The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) of o‐phenylphenol (OPP) and sodium o‐phenylphenol (OPP‐Na), considering all endpoints.
Bladder tumours were observed in rats after supplementation of food with OPP and OPP‐Na. The cause of these is regarded to be a cytotoxic effect in combination with species or gender‐specific factors and the effect is seen especially at high dosages at a saturation range in metabolism. A specific genotoxic effect could not be detected. OPP and OPP‐Na are therefore classified into Carcinogen Category 4; this means if the MAK value is observed, no carcinogenic effects are to be expected. The liver tumours which were observed in male mice are not taken into consideration for this evaluation due to their debatable relevance for humans.
After long‐term administration of 40 mg OPP/kg body weight and day via food supplements, rats showed no adverse effects. This NOAEL is equal to an air concentration of 98 mg/m3. In establishing the MAK value one must take into consideration the systemic effects and additionally the irritant effects of OPP or the corrosive effects of OPP‐Na. There are no data relevant to an evaluation of the local effects on the upper respiratory tract after repeated exposure either for humans or animals. Therefore a comparative structure analysis has been made for OPP to bisphenol A and a MAK value of 5 mg/m3 I established. For OPP‐Na, a structure analogy to calcium hydroxide was considered, based on its alkali strength, and a MAK value of 2 mg/m3 I was set.
Due to irritative effects, Peak Limitation Category I is established for both OPP and OPP‐Na. OPP was assigned an excursion factor of 1 based on the comparative analysis to bisphenol A. For OPP‐Na with its higher water solubility, a comparative analysis based on its alkali strength was made to calcium hydroxide and an excursion factor of 1 was also set.
As the NOAEL for developmentally toxic effects at workplace air concentrations is higher than the MAK value for OPP and OPP‐Na by a factor of 105 and 146, respectively, both substances are classified in Pregnancy Risk Group C.
Skin contact with either OPP or OPP‐Na is not expected to contribute significantly to systemic toxicity.