On household dust
The dust that settles on the various surfaces in your house may seem innocuous—a pesky inconvenience that disrupts the aesthetic of your home. However, dust carries many microscopic particles and organisms that can impact human health. Dust control is vital in creating healthier living spaces.
What is dust?
House dust is a heterogeneous mixture of substances from sources such as soil particles, clothing fibers, atmospheric particulates, hair, allergens such as mold and pollen, microorganisms including bacteria and viruses, insect fragments, ash, soot, animal fur and dander, skin particles, residues from cooking and heating, and bits of building materials.
A reproducible house dust sampling is challenging and highly dependent on the method. The Wikipedia article on dust cites the 1981 book “House dust biology: for Allergists, acarologists, and Mycologists,”—“dust in homes is composed of about 20–50% dead skin cells”. However, according to this newer 2009 study from the American Chemical Society, 60% of household dust comes from the outdoors, specifically soil resuspension, and track-in. Even more recently, the Australian Microplastic Assessment Project asked members of the public to collect house dust in specially prepared glass dishes, which was then analyzed by 360 Dust Analysis. They found 39% of the deposited dust particles were microplastics. It is likely that dust composition is very heavily location-dependent and has changed noticeably with time.
Effects on human health
Respiratory damage
Particles that evade elimination in the nose or throat tend to settle in the sacs or close to the end of the airways. The macrophage system is a crucial part of our body’s immune defense. When we breathe in dust or foreign particles, macrophages engulf and ‘eat’ these invaders, helping to keep our lungs clean. However, there’s a limit to how much a macrophage can handle. If there’s too much dust, the macrophages can become overwhelmed and not clear it all out. When this happens, the excess dust particles can accumulate in the lungs, leading to inflammation or other lung diseases.
Cooking, open fireplaces, and smoking indoors add fine dust to your home and contaminants of concern, which are associated with poor health outcomes. Each year, 3.2 million people die prematurely from illnesses attributable to household air pollution caused by the incomplete combustion of solid fuels and kerosene used for cooking (see WHO’s household air pollution data for details). Particulate matter and other pollutants in household air pollution inflame the airways and lungs, impair immune response and reduce the oxygen-carrying capacity of the blood.
Allergies
Dust mites, tiny organisms that feed off house dust and air moisture, are among the most common indoor allergens. In addition to allergic rhinitis, dust mite allergy can trigger asthma and cause eczema to flare.
Mold, pollen, and animal hair in dust can also trigger allergies. These allergens permeate our indoor spaces and become part dust. Exposure to them can lead to various allergic reactions, from mild symptoms such as sneezing, itching, and nasal congestion, to more severe responses like asthma attacks. Furthermore, constant inhalation of these allergens can lower one’s immune response over time, leading to chronic allergic conditions.
Toxicity
Dust can transport toxic substances, such as heavy metals and persistent organic pollutants, contributing to various health issues over time.
Chemicals used in pesticides, clothing, and furniture can combine with dust in our homes. Toxic flame retardants are used in countless domestic products and can make their way into dust. According to this 2005 American Chemical Society study, “Inadvertent ingestion of house dust is the largest contributor to [Polybrominated diphenyl ether (PBDE) - a type of flame retardant] exposure of toddlers through to adults.”.
Dust also contains microplastics from clothes, packaging, carpeting, and furnishings. They’re easily inhaled and ingested, especially by children who often put their hands in their mouths.
Lead in dust is a significant health concern, particularly in older homes and buildings where lead-based paint is often used. As the paint deteriorates or is disrupted, it generates lead dust that can be inhaled or ingested, especially by young children. According to the U.S. Environmental Protection Agency (EPA), even low levels of lead exposure can cause behavior and learning problems, lower IQ, hyperactivity, and other harmful health effects in children. In adults, lead exposure can increase blood pressure and decrease kidney function. Therefore, it is essential to maintain, test, and remediate older homes and buildings to prevent lead dust exposure.
Dust control
Dust is constantly being created, deposited, disturbed, and redistributed.
According to this NIH article, the amount of dust that settles in a household daily is strongly influenced by the number of people living there, with more activity such as sweeping and playing leading to more dust.
The rate at which dust particles resuspended in the air varies with size. Particles sized 5-25 μm are the most likely to become airborne again, and even mild activities like walking into a room can cause a significant increase in the concentration of these larger particles in the air. On the other hand, smaller particles sized 0.3 − 1 μm don’t tend to become airborne due to cleaning or walking.
Minimizing the potential health effects of dust begins with controlling dust levels. This can be achieved through regular cleaning and air filtering technologies.
Vacuuming
A simple way to reduce dust is vacuuming your house regularly with a filter-fitted vacuum. Vacuuming is more effective than dusting or using brooms, as this prevents dust from resettling. Central vacuum cleaners can particularly effectively remove dust, especially if exhausted directly outdoors.
Dusting with a wet cloth
Using a wet cloth for dusting can also be a simple but effective mitigation. The water acts as an adhesive, capturing dust particles and preventing them from becoming airborne, making removal more effective.
Care is required when removing dust to avoid causing the dust to become airborne again. For instance, a feather duster tends to agitate the dust, so it lands elsewhere.
Air filtering
Air filters differ significantly in their effectiveness. Certified HEPA filters can effectively trap 99.97% of dust at 0.3 micrometers. However, not all filters are created equal, and the performance can significantly vary depending on various factors.
One crucial quantity is the Minimum Efficiency Reporting Value (MERV) rating. The MERV scale goes from 1 to 16, with higher numbers indicating a greater ability to remove smaller particles from the air. For household use, filters with MERV ratings between 7 and 12 are generally considered adequate and balance performance and cost well. These filters can trap dust mites, mold spores, and even some types of pollen, significantly reducing the dust circulating in the home.
Another factor to consider when selecting an air filter is its Clean Air Delivery Rate (CADR). This measurement indicates the volume of filtered air a purifier delivers.
The condition of the filter is equally important. Even the most effective filters will eventually become saturated with particles and lose their effectiveness.
Moreover, some filters are specifically designed to be “electrostatic,” meaning they generate an electric charge that attracts and traps particles. These filters can be highly effective in trapping dust but may also require more regular cleaning or replacement.
Dehumidification
To reduce mold spores, a particularly harmful dust component, keeping the humidity level below 55 percent is helpful. Therefore, if you live in a humid or sticky climate, you may find it helpful to use a dehumidifier. You can also use a vent fan to remove moisture in bathrooms and the kitchen. Dust mites, one of the primary allergens in dust, also thrive in high humidity conditions—keeping indoor humidity levels low helps to control their populations.
Not wearing shoes in the house
Up to 60% of dust particles are tracked in from outside, therefore you can decrease that number by not wearing outdoor shoes past the front door.
Hardwood flooring
Wood flooring is generally better than carpets for controlling dust. Carpets can trap allergens like dust mites and mold spores deep within their fibers, making them harder to clean and potentially worsening indoor air quality over time. Additionally, dust visibility on wood floors can serve as a prompt for cleaning, and these floors are less likely to harbor mold and mildew since they are more resistant to humidity compared to carpets.
Clean areas where dust aggregates
Make these areas part of your regular cleaning routine.
Blinds: Dust often gathers between the slats of blinds.
Ceiling Fans and Light Fixtures: As dust floats in the air, these elevated surfaces are often the first to accumulate it. Regular cleaning can prevent a heavy buildup.
Upper Surfaces: Though often overlooked, the tops of doors, windows, and cabinets can gather significant dust.
Declutter
It’s harder to clean and remove dust if you have many items that create uneven areas for dust to settle and aggregate in.
Go forth and eliminate the dust!
Depends on your house, air quality outside, and air quality inside but a cheap air quality monitor has shown my that an open window can clean up the air 5x faster than an air purifier.
Even during the winter or summer there is usually a small window of time (excuse the pun) that the air temp outside is about the same as your desired temp. Lots of houses have an oversized heater to account for open windows in the cold.
Window fan can expedite the process, you can get sneaky about which direction you run fans to create circulation throughout the house. Try not to create negative pressure in your house (don’t blow more air out than in) especially in your basement due to radon and other bad things with negative pressure.
I try to use windows as a plan A and HEPA filters as a plan B. I recognize this is a luxury of having good air quality outside in my area.
Not all dust is created equal. You mention many types, but I would differentiate between the following two classes:
All kinds of particles that would also be present in the ancestral environment, independent of size, such as human skin, soil material, natural fibers, pollen, and microbes adapted to these.
All other, mostly artificial particles, such as paint, pesticides, synthetic fibers etc., that the human immune system is not adapted to.
While both can lead to health complications in high concentrations, I am much more worried about the latter. And if the Hygiene Hypothesis is correct, a moderate amount of the former might even be beneficial overall.
I haven’t given much consideration to the hygiene hypothesis but agree it seems likely that some types of particulate matter could be beneficial.
If you want to compare to the “ancestral environment”, it’s crucial not to forget about the amounts of dust that are breathed in. How much dust of what particle sizes do we breathe in outside, compared to inside a dusty home?
I would argue that at least partly enclosed shelter is part of the ancestral environment. Here is a ChatGPT-4 summary:
That seems mostly nonresponsive to his point, since those sorts of shelters are obviously going to let in a ton of outside air and where they do not, like caves, they will be concentrating smoke, and be so small & primitive that their endogenous dust levels don’t matter much compared to exogenous.
I also think it’s probably a bad idea to provide random GPT pastes if you haven’t factchecked them and they do not serve any particular point. The Star Carr part seems right, but the 100kya claim for caves seems badly wrong*, and the first use of caves for shelter more likely dates back at least 750,000 years ago (Carmel isn’t even mentioned in the cave-dwelling article, nor can I find a relevant one in its article or some searches, only an instance of a burial dated 100kya). Why do you think GPT-4 is any more accurate about, say, Luhmann or the Sequences than it is about human habitation of caves?
* Really, you found that plausible? Humans have been around for like a million years, and only ~100kya they noticed these warm comfy holes in the ground beloved by many other animals like bears and tried to live in them? Humans have clothing, seafaring, bone carving and beads etc ~100kya but still were figuring out ‘hey we can go into this cave thing!’?
Here are some actual sources as requested:
Sites of Human Evolution at Mount Carmel: The Nahal Me’arot / Wadi el-Mughara Caves go back up to 500.000 BP
Olduvai Gorge | Archaeological Site, Tanzania go back 2 million years BP
I don’t think ChatGPT is “correct” with sources or numbers because it has no deep understanding of either. I think it is “directionally correct”.
As to the “non-responsive” part: I should have been more clear that I meant that in the ancestral environment, there is much more dust carried into and accumulated in the shelter than in modern homes.
It would be useful to know relative dust levels in practice, given equipment + habits. E.g.: with such and such air filter running all the time, the air has X% less particulates of size Y; etc.
Agreed, it’d be better to understand the effect sizes more. Will consider following up with more investigation here.
I agree that indoor combustion producing small particles that go deep into the lungs is a major problem, and there should be prevention/mitigation. But on the dust specifically, I was hoping to see a cost-benefit analysis. Since most household dust is composed of relatively large particles, they typically do not penetrate beyond the nose and throat, and so are more of an annoyance than something that threatens your life. So I am skeptical if one doesn’t have particular risk factors such as peeling lead paint or allergies, measures such as regular dusting (how frequently are you recommending?), not wearing shoes in the house, having hardwood floors if you like the benefits of carpet such as sound absorption, etc would be cost-effective when you value people’s time.
What effects does dust have on cognition? I’m pretty sure that air quality has an impact on cognition, but I’m unsure what the mechanisms of action are.
There is a lot of research on mortality from household air pollution, but I wasn’t able to find anything on its passive effects. I wonder how regular exposure to “normal” levels of dust affects your life expectancy.