"Particularly for young children, it really makes you wonder about the additive nature of these flame retardants," Stapleton said.
The research appears online in the journal Environmental Science and Technology.
Much of the use of flame retardants is driven by a California law requiring upholstered furniture products sold in the state to meet a certain level of fire resistance.
"The other thing that's really sad," Blum said, "is that this California flammability standard has been in effect since the early 1980s but it's not clear it's made any difference for fire safety. For example, the National Fire Protection Association, the authority on U.S. fire statistics, says fire data isn't good enough to show whether it has saved any lives."
Unlike PBDEs, which persist in fat tissues, phosphate-based flame retardants are metabolized by the body, Stapleton explained. "Being metabolized doesn't necessarily mean it's better for you."
Little is known about the health effects of these compounds, she said, other than the 1978 study that found TDCPP was weakly mutagenic in studies of mammalian tissues in petri dishes.