Cups made with polystyrene foam are disappearing from the marketplace because a bevy of misinformation about their environmental effects, including claims styrene — the chemical used to make them — is a carcinogen.
But a new study issued by the consulting group Gradient Corp. questions claims this chemical poses cancer risks. Specifically, it undermines the National Toxicology Program’s classification of styrene in 2011 as “reasonably anticipated to be a human carcinogen.” The Gradient researchers find:
The epidemiology studies show no consistent increased incidence of, or mortality from, any type of cancer. In animal studies, increased incidence rates of mostly benign tumors have been observed only in certain strains of one species (mice) and at one tissue site (lung). The lack of concordance of tumor incidence and tumor type among animals (even within the same species) and humans indicates that there has been no particular cancer consistently observed among all available studies. The only plausible mechanism for styrene-induced carcinogenesis — a non-genotoxic mode of action that is specific to the mouse lung — is not relevant to humans. As a whole, the evidence does not support the characterization of styrene as “reasonably anticipated to be a human carcinogen,” and styrene should not be listed in the Report on Carcinogens.
Greens may criticize the Gradient study because it was funded by the styrene industry, but they can’t adequately dispute the data. In fact, the International Agency for Research on Cancer (IARC) ranks styrene cancer risks at a lower level than does the NTP. Rather than “reasonably anticipated,” IARC says styrene is “possibly carcinogenic to humans” — the same classification they give to pickles and the coffee I like to enjoy in a foam cup. Like the gradient study, IARC couldn’t even find significant risk among workers exposed to relatively high levels of styrene.
A big part of the problem, as Richard Belzer well documented in a paper for CEI, is that the NTP isn’t particularly scientific. Both its criteria and terminology for classifications are purely subjective, lacking scientific meaning.
Unfortunately, it may take a long time — if ever — for NTP to revise this classification. Consider that it took nearly 30 years for NTP to remove the harmless sugar substitute, i.e., saccharine, from its list of carcinogens. Somehow saccharine survived and remains on the market today. Hopefully, 30 years from now, if I am still alive, I will be able to drink my coffee from a foam cup.
Image credit: HeyRocker on flickr.