They're some of the hottest items on your kids back to school list, but some popular school supplies could be putting your kid's health at risk.

Phthalates are chemicals used to soften plastic, and the Center for Health, Environment and Justice found low levels of the chemical in 75 percent of school supplies they tested, including lunch bags and backpacks.

At high levels, phthalates have been linked to some serious health risks, such as reproductive birth defects and asthma.

If those items were toys, they would be illegal. But school supplies aren't considered toys, meaning the rules do not apply.

According to the Centers for Disease Control, the health effects from low levels of phthalates are unknown. Other experts say there?s no reliable evidence that the chemicals have caused harm.

Some researchers are pushing manufacturers to place a warning label on products that contain phthalates.

Center for Health, Environment and JusticeFull report on toxic chemicals inside back to school supplies

Centers for Disease Control Fact Sheet on Phthalates

American Chemistry CouncilPlastics industry response to Phthalates report