Assessment of styrene and cancer


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Most recent weight-of-evidence assessment of styrene and cancer

A careful weight of evidence assessment of competing theories of styrene carcinogenicity was submitted by styrene industry toxicologists to a National Academy of Sciences expert committee in February 2013.

Most recent study of cancer in composites industry workers

An update of a large study of reinforced plastic industry workers with relatively high exposures to styrene, published in the March 2013 issue of the journal Epidemiology, examined cancer risks associated with exposure levels. The study includes 15,826 workers who were exposed between 1948 and 1977 with vital-status follow-up from 1948 to 2008. The update found no coherent evidence that styrene exposure increases risk from cancers of the lymphatic and hematopoietic tissue, pancreas, or lung.


 

1993

Health Canada and Environment Canada in 1993 classified styrene as a possible human carcinogen but found that styrene is not entering the environment in a way that was harmful, is “not considered toxic” for regulatory purposes and “does not constitute a danger to human health.” [Health Canada, 1993]

1994

In a 1994 report in the journal Occupational and Environmental Medicine, Otto Wong and coauthors described an investigation of 15,000 styrene-exposed workers with 42 years of follow-up, which concluded “There was no evidence among the findings for a link between styrene exposure or styrene processes and increased mortality from any cause, including cancer. In particular, the study found fewer-than-anticipated cases of lymphoma and leukemia”. (A major update of this cohort was recently completed and the report published in the March 2013 issue of the journal Epidemiology - see reference below.)

2002

In 2002, an expert panel convened by the Harvard School of Public Health found that the styrene health effects data do not suggest that plant neighbors should be concerned about cancer.

In 2002, the International Agency for Research on Cancer reviewed newly available data and determined there is limited evidence in both experimental animals and humans for the carcinogenicity of styrene, and continued its 1987 characterization of styrene as "possibly carcinogenic to humans (Group 2B)". [IARC, 2002]

2007

The United Kingdom's Health and Safety Executive completed in 2007 a very thorough review of styrene data and concluded there is “no clear and consistent evidence for a causal link between specific cancer mortality and exposure to styrene”. The UK assessment was conducted on behalf of the European Union. (Complete EU assessment (also available here); download summary of cancer findings; download letter to NTP explaining the status of the EU styrene assessment.) [EU, 2007]

2008

A thorough assessment by the Texas Commission on Environmental Quality, completed in 2008, found that the data on styrene do not support a concern for cancer. [TX, 2008]

In 2008 an international panel of top epidemiologists reviewed the studies of more than 60,000 workers exposed to styrene, and determined that there is no support for a concern for cancer in humans. The Boffetta, et al. report was published in the Nov. 2009 issue of the Journal of Occupational and Environmental Medicine. Dr. Boffetta was formerly head of epidemiology at the World Health Organization.

2009

In a 2009 letter to NTP, leading styrene toxicity researcher Elizabeth Delzell argued "the available scientific evidence is not sufficient to conclude that styrene causes lymphoma, leukemia or other cancers".

The Agency for Toxic Substances and Disease Registry (ATSDR), which is affiliated with the U.S. Centers for Disease Control and Prevention, following a thorough assessment including peer review, concluded “taken together, the animal and human data indicate that styrene may possibly be a weak human carcinogen.” (ATSDR later disclaimed their original peer reviewed conclusion and issued a non-peer reviewed memo claiming that “may possibly be a weak human carcinogen” means the same as “reasonably anticipated carcinogen”.)

2011

The National Toxicology Program added styrene to its Report on Carcinogen (12th Edition) in 2011, concluding styrene meets NTP's criteria for "reasonably anticipated to be a human carcinogen". [NTP, 2011]

  • NTP advised that "[w]orkers and employers should practice good occupational health behaviors. This may include wearing protective clothing, respirators, and gloves. Work places should be well ventilated."

A review in 2011 by the Danish EPA concluded "based on human studies, there is no clear and consistent evidence for a causal link between specific cancer mortality and exposure to styrene", and "tumours seen in mice are unlikely to be of any relevance for human health". (p.50, 52) [Denmark, 2011]

Lorenz Rhomberg and his colleagues at Gradient Corp. concluded in 2011 "the weight of evidence does not support the listing of styrene as reasonably anticipated to be a human carcinogen". The Gradient review was published in January, 2013 in the journal Human and Ecological Risk Assessment.

  • A summary of the review was published in the March 12, 2012 BNA Daily Environment Report.

European Chemicals Agency Dec., 2011 guidance on compilation of safety data sheets uses styrene as an example, concluding that it is not classified as a carcinogen.

2012

In an appendix to a January 2012 report, Richard Belzer argued that NTP made several critical scientific and procedural errors when it listed styrene as a “reasonably anticipated” carcinogen in the Report of Carcinogens.

George Cruzan and coauthors concluded in a study published in the February 2012 issue of the journal Regulatory Toxicology and Pharmacology, “CYP2F2-generated metabolites, not styrene oxide, are a key event mediating the mode of action of styrene-induced mouse lung tumors”. This finding significantly undercuts NTP’s proposed styrene mode-of-action. A follow-up study is underway.

A journal paper argues “[the RoC] mislabels likely non-carcinogens as reasonably anticipated to be carcinogens. If the RoC were terminated there would be no loss or delay of information available to scientific, public health and regulatory communities.” 

2013

In a study published in the June 2013 issue of the journal Regulatory Toxicology and Pharmacology, genetically modified mice did not develop lung tumors following exposure to styrene or styrene oxide. These "transgenic" (or "humanized") mice have had the human form of the primary styrene metabolizing enzyme genetically inserted following removal of the mouse version of the enzyme.

The report (appendices) of a September 2013 industry-sponsored workshop states the available evidence is consistent with a mouse lung tumor mode of action not likely relevant to humans.

A careful weight of evidence assessment of competing theories of styrene carcinogenicity was submitted by styrene industry toxicologists to a National Academy of Sciences expert committee in February 2013. [SIRC, 2013]

An update of a large study of reinforced plastic industry workers with relatively high exposures to styrene, published in the March 2013 issue of the journal Epidemiology, examined cancer risks associated with exposure levels. The study includes 15,826 workers who were exposed between 1948 and 1977 with vital-status follow-up from 1948 to 2008. The update found no coherent evidence that styrene exposure increases risk from cancers of the lymphatic and hematopoietic tissue, pancreas, or lung. 

2014

A peer review report issued July 28, 2014 by the National Reserach Council of the National Academies endorsed the listing of styrene as "reasonably anticipated to be human carcinogen". [NRC, 2014]

2015

In March 26, 2015 comments to Cal-EPA, SIRC argued "Based on new human and mode of action studies, coupled with NTP’s failure to consider scientific data and well-established scientific principles in reinterpreting NCI (1979), there is no basis for OEHHA to list styrene under the authoritative bodies listing mechanism because it is clearly established that the sufficiency of evidence criteria were not met."