The most important thing with styrene is it has been put up to "probable" from "possible." The study that tipped the scales is discused here: https://www.sciencedaily.com/releases/2018/05/180530113105.htmIS this junk?
Styrene is widely used in the manufacture of synthetic rubber, resins, polyesters and plastics. Styrene and the primary metabolite styrene-7,8-oxide are genotoxic and carcinogenic. Long-term chemical carcinogenesis bioassays showed that styrene caused lung cancers in several strains of mice and mammary cancers in rats and styrene-7,8-oxide caused tumours of the forestomach in rats and mice and of the liver in mice. Subsequent epidemiologic studies found styrene workers had increased mortality or incidences of lymphohematopoietic cancers (leukaemia or lymphoma or all), with suggestive evidence for pancreatic and esophageal tumours. No adequate human studies are available for styrene-7,8-oxide although this is the primary and active epoxide metabolite of styrene. Both are genotoxic and form DNA adducts in humans.
However it is worth noting that the exposure levels in the 1960s and 70s in industrial settings were simply astounding. The problem I have with CA 65 is that it confounds rather than clarifies risk assessment. Indeed it even implicitly calls into question actual OSHA standards. (100 ppm for styrene).
Styrene carcinogenicy in humans has only been found measurable epidemiologically in industrial settings. Plast ic cups, styrene from drinking out of polystyren cups, using a surfboard, printing yourt resume, none of that is at all extrapolatable as a cancer risk. That is junk science. In this case the science is being junked up by CA rather than junk sceince being quoted (the latter is the glyphosate case).