We think of indoor pollution as airborne gunk that seeps in from outside. But in fact, the pollution in your home could be coming from your furniture, your carpet, your mattress, your cleaning supplies — even the paint on your walls — in the form of volatile organic compounds, or VOCs.

VOCs come from carbon-based chemicals (such as formaldehyde and lesser-known xylene, toluene and other “-enes”) that easily become vapors or gases. They are considered "volatile" because they can get into the air at room temperature according to John Drengenberg, consumer safety director for UL.

Depending on the product, VOCs can be emitted from paints, varnishes, sealants, floor wax, bug spray, permanent markers, mothballs, mattresses, synthetic carpet, pressed-wood furniture and more. If you get a whiff of fingernail polish, hair spray or scented cleaning products, or that "new car smell," you’re probably breathing in VOCs.

The suit you had dry-cleaned yesterday can also “off-gas” VOCs. And they can waft through your house from the “air freshener” you just sprayed around the room, says Drengenberg.

According to UL, there may be anywhere from 50 to hundreds of individual VOCs in indoor air at any one time.

Here are just a few of the VOCs that make their way into our homes according to the New York State Department of Health:

  • Benzene (found in furniture polish, paint and paint thinners, among other products)
  • Acetone and ethyl alcohol (found in nail polish and nail polish remover)
  • TCE, or trichloroethylene (found in dry cleaned clothes)
  • Heptane and butane (found in many aerosol sprays)
  • Formaldehyde (found in cigarette smoke, synthetic carpets, pressed wood and plywood)
  • Limonene and pinene (found in household cleaners and fragrances)

Related: Clearing the Air: 3 Dangerous Pollutants in Your Home

What’s the danger?

Not all VOCs appear to be harmful, but many can cause serious health problems, according to the Environmental Protection Agency (EPA). Some, such as benzene and formaldehyde, can cause cancer, according to the National Toxicology Program (NTP) and other agencies. If you smoke cigarettes, the NTP notes, you’re among those at highest risk of exposure to these cancer-causing VOCs.

According to the Minnesota Department of Health, short-term exposures to VOCs can cause:

  • Eye, nose and throat irritation
  • Headaches
  • Nausea / Vomiting
  • Dizziness
  • Worsening of asthma symptoms

Long-term exposure to high levels of VOCs may increase your risk of:

  • Cancer
  • Liver damage
  • Kidney damage
  • Central nervous system damage

Studies have shown that the level of VOCs indoors is two to five times higher than the level outdoors, according to the EPA. Children (especially babies), pregnant women and the elderly are particularly at risk for these toxic emissions, according to Drengenberg.

How to lower your risk

Be paint-savvy. Buy a brand that has low-VOC emissions. Drengenberg recommends looking for a paint that is GREENGUARD Certified. And watch when you paint. For example, “You shouldn’t paint a nursery the day before baby comes home from the hospital,” says Drengenberg. “Try to paint at least two weeks before using the room.” Keep the windows open while painting.

Related: The Hidden Dangers in Paint

Look for cleaning products that are certified for low-VOC emissions. An example is a product that bears the GREENGUARD Certification mark. “While it’s nice to have that clean smell after you use something, it’s still producing chemical emissions,” Drengerberg says. “Try to get the unscented ones.”

Don’t spray air freshener or other scented products around your house. Even burning scented candles can cause eye and throat irritation by giving off VOCs, according to allergist Stanley Fineman, MD, of the American College of Allergy, Asthma & Immunology.

Buy only the amount of cleaning products you need, Drengenberg says. Don't stock up on extras. Remove bottles and canisters of unused chemicals from your home. Even sealed containers can leak VOCs.

Use as much ventilation as possible. Cooking without running an exhaust can fill the kitchen air with fumes and soot, so turn on the overhead vent fans when cooking, advises Drengenberg.

Store new furniture and mattresses in the garage for a couple weeks. Materials used to manufacture furniture can give off unhealthy emissions for several weeks or months after they’re in your home. Look for furniture and mattresses that have been GREENGUARD Certified for low chemical emissions because they won’t contribute to poor indoor air quality. Or, you can let items off-gas in your garage before you bring them in, or provide extra ventilation in the room. “Use fans and keep windows open, if possible," says Drengenberg. "Today a lot of the wood in new furniture is pressed wood, which means glue holding compressed woodchips together. These glues can give off formaldehyde. Even a new mattress can irritate people with breathing sensitivities.”

An easy resource for finding low-emitting products is UL’s Sustainable Product Guide, where you can find thousands of GREENGUARD Certified products.

Related: 8 Ways to Have Cleaner Indoor Air This Winter

Steve Evans, MA, is an award-winning journalist with more than 20 years experience in daily news, investigative, health and business journalism. Among other jobs, he has served as managing editor of the Central Virginia Newspaper Group, as a senior writer for SNL Financial and as a staff writer for The Progress Index and the Richmond Times-Dispatch.