How Biological Pollutants Effect Indoor Air Quality

When people think about air quality, they usually consider the air for large areas, like cities or towns. However, the air quality inside is at least as important, and often more important because most of us spend more time inside than outside. There are many biological contaminants that can affect the air quality in your office, school, or home. One of the primary reasons to be concerned about these biological contaminants is because of how quickly some of them can proliferate, reducing the quality of the air you breath and having an adverse effect on your health.  

According to the American Academy of Allergy Asthma & Immunology, between 10 and 30% of people around the world suffer from allergic rhinitis, and as much as 40% of the human population has sensitization to foreign proteins. With people spending more time inside than outside, it is living in close proximity to allergens and other air pollutants that is likely contributing to the rising respiratory problems. 

Fortunately, it is much easier to start cleaning the air in your home or other indoor space than a much larger area. Whether you suffer from a respiratory condition, including asthma and allergies, or not, you can easily remove air pollutants with some basic air cleaners. There will be times when basic measures won’t be adequate, air cleaning devices can take care of the smaller and more frequent types of pollutants, particularly those that are prolific during allergen season.To reduce the pollutants in your home, you’ll need to understand the different types of contaminants, their sources, and how they affect your health. 

A Quick Look at Biological Contaminants in the Air and Water in Our Homes

It’s not exactly something that we like to think about, but our homes are full of many different kinds of biological contaminants. If you have a cat or dog, you are probably much more aware of the kinds of contaminants that come with shedding and the resulting fur balls around your home. However, you don’t have to have pets to have all of the same kinds of contaminants, they just aren’t as easily noticed. 

The truth is that every living organism creates biological by products that make the air and water less clean. Even you contribute to biological contaminants because you shed skin cells and hair every day. Unfortunately, even the cleanest home has other little visitors that you probably don’t want, including dust mites, cockroaches, spiders, and bugs. 

The term biological contaminant is a very broad term that includes things found in most homes, including the following:

  • Bacteria and viruses
  • Human skin cells and hair
  • Animal dander and saliva
  • House dust and mites
  • Cockroaches and other arthropods
  • Pollen (it is a biological byproduct of plants)

It is impossible to keep these out of your home, which means you should have some way of cleaning your air and water to reduce the risks these pose to your health. The Harvard T.H. Chan School of Public Health has created a list defining the most common biological pollution, as well as the risks they pose to your health. 

Indoor Biological Pollutants

Size in microns




4-20 microns


0.3 - 60

Dust Mites

100 - 300

Skin flakes

0.5 - 10


0.005 - 0.3


5 - 200

Household dust

0.05 - 100

Human Hair

40 - 300



Health Risks of Biological Contaminants

In the short term, biological contaminants can cause minor irritation, such as sneezing and coughing. Polluted air in the home is more detrimental to people with respiratory issues, even something as mild as allergies, even in the short term. 

As mentioned, it is guaranteed that you have biological contaminants in your home. The more severe the pollution, the more likely you are to see symptoms associated with those contaminants. Mild pollution will trigger more minor symptoms, including the following:

  • Sneezing
  • Watery eyes
  • Coughing
  • Shortness of breath
  • Dizziness

Over time, those symptoms can develop into something more severe, with the following symptoms being more likely for more contaminated air:

  • Lethargy
  • Fever
  • Digestive problems

These symptoms may be largely a nuisance to most people, but there are several demographics for which biological contaminants are far more harmful. Both children and elderly people are also more susceptible to being adversely affected by biological contaminants and other microorganisms that can be inhaled. If someone in your home is suffering from a respiratory ailment, the symptoms can be much worse, triggering allergies or asthma attacks. People who have more severe aliments, such as Legionella, measles, tuberculosis, and lung cancer, often require cleaner air in the home. Even if you have more common ailments like the flu or bronchitis, biological contaminants can cause more severe symptoms and hamper the recovery process. 

Even if you aren’t currently suffering symptoms, the vast majority of allergic reactions require that a person be repeatedly exposed to the allergen before it begins to trigger an allergic response. Consider when you move to a new place and you are able to enjoy the spring with little to no allergies. The next year you may feel like you are having a more severe allergic reaction, and unfortunately, you are probably right. You will have a stronger allergic reaction upon repeated exposure to something that didn’t bother you the last time you were exposed to it. 

With so many potential contaminant sources and the high likelihood that they will eventually result in allergies is probably enough reason to start taking clean air more seriously. Allergies are a nuisance, and they often get worse over time as you develop allergies to other pollutants. Fortunately, there are a lot of things you can do to start significantly clean up the air in your home or other indoor spaces. 

Beyond Regular Cleaning - How You Can Reduce 

Regular cleaning can go a long way to helping reduce most of these pollutants and allergens. Unfortunately, most types of cleaning also knock these contaminants into the air, increasing the odds that you will inhale them. Good housekeeping on a daily basis will ensure that there is less contamination circulating during each clean. Using things like UVC can help to eliminate many of the biological contaminants without introducing new pollutants (particularly chemicals). However, there is more to good cleaning habits that are required to keep your air cleaner. 

Beyond good cleaning habits, there are several things that you can do to reduce biological pollutant exposure. 

  • Exhaust fans vent air to the outside, so having them installed and using them in your home can help reduce biological contaminants for rooms where they are commonly found. Kitchens, bathrooms, and laundry rooms tend to be the places where pollutants are most likely to be introduced. Cooking and baking inherently introduces more contaminants into the air because of all the activity, particularly things like flour and other ingredients. We clean ourselves in the bathrooms, making them the place with the most skin cell and hair remains. Laundry rooms are a mix of a lot of dirty clothing, with dirt and allergens from the outside. Exhaust fans can shift a lot of the pollutants from the air outside your home. 
  • Ventilating your attic and crawl spaces can reduce moisture, reducing mold and mildew spores. 
  • Humidifiers are great for keeping the air from getting too dry, but they also need to be cleaned regularly to ensure they aren’t introducing pollutants into the air. As useful as these devices are, they are breeding grounds for a lot of microbial contaminants. Follow all maintenance recommendations to keep your humidifiers from spreading pollutants. 
  • Follow all maintenance recommendations for your appliances and vent systems, particularly your HVAC unit. Make sure to change out the filters at least as often as recommended. However, it should be based on how dirty the filter is, so you may need to change filters more frequently than the recommendations. 
  • Remove equipment and materials that have been soaked or are damp with water. For example, if you have a water leak in the bathroom, get all affected rugs and tools out of your home as soon as possible to reduce mold and bacteria. You will need to clean everything well before returning it back to its original location. If your carpet has sustained water damage, get it cleaned within 24 hours if possible. 
  • Ensure you have good housekeeping practices in the basement. This room of the home tends to have a higher amount of air pollutants, so typically requires more stringent cleaning and ventilation to keep the air as clean as the other parts of the home. 

In addition to these best practices, you can install filters in your home to help reduce contaminants. 

How EPA Air Filters Work

Air cleaners and filters are one of the best ways to keep indoor air clean, particularly when you get busy and fall behind in your house cleaning. The best filters are efficiency particulate air (EPA) filters. They were developed to manage the vast amounts of air pollutants that came with industrialization. Today, the technology is both cost effective and easy to use. 

The EPA filtration process draws larger particles toward the center, catching those particles as they pass through the filter. As the air passes through the filter, the particles continue to be captured, removing a large percentage of the particulates. The holes through which the air passes are unevenly situated in the filter, creating a structure similar to a maze, making it very difficult for the particulates to escape the filter. The filters are effective enough to capture dirt from 0.1 microns to 10 microns in size. A 0.1 micron particle is smaller than most individual viruses, meaning that it can significantly reduce some of the most potentially dangerous pollutants. Most EPA filters are designed to filter 0.1 micron particles, which removes about 99.95% of all dirt from the air. 

There are actually three capture methods for EPA filters. 

  • Impaction or inertial filtration captures the largest particles (roughly 0.5 microns). These larger particles essentially slam into the filter because they are moving too fast to change the direction they are going. 
  • Interception filtration captures particles that are just under 0.5 microns. These particles are small enough to move as they pass through the filter, but eventually the majority of them come into contact with the filter and stick to it. 
  • Diffusion filtration catches the smallest particles. These pollutants bounce off of other atoms and molecules, and once they touch the filter, they stick. 

Source: Courtesy from R. Vijayakumar

EPA filters are highly effective because they do not impede the circulation of air; they just remove the pollutants from the air. Smart Air and Smart Air Pro are great examples of effective EPA filters. 


  • Seltzer, J.M. (1994) Biological contaminants. J Allergy Clinical Immunol, 94(2.2), 318-326. 
  • EPA. (2020) Biological Pollutants’ Impact on Indoor Air Quality. Retrieved on February 18, 2021 from
  • EPA. (2021) Air Cleaners, HVAC Filters, and Coronavirus (COVID-19). Retrieved on February 18, 2021 from
  • Harvard T.H. Chan School of Public Health. (2021) Biological Pollution. Retrieved on February 18, 2021 from
  • Consumer Product Safety Commission. Biological Pollutants in Your Home. Retrieved on February 18, 2021 from
  • US Home Filter. (2020) Biological Pollutants Facts and Impacts. Retrieved on February 18, 2021 from
  • American Academy of Allergy Asthma & Immunology. (2021) Allergy Statistics. Retrieved on February 19, 2021 from