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"By denying scientific principles, one may maintain any paradox." – Galileo Galilei

Iarc says plastics component styrene is ‘probably carcinogenic’


Agency also reviewed quinoline and styrene-6,8-oxide

9 May 2018 / CMRs, Global, Toxicology
By Andrew Turley

Styrene, a key component for many plastics, is “probably carcinogenic to humans”, according to the WHO’s International Agency for Research on Cancer (Iarc).

The conclusion corresponds to group 2A of the agency’s classification scheme and could have immediate implications, wherever local chemicals legislation incorporates Iarc classifications as regulatory ‘triggers’, for example in California.

Styrene previously had group 2B classification (“possibly carcinogenic to humans”), based on a 2002 monograph.

Globally, manufacturers produce about 20m tonnes of styrene a year, according to the International Styrene Industry Forum (ISIF). This is used primarily as a monomer in the production of plastics, particularly polystyrene, which accounts for about half of global production.

Other materials incorporating the substance include:

  • acrylonitrile-butadiene styrene (ABS);
  • styrene-acrylonitrile (SAN);
  • styrene-butadiene rubber (SBR);
  • unsaturated polyester resin (UPR), more commonly known as fibreglass; and
  • polystyrene foam, which comes in two types, extruded and expanded.

The evidence from human studies – which focused on workers making reinforced plastics – was “limited”, says Iarc’s monograph working group, in a summary paper published in The Lancet Oncology. The studies did provide “credible evidence that exposure to styrene causes lymphohaematopoietic malignancies”, but there was no way to rule out “confounding, bias or chance”.

In contrast, the evidence from animal studies was “sufficient”, and there was strong evidence of a mechanism that operates in humans and that it is genotoxic.

The same working group also reviewed the evidence for quinoline, a high production volume chemical used to make drugs and dyes; and styrene-6,8-oxide, which is primarily used to make epoxy resins. It concluded that both were also group 2A substances (“probably carcinogenic to humans”).

Upcoming meetings

Iarc monograph working groups will meet on:

  • 5-12 June, to review “isobutyl nitrite, β-picoline and some acrylates”; and
  • 9-16 October, to review “some nitro-benzenes and other industrial chemicals”.

And a Iarc advisory group will meet on 12-13 November to recommend an update to the Monographs Preamble. This describes evidence that should be evaluated under the monographs programme.

However, the American Chemistry Council (ACC) says the meeting should be delayed until January 2019, when current Iarc director Christopher Wild completes his term and the role is handed over. The ACC expects the agency’s governing council to appoint a new director “within weeks”.