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Another article from results of the crowdsourced study in which household dust samples were sent to researchers at the University of Colorado from approximately 1200 homes across the United States. Some findings after the dust was analyzed: differences were found in the dust of households that were occupied by more males than females and vice versa, indoor fungi mainly comes from the outside and varies with the geographical location of the house, bacteria is determined by the house's inhabitants (people, pets, and insects), clothes do not prevent the spread of bacteria from our bodies, and dogs and cats had a dramatic influence on bacteria in the home. In other words: where you live determines the fungi in the house and who you live with determines the bacteria in the house. From Discovery News:

Household Dust Packed With Thousands of Microbes

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, finds a new study that includes some surprising revelations. Homes with a greater ratio of male occupants, for example, were found to contain large amounts of skin and fecal-associated bacteria, while women-dominated households contained an abundance of vaginally shed bacteria that somehow wound up in dust.

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 used volunteers to help collect the material. 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.“If you want to change the types of fungi you are exposed to in your home, then it is best to move to a different home, preferably one far away,” Fierer and his team said.

Bacteria, on the other hand, were largely predicted by the home’s possible inhabitants, including humans, pets and even insects. Fierer said, “Our bodies are clearly the source for many bacteria that end up in our homes.” The researchers suspect that body size, relative abundance, and hygiene practices are why men tend to shed more Corynebacterium and Dermabacter (the skin-associated species), as well as the poop-associated Roseburia.

The vaginal-linked bacteria Lactobacillus, 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. Members of this genus are actually thought to protect against allergies and asthma, based on earlier research, but further studies are needed to confirm how this, and other bacteria found in dust, impact human health.

Dogs and cats had such a dramatic effect on dust bacterial communities that the researchers could predict, with around 92 percent accuracy, whether or not such animals were in the home, just based on bacteria alone....So far, the news is good for dog lovers, as he pointed out that “previous work conducted by other groups has shown that living with a dog at a young age can actually reduce allergies.”