(CNN) -- More than half of all young children in the United States attend a day care center or preschool, sometimes spending up to 50 hours a week at these facilities. Their parents should listen up:
A new study, published in the journal Chemosphere, finds these child care centers can host high levels of dangerous, flame-retardant chemicals.
Lead study author Asa Bradman recalls first learning about the dangers of some of these chemicals when he was in high school.
"You know, 35 years later, I'm surprised to find these materials in an environment where young children spend a lot of time," he said.
Bradman is associate director of the Center for Environmental Research and Children's Health at University of California, Berkeley's School of Public Health.
The study authors evaluated the dust and air of 40 child care centers in California, ranging from in-home day care to private schools to government-funded preschool programs. Bradman and his colleagues surveyed the samples for 18 flame-retardant chemicals, including a family of chemicals known as PBDE's, some of which are banned by the European Union.
All of the dust samples had flame-retardant chemicals in them. The concentration levels were similar to what previous studies have found in homes, the study authors say. While all the dust samples were found to have traces of the tested compounds, flame-retardant levels in air samples were much lower.
There's a growing body of scientific evidence linking these chemicals to low birth weights, hormone imbalances and even cancer.
Arlene Blum, director of the Green Science Policy Institute, said the chemicals' potential impact on the brain and reproductive systems are of particular concern for young children because their systems are still developing. Young children are particularly vulnerable, explained Blum, because they "tend to crawl in the dust and put their hands in their mouths."
Blum, who was not involved in the study, said these flame-retardant chemicals likely made their way into the dust and air of schools from the foam of couches, furniture and children's products such as sleeping mats.
Bradman and his colleagues found that schools using upholstered furniture and foam napping mats had the highest concentrations of the chemicals.
"Child care environments aren't unlike other home and indoor environments," Bradman explained. "The message here is that child care is not uniquely unsafe for kids. Rather it's an environment that we haven't looked at much."
In a statement, the North American Flame Retardant Alliance said, "Independent research shows that flame retardants play an important role in protecting people from the devastation of fire. This layer of protection is particularly important for vulnerable populations, including the elderly and young children, who are disproportionately affected by fires."
“It’s important to remember that flame retardants, like all chemicals, are subject to review by the EPA and other governmental agencies in the U.S. and around the world.”
Blum said that there is good news in this. While foam companies long used flame retardants to meet safety standards, those standards are changing.
So how can parents tell if their child's day care's couch - or even their own furniture at home - has flame retardants in them? Look for a tag that says "CA TB-117," which indicates the product has flame retardant foam in it. A tag with "TB 117-2013" means no flame retardants are included.