Warnings about the toxicity of polymer clay have been circulating since the late 1980s, and many people avoid the stuff for fear that it will cause cancer or health problems. While there are different formulas of polymer clay available, all are safe to handle in small amounts and many are safe for kids. It's simply a matter of reading the label.

Polymer Clay Hazards
Polymer clay is a mixture of PVC plastic and phthalates, chemicals used as plasticizing thinners to keep the clay soft and moldable. PVC plastics are used in many products, and they're commonly found in drain pipes in homes. PVC in its finished form poses no known dangers, though there are environmental pollutants released when it's manufactured, and chemicals may be released when PVC catches fire or starts to break down in landfills. As a general rule, PVC is safe. It's so safe, in fact, that it's commonly used in children's toys.

Phthalates tend to be a greater cause of concern. Phthalates as a group got a bad name when research revealed a link between dioctyl phthalate and insulin resistance, a potential precursor to diabetes, and small genetalia in baby boys. Dioctyl phthlate has been banned from polymer clays and children's toys and is no longer used in the manufacture of polymer clay in the United States.

Checking Product Labels
Reading the labels of polymer clays can tell you a lot about their safety. If you see the letters AP on the label, that certifies that the product has been tested by the Arts & Crafts Materials Institute and has been certified to be non-toxic. This testing is conducted with the assistance of medical doctors and the results are reviewed by a medical board. Any product with an AP is safe for children to handle.

If the label has the letters CP instead of AP, it means that the product has been tested but has yet to receive final certification. These products should only be used by adults. A clay label that says the product conforms to the ASTM D-4326 standard has been approved as non-toxic for adults only, and shouldn't be used by children.

Polymer Clay and Food
Some people get confused when they see the words "non-food-grade" or "not for use with food" on clay labels, believing that something sinister will seep from the clay into their dinner. In reality, the opposite is true. Since clay is so porous, there's no way to clean out every bit of food residue, making a homemade bowl a haven for bacteria that can cause food-borne illnesses.

It's safe to allow polymer clay to contact food, but you shouldn't use homemade clay pieces for storage or serving. You should also thoroughly clean your oven after baking clay pieces to make sure there are no bits of clay left behind. When clay is heated, it releases hydrochloride gas. The smell is unpleasant and the gas can irritate eyes and mucus membranes, but it doesn't lead to chronic health problems.