Forget your human roommates. You're likely sharing your living space with thousands of little friends.
Those dust bunnies in your house are cute, but likely full of hazardous chemicals. More specifically, phthalates, phenols and flame retardants are released into the air via consumer products in the home and settle into household dust.
Researchers collected data from 26 peer-reviewed studies and one unpublished data set from 14 states. They identified 45 chemicals; the 10 most common chemicals were found in more than 90 percent of the dust samples collected. Their analysis was published in Environmental Science & Technology.
“The findings suggest that people, and especially children, are exposed on a daily basis to multiple chemicals in dust that are linked to serious health problems,” said study co-author Ami Zota, an assistant professor of environmental and occupational health at George Washington University's Milken Institute School of Public Health.
Children are likely at higher risk, the researchers said, because they play and crawl on the floor and often put their hands in their mouths. They also may be more vulnerable to the effects of the chemicals because their brains and bodies are still developing.
The chemicals originally came from a variety of products ranging from cleaning products and vinyl flooring to perfume and even pizza boxes.
Their tips? Keep household dust to a minimum, of course, and wash hands frequently with plain soap and water.
Dust and obesity
A newer, 2019 study that looked specifically at a link between household dust and its potential link to weight gain found that dust could promote the growth of fat cell development. Researchers discovered that dust contains endocrine-disrupting chemicals. Previous observational studies have found a link between exposure to these chemicals and weight gain in people.
"This is some of the first research investigating links between exposure to chemical mixtures present in the indoor environment and metabolic health of children living in those homes," said lead researcher Christopher Kassotis, Ph.D., of Duke University's Nicholas School of the Environment, in a statement.
For the study, researchers collected samples of dust from 194 homes in North Carolina. They extracted the chemicals found in the dust to test whether they would fuel the growth of fat cells. They found that even very low concentrations of dust were able to promote fat cell growth.
"We found that two-thirds of dust extracts were able to promote fat cell development and [could] promote precursor fat cell proliferation at 100 micrograms, or approximately 1,000 times lower levels than what children consume on a daily basis," Kassotis said.
In addition, the researchers found several chemicals were significantly elevated in the dust samples collected in the homes of children who were overweight or obese.
Microbes and fungi
But chemicals aren't the only problem. The dust in our homes also contains around 9,000 different microbes, including about 7,000 types of bacteria and 2,000 varieties of fungi, another recent study suggests.
In another project, researchers analyzed household dust from all over the country and found that the type and amount of fungi and bacteria in our homes depends on where exactly we live and who we share our space with.
Volunteers from 1,200 homes across the U.S. scooped up dust samples from the tops of doorframes (places often overlooked when people dust) and sent them in to researchers as part of a citizen science project called The Wild Life of Our Homes.
On the swabs, researchers found more than 40,000 species of fungi and more than 80,000 kinds of bacteria.
"In the thousand houses people have sampled, we have found evidence of more species than there are kinds of birds and mammal species on Earth, nearly 10 times more," wrote biologist and study co-author Rob Dunn of North Carolina State University on the Wild Life of Our Homes blog.
Fortunately, they didn't find quite that many in the average house.
The type of fungi found in your home depends on where you live — desert versus forest, cold versus hot — because what's in your house didn't just pop up there.
“Most of the fungi we are seeing in the home appears to be coming from outside the home,” Noah Fierer, co-author and associate professor of ecology and evolutionary biology at the University of Colorado Boulder, told the BBC.
“They enter the home on our clothing, or through open windows or through doors. Therefore the best predictor of what types of fungi are in your home is where your home is located.”
Staphylococcus is just one of the thousands of bacteria that could be hanging out at your house. (Photo: Knorre/Shutterstock)
In addition to location, your roommates (human and otherwise) make an impact on the bacteria in your home, researchers found.
"We found distinct bacteria in homes that had women and homes that were male-only," said Fierer.
"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."
But the biggest influence on your personal microbial environment is whether you share your home with pets.
"Bringing a dog or cat into your home really has a significant effect on the bacteria you find in your home," said Fierer.
"It was surprising to us that it was such a strong influence — stronger than any other factor, stronger than where your home was located or the design of your home, for example."
But don't rush out and buy a monstrous-size jug of bleach. A few of these microbes might be linked to allergies or disease, but the vast majority won't hurt you, said Fierer.
"People do not need to worry about microbes in their home. They are all around us, they are on our skin, they're all around our home — and most of these are completely harmless."
This story was originally written in August 2015 but has been updated with more recent information.