UNDATED (CNN) -- A just-released study says more than half of children's car seats sold in the U.S. contain hazardous chemicals.
Environmental group "Ecology Center" tested more than 150 car seats. Researches discovered 60-percent of the seats were made with chemicals like chlorine and lead, which are sometimes used as additives in plastics.
The group did not say the levels discovered were high enough to be harmful. But, it says there's been a 64-percent improvement between the 2008 and 2011 models.
The study's list of the least toxic car seats can be found online at HealthyStuff.org.