Carcinogenicity of Styrene

Abstract

Styrene is a high production volume chemical primarily used to produce polystyrene polymers and it is found in workplace air in the reinforced plastics industry. Styrene is also present in tobacco smoke, and in air pollution. In March 2018, a Working Group of leading scientists from 24 countries met at the International Agency for Research on Cancer (IARC) in Lyon, France, to re-evaluate the carcinogenicity of styrene (in addition to styrene-7,8-oxide and quinolone, not addressed here), based on published human, animal and mechanistic data. The most informative epidemiological studies were occupational cohort studies conducted in different countries in the reinforced plastics industry, suggesting that exposure to styrene causes lymphohaematopoietic malignancies, with higher consistency in the evidence for leukaemias and in particular myeloid leukaemia. However, confounding by other co-occurring occupational exposures such as butadiene, or the presence of biases or chance due to, for example, small sample sizes could not be ruled out. Evidence in humans for other cancer sites, including lung cancer, was sparse or inconsistent. Inhalation studies in rodents showed increased risk for different types of tumours in both sexes. A large body of mechanistic evidence showed that styrene is rapidly absorbed, distributed and metabolized in humans, potentially leading to genotoxic effects in exposed humans and it can modulate receptor-mediated effects and cell proliferation in various human cell lines and animal models. The conclusion of this evaluation of styrene regarding its carcinogenicity in humans is currently under embargo due to publication in The Lancet Oncology, but results will be presented in full at the time of the ISEE meeting.