The effects of that exposure may be hard to detect in individual children, but scientists can see them when they look across the population. Researchers from the Center for Children’s Environmental Health, at Columbia University, measured a class of flame retardants known as polybrominated diphenyl ethers, or PBDEs, in the umbilical-cord blood of 210 New York women and then followed their children’s neurological development over time. They found that those with the highest levels of prenatal exposure to flame retardants scored an average of five points lower on I.Q. tests than the children with lower exposures, an impact similar to the effect of lead exposure in early life. “If you’re a kid who is at the low end of the I.Q. spectrum, five points can make the difference between being in a special-ed class or being able to graduate from high school,” says Julie Herbstman, the study’s author.

There are many flame retardants in use, the components of which are often closely held trade secrets. Some of the older ones, like the PBDEs, have been the subject of thousands of studies and have since been taken off the market (although many of us still have them in our furniture). Newer ones like Chemtura’s Firemaster 550 are just starting to be analyzed, even though it is now one of the most commonly used flame retardants in furniture.

Logic would suggest that any new chemical used in consumer products be demonstrably safer than a compound it replaces, particularly one taken off the market for reasons related to human health. But of the 84,000 industrial chemicals registered for use in the United States, only about 200 have been evaluated for human safety by the Environmental Protection Agency. That’s because industrial chemicals are presumed safe unless proved otherwise, under the 1976 federal Toxic Substances Control Act.

When evidence begins to mount that a chemical endangers human health, manufacturers tend to withdraw it from the market and replace it with something whose effects — and often its ingredients — are unknown. The makeup of the flame retardant Firemaster 550, for instance, is considered a proprietary trade secret. At a recent conference, Stapleton discussed a small, unpublished study in which she fed female rats low doses of Firemaster 550. The exposed mothers’ offspring gained more weight, demonstrated more anxiety, hit puberty earlier and had abnormal reproductive cycles when compared with unexposed offspring — all signs that the chemical disrupts the endocrine system.

This small study hardly constitutes definitive proof, however. In a written response to my questions, Chemtura said that the rat studies it performed and submitted to the E.P.A. “indicated no observable adverse health effects at exposure levels significantly higher than would be expected from the use of the product.” And while that product’s components have been found in household dust in Boston, treated sewage in San Francisco and in the air in Chicago, no one can say for sure that the compounds originated from Firemaster 550. “There are other sources for these substances,” Chemtura wrote.

One day last year, I unzipped the covering around one of my couch cushions, snipped off a small sample of the foam and mailed it to Stapleton’s lab to be analyzed. Several months later, the results came back. My couch, where my son does his homework, contains chlorinated Tris.

The question was what to make of this information. The Consumer Product Safety Commission considers chlorinated Tris to be a probable human carcinogen and has said that adding it to furniture exposes children to a daily dose significantly higher than what the agency considers acceptable. The two companies that sell the flame retardant, I.C.L. Industrial Products and Albemarle, say I have nothing to worry about, citing a European Union Risk Assessment from 2008 that concluded consumer exposure to the chemical is too low to cause significant health problems. Dr. David Clary, Albemarle’s chief sustainability officer, says that the kind of testing done by Bruce Ames that first flagged chlorinated Tris as a mutagen could be used to condemn peanut butter and broccoli. “According to the Ames test,” he says, “almost everything causes cancer in high doses.”