Why does the size of dust particles matter? How large is a piece of each common dust? How to get dust under control?

Dust is made up of tiny particles that are hard for us to see individually. If we could see them, we’d notice various colours representing bacteria, fungi, pollen, hair, and skin fragments, as well as some inorganic materials like bits of sand, rock, and salt.

A close-up view of household dust reveals plant matter, rock specks, and many other minuscule elements too small to be seen clearly.

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Why Does the Size of Dust Particles Matter?

The smallest particles, invisible to the naked eye, pose the greatest threat as they can enter our bodies. Our lungs have defences—tiny hairs called alveoli covered in sticky mucus—that catch and expel potential invaders. However, particles smaller than what we can see can bypass these defences and reach deep into the lungs, where gases like oxygen are absorbed into the bloodstream. Since oxygen circulates throughout the body, any toxins or pathogens carried by these particles can spread everywhere.

Although our lungs can filter particles as small as one micron, the smallest visible particles are around 100 microns, close to the width of a hair. For comparison, the graphite in a mechanical pencil is about 0.7 millimetres (700 microns), and human hair is roughly one-tenth that size, at around 70 microns.

Particles larger than about 10 microns, roughly one-seventh the width of a human hair, are usually intercepted by lung defences. Those around 1 micron may enter the lungs but generally stay there. However, particles 0.1 microns and smaller can enter the bloodstream, and research suggests they are linked to various health issues, including cancer, dementia, multiple sclerosis, and diabetes.

Exploring the components of dust and understanding how they form can provide insight into the significance of dust particle sizes.

How Large is a Piece of Each Common Dust?

Dust Mite Size

Dust mites, which are found in at least 84% of homes worldwide, are tiny creatures measuring about 250 microns. Despite their small size, they expertly hide in fabrics and avoid light, making them difficult to spot. Their droppings, ranging from 10 to 40 microns, can cause allergic reactions when they enter the bloodstream. These allergens, found on the droppings, are even smaller.

Dust mites and their droppings aren’t light enough to stay airborne for long, so exposure mostly occurs when dust is disturbed or from dust on pillows and bedding. The actual allergen is a tiny protein, around 10 nanometers or 0.01 microns. Even if the droppings break into smaller pieces, they can still trigger allergies.

Picture from Wikipedia

Pollen and Mould Spores Size

Fungi and many plants spread spores or pollen in the wind for reproduction, creating a fine dust covering our world. Pollen grains, ranging from 20 to 100 microns, vary in size based on the plant. If pollen doesn’t find another plant, it dries out and biodegrades. Mould spores, waiting for suitable conditions, can be as small as 3 to 10 microns, triggering allergies and asthma.

Most pollen grains and mould spores break into tiny fragments smaller than 1 micrometre if they don’t find a neighbouring plant. These fragments, 200 times more likely to penetrate the lungs than whole spores, pose a greater risk, especially for infants who may inhale 4 to 5 times more tiny particles. Small particles not only evade lung defences but also linger in the air, increasing the chances of being breathed in.

Dander and Skin

Our skin and our pets’ skin continuously grow, with a new layer forming below and the top layer shedding about every day. The skin typically flakes off in hexagon-shaped pieces, approximately 40 µm wide and 0.1 to 0.5 µm thick. Despite their small size, these skin cells can dry up into fragments smaller than a micrometre, allowing them to evade the lungs’ defences and enter the bloodstream. Allergies in animals, such as cats and dogs, are often triggered by these tiny fragments rather than the whole skin scales.


Apart from skin and dander, particles from the soil contribute to household dust and air. While the soil itself is generally harmless, it may carry pollen, mould spores, car exhaust, and other pollutants. Soil particles can vary in size and commonly enter homes from the outside.

Another Thing You Might Need to Know

Objects of any size can harbour harmful Volatile Organic Compounds (VOCs) that settle out of the air. For instance, tobacco smoke introduces VOCs into settled dust, creating a form of third-hand smoke that can affect people in the room even days after the last cigarette was smoked.

House dust may also contain heavy metals like lead. When attached to small particles, these contaminants can penetrate deep into the lungs and enter the bloodstream. Children, being closer to the ground where dust settles, tend to have higher exposure to dust-containing allergens, VOCs, household chemicals, and pollutants. Regardless of the dust source, it’s advisable to sweep, wipe, or vacuum it up.

Air purifier with digital monitor screen and house plant in living room for fresh air and healthy life.

How to Get Dust Under Control?

Now that we understand the diverse sources of dust and its potential health implications, let’s explore ways to manage and reduce dust in our living spaces:

  1. Regular Cleaning: Sweeping, wiping, and vacuuming surfaces can effectively remove settled dust. Pay attention to commonly overlooked areas like vents, carpets, and upholstery.
  2. Air Purification: Consider using air purifiers equipped with HEPA filters to trap and remove airborne particles, including dust, allergens, and pollutants.
  3. Humidity Control: Dust mites thrive in humid environments. Maintaining indoor humidity levels below 50% can help deter their growth.
  4. Seal Entry Points: Prevent outdoor dust and pollutants from entering your home by sealing gaps around windows and doors. Use weather stripping and caulk to seal these openings.
  5. Reduce Clutter: Minimize the number of items in your home that can collect dust. Decluttering makes cleaning more manageable and reduces dust buildup.
  6. Wash Bedding and Curtains: Maunder bedding, curtains, and other fabric items regularly to remove accumulated dust, dander, and allergens.
  7. Choose Dust-Resistant Furnishings: Opt for furniture and decor that is easy to clean and less likely to harbour dust.

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