Try This: How Indoor Air Quality Impacts Your Brain And What to Do About It

When it comes to air pollution, most of our collective attention is focused on outdoor air quality, especially with wildfires and general pollution on the rise.

But what if I told you that our indoor air can be anywhere from 200% to 500% more toxic than our outdoor air? And sometimes, according to the EPA, even 1000% more toxic than outdoor air (1).

In today’s newsletter, not only am I going to tell you why indoor air quality deserves attention, but I’m also going to share some free and cheap solutions to radically improve your air quality today.

What Poor Indoor Air Does to the Body

Air pollution can affect us in a lot of different ways. Symptoms like headaches, dizziness, itchy or watery eyes, and fatigue show up right away.  More aggressive things like cardiovascular disease and cancer can develop later down the line due to chronic, long-term exposure (1)(2).

The level of exposure to air pollution that causes symptoms is different for everyone. Some factors that make you more susceptible are your age, pre-existing medical conditions, or how sensitive to environmental toxins you are (2).

Symptoms of poor indoor air quality often go overlooked. They can be easily mistaken for a cold or allergies, so it’s super important to pay attention to where you are if symptoms come up (2). And I’m not just talking about the air that’s inside your home! Pay attention to how you feel wherever you spend a lot of time: a friend or family member’s house, nursing home, office, garage, basement, just about anywhere that’s inside.

For me, one of the wildest effects of indoor air pollution I’ve heard about (and even experienced myself) is its effects on brain health, cognition, and productivity. 

But before we get into that, I want to discuss a few common sources of indoor air pollution and the global impact it has on our health and the economy. To do this, first I have to explain particulate matter and why it’s so important.

What is Particulate Matter?

Particulate matter, more specifically PM2.5, are microscopic airborne particles 2.5 micrometers in diameter or less (that’s about 30 times smaller than a strand of hair!). PM2.5 is a concerning source of air pollution that comes from dust, spores, pollen, smoke, and burning fossil fuels.

PM2.5 is pretty much invisible unless there’s so much of it that it creates a smog or hazy appearance. (Ever see those pictures of cities in India or China where you can barely make out the skyline? That’s PM2.5)

Sources of Indoor Air Pollution

Indoor air pollution comes from a variety of sources. This review paper published in the International Journal of Environmental Research and Public Health gives an excellent overview of common indoor air pollutants and how they affect our health.

Some heavy-hitters in the paper are volatile organic carbons, or VOCs, which are a byproduct of off-gassing from new furniture, mattresses, carpeting, cabinets, and vinyl flooring.

Other sources of VOCs include formaldehyde, pesticides, paint fumes, mold, smoke from cigarettes, charring or burning food, and indoor fireplaces. Cleaning products, candles, and deodorizers are other common sources of VOCs (3)(4).

The impact that these toxins have on indoor air quality depends on how old the source is, how often it’s in use, and whether it’s emitting toxins all the time (like mold, air fresheners, central heating, or air) or periodically (like painting, smoke, candles, or cleaning products) (2).

The Costs of Air Pollution

A total of 7 million premature deaths a year are from air pollution (5)—that’s five times the number of deaths a year from car crashes (6) and more than twice the number of deaths from Covid worldwide in 2020 (7). That doesn’t make these deaths (or any deaths) any less serious, but it does put into perspective the serious impact that air pollution has on our health.

The majority of premature deaths from air pollution come from breathing in polluted air over time. PM2.5 enters the lungs and triggers inflammation, which increases the risk for heart disease, stroke, lung cancer, COPD, and respiratory infections (8).

Of the 7 million people who die prematurely every year from air pollution, 3.8 million are from indoor air pollution. (9)(10). Many of these deaths come from underdeveloped countries where people use wood, charcoal, and other combustible fuels for cooking and heating their homes (11). Even though those sources of poor indoor air are not of concern for most of the Western world, poor air quality in developed countries causes major health issues, too, and can prevent us from stepping into optimal health.

The cost of air pollution is enormous. It accounts for more than 3 percent of our global gross domestic product, or $3 trillion a year due to its economic impact from medical expenses related to asthma, diabetes, chronic respiratory diseases, and missing work (12).

Air Pollution And Your Brain

The economic costs of air pollution are massive, but how much of it comes from the loss of productivity? Today’s economy relies on both physical and mental labor. Not only is our physical health affected, but cognition, concentration, and work performance go down as well on days that air quality is poor.

One study observed the association between the accuracy of professional umpire’s calls and air quality. What the researchers found was pretty shocking. Carbon monoxide and PM2.5 significantly increased the likelihood of umpires making incorrect calls—a pretty big deal if it comes down to the final pitches of a baseball game (13). Even more concerning is that the levels were still well below what the EPA considers safe.

So, the stakes of outdoor air pollution are high, but studies show the stakes are just as high, if not higher, for indoor air pollution. 

A study looked at Israeli high school student’s performance on exams required to get into university and found that students were less likely to receive a passing score on days where PM2.5 levels were high (14). Imagine your entire future riding on the air quality of your classroom the day of a big exam.

Working-class adults’ cognition is also affected. An interesting analysis of the speeches made by Canadian politicians showed that when indoor PM2.5 levels were high, speech quality went down, equal to losing about four months of education (15)(16).

More recently, a study on office workers in several different countries found that higher levels of PM2.5 significantly impacted employees’ cognition and performance (17)(18).

PM2.5 has been associated with memory disturbances, fatigue, and reduced mental sharpness by triggering inflammation in the brain. In fact, the neurological damage caused by PM2.5 has been observed in Alzheimer’s and Parkinson’s diseases (19)(20).

As you can see, indoor air quality directly impacts our physical health as well as our brain health. Even though it might not be obvious right away, the adverse effects of indoor air pollution can be serious and are often overlooked.

Now that we know the different ways we’re exposed to indoor air pollution and why it’s so important to lower our exposure, let’s get into some strategies you can try today to improve your indoor air quality. That way you can feel good about where you spend most of your time indoors.

The Protocol

I. Open your windows. This is the cheapest and easiest solution to poor indoor air quality. Yes, it would be nice to have a fancy filter, but not everyone can afford that. That’s why when in doubt, you can open your windows to increase air circulation indoors.

When it comes to this no-cost solution, there’s no hard and fast rule here, but if it’s a nice day out and the Air Quality Index (AQI) is at a safe level, opening your windows for at least 20 to 60 minutes can help let fresh air in and stagnant air out. This is especially important if you just put in a new carpet or piece of furniture.

If you’re cooking anything in the kitchen that accidentally chars or burns, open a kitchen window or one that’s nearby. Ideally, keep it open for the whole time you’re cooking. And even better, if you have an exhaust hood, make sure you’re using that, too! Breathing in smoke from charred foods is another less-obvious source of indoor air pollution. My high-quality air filter automatically detects when my indoor air quality is poor and it always freaks out when I’m cooking!

Outdoor air quality is going to impact indoor air quality when you open your windows. Chances are, your outdoor quality is going to be better than your indoor air quality. But just to be safe, it’s good to check what the outdoor levels are first. You can check your air quality using a website or app like the ones I have listed below.

Try This:

1. Smart Phone Weather App. Both iPhone and Android smartphones have exact readings on PM2.5 built into their weather apps. One note is that the readings are usually averaged based on the city you are in. I live in Los Angeles which is a big city so if I want neighborhood-level data I’ll use the next recommendation.

2. PurpleAir. For more detailed readings I use this website called PurpleAir to check the air quality around me because it gives you an AQI measurement wherever you are in real-time that’s super specific to neighborhoods, even streets! It’s updated frequently so you can check the air quality around you or see what the air quality is like if you’re headed out somewhere.

Just remember, don’t freak out too much if outdoor air quality is poor. As we mentioned earlier, indoor air quality is often so bad that most people would benefit from opening the windows if they haven’t taken measures to improve indoor air. It’s all a balancing act.

II. House plants. Indoor house plants are totally underrated as a means of air filtration—they’re pretty remarkable and highly cost-effective. Plus, they bring an aesthetic value that brings a lot of joy to people.

Certain plants can absorb and filter out VOCs, PM2.5, and ammonia. They can even filter out viruses and bacteria (which might even have some implications for Covid—check this study out).

Below I listed some of the top plants I use for air filtration in my home based on this TED Talk by Kamal Meattle titled “How to Grow Fresh Air.” In his talk, Kamal describes findings from a study in Delhi, India, a city with some of the most polluted air in the world.

When the plants listed below were placed in a Delhi office building, eye irritation went down by about 50%, respiratory symptoms by 30%, headaches by 20%, breathing issues by 10%, and productivity went up by a whopping 20%.

Try This:

1. Areca palm: filters out benzene, carbon monoxide, formaldehyde, and other VOCs. They are non-toxic to animals and like plenty of light (great for living rooms).

2. Mother-in-law’s tongue: great for bedrooms because it converts carbon dioxide into oxygen at night. It also gets rid of formaldehyde and other VOCs.

3. Money plant: filters formaldehyde and other VOCs. This plant can go in any room, but keep it out of reach of animals and children since it’s toxic if ingested.

III. Minimize or avoid anything that has fragrance or perfume. Air fresheners, scented candles, incense, fragrances, and other perfumes are now being called “the new secondhand smoke,” They release harmful VOCs and other toxic chemicals into the air that can impact your health and breathing.

Have you ever gotten a headache after riding in someone’s car (or an Uber) that has a ton of air fresheners? Maybe you went on a date with someone who wore too much perfume or cologne? If so, you know what I’m talking about! That’s another form of indoor air pollution.

If you get headaches, lightheadedness, dizziness, shortness of breath, or feel tired and have air fresheners in your home, car, or workspace, it’s probably a good idea to ditch them. Try something more natural, like essential oils. When it comes to essential oils, stick to quality brands like Doterra, Young Living, and Aura Cacia.


I. High-quality air filter. AirDoctor (partner and affiliate link) is the best air filter I’ve seen and the one I use at home. It’s 100 times more effective than a regular HEPA filter. It traps and removes VOCs and PM2.5. Plus, it’s super quiet and sets off an alert when it’s time to change the filter. I first became aware of AirDoctor from my friend Ocean Robbins back in 2017, and I was so impressed with their device that I told them they have to partner with me and Dr. Hyman because we loved them so much.

II. Air quality monitor. I’m always on the lookout for devices and new tech that can help me and my readers measure in detail the true quality of the air.

About a month ago, someone reached out and highly suggested I check out ATMO, a portable device that’s linked to your smartphone and gives you super-detailed real-time data on your air quality. I’m always a little skeptical of portable devices, but ATMO blew me away.

Even though the device is a little pricey at $169, it’s much cheaper than a lot of the other solutions I’ve seen out there and provides way more data than the other monitors I use that are double-to-triple the cost. And the best part is that the device is portable, which means I can take it into different rooms or even into my office to see how the air quality shakes up.

If you want to splurge a bit, have room in your budget, and care about air quality, ATMO is the best air quality monitor I’ve seen so far. And if I ever come across something better or cheaper, I’ll be sure to let you know.

Final Thoughts

The EPA reports that indoor air can be up to 1000% more polluted than outdoor air. Considering that, on average, 90% of a person’s time is spent indoors, this is definitely an issue we need to pay attention to (1)(21). And given the fact that high levels of PM2.5, carbon monoxide, VOCs, and other air pollutants directly affect cognitive function and productivity, it might be time to start looking into the sources of air pollutants in your life and try to filter them out as best you can.

Like all things, it’s not about being perfect. If all you get from this newsletter is to open your windows more often, especially when cooking, that’s a huge takeaway.

Try my protocol and let me know what you think with the feedback feature below.

Further Listening: 

This Freakonomics podcast was a huge inspiration for me to write this Try This newsletter. Give it a listen for more information on the effects of indoor air pollution on our brain health.

Here’s to your health,
Dhru Purohit

  3. Vardoulakis S, Giagloglou E, Steinle S, et al. Indoor Exposure to Selected Air Pollutants in the Home Environment: A Systematic Review. Int J Environ Res Public Health. 2020;17(23):8972. Published 2020 Dec 2. doi:10.3390/ijerph17238972
  8. Lee BJ, Kim B, Lee K. Air pollution exposure and cardiovascular disease. Toxicol Res. 2014;30(2):71-75. doi:10.5487/TR.2014.30.2.071
  13. James Archsmith, Anthony Heyes, and Soodeh Saberian. Air Quality and Error Quantity: Pollution and Performance in a High-Skilled, Quality-Focused Occupation. Journal of the Association of Environmental and Resource Economists 2018 5:4, 827-863.
  18. Jose Guillermo Cedeño Laurent et al. Associations between acute exposures to PM2.5 and carbon dioxide indoors and cognitive function in office workers: a multicountry longitudinal prospective observational study. 2021. Environ. Res. Lett. 16 094047.
  19. Shou Y, Huang Y, Zhu X, Liu C, Hu Y, Wang H. A review of the possible associations between ambient PM2.5 exposures and the development of Alzheimer’s disease. Ecotoxicol Environ Saf. 2019;174:344-352. doi:10.1016/j.ecoenv.2019.02.086
  20. Palacios N, Fitzgerald KC, Hart JE, et al. Particulate matter and risk of Parkinson disease in a large prospective study of women. Environ Health. 2014;13:80. Published 2014 Oct 7. doi:10.1186/1476-069X-13-80
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