You might want to reconsider your tendency to curl up on your couch after a long, grueling day. A new study from the journal Environmental Science and Technology found that many sofas contain chemicals linked to cancer, fertility problems, and developmental delays in children, and a lot of these toxins aren't labeled.

A little background: Every year, manufacturers use 3.4 billion pounds of flame-retardant chemicals in furniture and other household items to prevent them from catching fire when exposed to open flames. California requires upholstered furniture to be flame-retardant, and, according to NPR, "most manufacturers find it easier to use the same foam in all their furniture, rather than just use retardants in sofas that are bound for California." But many of these chemicals are dangerous for humans — they tend to "leach" into the air, showing up in dust particles we breathe — and studies have found that they're not even effective at retarding flames 

For this study, researchers examined foam samples from couches found in California homes and bought between 1985 and 2010. Among the flame-retardant chemicals that have been used in couches, the most common is Tris phosphate, which was listed by the state of California as a carcinogen in 2011 and was banned from baby clothes in the '70s. PentaBDE, the second most common chemical, was banned in 172 countries and 12 U.S. states after being linked to fertility problems and lower IQ and motor-function problems in children. And then there's Firemaster 550, which has been linked to rapid weight gain and early onset of puberty.

Researchers discovered that 85 percent of the couches they studied contained these flame-retardant chemicals. Sixty-four percent of those couches had no label. "There's no way to find out if [a sofa] does or doesn't" contain flame retardants, says Heather Stapleton, an associate professor of environmental chemistry at Duke University and author of the study. While some of these chemicals have been banned or phased out in recent years (PentaBDE was banned in California in 2004), most people keep their couches for 15 years or more.

The American Chemistry Council says that, although these chemicals are present, the study does not indicate "that the levels of flame retardants found would cause any human health problems." If you want to take precautionary measures, but aren't ready throw out your couch, a co-author of the study suggests regular vacuuming or wet-mopping to help reduce dust levels.

Sources: NPR, CNN, Mother Jones, North County Times