Indoor Air Pollution: Sources and Effects

by | Energy Conservation

Whether it’s in school, the office, on the subway or simply at home, most people spend about 90% of their time indoors. And while we often talk about the amount of pollution in our atmosphere, we rarely consider the quality of the air that we’re breathing when we are inside.

However, indoor air pollution has been shown to have considerable effects on both long and short term health and is thought to be responsible for 4.3 million deaths each year.[1] Find out what you can do to improve the quality of air in your home.

What Is Indoor Air Pollution?

Simply put, indoor air pollution refers to any contamination of the air within a building. Pollutants are generally grouped into the following categories: molds, solvents, pesticides, smoke, pet dander, and gases. Most properties will suffer from indoor air pollution to some degree. The quality of your indoor air (IAQ) is a measure of how the air inside of a building affects its occupants’ health and comfort.

Indoor air pollution has become a more pressing concern in recent years due to the construction of more energy-efficient homes. These properties tend to be relatively airtight, meaning that the air inside can quickly become stagnant and pollutant levels rapidly rise.

Elsewhere, the burning of fuels such as coal, wood, and gas for heating and cooking produce a large number of toxic chemicals. These include formaldehyde and carbon monoxide, as well as particulates and other dangerous compounds. Without effective ventilation, these chemicals are inhaled and can cause serious damage to your health in a myriad of ways.

How Does Indoor Air Pollution Affect Human Health?

A reduction in fresh air exchange in modern buildings has given rise to a phenomenon known as “sick building syndrome”, or SBS). This is commonly caused by a combination of poor ventilation and poorly-maintained air conditioning.

The symptoms of sick building syndrome improve when you leave the premises and get worse the longer you stay there. The most common symptoms include:

  • Headaches
  • Blocked sinuses or a runny nose
  • Skin rashes
  • Itchy eyes
  • Drowsiness
  • Difficulty breathing

Bear in mind that these symptoms are extremely common and can be caused by a wide range of issues including typical allergies. If you are experiencing these symptoms sporadically, or continually no matter where you are, it is unlikely that sick building syndrome is the cause.

If, however, you experience these symptoms—and they continue to get worse—every time you are in a certain building, SBS may be to blame. To alleviate the symptoms yourself, you can try the following:

  • Open windows or doors to let fresh air in
  • Reduce the thermostat to about 66°F
  • Try taking more regular breaks from your desk
  • Where possible take in some fresh air by walking outside

If you are experiencing these symptoms while you are at work you should ask your manager or employer to look into the cause of the problem. Alternatively, if this occurs in another building you rent, talk to your building manager or landlord. Some of the causes of sick building syndrome can be highly dangerous given continued exposure and should not be treated lightly.

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Sources of Indoor Air Pollution

There are many sources that can be responsible for indoor air pollution, some of which are recognizable due to their odor, but there are many that fly under the radar.


Mold is a form of fungus which grows from spores that latch onto damp areas in buildings. It digests the materials it lands on, and can grow on many types of surfaces. It is prevalent in moist environments and is most common during the winter months and in more humid climates.

As there are many types of fungus that cause mold, it can take on a wide variety of features. Mold may be white, black, green or yellow, and can appear to be slick, fuzzy or rough in texture. Worryingly, mold can release a range of hazardous toxins into the air and can cause many different symptoms—and is a particular concern to babies, children, older adults, and those with existing skin problems, respiratory problems, or weakened immune systems.

Tobacco Smoke Indoor Air Pollutionsource

Tobacco Smoke

A major cause of indoor air pollution, environmental tobacco smoke, or secondhand smoke—causes over 40,000 deaths in the U.S. each year.[2] The inhalation of cigarette smoke is particularly harmful to children, increasing the risk of sudden infant death syndrome (SIDS), severe asthma, ear problems, and acute respiratory infections.[3]

Moreover, cigarette smoke contains at least 70 carcinogens, chemicals that have been proven to cause cancers, as well as around 7,000 other chemicals that your body could do without.[4] When inhaled, these chemicals can cause illnesses such as chronic obstructive pulmonary disease (COPD) and other cardiovascular diseases which lead to heart attacks, as well as other serious complications.


Carpets act like traps for indoor pollutants, easily absorbing mold spores, particulates from smoke, allergens, and other harmful substances. Research has found that even some toxic gases can settle into carpets.[5] While some may argue that this trap keeps occupants safe, pollutants caught in carpets can be easily disturbed simply by walking on them.

Household Products

Many day-to-day products present in almost every home can cause indoor air pollution. These include:

  • Cleaning agents and disinfectants
  • Paints
  • Glues and solvents
  • Personal care products
  • Air fresheners
  • Candles

These products may emit volatile organic compounds (VOCs), which can cause issues such as eye, nose or throat irritation, headaches, nausea, organ damage, and even cancer in some extreme cases.[6]


Many homes and offices contain space heaters, ovens, furnaces, fireplaces and water heaters that burn fuels such as gas, kerosene, oil, coal or wood for energy. As combustion can be extremely dangerous, most appliances are rigorously tested to ensure they are safe for use. However, if the appliance is faulty, it can produce toxic gases such as carbon monoxide, sulfur dioxide, and other compounds including hazardous aldehydes.


A completely odorless and inert gas, radon can seep up through the ground and diffuse into the air in your building. When it undergoes decay, radon emits radiation which can attach to dust particles and pass into the lungs causing damage. Although it may seem strange, surveys have shown that radon concentration indoors is an order of magnitude higher than those typically found outdoors.[7]

Pet Dander

You might not think of pet dander when you think of indoor pollutants, but for many allergy sufferers, it’s an acute irritant that can make some indoor environments vexing.  Pet dander is comprised of microscopic flakes of skin shed by household pets, meaning that hairless breeds can cause symptoms like coughing, sneezing, watery eyes, and chest tightness.[8]

It is important to note that air temperature, humidity, and circulation can produce symptoms similar to those of indoor air pollution, and simply turning down the thermostat may help.

How to Improve Indoor Air Quality

So if you are suffering from indoor air pollution, how do you improve the quality of the air you’re breathing in? Let’s take a look at a few solutions.

HEPA filters

High-efficiency particulate air (HEPA) filters can be employed as air purifiers or attached to vacuum devices in order to remove dust, spores, mites and other particles from the air. According to The Institute of Environmental Sciences and Technology[9], an appliance can only be considered a HEPA filter if it traps 99.97% of particles 0.3 microns or larger. For context, emissions from a car starting up begin at 1 micron.


Vacuuming is extremely important to improve indoor air quality, especially if you have carpets and pets. It is recommended that you vacuum at least 3 times a week in order to keep dust levels low.

HVAC filters

Heating, ventilation, and air conditioning filters, HVAC filters purify the air that enters and exits the various units located throughout your property. These filters ensure that your systems work efficiently and reduce the amount of irritating particles circulating in the air.

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Houseplants have been shown by NASA to be “nature’s life support system”, and are an essential component in improving indoor air quality. They not only absorb carbon dioxide from the air, but particulates that attach to CO2 too. Microorganisms in the soil have also been found to remove volatile organic compounds from the air.[10]

These same NASA findings also suggest that indoor plants are an excellent way to help control air pollution and mitigate its effects.

Reduce clutter

The more clutter you have in your home, the more places there are for dust to hide. Decluttering will not only help clear your mind, but help clean the air too!

Outdoor Air Pollution | City Foggy Pollutedsource

Next Steps in Reducing Air Pollution

Aside from all the household sources of indoor air pollution, you might also be worried about outdoor air pollution, especially if you live in an area with lots of car traffic or local industry. Outdoor air pollution is a public health problem in many densely populated areas, but anywhere you live, you can make an effort to reduce your contribution by using less energy at home. Adopt a smart thermostat, buy green energy, or even go car-free certain days of the week to help lower your individual footprint!

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2 “Health Effects of Secondhand Smoke.” (n.d.). Retrieved from

3 “Tobacco smoke particles and indoor air quality (ToPIQ)” – the protocol of a new study. (n.d.). Retrieved from

4 “Harmful Chemicals in Tobacco Products”. American Cancer Society. (n.d.). Retrieved from

5 “Carpets.”  American Lung Association (n.d.). Retrieved from

6 “Volatile Organic Compounds’ Impact on Indoor Air Quality”. United States Environmental Protection Agency. (2018, November 6). Retrieved from

7 “Indoor air quality & its impact on man”. The European Communities. (1988, November). Retrieved from

8 “Pet Dander: What Is Pet Dander?”. Healthy Air. The American Lung Association. (n.d.). Retrieved from 

9 “HEPA and ULPA Filters”. IEST-RP-CC001: (n.d.). Retrieved from

10 “Interior landscape plants for indoor air pollution abatement.” NASA. September 15, 1989. Retrieved from