From: Health Canada

Health Canada is advising Canadians not to buy an unregistered, highly toxic pesticide product being imported from China and sold in various retail outlets as “insecticide chalk.” The product is sold under names such as “Miraculous Insecticide Chalk,” “Insecticide Chalk,” and “Cockroach Chalk.”

Insecticide chalk is not registered for use in Canada. Samples tested contain deltamethrin, a pesticide that can cause serious health effects when used inappropriately. Children are especially at risk from insecticide chalk because they can easily mistake the product for blackboard or sidewalk chalk and play with it or put it in their mouths.

Overexposure to some chemicals found in insecticidal chalk can cause vomiting, stomach pains, convulsions, tremors and loss of consciousness. Serious allergic reactions are also possible.

Click on the above link for more information on this warning.