Indoor dust is filled with antibacterial chemicals, says a new study published in the journal Environmental Science & Technology, and they could be contributing to deadly global health crisis of antibiotic resistance.

Last week, the FDA ruled that several of these chemicals—such as triclosan and triclocarban—can no longer be added to household soaps. Not only do they not make products any more effective at killing germs and preventing illnesses, say scientists, but they have also been linked to hormone disruption, bacterial resistance, and cancer.

That’s a good first step, says Erica Hartmann, Ph.D., assistant professor of civil and environmental engineering at Northwestern University and author of the new report on indoor dust. But her study shows that it won’t solve the problem completely.

That’s because antibacterial chemicals like triclosan are found in a lot of different products—including building materials, plastics, and cosmetics. “The FDA ruling doesn’t have any impact on paints, baby toys, bedding, kitchen utensils, the list goes on,” she says.

The chemicals are added to these products during their manufacturing, but they don’t stay there; they make their way into the air, and into dust we breathe in and pick up on our bodies.

“Triclosan has been found in almost every dust sample that has ever been tested worldwide,” says Hartmann. “Given the widespread use of antimicrobial products, I wouldn't be surprised if most people had this kind of dust in their homes.”

For her study, Hartmann and her colleagues analyzed dust samples from a mixed-use athletic and educational facility, and found that samples with higher amounts of these chemicals also had high levels of genes associated with resistance to multiple drugs. In all, they found six separate links between antibacterial dust and antibiotic-resistant genes.

The findings couldn’t definitively show that the chemicals caused the presence of these genes, but they do support a growing body of evidence that the two are closely related. And while indoor dust tends to contain much lower levels of these ingredients than, say, toothpaste or antibacterial soap, Hartmann says that exposure could still be significant. After all, she writes, humans spend up to 90 percent of their time indoors.

More research is needed to determine the exact role that indoor dust plays in antibiotic resistance, Hartmann says—and to figure out what, exactly, people can do about it. “My recommendation would be to not use antimicrobial products unless you have a specific reason to—for example, people who are immune-compromised,” she says.

Keeping your home ventilated might help, as well. “We know that whether a building has a mechanical air handling system (like air conditioning) or gets its air directly through the windows has an effect on which bacteria we find indoors,” she says, “but we haven’t finished the follow-up study looking at chemicals.”

Hartmann is now studying dust from additional buildings, including residential homes. She hopes her work will add to other research showing that antibacterial chemicals can often do more harm than good, and help shape policy and smart-decision making about their use.

“I think we need to find responsible ways to use antimicrobials and antibiotics everywhere—at home, in agriculture, and in medicine—to truly tackle the problem of antibiotic resistance,” she says. “In some cases, like in household soaps, that may mean not using them at all.”

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