Orthophenyl phenol

Sodium ortho-phenylphenate produced urinary bladder carcinomas and liver tumours in rodents. IARC classified it as Group 2B, possibly carcinogenic to humans, based on sufficient animal evidence and the absence of human epidemiological data.

Ortho-phenylphenol itself was classified IARC Group 3 (not classifiable as to carcinogenicity in humans) on the basis of limited and inconsistent animal data and no human data.

The carcinogenic mode of action in the bladder is indirect: reactive quinoid metabolites cause cytotoxicity and cell proliferation at neutral or alkaline urinary pH. Evidence for direct DNA binding by OPP or its metabolites is equivocal across more than 130 genotoxicity studies.

Re-evaluation of developmental studies found decreased fetal body weight, increased delayed skeletal ossification and post-implantation losses in rats and mice; increased cleft palate in mice; increased resorptions in rabbits. The authors concluded fetal effects may occur independently of maternal toxicity.

In vitro studies identified very weak oestrogenic activity for OPP, but this was not confirmed in vivo. The French agency ANSM flagged OPP as likely to be an endocrine disruptor, prompting a European cosmetics re-evaluation.

OPP was found in 40 of 60 canned beer samples from multiple countries at concentrations of 1.2 to 40 micrograms per litre, traced to OPP used in can-end sealing compounds.

OPP was also detected in canned soft drinks sampled in the United States and Germany, confirming migration from can materials is a widespread rather than isolated phenomenon.