Last year, volunteers mailed in dust samples taken from above interior and exterior door frames in 1,200 homes across the US as part of a citizen science project called Wild Life of Our Homes. Now, scientists are reporting in the journal Proceedings of the Royal Society B that our dust reveals a lot about who we are and where we live. There are 9,000 unique species of microbes in our dust, reports the BBC, with an average of 7,000 of those being bacterial. There are also insect parts, pollen, dead animal cells, dry wall powder, carpet fibers, and soil particles. "I don't want any readers to be paranoid about this," Noah Fierer, a microbial ecologist at the University of Colorado at Boulder, tells the Los Angeles Times. "Most of the organisms are completely innocuous, and some may be beneficial."
The No. 1 thing researchers can now predict about a home based on a simple analysis of dust? Whether cats or dogs live there. The type of fungi tends to be indicative of a home's geographical location, but bacteria change depending on who lives there—and that doesn't just mean what types of pets, but even whether a home is inhabited primarily by men or women. "There are some kinds of bacteria that are more common on women's bodies than on men's, and we can see the impact of that on the bacteria found in house dust," says Fierer. And while most of the fungi and bacteria are likely harmless, some could be linked to diseases and allergies, something scientists want to study further to discern how our dust specifically affects our health. (Did you know there's more dust in the world now than ever?)