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What Is Dust Made Of?

Dust is everywhere, floating in the air we breathe and settling on surfaces in our homes. But what exactly is dust made of, and how does it affect our health? In fact, household dust is made of many different biological and non-biological substances, including shed skin cells, hair, dust mites, smoke, pollen, pet dander, microbes, and more.

The size of dust particles varies greatly from microscopic to visible. Understanding the components of dust, their potential health effects, and how to filter them from the air can help you take steps to minimize their impact on your well-being.

How Does Dust Particle Size Affect Your Health?

The size of dust particles is crucial in determining their potential health effects. Larger particles, including those easily visible to the naked eye, are generally less harmful. They are too big to be inhaled deeply into our lungs. However, smaller particles, particularly those less than 10 microns in diameter, can be inhaled and may cause respiratory issues.

Particles smaller than 2.5 microns, known as fine particulate matter or PM2.5, can penetrate deep into the lungs and may enter the bloodstream, potentially leading to more severe health problems.

Human Skin Cells and Hair

Our skin continuously sheds dead cells, which accumulate in our environment and contribute to dust buildup. You shed millions of skin cells daily, enough to completely replace your outer layer of skin every six weeks or so, a process called desquamation. Similarly, human hair, which falls out naturally as part of the hair growth cycle, adds to the dust in our homes. 

Skin cells are typically around 20–40 microns in size, and hair fibers range from about 18 to 180 microns in diameter.  While skin cells and hair are not inherently harmful, they can serve as a food source for dust mites, triggering allergies in some individuals.

Dust Mites and Dust Mite Body Parts

Dust mites are microscopic arachnids related to spiders that thrive in warm, humid environments. They are around 0.2-0.3 mm in length, and they eat dead skin cells shed by humans and pets. 

Dust mites themselves are not very harmful. However, their fecal pellets and body fragments, known as dust mite debris, can trigger allergic reactions in sensitive individuals. The debris is typically 10–20 microns in size, small enough to float in the air, causing respiratory issues such as asthma and allergic rhinitis


Pollen is a common outdoor allergen that can make its way into our homes and become part of the dust we breathe. Pollen grains from flowering plants vary in size depending on the species, ranging from less than 10 to 100 microns in diameter.

When inhaled, pollen can trigger hay fever symptoms like sneezing, a runny nose, and itchy eyes in individuals with pollen allergies. Keeping windows closed during high pollen seasons, using HVAC air filters, and cleaning regularly can help reduce the amount of pollen in household dust.

Pet Dander

Pet dander consists of tiny flakes of skin shed by animals, which can be a potent allergen for some individuals. Pet dander size varies, with particles typically ranging from about 5 to 10 microns. However, in some cases, up to a quarter of dander particles can measure smaller than 2.5 microns, making them easily inhalable.

Microbes, Mold, and Mold Spores

Household dust also contains various microorganisms, including bacteria, mold, and mold spores. These microbes thrive in damp environments and can contribute to poor indoor air quality. Bacteria found in dust typically range from 0.2 to 5 microns in size, while mold spores are slightly larger, usually between 1 and 40 microns, with most falling in the 2-10 micron range.

Exposure to mold and certain bacteria can lead to respiratory issues, allergic reactions, and, in some cases, more severe health problems.

Smoke and Vehicle Exhaust Fumes

Smoke particles from tobacco use, cooking, fireplaces, wildfires, and vehicle exhaust fumes can infiltrate our homes and become part of the dust we breathe. Smoke particles are typically very small, around 2.5 microns in diameter, making them easily inhalable and potentially harmful to respiratory health.

Long-term exposure to smoke and vehicle exhaust has been linked to health outcomes that include lung cancer, heart disease, and asthma.

Other Components of Dust

In addition to the components mentioned above, household dust can contain a variety of other particles, such as:

  • Soil and outdoor particles: Dust can include soil particles and outdoor debris tracked into the home, ranging from under 2 microns (clay) up to 1000 microns (sand).
  • Textile and paper fibers: Fibers from clothing, upholstery, and paper products can contribute to dust, with sizes varying based on the material (e.g., silk filaments around 10 microns).
  • Car tire dust: As tires wear down, they release microscopic fragments that become airborne and settle in household dust.

Dust Particle Sizes and HVAC Air Filtration

The wide range of particle sizes in household dust makes choosing the right HVAC air filter crucial to improving indoor air quality. Air filter effectiveness is typically measured using the Minimum Efficiency Reporting Value (MERV) rating system, which assesses a filter's ability to capture particles of varying sizes.

  • MERV 8 air filters capture 70% of particles in the 3.0-10.0 micron range and 20% in the 1.0-3.0 micron range. These filters trap most mold spores, dust mite debris, pet dander, and larger textile and carpet fibers. While MERV 8 filters may not capture the smallest particles, such as bacteria and smoke, they balance filtration efficiency and affordability, making them a popular choice for residential settings.
  • MERV 11 air filters offer a higher level of filtration, capable of capturing over 65% of particles in the 1.0-3.0 micron range and over 85% of particles in the 3.0-10.0 micron range. They trap a significant portion of dust mite allergens, pet dander, mold spores, and larger bacteria.
  • MERV 13 air filters are an excellent choice if you need even better air quality. These filters can capture over 50% of particles in the 0.30-1.0 micron range, 85% in the 1.0-3.0 micron range, and 90% in the 3.0-10.0 micron range. They are highly effective at trapping most tobacco smoke, sneeze droplets, and smaller bacteria, providing a higher level of protection against respiratory irritants.
Filter Rating Particle Size Range (microns) Efficiency Typical Particles Trapped
MERV 8 3.0-10.0 70% Mold spores, dust mite debris, pet dander, larger textile and carpet fibers
1.0-3.0 20% -
MERV 11 3.0-10.0 >85% Mold spores, pet dander, larger bacteria, dust mite allergens
1.0-3.0 >65% -
MERV 13 3.0-10.0 90% Tobacco smoke, sneeze droplets, smaller bacteria
1.0-3.0 85% -
0.30-1.0 >50% -


Household dust is a complex mixture of particles, each with unique characteristics and potential health effects. By understanding the components of dust and their sizes, we can minimize their impact on our well-being through regular cleaning, proper ventilation, and appropriate air filtration systems. 

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