How Biological Pollutants Affect Your Indoor Air Quality

What usually comes to mind when people think about air quality is the quality of air in their town, city, or state. However, indoor air quality is equally important, and for some folks, more significant. Many biological contaminants can affect the air quality in your office, school, or home. 

One of the primary reasons to be concerned about these biological contaminants is how quickly some of them can increase, reducing the quality of the air you breathe and adversely affecting your health.  

According to the American Academy of Allergy Asthma & Immunology, between 10 and 30% of people worldwide suffer from allergic rhinitis. As much as 40% of the human population has sensitization to foreign proteins, with people spending more time inside than outside, living near allergens and other air pollutants that are 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 in 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 essential 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 pollutants, particularly those prolific during allergen season. To reduce the contaminants in your home, you'll need to understand the different types of pollutants, their sources, and how they affect your health. 

Biological Contaminants 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 types of pollutants that come with shedding and the resulting fur balls around your home. However, you don't have to have pets to have contaminants in your home.

The truth is that every living organism creates biological byproducts that make the air less clean. Even you contribute to biological contaminants because you shed skin cells and hair every day. Unfortunately, even the most pristine home has little visitors that you don't want, including dust mites, cockroaches, spiders, and bugs. 

The term biological contaminant is an extensive 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 primarily a nuisance to most people, but there are several demographics for which biological contaminants are far more harmful. Both children and older adults 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 ailments, 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 recovery. 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 can enjoy the spring with little to no allergies. The following year you may feel like you are having a more severe allergic reaction, and unfortunately, you are probably right. You will have a more robust allergic response 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, it 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 many things you can do to start significantly cleaning 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 daily will ensure that there is less contamination circulating when you clean. 

        Using like UVC-Air cleaners can help eliminate many biological contaminants without introducing new pollutants (particularly chemicals). However, more good cleaning habits 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 installing and using them in your home can help reduce biological contaminants. Kitchens, bathrooms, and laundry rooms tend to be where pollutants are most likely to be introduced. Cooking introduces more pollutants into the air because of smoke creation. We clean ourselves in the bathrooms, making them the place with the most skin cell and hair remains. Laundry rooms are a mix 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 helpful 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 the dirty filter, 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 it 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 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 them 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, which 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 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 their direction. 
          • 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, most 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. Link 

              EPA. (2021) Air Cleaners, HVAC Filters, and Coronavirus (COVID-19). Retrieved on February 18, 2021. Link

              Harvard T.H. Chan School of Public Health. (2021) Biological Pollution. Retrieved on February 18, 2021. Link

              Consumer Product Safety Commission. Biological Pollutants in Your Home. Retrieved on February 18, 2021. Link 

              US Home Filter. (2020) Biological Pollutants Facts and Impacts. Retrieved on February 18, 2021. Link

              American Academy of Allergy Asthma & Immunology. (2021) Allergy Statistics. Retrieved on February 19, 2021. Link