More than half of children's car seats sold in the United States contain hazardous chemicals, according to a study published Wednesday by a non-profit environmental group.
Sixty percent of 150 car seats tested by the Michigan-based Ecology Center were found to contain chemicals that can be harmful to human health such as bromine and chlorine, which points to the presence of polyvinyl chlorate (PVC).
Studies in lab animals have found that bromine-containing flame retardants can permanently affect the developing brain, while PVC has been classified by the US Environmental Protection Administration as a known human carcinogen.
When PVC is burned or dumped in landfills, dioxins -- highly toxic chemicals that build up in the food chain and can cause cancer, as well as harm the immune and reproductive systems -- are released into the air and water.
"Heat and UV-ray exposure in cars can accelerate the breakdown of these chemicals and possibly increase their toxicity," the Ecology Center said in a statement.
"Babies are the most vulnerable population in terms of exposure, since their bodily systems are still developing and they spend many hours in their car seats."
Ecology Center researchers compiled a list of the best and worst car seats in terms of the chemicals found in them, and posted it on the HealthyStuff.org website.
Levels of bromine varied between different models of the same make of car seat, with the source usually being a flame retardant used in the upholstery or cushioning, research team leader Jeff Gearhart told AFP.
The least toxic infant seats were Italian brand Chicco's KeyFit 30 in the Limonata color scheme, Graco Snugride 35 in Laguna Bay and Combi Shuttle 33 in Cranberry Noche.
Two Graco infant seats with different upholstery -- the Snugride 35 in Edgemont Red/Black and Snugride 30 in Asprey -- were meanwhile among the most toxic.
Using an x-ray fluorescence machine, which identifies the make-up of materials in less than 60 seconds, the Ecology Center has conducted more than 20,000 tests for toxic chemicals on some 7,000 consumer products since 1997.