Research has shown that a single home in the country can accumulate up to 40 pounds of dust annually. Dust refers to the different types of organic and inorganic particles that can collect over a period of time in our homes. A lot of dust particles are not visible to the naked eye and despite regular cleaning, can continue to exist inside the house. Dust is a mixture of various things like human skin cells that are shed each day, paint particles, fabric fibers, sand and soil particles, bacteria, pollen, dust mites, pet dander and feathers, and mold spores to name a few. (1)
Household dust is full of living organisms that are determined, in large part, by where the home is located and who is living in it. Homes with a greater ratio of male occupants, for example, contain large amounts of skin and fecal-associated bacteria, while women-dominated households contain an abundance of vaginally shed bacteria that somehow winds up in the dust. (2) This vaginal-linked bacteria discovered in homes with a larger ratio of women provides evidence that clothes do not fully contain the spread of microorganisms produced by our bodies. Dogs and cats had such a dramatic effect on dust bacterial communities that researchers could predict with around 92 percent accuracy, whether or not such animals were in the home, just based on bacteria alone.
This is from a recent study published in the Proceedings of the Royal Society B, and is believed to be the most extensive ever on microorganisms found in household dust. Senior author Noah Fierer says that there are 'millions of bacteria and fungi living inside our homes.' (3)
He and his colleagues used DNA sequencing and high tech imaging to analyze dust samples from approximately 1,200 homes across the United States. They discovered that indoor fungi mostly originates outside of the home, such that the geographical location of any home strongly predicts the types of fungi existing within dust.
The study found more than 9,000 different species of microbes, also know as microorganisms. In addition to all the different kinds of microbes, the researchers also found about 2,000 different types of fungi. (4)
Bacteria wee largely predicted by the home's possible inhabitants, including humans, pets and even insects.
Most of the fungi in homes appears to come from outside the home. They enter the home on our clothing, or through open windows or through doors.
About 50 percent of aerosols in North America come from overseas, primarily dust and pollution from trans-Pacific transport, and also a little bit of dust from trans-Atlantic transport from Africa. (5)
The biggest pollutant coming out of Asia, at least in terms of shear mass, could be dust from the region's swelling deserts. About every three years, a huge dust storm over China sends enormous clouds across the Pacific. Chinese dust has obscured vistas in US national parks, even on the East Coast. (6)
Another recent study uses the air as a dust cloud focus. The American Council on Science and Health reports that this study elicits images of Pig-Pen., the aptly named character from the famous cartoon strip Peanuts. In short, scientists, working at the University of Oregon have concluded that everyone travels around with a bacterial cloud and that the constituents of this cloud might be unique to each one of us. (7)
The researchers used 11subjects and had them stand, for four straight hours, in a sterile chamber equipped with air filters and petri dishes. The researchers than sequenced the bacteria in the cloud to identify what bacteria were being emitted by each subject. Many common skin flora bacteria were found, such as various member of the genera Staphylococcus and Corynebacterium. However, the study also turned up some surprises, including Lactobacillus, a commensal of the vagina, and Citrobacter Freundii, a nitrogen-fixing environmental organism, which also causes many opportunistic infections.
Also, for 8 of the 11 subjects, the combination of the constituents of each microbial cloud were unique enough to identify blindly if a particular subject had occupied a space or not.
We have known for some time that each of us emits about a million biological particles an hour, but the constituents have not been previously studied until now. The study's results and future implications have significance in understanding how we may transmit diseases through our microbial clouds. (7)
So there you have it. Dust is everywhere and comes from just about everything. Besides that we even carry around our own little dust cloud. Also, we even receive some dust from countries on both sides of the oceans.
Jack Dini
Livermore, CA
References
1. “Dangers of dust in the home,” redbeacon.com, accessed October 25, 2015
2. Jenifer Viegas, “Household dust packed with thousands of microbes,” news.discovery.com, August 25, 2015
3. Albert Barberian et al., “2015, “The ecology of microscopic life in household dust,” Proc. R. Soc. B, 282, 20151139
4. Russell Westerholm, “Household dust contains thousands of different kinds of microbes, fungi,” University Herald, August 26, 2015
5. “Q & A with atmospheric Scientist Hongbin Yu,” nasa.gov/topics, August 2, 2012
6. David Kirby, “ILL wind blowing,” Discover, April 2011
7. “Investigating what's in Pig Pen's dust cloud,” American Council on Science and Health, September 23, 2015
