As homes have become better weatherized, keeping our energy bills down, they’ve also become better at trapping air pollutants. Add to this the mix of chemicals ubiquitous in furniture, building materials, carpets and home cleaning products, and many of us wind up exposing ourselves to unhealthy levels of toxins right in our homes.

Three indoor-air pollutants stand out as particularly prevalent — and worrisome, according to Elliott Horner, PhD, lead research scientist at UL Environment:

  • formaldehyde
  • volatile organic compounds (VOCs)
  • fine particulate matter

Here's what they are and where they come from.

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Gassy formaldehyde. Formaldehyde, is used in building materials, furniture and textiles. It’s found in adhesives and wood products like particle board, plywood and drywall. “Almost everything in your home, from furniture to wood flooring to textiles, has formaldehyde,” says Scott Steady, product manager for indoor air quality at UL. “It’s omnipresent in industry and in the home.”

Higher levels are usually found in newer homes or homes that have been recently renovated. Levels decrease over time, but they increase in hot or humid conditions, which cause the formaldehyde to leach out of the furniture or other sources.

At low levels, formaldehyde can be an irritant, causing sore throat, cough or itchy eyes, and can exacerbate asthma, bronchitis or other breathing conditions. Children and elderly people are more sensitive to formaldehyde. “At high levels it’s a known carcinogen,” says Horner. Studies have not shown what level of formaldehyde exposure causes cancer, but the higher the level and the longer the exposure, the greater the risk.

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VOCs. VOCs are chemicals that linger in the air. If you notice an odor, either good or bad, it's likely from a VOC. These compounds occur naturally but they are also widely produced for industrial purposes, and they are ubiquitous in our homes. VOCs such as tolulene and benzene are found in construction materials, glues, paints, fabrics, carpeting and flooring, as well as personal care and cleaning products.

Though a lot of VOCs are relatively benign, exposure to others may irritate the eyes, nose and throat. VOCs can cause headaches, nausea, and nerve problems. Animal studies have shown that long-term exposure to some types of VOCs may increase the risk of getting cancer, according to the Environmental Protection Agency.

Invisible dust. Fine particulate matter is the type of dust that’s invisible to the naked eye. And that’s what makes it potentially harmful. “It’s small enough to penetrate deeply into your lungs,” says Horner. Fine particulates have been associated with cardiovascular disease and respiratory problems. They’re a byproduct of combustion, or burning, from cooking and fireplaces, gas and hot water heaters, and they also come in from the outdoors, cars and industry.

Clearing the air

Here, the experts share their tips on how to protect you and your family:

  • Open up. Open windows as often as possible (even for short periods of time in the winter) to let fresh air in. If your house is “air-tight” this is great for energy conservation, but not good for your health.
  • Keep windows open when using cleaning products, nail polish or other scented items.
  • Keep it cool. Keep the temperature from getting too hot or muggy. Air conditioning units and dehumidifiers can help. Formaldehyde tends to off gas at a greater rate in hot and humid conditions.
  • Vent the stove properly. Make sure the exhaust over your stove in your kitchen blows air outside and not just around the room. Cooking is a very big source of indoor pollution.
  • Air out new furniture. When you buy new furniture, keep it in your garage for a week if possible to allow it to off-gas outside. If not possible, just be sure to keep windows open as much as possible in your house to allow formaldehyde and VOCs to escape. This could take two to three months.
  • Upgrade your filters. To reduce airborne dust, use better filters. MERV is a rating system for filters and corresponds to the level of dust particles the filter can capture. “For home furnaces, the filter needs to be about MERV 5 or MERV 6 to start capturing the coarse particles and at least MERV 7 or MERV 8 to capture much of the fine particulate matter, says Horner, adding “Not all home heating/AC units can accept filters higher than MERV 5 or MERV 6, but they should be used if possible.” If you have central air conditioning, investing in a more expensive filter (about $10) will help clean the air of particulate matter in your home.

Don’t depend on a home filtration to capture VOCs. “Very few home filtration systems are able to capture VOCs,” says Horner. “Some will include sorbents to remove VOCs and odor and can help in theory. However, except for commercial systems, the capacity to remove VOCs is usually minimal.”

What about those indoor air quality home-testing devices that measure formaldehyde and VOC levels that you can buy for around $200? “I’m not sure testing is worthwhile for the average consumer,” says Steady. “They’d be better served to address ventilation and pollutant source issues in the home.”

Limit pollutants

According to the Environmental Protection Agency, “source control,” aka limiting the introduction of new pollutants, is the best way to ensure better indoor air quality and reduce chemical exposure from indoor air.

  • Don't smoke indoors. Any type of combustible, like cigarettes, emits formaldehyde and other chemicals.
  • Look for low formaldehyde-emitting and low VOC-emitting furniture and products. You can look for the UL GREENGUARD Certification or a certification from other reputable organizations. GREENGUARD Certification ensures that a product has met rigorous and comprehensive standards for low emissions of formaldehyde, VOCs fine particulate matter into indoor air. Check this product guide for certified household products.
  • Skip the fragrances. Reduce the amount of products with fragrances you use. Choose fragrance-free or unscented products whenever possible. “'Natural” oils aren't any better than 'unnatural' oils, and can actually be less refined and therefore contain more harmful contaminants,” warns Steady.
  • Practice green cleaning. Consider using cleaning products that do not contain VOCs such as baking soda, vinegar or borax. Or look for third party certified cleaning products bearing the UL ECOLOGO or UL GREENGUARD mark.
  • Store strong-smelling products elsewhere. Store paints, glues, solvents and pesticides in a garage or shed, rather than in your basement, to reduce your exposure to any VOCs that leach out.

Laurie Tarkan is an award-winning health journalist for the New York Times, national consumer magazines and websites.