Four brands of children’s crayons and two kids’ crime scene fingerprint kits were found to contain asbestos, according a report released Wednesday.

The tests were commissioned by the Environmental Working Group (EWG) action fund, a government-certified laboratory and confirmed by another government-certified laboratory.

Of the 28 boxes of crayons tested, four tested positively for asbestos. Several were marketed under the names of the popular characters Mickey Mouse, Power Rangers and Teenage Mutant Ninja Turtles.

As contaminated crayons are used, they can release microscopic asbestos fibers. The average child uses 730 crayons by age 10, according to a news release from EWG.

Crime scene fingerprint kits were also tested and two of the 21 were found to contain asbestos.

The kits, which instruct children to use dusting powder to identify fingerprints on surfaces, could contaminate children by way of airborn asbestos fibers.

According to the news release, the contaminated crayons were purchased from February to May 2015 from PartyCity and Dollar Tee, in a suburban county near San Francisco. The crime scene toys were purchased through Amazon.com and ToysRUs.com.

The risk of asbestos exposure from the items tested is low, federal regulators said, but scientists and health officials agree that no level of asbestos is safe, the news release noted.

“Asbestos in toys poses an unacceptable risk to children, today as it did in 2000 and 2007, the last time tests found the deadly substance in these children’s products,” Dr. Philip Landrigan, professor of pediatrics and preventive medicine at Mount Sinai Hospital in New York, said in the news release. Landrigan is an internationally recognized asbestos expert and former senior adviser to the U.S. Environmental Protection Agency on children’s environmental health.

The crayons and toys that contained asbestos were made in China and imported in the U.S., according to the package labels.

According to the National Institutes of Health (NIH), breathing in high levels of asbestos over a long period of time can lead to build-up of the fibers in the lungs, which causes scarring, inflammation, and breathing disruption. Long-term consequences include lung cancer and cancer affecting the lining of the lungs or abdomen.