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12 Common Indoor Air Pollutants

Last updated May 24, 2023

Danny as been writing about air purifiers for 10+ years. He is a major fan of home technology, which makes him the perfect person to test and evaluate products for HouseFresh

Our verdict:

The United States Environmental Agency (EPA) lists 12 types of indoor air pollutants to be aware of. 

  1. Asbestos
  2. Biological Pollutants
  3. Carbon Monoxide (CO)
  4. Cookstoves
  5. Formaldehyde
  6. Lead (Pb)
  7. Nitrogen Dioxide (NO2)
  8. Pesticides
  9. Radon (Rn)
  10. Indoor Particulate Matter
  11. Secondhand Smoke/ Environmental Tobacco Smoke
  12. Volatile Organic Compounds (VOCs)

While these pollutants are serious, plenty of measures exist to conquer them. An air purifier equipped with HEPA and an activated carbon filter is one great way to tackle air pollutants within your home.

We’re all aware of the pollutants outside of our homes. From pollen to car exhaust fumes, they’re everywhere! But do you know what you can find inside your home, too?

Indoor air pollution is a serious problem, but it’s one that most people know little about. The American Lung Association states that poor indoor air quality is responsible for lung diseases, such as repeated infections, lung cancer and asthma. 

The World Health Organization estimates that in 2020, household air pollution was responsible for around 3.2 million deaths. 237,000 of these were children under the age of five. Indoor air pollution is a big problem—with 90% of us now spending our time indoors, we should all be taking it much more seriously.

But where does it come from and what can you do about it?  Well, according to the EPA, there are 12 common causes of indoor air pollution that you should be aware of. 

Let’s get into it!

Cause of Indoor Air Pollution #1: Asbestos

Warning ⚠️ If you have asbestos in your property or suspect you do, never try to deal with it alone. A local asbestos testing company can perform proper tests safely and should always be your first port of call.

Asbestos is a mineral fiber that occurs naturally in rock and soil, has strong fibers and is heat resistant. In the past, it was used widely across the home in various building materials. 

You can often find asbestos in:

🏠 Roofing shingles

🧱 Ceilings, floor tiles and cement products

📜 Paper products

We know now that high-level exposure to asbestos can increase your risk of lung disease, including cancer and asbestosis. It can also take many years to develop following exposure. 

But, asbestos exposure only occurs when the material is damaged during construction or some other form of disturbance that causes it to release particles and fibers into the air, which we can breathe in.

✅ An air purifier can help with air pollution from asbestos. 
HEPA (high-efficiency particulate air) air filters are built to deal with particles around 0.3 microns. Asbestos particles are generally about 0.7—90 microns, making an air purifier perfect for capturing them. Check out our list of the best air purifiers to see which ones we recommend. 

Cause of Indoor Air Pollution #2: Biological Pollutants

There are a variety of biological pollutants in your home, which can include:

🧫  Bacteria

🦠 Viruses

🐕 Animal dander

🐈 Cat saliva

🧹 Dust mites

🪳 Cockroaches

🌼 Pollen

Many of these are tiny and enter your body by being inhaled. As they’re living things, moisture and food are ideal conditions for them to survive and thrive. 

😮Scary fact: Did you know mold spores are only about 2 —100 microns but can quickly grow into vast and thriving colonies? 

Without proper care and attention, your home can quickly become a hotbed of biological pollutants. The health effects can be wide-ranging and severe in some cases. 

Along with allergic reactions and asthma, you may also experience:

🤧 Sneezing 

👁️ Watery eyes

😮‍💨 Shortness of breath

💫 Dizziness

😫 Lethargy

🌡️ Fever

🍲 Digestive issues

✅ An air purifier can help with air pollution from biological pollutants.
Air purifiers are incredibly efficient at removing biological pollutants. HEPA filters can remove up to 20% of these particles on average. 

Cause of Indoor Air Pollution #3: Carbon Monoxide (CO)

Carbon monoxide is a toxic gas that is both odorless and colorless. As it’s hard to detect, you could fall victim to carbon monoxide poisoning before you’re even aware it’s in your home. Health effects include fatigue and chest pain at low concentrations and can even be fatal at high concentrations.

You can find carbon monoxide in:

☢️ Unvented kerosene and gas space heaters

🏠 Leaking chimneys and furnaces

🍳 Gas stoves

⛽ Gasoline-powered equipment, such as generators

🚙 Car exhaust fumes

🚬 Tobacco smoke

🔥 Damaged or poorly maintained combustion devices, such as boilers and furnaces

✅ An air purifier can help with air pollution from carbon monoxide.
Air purifiers with activated carbon filters can help to remove carbon monoxide from the air. Installing a carbon monoxide detector in your home will also help you with early detection.

Cause of Indoor Air Pollution #4: Cookstoves

According to the EPA, more than 40% of the world’s population cook their food and light and heat their home using coal and other biomass fuels. When these are burnt indoors, dangerous particulate matter, carbon monoxide and other pollutants are released into the air. 

Exposure to these fuels can lead to various lung-related health issues. Strong evidence has found that it exacerbates childhood pneumonia and increases the risk of stillbirth in pregnant women.

✅ An air purifier can help with air pollution from cookstoves.
HEPA and activated carbon filters can remove gas and particulates from wood-burning and gas stoves. 

Cause of Indoor Air Pollution #5: Formaldehyde

Formaldehyde is a chemical widely used to manufacture building materials and household products. It also occurs naturally as a by-product of combustion, amongst other natural processes. It is colorless, flammable and has a strong odor. 

High levels of formaldehyde (which can be inhaled) can irritate the skin, eyes, nose and throat and cause some cancers.

In your home, you may find formaldehyde in:

🪵 Resins in composite wood products (hardwood plywood, particleboard and medium-density fiberboard)

🏠 Building materials and insulation

🎨 Paint, glues, lacquers and finishes

💊 Medicines, cosmetics, dishwashing liquids and fabric softeners

🚬 Cigarette smoke

⛽ Fuel-burning appliances

🌱 Fertilizers and pesticides

✅ An air purifier can help with air pollution from formaldehyde.
Air purifiers fitted with an activated carbon filter have a high-efficiency rating regarding the removal of formaldehyde. 

Cause of Indoor Air Pollution #6: Lead (Pb)

Warning ⚠️ If you suspect you have lead paint in your home, hire a certified lead professional. They can test your home and do any work safely, reliably, and effectively. If you suspect that you have lead poisoning in your water, contact your water utility provider and request a copy of their latest Consumer Confidence Report, required annually by the EPA.

Lead is an element in the natural world within the earth’s crust. Historically, it’s been used in a wide variety of products and around the home, including:

🖌️ Paint

🫖 Ceramics

🏠 Pipes and plumbing materials

⛽ Gasoline

🔋 Batteries

💅🏽 Cosmetics

However, it can be toxic to both humans and animals and result in cardiovascular, kidney and reproductive issues. In the worst-case scenario, lead poisoning can lead to death.

✅ An air purifier can help with air pollution from lead.
A HEPA air purifier is able to capture lead particles in the air, which are often around 15.1 microns. 

Cause of Indoor Air Pollution #7: Nitrogen Dioxide (NO2)

Nitrogen Dioxide (NO2) is a toxic gas, a highly reactive oxidant and corrosive. In addition to being an irritant, which can affect your eyes, nose, throat and respiratory tract, high exposure can lead to acute or chronic bronchitis.

You can find NO2 in your home in:

🍳 Unvented appliances, such as gas stoves

🚬 Tobacco smoke

🥵 Kerosene heaters

✅ An air purifier can help with air pollution from nitrogen dioxide.
An air purifier with HEPA and carbon can decrease indoor NO2 concentrations. 

Cause of Indoor Air Pollution #8: Pesticides

Pesticides are toxic chemicals used to kill pests. 

You can commonly find them in products used to kill household pests in the home. They can also be tracked into the home from outside sources, such as lawns and gardens. Chronic exposure can damage the liver, kidneys and endocrine and nervous systems, irritation to the eyes, nose and throat and increase the risk of cancer.

✅ An air purifier can help with air pollution from pesticides
Carbon filter air purifiers will help to remove the gasses produced by pesticides from the air. 

Cause of Indoor Air Pollution #9: Radon (Rn)

Radon is a radioactive gas that is both odorless and colorless. However, it can have a huge impact on indoor air quality and, with high levels of exposure, can cause lung cancer. Found in soil, radon is formed when uranium naturally decays. The gas then moves up through the earth and into the air, and, potentially, into your home through cracks and holes in the foundation. Once trapped inside your home, it can build up to high levels. 

✅ An air purifier can help with air pollution from radon
An air purifier with activated carbon can help to remove radon from the air. The activated carbon absorbs odors and gasses like radon. Be sure to look at what we think is the best home radon detector so you can know if you have a problem before investing in an air purifier.

Cause of Indoor Air Pollution #10: Indoor Particulate Matter

Indoor particulate matter, also known as PM2.5, is particulate matter with a diameter of 2.5 micrometers or less. Once they are 10 micrometers or smaller, they can be inhaled, which can lead to various health issues.  These health effects can include irritation of the eyes, nose and throat; worsening of symptoms of heart and respiratory diseases; and, in extreme cases, premature death.

PM2.5 can be found both within and outside of the home. Within the home, it can be found when:

🍳 Cooking

🕯️ Lighting candles of fireplaces

🔥 Using space or kerosene heaters in unvented areas

🚬 Smoking cigarettes

✅ An air purifier can help with air pollution from indoor particulate matter
HEPA filters are especially good at removing indoor particulate matter around 0.3 microns. You should also ensure your home is properly vented, particularly when cooking or using heaters.

Cause of Indoor Air Pollution #11: Secondhand Smoke/ Environmental Tobacco Smoke

Secondhand smoke, or environmental tobacco smoke (ETS) is found when tobacco products (eg. cigarettes, cigars and pipes) are burned and exhaled by smokers. Others then inhale the smoke and PM2.5 produced.

Secondhand smoke is just as dangerous as smoking, particularly in non-smokers and can lead to numerous health effects, including lung cancer, heart disease and stroke, asthma and sudden infant death syndrome.

Of course, as smoke can travel, it isn’t limited to smokers within your home. Secondhand smoke can also be found outside the home, traveling inside through open doors and windows. For more information about the ground-level gasses around us that affect our health, you should also check our article about where ozone comes from.

✅ An air purifier can help with air pollution from tobacco smoke
Air purifiers with HEPA and activated carbon filters can help trap PM2.5 caused by smoking and remove the smoke from the air. 

Our buying guides for different types of smoke:
Best cigar smoke air purifier
Best air purifier for cigarette smoke
Best air purifier for marijuana smoke

Cause of Indoor Air Pollution #12: Volatile Organic Compounds (VOCs)

Volatile Organic Compounds (VOCs) are widely used chemicals, often found in our homes. 

Used in anything from building materials to home and personal care products, they can also be created through activities such as smoking, printing and photocopying, cooking, and burning fuels.

A few sources include:

🖌️ Paints

☢️ Aerosols

🧼 Cleaning products and disinfectants

👚 Dry-cleaned clothing

🪲 Pesticides

📝  Correction fluids

While little is known about the long-term health effects of VOCs, they can cause eye, nose, and throat irritation, headaches, damage to the liver, kidneys and central nervous system and is suspected to cause cancer.

✅ An air purifier can help with air pollution from VOCs
Air purifiers with an activated carbon filter are very good at removing odors, VOCs and gasses from the air in your home. This is due to their absorption qualities. In fact, we have a round-up of the 6 best air purifiers for VOCs which you should check out.

Final Thoughts

As you can see, indoor air pollutants are all around us. You could be exposed to any number of these in the home without ever knowing. However, it’s not all bad news because an air purifier is undoubtedly an excellent protection against the most common pollutants.

Be sure to research and look for a HEPA air purifier with activated carbon filters for the best protection. Remember, though, that as good as an air purifier is, it should only be one component in your battle over indoor air pollutants.


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Achoo Allergy. How to Protect your Children from Lead Poisoning. 

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