Chalk is not manufactured with talc, a binding agent that is used in some brands of crayons, according to CPSC. Talc can sometimes be contaminated with other minerals such as asbestos or "transitional" fibers.
CPSC tested the chalk of five major manufacturers after reports that chalk and children's crayons may contain asbestos. In June, the commission announced test results that found a trace amount of asbestos and larger amounts of "transitional" fibers in some crayons made by Crayola and Prang. The risk of exposure to these fibers was very low. Still, CPSC asked manufacturers to reformulate their crayons to eliminate the fibers, which they will do within one year.
Because tests concluded that there was no cause for concern, Crayola and Prang crayons can continue to be used and purchased, according to CPSC.