The National Research Council Monday reaffirmed that styrene -- the key chemical component of foam cups and other food service items -- might cause cancer in people.
A panel of 10 experts in medicine, chemistry and toxicology used a rather stilted definition, "reasonably anticipated to be a human carcinogen," to uphold the same finding from three years ago by the National Toxicology Program in its 12th Report on Carcinogens.
"I think it's important to keep in mind that this is a hazard assessment," said Dr. Jane Henney, who chaired the research council's committee of experts.
"Our report says this chemical could be a problem, but a full risk-assessment on dose, exposure, quantification and further characterization of the risk would need to be done before one would think about regulation in this area," added Henney, who headed the U.S. Food and Drug Administration during the Clinton administration.
Henney said her panel's conclusion -- "reasonably anticipated to be a human carcinogen" -- means there is scientific evidence suggesting that styrene causes cancer, but that there might be "alternative explanations, such as chance, bias, or confounding factors," according to the report.
Another definition, "known to be a carcinogen," sets a much higher bar. It states overwhelming scientific evidence and leaves no element of doubt. Neither the council nor the toxicology program used that definition.
The National Toxicology Program is part of the National Institutes of Health. The National Research Council is a major policy body and division of the National Academies, which includes the Institute of Medicine, the National Academy of Science and the National Academy of Engineering.
Styrene is a widely used compound in resins and plastics, but is best known to the public as the polymer polystyrene, which is widely used in plastic foam products.