A new study by researchers at the University of California at Berkeley has found that flame-retardants are prevalent in preschools. Flame-retardants may expose young children to chemicals that are known to be hazardous.

The researchers looked at 40 childcare centers that watch close to 2,000 children in Monterey and Alameda counties. The researchers collected air and floor dust samples when the children were present and tested for 14 different flame retardant products.

The study found flame retardant chemicals in all of the dust samples collected, but not in the air samples.

“These findings underscore how widespread these materials are in indoor environments,” said Asa Bradman, lead author of the study and associate director of the Center for Children’s Environmental Health Research at UC Berkeley. “A growing body of research has found links between flame retardants and a range of human health effects, including neurodevelopmental delays in children. Children are more vulnerable to the health effects of environmental contaminants, so we should be particularly careful to reduce their exposure to harmful chemicals.”

Among the products that contained the chemicals were sofas and nap mats.

California banned some of the chemicals found in the study in 2006. Furniture manufacturers began phasing them out, according to the researchers, but products made before the ban are still found in many homes and facilities.

Gov. Jerry Brown has updated rules that go into effect next year requiring fabrics on upholstered furniture to be able to withstand smoldering flames, such as that of a cigarette. The researchers say furniture manufacturers will be able to meet that standard without using the banned chemicals.

The study was published in Chemosphere.