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eggshaped
150597.  Fri Feb 23, 2007 5:42 am Reply with quote

This could be a classic piece of ignorance, but I can't quite get a handle on it.

What is house dust mostly made from?

According to this article, the answer is not dead skin, which is what almost everyone on the net claims.

Quote:

This is one of those “Eww! Gross!” factoids that sound very scientific, but isn’t really true. Sometimes a specific percentage of dust is said to be skin, usually about 70 or 80 percent, but unless you’re a molting bird or reptile (or you work in Dr. Frankenstein’s laboratory), very little of your environment is composed of dead body parts.

There are far more common sources of dust pollutants, including animal dander, sand, insect waste, flour (in the kitchen), and of course lots of good, old-fashioned dirt.

Every time we open a window or a door, we stir up and move around tiny, airborne particles that eventually settle around the house. Humans do shed dead skin, but most of it is carried away by water when we shave or bathe, ending up not on our floors but in our sewers. Now don’t you feel better?


I wonder if anyone can find something more authoritative? I gave away my dust book to the winner of my Gabbly quiz.

 
Flash
150604.  Fri Feb 23, 2007 5:55 am Reply with quote

Yes, that's a good one. I wonder where the "human skin" factoid originated?

Mat, have you ever covered this?

Just goes to show, you should never give away a book.

 
MatC
150616.  Fri Feb 23, 2007 6:18 am Reply with quote

Flash wrote:
Yes, that's a good one. I wonder where the "human skin" factoid originated?

Mat, have you ever covered this?

Just goes to show, you should never give away a book.


Ain't that the truth ...

No, I've never done this one - but I will, Oscar, I will! I don't think I've got anything on it, but I'll have a look. If stand-uppable, it'll be a smasher.

 
Flash
150618.  Fri Feb 23, 2007 6:23 am Reply with quote

There's a Straight Dope article about a belief which apparently exists in America (promulgated by mattress manufacturers) that half the weight of a mattress can be made up of dust mites and associated detritus. Not true, apparently. Does this idea exist over here? I don't think I've ever encountered it.

It could be put in the notes to egg's question, though.

http://www.straightdope.com/columns/000407.html

 
MatC
150634.  Fri Feb 23, 2007 7:09 am Reply with quote

Flash wrote:
There's a Straight Dope article about a belief which apparently exists in America (promulgated by mattress manufacturers) that half the weight of a mattress can be made up of dust mites and associated detritus. Not true, apparently. Does this idea exist over here? I don't think I've ever encountered it.

It could be put in the notes to egg's question, though.

http://www.straightdope.com/columns/000407.html


I think it - or something like - does, Flash; I'm always seeing claims of this sort in adverts for anti-allergy products, such as special hoovers etc.

 
Flash
150668.  Fri Feb 23, 2007 8:13 am Reply with quote

Probably worth mentioning then, even if it mightn't make a question in its own right.

 
Flash
180400.  Tue Jun 05, 2007 4:54 am Reply with quote

Quote:
Composition of house dust

The US EPA defines house dust as ‘‘a complex mixture of biologically-derived material (animal dander, fungal spores, etc.), particulate matter deposited from the indoor aerosols, and soil particles brought in by foot traffic . . . The indoor abundance depends on the interplay of deposition from the airborne state, re-suspension due to activities, direct accumulation and infiltration’’. The precise composition of a house dust sample is a function of numerous factors including environmental and seasonal factors, ventilation and air filtration, homeowner activities, and indoor and outdoor source activities. The penetration of outdoor particles into the indoor environment has been shown to be a significant source of indoor particles. In the outdoor environment, natural sources of dust particles include pollen, soil, forest fire emissions and volcanic debris. Anthropogenic sources of outdoor dust particles include fossil fuel combustion (e.g., coal, oil), wood combustion, waste incineration, and a variety of industrial processes (e.g., iron founding, construction).

In the indoor environment, dust sources include skin, hair, mites, fibres from clothing and furnishings, cooking emissions, heating emissions and cigarette smoke. This variety of indoor and outdoor sources yields a complex matrix that can be extremely heterogeneous in nature with temporal and spatial variability in particle size, particle shape, particle composition, and contaminant concentration. Consequently, the composition of SHD can differ considerably between rooms of a given house, as well as between houses, and among geographic locations in a
study area.

http://www.ecy.wa.gov/programs/eap/pbt/rule/docs/rulecomments/Dust_Review.pdf

SHD = Settled House Dust

 
Flash
180405.  Tue Jun 05, 2007 5:00 am Reply with quote

This site: http://www.cseg.ca/conferences/2000/2000abstracts/506.PDF
contains an analysis of the elements in household (and other) dust in Ottawa, but doesn't really help us for present purposes (as it says there's lots of, eg, zinc, but not where it comes from).

 
Flash
180410.  Tue Jun 05, 2007 5:12 am Reply with quote

Quote:
According to the Environmental Protection Agency, many of the components of house dust are considered "biological contaminants" of indoor air.

"Biological contaminants," says the EPA website, "include bacteria, molds, mildew, viruses, animal dander and cat saliva, house dust mites, cockroaches, and pollen. There are many sources of these pollutants. Pollens originate from plants; viruses are transmitted by people and animals; bacteria are carried by people, animals, and soil and plant debris; and household pets are sources of saliva and animal dander. The protein in urine from rats and mice is a potent allergen. When it dries, it can become airborne. Contaminated central air handling systems can become breeding grounds for mold, mildew, and other sources of biological contaminants and can then distribute these contaminants through the home...

In addition, new studies are finding that toxic chemicals and metals can attach to house dust, which we then inhale. A study on the house dust in Ottawa, Canada found elevated levels of lead, cadmium, mercury, arsenic, and other metals in common house dust. Another study done by Greenpeace in the United Kingdom found styrene, pesticides and plasticizers in house dust. And a study done in the United States, just released in March 2005, showed that seven groups of toxic chemicals--phthalates, alkylphenols, pesticides, polybrominated diphenyl esters, organotines, and perfluorinated chemicals--were found to be present in the vacuum dust of all sample homes tested. Phthalates, which are used primarily as plasticizers for polyvinyl chloride plastics (PVC)--also known as "vinyl"--made up nearly 90 percent of the total concentration of chemicals found in the dust.

Of course, if you don't have sources of toxic chemicals in your home, you wouldn't have much in your house dust, but these chemicals may be present in places that are not obvious. Wool carpets may have pesticide residues that can attach to house dust. PVC could be coming from shower curtains, flooring, black-out curtains, air beds, and other soft plastic products.

Most surprising to me was to find out from the Bau-Biologists that molecules of toxic substances can enter your home in various ways and then attach themselves to house dust. In addition to traveling indoors through open windows and on clothing and shoes, negative air pressure caused by forced air heating and cooling can cause houses to pulls up dust from under the house. If it's an older home, that dust can be loaded with pesticides such as chlordane and even DDT.

http://www.dld123.com/debraslist/athome/athome.php?id=22

 
Flash
180424.  Tue Jun 05, 2007 5:30 am Reply with quote

http://findarticles.com/p/articles/mi_m0CYP/is_10_110/ai_94537457/pg_4

Quote:
... limited data are available that can accurately describe the distribution of basic major constituents of house dust in American residences or in residences in other countries. However, we have acquired information on the distribution of particular toxicants that accumulate on surfaces and within rugs and carpets in residences, and a summary of typical results are found in Tables 1 and 2. From the standpoint of analysis of exposure, one would also like to have baseline information on other materials present within a large number of statistically representative houses, in the United States and elsewhere, and in locations that have a variety of indoor and outdoor sources.

Information available on the basic composition of house dust comes from very few studies, and results suggest that the composition varies throughout a home as well as between homes, across seasons, and among locations within a given country...

One investigation on household dust loading obtained samples from 10 homes in 7 diverse U.S. cities. The analyses indicated that the dust partitioned between fibrous and nonfibrous components. However, among and within the homes sampled, individual rooms could have very high fiber content or equivalent levels of fiber and nonfiber, or low fiber content (Table 3). Because the study was limited in the number of homes sampled, one cannot say which type of loading is most representative of U.S. residential stock. The study did, however, provide some insight as to what general types of materials can be found in households. The room with low nonfibrous dust loadings was frequently the kitchen, and the homes with high fiber dust appeared to have pets. All rooms sampled could have material that ranged from high to low fiber content. The basic composition of dust in a kitchen, however, would not necessarily be similar to the composition found in the bedroom or in the bathroom. This is primarily due to the presence of different sources and major activities associated with each type of room; however, many of the major components of dust are found in each type of room. Similarities in dust composition, for particles > 75 [micro]m in diameter, would include the presence of crumbs, hair, synthetics, soil, starch, plant parts, skin, insect parts, and pollens.


The tables referred to are at http://findarticles.com/p/articles/mi_m0CYP/is_10_110/ai_94537457/pg_25 but, again, don't really help. They say that skin is found in 85% of samples, but not how much, and again the analysis is by reference to chemical elements as far as I can make out.

 
Flash
180444.  Tue Jun 05, 2007 6:11 am Reply with quote

This is what I'm going with for the script note:

Quote:
The composition of house dust is studied because of its rôle in allergies. However, it's difficult to get meaningful data, in part because dust varies so widely from country to country, house to house, and even room to room, as well as varying by season and in response to lifestyles (whether you have a pet, how often you clean, whether you open the windows, etc). What is clear from a review of the studies that have been done, however, is that the often-quoted figure of 70% human skin is a) a complete invention and b) wildly exaggerated.

The components of house dust include: animal and human skin ('dander'), soil, sand, pollen, clothing and carpet fibres, soot, cigarette and wood smoke, brick and concrete dust, dust mites, bits of dead insects, rat and mouse droppings, industrial pollutants, styrene, pesticides, tiny bits of plastic, PVC and vinyl, flour, crumbs, hair, fungal spores and plant parts. A US study released in March 2005 found seven groups of toxic chemicals in the dust in vacuum cleaners, 90% by concentration being phthalates, which are used in the manufacture of PVC / vinyl.

Much of the dead skin shed by humans is actually drained away in bathwater.

There's a story promulgated by mattress manufacturers (particularly in the USA) that as much as half the weight of a mattress can be made up of dead mites and their detritus; this isn't true either.

 

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