Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: On household dust, published by NinaR on June 30, 2023 on LessWrong.

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...