Main content

What's in your carpet? You sure about that?


If you’re the kind of person who likes to keep meticulously clean, it can be disturbing to ponder that you are populated by hordes of unseen bacteria, thriving fungi and even tiny mites. These invisible residents can be found inside your body, in the air and all over the things you touch.

You are, in fact, more or less a walking habitat.

Most of us might prefer to ignore all that, but scientists see an exciting field with lots going on and plenty to learn.

Take carpets: simple flooring to you, a forest for tiny organisms. And every time you walk into a room, you stomp on that forest and kick up clouds of dust and microbes into the air. 

“We really do need to get a more comprehensive picture of what a healthy indoor microbiome is,” said Karen Dannemiller, an interdisciplinary researcher with Ohio State’s Sustainability Institute. She’s one of a number of scientists looking into just what lives and grows and sits in our carpets, and how that impacts our health.

Your carpet is full of stuff

Here’s a short list of some of what they’ve found in your carpet: bacteria, fungi, phthalates (a substance that can be found in dust) and volatile organic compounds — which, as the National Institutes of Health explains, are chemical compounds that easily become vapors or gases. These compounds are often not at all good for you — formaldehyde, for one — and they’re found in all kinds of consumer products, not just carpets.

Phthalates, too, aren’t ideal: They are endocrine disruptors, which means they can mess with your hormones. And all these chemicals and microbes can interact with each other in ways we don’t really understand. 

Given all that, finding out how carpets and their contents affect allergies, asthma and overall human health is of great interest to Ohio State researchers. They’ve only scratched the surface, but have made some discoveries, including recent insight that indoor humidity plays a key role. 

The problem, Dannemiller notes, is not that there are fungi in carpets — as noted before, we breathe in fungi all the time even if we don’t want to admit it — but that under the right conditions, organisms can get out of balance and start growing out of control. 

So, like good researchers, Dannemiller and others set about putting conditions out of balance on purpose and watching what happened. 

But don't rip it out just yet...

“A lot of times when we’re thinking about mold growth, we’re thinking about our walls,” Dannemiller said. She wanted to explore exposure to mold in dust that gets kicked up from carpets. 

The researchers ratcheted up indoor humidity to absurd levels. What they found was that mold doesn’t need water condensation to grow in a carpet: Elevated relative humidity suits it fine.

The EPA recommends about 30% to 50% indoor humidity. Above 60% is a problem. In the study, growth really picked up at about 80% humidity — a condition, Dannemiller noted, that isn’t found in a typical home except in a bathroom. However, humidity can be higher in the carpet itself than in the air. 

There’s a lot left to research. They’re still looking at microbial growth in lower levels of humidity that might be found in a typical home, and much is unknown about what kinds of microbes humans need and in what levels.

Dannemiller noted studies have found that children exposed to a wide range of fungal species can have a lower risk of asthma later in life. One noteworthy example was extremely low rates of asthma among people living alongside livestock such as cows. 

So while you wait for researchers to find out more, should you buy a cow and rip up your carpet?

Dannemiller definitely isn’t recommending that. 

Tips for living with carpet

Here are some things you can do, though: 

  • Be careful where you put carpet, taking into account moisture in the air. (If for some reason you are tempted to carpet your bathroom, for example, restrain yourself). 
  • Keep it clean. Vacuuming can kick up dust, but if you’re thorough, it also removes a lot. If you shampoo a carpet, make sure you dry it out quickly.
  • Deal with health issues holistically. Dannemiller said they couldn’t find an instance when just taking up carpet improved health, but she added that step can be effective when it’s done as part of other remedies for allergies and asthma. 
  • Be aware of chemicals when you’re buying carpet. Carpets that are Green Label Plus certified come with fewer volatile organic compounds.