Formaldehyde, used in composite wood products, plastics, as a lab preservative and in some hair straightening products has been added to the US government’s Report on Carcinogens. It’s been listed as “known to be a human carcinogen,” says an announcement. Styrene, the chemical used in the manufacture of styrofoam, has been listed as “reasonably anticipated” to cause cancer. Cautions the announcement, “A listing in the Report on Carcinogens does not by itself mean that a substance will cause cancer. Many factors, including the amount and duration of exposure, and an individual's susceptibility to a substance, affect whether a person will develop cancer." The risk, say experts, largely comes from the substances’ uses in industry. There are now 240 substances on the list.