Good Night Styrene

Perri Klass is a pediatrician who writes fiction and non-fiction. Her editorial article on “disruptive chemicals,” in this week’s Science Section of the New York Times contained large segments of fiction.[1]  The Times gives Dr. Klass, along with Nicholas Kristof and others, a generous platform to advance their chemophobic propaganda, on pesticides, phthalates, bisphenols, and flame retardants, without the bother of having to cite evidence. It has been just two weeks since the Times published another Klass fear piece on hormone disrupters.[2]

In her Science Times piece, Klass plugged Leonardo Trasande’s book, Sicker, Fatter, Poorer: The Urgent Threat of Hormone-Disrupting Chemicals to Our Health and Future . . . and What We Can Do About It (2019), to help wind up parents about chemical threats everywhere. Trasande, is “an internationally renowned leader in environmental health” expert; his website tells us so. Klass relies so extensively upon Trasande that it is difficult to discern whether she is presenting anything other than his opinions, which in some places she notes he has qualified as disputed and dependent upon correlational associations that have not established causal associations.

When it comes to recyclable plastic, number 6, Klass throws all journalistic caution and scientific scruple aside and tells us that “[a] number 6 denotes styrene, which is a known carcinogen.”[3] Known to whom? To Trasande? To Klass? To eco-zealots?

The first gaffe is that number 6 plastic, of course, is not styrene; rather it is polystyrene. Leaching of monomer certainly can occur,[4] and is worth noting, but equating polystyrene with styrene is simply wrong. The second gaffe, more serious yet, is that styrene is not a “known” carcinogen.

The International Agency for Research on Cancer, which has been known to engage in epistemic inflation about carcinogenicity, addressed styrene in its monograph 82.[5] Styrene was labeled a “2B” carcinogen, that is possible, not probable, and certainly not “known.” Last year, an IARC working group revisited the assessment of styrene, and in keeping with its current practice of grade inflation bumped styrene up to Group 2A, “probably carcinogenic to humans” based upon limited evidence in human being and sufficient evidence in rats and close relatives.[6] In any event, the IARC Monograph number 121, which will address styrene, is under preparation.

A responsible journalist, or scientist, regulator, or lawyer, is obligated however to note tha “probably” does not mean “more likely than not” in IARC-jargon.[7] Given that all empirical propositions have a probability of being true, somewhere between 0 and 100%, but never actually equal to 0 or 100%, the IARC classifications of “probably” causing cancer are probably not particularly meaningful.  Everything “probably” causes cancer, in this mathematical sense.[8]

In the meanwhile, what does the scientific community have to say about the carcinogenicity of styrene?

Recent reviews and systematic reviews of the styrene carcinogenicity issue have mostly concluded that there is no causal relationship between styrene exposure and any form of cancer in humans.[9] Of course, the “Lobby,” scientists in service to the litigation industry, disagree.[10]


[1]  Perri Klass, “Beware of Disruptive Chemicals,” N.Y. Times (April 16, 2019).

[2] Perri Klass, “How to Minimize Exposures to Hormone Disrupters,” N.Y. Times (April 1, 2019).

[3]  Klass (April 16, 2019), at D6, col. 3.

[4]  See, e.g., Despoina Paraskevopoulou, Dimitris Achiliasa, and Adamantini Paraskevopoulou, “Migration of styrene from plastic packaging based on polystyrene into food simulants,” 61 Polymers Internatl’l 141 (2012); J. R. Withey, “Quantitative Analysis of Styrene Monomerin Polystyrene and Foods Including Some Preliminary Studies of the Uptake and Pharmacodynamics of the Monomer in Rats,” 17 Envt’l Health Persp. 125 (1976).

[5]  IARC Monograph No. 82, at 437-78 (2002).

[6]  IARC Working Group, “Carcinogenicity of quinoline, styrene, and styrene-7,8-oxide,” 19 Lancet Oncology 728 (2018).

[7]  The IARC Preamble definition of probable reveals that “probable” does not mean greater than 50%. See also “The IARC Process is Broken” (May 4, 2016).

[8] See Ed Yong, “Beefing With the World Health Organization’s Cancer Warnings,” The Atlantic (Oct 26, 2015).

[9]  Boffetta, P., Adami, H. O., Cole, P., Trichopoulos, D. and Mandel, J. S., “Epidemiologic studies of styrene and cancer: a review of the literature,” 51 J. Occup. & Envt’l Med. 1275 (2009) (“The available epidemiologic evidence does not support a causal relationship between styrene exposure and any type of human cancer.”); James J. Collins & Elizabeth Delzell, “A systematic review of epidemiologic studies of styrene and cancer,” 48 Critical Revs. Toxicol. 443 (2018)  (“Consideration of all pertinent data, including substantial recent research, indicates that the epidemiologic evidence on the potential carcinogenicity of styrene is inconclusive and does not establish that styrene causes any form of cancer in humans.”).

[10] James Huff & Peter F. Infante, “Styrene exposure and risk of cancer,” 26 Mutagenesis 583 (2011).

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