The most common one detected was a chemical referred to as tris, which was removed for safety reasons from kids' pajamas in the 1970s.
Five samples contained PentaPBDE - another type of flame retardant - that has been banned by nine states and the European Union because of concerns about not only its toxicity, but also its effects on the environment.
These and similar flame retardants are now widespread in nature. They've been found in California peregrine falcons, Puget Sound orca whales, and Greenland sled dogs.
But back to the babies.
One reason flame retardants are in children's products is California. The state has flammability standards requiring that upholstered products - including baby furniture - containing polyurethane foam be able to withstand exposure to a small, open flame for 12 seconds.
Rather than make separate products for just one state, some manufacturers add flame retardants to all.
But how many products? And how much of the stuff is in them?
It's not clear whether they work as intended. One of the study authors, Arlene Blum, a visiting chemistry scholar at the University of California, Berkeley, says the fabric covering the foam is not required to be flame resistant. She plans to present a study at a fire science meeting in June showing that the flame retardants don't make these products safer to any measurable degree.
Scientists have recently begun to take a much closer look at these chemicals in children's products, particularly because they aren't chemically bound to the product. They tend to "offgas" into the air, so children might breathe them. Or they get in dust that children get on their hands.
And we all know where their little hands go next: into their mouths.
Plus, tiny children are more susceptible to concentrations that adults might easily withstand.
In 2008, Philadelphia University's David Brookstein, dead of the school of engineering and textiles, and Jeffrey Ashley, associate professor of chemistry, also investigated car seats and found potentially toxic "brominated" flame retardants.
But they didn't have equipment that would identify the precise formulations, which is what Stapleton's study did.
Some companies are using these chemicals "at fairly high concentrations," Ashley said. "Consider how much time a child potentially sits in a car seat. That may represent a significant exposure to these chemicals."
He said the presence of the chemicals is more cause for concern than alarm. More study is needed.
But in general, "there's substantial data out there showing that these things are plainly not good," Ashley said.
The industry says its products are beneficial and safe.
In response to the Duke study, the North American Flame Retardant Alliance - a group within the American Chemistry Council - issued a statement: "Flame retardants are well-studied and provide important fire safety benefits in homes, cars and public areas.
"The flame retardants currently in use are allowed by the relevant regulatory authorities. Our member companies are on the forefront of innovating new flame retardants, which undergo extensive testing by manufacturers and the safety data are scrutinized by government agencies in the U.S. and abroad," it said.
Stapleton's study was published in the peer-reviewed journal Environmental Science & Technology.
The world of flame retardants she describes is dizzying. There are numerous types and various commercial formulations.
So it's not quite right to lump them all together, but is next to impossible for anyone but a scientist to sort them out.
Stapleton did not identify any brands in her study. She says that baby products that have polyurethane foam and a label indicating that they conform to "CA Technical Bulletin 117" - the California foam law - are very likely to contain flame retardant additives.
But others may have flame retardants, too. Or not.
What to do?
Ashley has two children, ages 2 and 5.
Just to be on the safe side, he and his wife started putting a fabric pad over the car seat to minimize exposure.
Stapleton had her second child just weeks ago, and she's trying to stay away from foam products altogether.
Some suggest buying products filled with polyester, cotton or wool instead.
Contact staff writer Sandy Bauers at 215-854-5147 or firstname.lastname@example.org. Visit her blog at http://go.philly.com/greenspace