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Are Air Purifiers Worth It?-3 (new) medical studies decide

Are Air Purifiers Worth It?-3 (new) medical studies decide

This is a great question, one that gets more interesting the more you think about it. Most of us spend 90% of our time indoors in homes and workplaces that are better insulated and sealed than ever. So any pollutants or particles have a hard time getting out and tend to buildup in the recirculated air. This can lead to an indoor air quality that is worse than the outdoor air quality.

There is overwhelming evidence that particles in the air damage health, causing heart attacks, dementia, premature death and many other medical conditions. Air purifiers used properly can reduce particle count in the air as well as chemicals by 80% or more.

The effect of particles on human health is a fascinating subject. You may not yet realize it, but the epidemiological/clinical data suggests that if you reduced the particle count in your air, you would be smarter, happier, and even better looking!

So let us now look at some of these studies and decide are air purifiers worth it.

Health Effects of Airborne Particles

Air pollution has been shown in clinical or epidemiological studies, often multiple studies, to cause-

  1. Coronary heart disease-heart attacks
  2. Strokes
  3. Premature aging of the lungs
  4. Chronic obstructive pulmonary disease
  5. Pneumonia
  6. Cancer
  7. Lymphoma
  8. Diabetes
  9. Skin problems including skin aging
  10. Autoimmunity
  11. Osteoporosis
  12. Diabetes
  13. Kidney disease
  14. Dermentia
  15. Cognitive decline-decrease in thinking ability
  16. Parkinson’s disease
  17. Vision impairment-age related macular degeneration and glaucoma
  18. Impairment of sense of smell
  19. Sleep disturbance
  20. Depression
  21. Anxiety
  22. Increased risk of psychiatric problems
  23. Decrease in fertility
  24. Increased miscarriage
  25. Exposure during pregnancy linked to neurological problems, asthma, lower IQ in child
  26. Children-lower intelligence and delayed psychomotor development, faster decline in cognitive function in adulthood
  27. Children-chest infection, asthma
  28. Children-increased obesity
  29. Children-increased psychiatric problems
  30. Children-death rate increased
  31. Premature aging?-ultrafine particles speed up several processes involve in aging
  32. Premature death

You may like me be struck by the severity of the effects on the fetus and child. However stroke, dementia, breast cancer, blindness and premature death in adult life are also fairly severe consequences of particle pollution. There are more health conditions related to air pollution, this is a basic list-for further details please see this article.

Parents please note that air filters in classrooms in a US school increased pupils English and Math scores. In China air pollution was found to reduce cognitive (thinking) ability so much it was equivalent to 1 years less schooling.

An air purifier in a room

Air Purifiers Reduce Particle count

There is no doubt that air purifiers reduce airborne particles. A true HEPA filter is the cornerstone of modern air purifiers. UV light and ionic air purifiers do not deal with particles as effectively as a HEPA air purifier does. A HEPA filter easily deals with large particles such as pet dander, mold spores, dust, and dust mite but also fine particulate matter such as tobacco smoke.

To illustrate how well air purifiers can reduce particle count, I performed an experiment. I used an iQair HealthPro Plus air purifier on its maximum setting providing 9.4 air changes per hour, in a room with the door and windows closed. The readings were on normal room air and I used a Trotec PC200 particle counter to count 0.5um diameter particles. This size is the smallest particle size that laser diffraction technology can accurately measure.

So you can see with the air purifier on its maximum setting and providing 9.4 air changes per hour, the reduction in particle count only mildly exceeded the EPAs minimum target. This shows that it is best to be careful in buying an air purifier and to check that it really will deliver a minimum of 5 air changes per hour for your room on its second to highest setting. In general, you will never be able to tolerate an air purifier on its maximum setting for long as it is too noisy.

However, there are other airborne pollutants such as chemicals, so nearly all air purifiers also have an activated carbon filter. Activated carbon filters remove a wide range of chemicals particularly volatile organic chemicals and even ozone. Volatile organic compounds are responsible for odor and so an activated carbon filter will remove or at least markedly reduce an unpleasant odor.

An HVAC whole house air purifier is possible, but a HEPA specification one will probably need remodeling of your HVAC system. HVAC filters can be very poor at dealing with indoor air pollution. You should check that your HVAC system has a minimum of a MERV13 filter as lower MERV specification filters can be so poor that they remove less than 50% of airborne particulates, as explained in this article. Before you upgrade your HVAC filter to create a whole home air purifier, you should check with an HVAC engineer as an upgraded filter will reduce airflow through the system and may damage it, as explained in this article.

Air purifier in a bedroom

Air Purifiers Also Reduce Chemicals

Air purifiers have carbon filters to remove chemicals. The most common chemicals that need removing are those in cigarette or wildfire smoke.

The main chemicals in wildfire smoke are-

  1. Acrolein
  2. Formaldehyde
  3. Benzene
  4. Hydrogen cyanide

Most of these chemicals have been linked to cancer.

These chemicals can be removed by absorption onto activated carbon in air purifier filters. This is explained in more detail in this article.

Different air purifiers have different amounts of activated carbon in their filters and so a different ability to remove chemicals. There is an article outlining the best air purifiers for reducing chemicals in this article.

Air Purifiers are Worth Buying For People With Some Medical Conditions and Possibly for Pregnancy/Children

If you have a medical condition, then you should ask your doctor if it could be affected by particles in the air and if so consider using an air purifier. It would be a good idea for anyone who has any condition on the above list of medical conditions or in this article to have air purification at home. Also women who are pregnant or are intending to become pregnant should consider using an air purifier, especially if they are living in a polluted environment. An air purifier should be used especially at home but possibly even at work-there are good desktop personal air purifiers.

There are 24 million people in the U.S. with asthma, including 6 million children, it would be wise for these people to at least try a good air purifier with good technique to see if reducing airborne allergens makes their asthma any better. In addition, there are at least 6 million more with seasonal and perennial allergic rhinitis who should at least try an air purifier to reduce airborne allergen to see if this eases their symptoms.

For People Without Medical Conditions

Living in Highly Polluted Areas

If you live in a highly polluted area, it is essential to have an air cleaner/purifier to lower your pollution risk.

Examples of such areas-

  • near busy roads
  • areas that have forest fires
  • cities
  • near some forms agricultural production

For People in Areas With Low Pollution Levels

Ultrafine Particles

Even in low pollution areas there are 1-2 million ultrafine particles per cubic liter of air. A liter is about 1/4 of a gallon. You will be breathing in about 600 litres of air per hour containing about 1 billion ultrafine particles. As explained above ultrafine particles can reach the deepest parts of the lungs and enter our bloodstreams.

Ultrafine particles may also increase the rate at which we age! For further information please see this article on ultrafine particles-Airborne Ultrafine Particles-do they accelerate aging?

California Wildfire. Los Angeles Fire Near the City. Fires in the United States. Smoke and fire in the mountains of California. State of emergency. Plumes of smoke into the air

So it is possible that everyone would benefit from an air purifier-unless of course particles entering our bloodstreams and our brains is a good thing!

Fine Particles

Although it is not well known, the studies of the impact of fine airborne particles, PM 2.5, on human health are looking more and more serious. For instance, heart attacks and strokes, are seen at even low levels within the EPA safe range. A similar finding of increasing risk of dying with fine particle exposure even at low levels was found in a study of 652 cities. These findings were published in the world’s top cardiac journal Circulation and top medical journal The New England Journal of Medicine.

There has since been additional studies showing the increase in mortality at low PM2.5 airborne particle counts.

A study from Europe, also showing increased mortality at airborne particle counts under the EPA’s limit.

A study from Harvard looked at the effect of low levels of air pollution, PM 2.5 less than 12 µg/m3 on mortality. All patients aged at least 65 years enrolled in Medicare from 2000 to the end of 2016 were studied, so more than 50 million people. It was found even within this of range particle concentrations, considered to be safe, that annual mortality increased 0.073% for each 1 mcg/m³ increase in PM 2.5. So a decrease in PM 2.5 particle count of 10ug/m3 would reduce absolute mortality by 0.73% which for this population represents a percentage mortality reduction of approximately 14%. This is easily achievable with an air purifier.

For those over 85 years old the risk was approximately 7 times as great as for those between 64 and 75 years old. So this study also showed that the elderly are a vulnerable group, and so have more to gain from airborne particle reduction with an air purifier.

A recent study from Canada, which looked at changes in long-term residential exposure to particulate matter PM 2.5 and found when people move from one area of the country to another which had a different pollution level. The people who moved from a high pollution area to a low pollution area went from an average PM 2.5 level 10.6 mcg/m³ to 5 mcg/m³. The people that went from a low pollution area to a high pollution area increased their PM 2.5 from 4.6 mcg/m³ to 9.2 mcg/m³. Over 5 years those people who moved from high to low levels of PM 2.5 pollution had a 6.8% reduction in mortality, mainly from cardiovascular causes and diabetes. Conversely those people who moved from a low to higher-level pollution had an increase in mortality, particularly from respiratory disease.

So here we have a study which directly suggests that lowering PM 2.5 levels in humans leads to lower mortality.

The World Health Organization has now lowered the safe limit for PM 2.5 fine airborne particles to 5 mcg/m³.

According to EPA statistics, covering 200 million people in the US, 98% of US citizens are living in areas with PM 2.5 concentrations above the new WHO guidelines. These statistics are flattering to outdoor air particle count as they were collected during the COVID epidemic, when activity both industrial and vehicular was reduced, so the real picture with a fully functioning economy may be even worse. In addition the situation is actually worse than these outdoor measurements, as indoor air pollution is often worse than outdoor air pollution, for instance when we cook or even make toast particle count in our homes increases dramatically above the background level. Moreover, even these WHO guidelines seem to be aiming for particle count that is higher than those leading to the lowest mortality rates, please see the graph below-

A diagram to illustrate that increases in fine particulate pollution PM2.5 even at low levels increase mortality.
This is based on data from the first 2 studies referenced above.

The percentage reduction in mortality from using an air purifier may seem to be small. However-

  1. This is an average and particularly vulnerable adults may have more to gain. The Harvard study mentioned above only considered people older than 64 who were medicare enrolees and found an effect that was double that in the graph above.
  2. Also death is obviously an enormously significant endpoint, but there are a whole range of disease and disability short of actual death that is caused by airborne particles.
  3. Even using the EPA’s air quality standard of 12 ug/m3, about a million years of American’s lives are lost each year due to air pollution so the scale of the problem is huge. If we now consider anything above 5 ug/m3 as abnormal the problem is many fold greater as so many more people are affected by being considered to live in a polluted area and the potential increase in numbers dying considered to be due to air pollution will be much greater.

So if we choose to use air purifiers to alter our airborne particle count, and if we use them properly we should be able to reduce the particle count to under 1 mcg/m3. The graph shows that the lower the PM 2.5 particle count the greater the reduction in mortality per unit of PM2.5 reduction.

However, the really important observation is that these effects are apparent at levels of particles in the air that we think of as “normal”, well below the limits at which “pollution” starts. So we may need to change our attitudes away from only those in polluted areas needing air purifiers, towards the possiblility of everyone potentially benefiting from breathing purified air for at least part of their day.

So should people without medical condition living in low pollution level areas consider purifying their air? I would suggest that you buy an air quality sensor/meter and measure the air quality in different rooms in your home. Certainly if the PM 2.5 is above 5 g/m3, the WHO safe level, then it probably would be wise for you to buy air purifiers and reduce particle count in the air. However even if the PM 2.5 is below this level you may wish to look at some of the recent medical evidence outlined in this article. Also you may live in an area with particular pollution problems for instance with chemicals, and that may be the main reason that you need to use an air purifier.

If you are going to stake your future health on measuring the air quality in your home, I would recommend the iQair AirVisual Pro. There is a helptul article here-“How to test air quality in your home

Are Air Purifiers a Waste of Money?

For an air purifier to be a waste of money an enormous amount of scientific evidence concerning the effect of low levels of airborne particles on health would have to be wrong. Or you would have to be in the 2% of the population that live in a very low pollution area, as well as not producing much indoor air pollution in your home by for instance cooking for long periods.

Are Air Purifiers Good?

As a whole, the scientific and medical evidence clearly points to many adverse health effects from airborne particles. Air purifiers can lower these more than 80%. So on balance using an air purifier seems an extremely good idea. However, no one is likely to notice beneficial effects immediately, but over the years an air purifier user would be expected to have better health.

If you do Decide an Air Purifier is Worth it-important points in buying and using an air purifier

In one review of studies where air purifiers were used, fine particulate matter was reduced between 23-92%. Bear in mind the EPA recommends a minimum reduction of 80%. So even in experimental studies with training in how to use the air purifiers, most air purifier users failed to hit this target. On the other hand, it shows that air purifiers, when used well, can decrease particle count by 90%. This just emphasizes the importance of how you use the air purifier.

  • Buying an air purifier-the air purifier should have a true HEPA filter, adequate air flow (CADR) at a noise that you can tolerate for long periods. The air purifier should be “smart” that is programmable or capable of being made smart. The most difficult part is buying one with an adequate air flow at a noise that you can tolerate for long periods as most air purifiers are too loud on their maximum fan speed and manufacturers usually do not give data on air flow and noise at lower fan speeds. There is helpful advice about buying an air purifier here-“Buying an air purifier”. Alternatively, just buy the recommendations on this site. If you want the quietest air purifier you may wish to read this article-“Best Quiet Air Purifiers“, if you need one that will remove particles very well but is particularly good at removing chemicals from the air, for example from forest fires, please see this article-“Best Air Purifier for Smoke“.
  • Position the air purifier at least 12 inches from any wall-so that the air coming out of the air purifier joins in with the circulation of air in the room. There is advice about using an air purifier in this article-“How to Use an Air Purifier“.
  • Run the air purifier for at least 30 minutes before entering the room. This is because it takes an air purifier this long to reduce the particle count in the room. So the air purifier that you buy needs to be smart or capable of being made smart by plugging it into a smart plug.
  • Run the air purifier continuously when you are in the room at the highest setting that you can tolerate long term. This is because the higher the setting that you run the air purifier on the lower the particle count in the air will be. There is no lower threshold known below which human health does not improve, so the lower the particle count/PM2.5 the better. Health aspects of particle count/PM2.5 are outlined in this article-“Airborne Particles and Chemicals Affect Us All Now“.
  • Never run the air purifier using its inbuilt sensor-there are 7 reasons that you should not do this as outlined in this article-“How to Use an Air Purifier“.
  • Always test the air with an air quality meter where you are going to sit at the height in the room where your mouth and nose are. Comparing the measurements before and 45 minutes after switching the air purifier on there should be at least an 80% reduction in particle count as the EPA recommends. Testing that the particle count/PM2.5 is adequately reduced by your air purifier is the most important thing that you need to do. Air quality meters can be brought really quite cheaply eg $35, there is a helpful article about them here-“How to Test Air Quality in Your Home“.
  • How many air purifiers do I need?-at least 2 but maybe 5 or more. Please see this article “How many air purifiers“.


There is no doubt that inhalation of particulate matter harms human health. There is also no doubt that air purifiers when used with good technique lower particle count more than 80%. When particle count is lower in the environment, there are fewer heart attacks and strokes. So it may seem obvious that you should use an air purifier.

However, there are no long-term trials showing a benefit from using an air purifier so you may prefer to wait until there are long-term trials of air purifier use. The downside of this approach is you that you may wait 20 years or longer only to find out that you should have been using an air purifier all along.

Now it is not an exact analogy, but in another form of pollution there may be parallels. For many years even doctors said that there was no evidence that cigarette smoking harmed health and that there was no evidence that stopping was beneficial. Similarly, there is currently no conclusive evidence that using an air purifier is beneficial although there is overwhelming evidence that particles in the air damage health even at low levels and that air purifiers effectively reduce particle count in the air. Anyway, it would be impossible for conclusive evidence to be available currently as no clinical trials with the right protocol have even been done.

So I hope that this helps you one way or another to decide about whether it is worth buying an air purifier.

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