice to PM2.5 has been shown to result in lung and brain abnormalities in offspring. Though none of these studies used low PM2.5 exposure levels (i.e., under the limits set by EPA guidelines), they nevertheless provide mechanistic proof of principle for the reported effects of pollution on human health.
How to reduce exposure to particulate air pollution

What can be done to reduce our own exposure to particulate air pollution? Taking cars off the road or banning burning of fossil fuels aren’t practical solutions, at least in the foreseeable future. While we might have limited power to impact our outdoor air environment, countermeasures can be taken within the home to reduce our individual exposure. Limiting smoke production from wood-burning fireplaces and other sources is one strategy for reducing pollution originating from within the home. Another strategy – which also reduces pollution that enters the home from outdoors – is to use a HEPA filter in everyday life.

HEPA (High-Efficiency Particulate Air) filters are designed to capture particles in the air that are 0.3 µm or larger. Although dependent upon the PM2.5 levels, filter size, room size, and room ventilation, one may expect a typical portable HEPA filter to reduce PM2.5 by approximately 40%, according to a study that measured PM2.5 inside and outside of homes in Vancouver, Canada. PM2.5 inside homes with HEPA filters was reduced from 7.3 to 4.7 µg/m3 and from 6.5 to 3.4 µg/m3 in areas exposed to traffic-related air pollution or woodsmoke, respectively. In more extreme cases, such as in coal and wood-burning communities in Ulaanbaatar, Mongolia, use of portable HEPA filters in apartments was reported to reduce indoor PM2.5 by 40% (relative to controls with no air filters) during the first week of use and by 15% by the fifth month of use, with the largest reduction of 45 to 29 µg/m3 during the winter months when burning wood and coal for energy is highest. Furthermore, they collected blood data from pregnant female inhabitants using HEPA filters indoors and found a 14% reduction in levels of blood cadmium, a heavy metal linked to fetal disorders, cancers, and kidney disease. These studies demonstrate that portable HEPA filters are effective in reducing both high and low levels of air pollutants, potentially improving health significantly.

In addition to these strategies for improving air quality in our own homes, we can also take steps to reduce the outdoor exposure and the impact that ambient pollution has on our health. A variety of websites and free apps are available for monitoring outdoor air quality in various cities or regions. Using this information, we can modify our behavior in order to minimize exposure to (and damage from) PM2.5. Exercise, for instance, increases the body’s demand for oxygen, thus increasing the volume of air we inhale over a given period of time. So when outdoor air quality is especially poor (typically regarded as ≥35µg/m3 for a 24-hour exposure, as was the case for many areas during the Western wildfires of 2021), an indoor treadmill session might be a safer option than a jog around the neighborhood. When we must be outdoors in polluted conditions, we can reduce our exposure by wearing a particulate respirator mask or by choosing times of day when air quality is at its best – typically in the evenings.
The bottom line.

Taken all together, the large body of literature with consistent findings indicate there may be significant benefits to lowering the total amount of air pollutant exposure one receives over a lifetime. In fact, the EPA is currently proposing to revise the annual standard to below the 12 µg/m3 limit based on scientific evidence gathered during their 2020 policy assessments. Since the time of the ELAPSE project, the World Health Organization (WHO) has already lowered its own recommendations for safe PM2.5 limits from 10 µg/m3 in 2005 to 5 µg/m3 in its 2021 guidelines. Even in “green cities” where PM2.5 exposure is comfortably below the current U.S. EPA limit, efforts to further reduce exposure are likely to be beneficial for long-term health, and HEPA filters are a relatively affordable option for doing so.