Is house dust mostly made up of human skin?

Question

^{Fortean Times}

I first heard the claim that house dust is mostly made up of human skin on a TV show, when I was a kid (probably Cheers, where Cliff makes this comment at the beginning of a Season 9 episode), but even today I often hear this "fact" being repeated.

From Better Health:

The main component of dust is shed skin flakes

MicrobiologyBytes even gives a percentage:

About 80% of the material seen floating in a sunbeam is actually flakes of skin

But according to the Fortean Times:

There’s no evidence to suggest that dust is mostly made up of any one ingredient; rather, it is a delightful salmagundi or potpourri of everything that is likely to be drifting around your house.

The precise ingredients and proportions present will presumably depend in part on where you live, as well as how.

My question:
Is house dust mostly made up of our shed skin flakes?

Answer 1

You have three claims described there. Skin is more than 80%, more than 50% or less than 50%.

Well, I only have a partial answer. I can show that it is less than 69%. [*]

Calabrese EJ, Stanek EJ, "What proportion of household dust is derived from outdoor soil?", Journal of Soil Contamination [J. SOIL CONTAM.]. Vol. 1, no. 3, pp. 253-263. 1992.

This report estimated the amount of outdoor soil in indoor dust [...]. The estimate used data on outdoor soil and indoor dust in the homes of 60 children with eight tracer elements (Al, Ba, Mn, Si, Ti, V, Y, and Zr). The model estimated that 31.3% of indoor dust had an origin of outdoor soil.

If 31.3% comes from outdoor soil, then only 68.7% can come from other sources (inside or out), putting an upper figure on the human skin cells.

[*] For a sample of 60 homes. I imagine it is very dependent on the home. Anecdotally, when I lived near an intersection, it struck me that the dust on the side of my home closer to the road was grimier and darker than the dust on the other side, suggesting even within one house they proportions can be significantly different.

Answer 2

According to Elemental concentrations and metal bioaccessibility in UK household dust Science of the Total Environment vol. 371, pages 74–81.

Household dust has many internal and external sources, including garden soil, road dust, human hair and skin, carpet and clothing fibres, paint chips and fungi, resulting in a heterogeneous matrix of organic matter and inorganic and metallic particles.

The study analyzed the carbon to nitrogen ratio of household dust and found "mean C:N ratio of 8.5"

The study also states that collagen has a C:N ratio of between 2.9-3.6.

Because the experimental value 8.5 is more than twice the value for skin/collagen, the possibility that at least half the dust is skin is ruled out.

In other words, analysis of the dust shows too little nitrogen content for half the dust to be from skin.

Separately, according to House dust in seven Danish offices Atmospheric Environment 34 (2000) 4767-4779:

only 4% of dust was found to be of human origin (which included hair and skin)

54% was mineral (such as Quartz, calcite, feldspar, gypsum, salt)