2-PHENYLPHENOL AND ITS SODIUM SALT EXPLANATION First draft prepared by Professor C.L. Berry, London Hospital Medical College, United Kingdom 2-Phenylphenol (OPP, o-phenylphenol) and its sodium salt (SOPP) were previously reviewed by the Joint Meeting in 1969, 1983, 1985, and 1989 (FAO/WHO 1970ab, 1984, 1986ac, and 1989b. A temporary ADI was allocated in 1983, which was extended in 1985 and 1989. EVALUATION FOR ACCEPTABLE INTAKE Toxicological studies Reproduction study One hundred forty male and 140 female albino Sprague-Dawley rats, nine weeks old at the start of the study, were divided into four dose groups of 35 rats/sex/group, and fed 0, 40, 140 or 490 mg/kg bw/day of technical grade OPP (99.4 - 99.5% pure) administered in the diet in 1% corn oil (actual doses were 25, 125, and 460 mg/kg bw/day based on analysis of the diet consumed). Adjustment of dosage during the pre- mating period was made according to body weight changes. During lactation adjustments in dose were made to avoid overdosing the pups but this was later considered unnecessary. A number of animals were removed from the study in order to examine the heritability of hypotrichosis (two high dose F1 females and 12 F2a pups). Parents (F0) for the F1 generation were randomly assigned to dosage groups. For F1 parents the genealogy of the F1b pups was checked to prevent the mating of litter mates. For the production of the F2 generation, a total of 132 male and 134 female F1b pups were randomly selected using one or more pups/sex/litter as parents (F1) and divided into 35 pairs of rats per dose group except for the controls which had 27 males and 29 females. Estrus cycles were studied by vaginal smears. The animals were examined daily and routine observations of birth statistics and pup weights were made and culling to eight pups was performed where necessary. Standard observations with the addition of extensive examination of the histology of the urinary tract were carried out when the animals were sacrificed. There were no treatment related effects on clinical signs, gestational or lactation body weight gain or any of the reproductive variables examined. Histological examinations of the adults and pups revealed no significant changes in the reproductive tracts. The following changes were observed: 1. There was a treatment related decrease in body weight in the high dose F0 and F1 animals which was not clearly related to decreased food consumption. 2. There was a significant decrease in weight in the high dose F1b, F2a, and F2b pups at 14 and/or 21 days during lactation, an effect not seen in the first week of post- natal life. This indicated that development had not been disturbed. A no reproductive effect level of 490 mg/kg bw/day was set. Relative renal weight was increased in a dose related manner in the absence of other organ weight changes, in high dose F0 and F1 males. The incidence of calculi in the urinary tract was increased in male rats in the 140 and 490 mg/kg bw/day groups. Transitional cell hyperplasia occurred in the urinary bladder. The report defines this change as "an area (focal or diffuse) of at least three to four cells thick (of cuboidal cells) in an inflated bladder" where normal bladders had a cell thickness of one or two flattened cells. These changes were quantified by simple morphometry which indicated a compound related effect in the bladder in 140 and 490 mg/kg F0 males and females and in the 490 mg/kg F1 males. Neoplasms of the urinary tract were found in 4 rats, 1 bladder and 1 ureteric tumour in the 140 mg/kg group and 2 bladder tumours in the 490 mg/kg group. The NOAEL for these effects was 40 mg/kg bw/day (Eigenberg, 1989). Special studies on interactive effects (ascorbic acid, saccharin and hippuric acid) Male F344 rats were given OPP or SOPP at 2% in feed for a period of 24 weeks. Groups of treated animals also received ascorbic acid (AS) sodium ascorbate (SA) acid saccharin (SAC), sodium saccharin (SSAC), hippuric acid (HI) or sodium hippurate (SHI) at 5% in the feed (20 animals/group). Urinary sodium concentration was increased in all animals receiving sodium salts in the diet and in SOPP treated animals. The pH value of the urine increased after SOPP, SA and SSAC and urine osmolarity was decreased by SOPP, SA and SHI. OPP decreased osmolarity but did not affect urinary pH or sodium concentrations. Histopathologically, the bladders showed epithelial thickening (4-8 cell epithelial thickness) at 8, 16, and 24 weeks after SOPP and papillary and nodular changes at 16 and 24 weeks. Treatment with other sodium salts provoked "slight to moderate" hyperplasia at 8 and 16 weeks but no papillary or nodular changes; these changes had regressed by 24 weeks. A combination of raised urinary pH and sodium acted as promoting agents for SOPP; SHI raised urinary sodium but not pH and was without effect (Fukushima et al., 1986). An essentially similar study was done in male F344 rats (31 animals/group) using NaHCO3 to raise the urinary pH and NH4C1 to lower it. Both OPP and SOPP were examined (at 1.25% and 2% in the diet respectively). Changes were seen in all 4 groups and can be summarized as follows: hyperplasia of the bladder epithelium occurred with OPP, OPP, and bicarbonate and SOPP. SOPP with NH4C1 had no significant effect. Tumours were significantly increased after OPP (12/31), SOPP (22/31) and OPP plus NaHCO3 (20/31). Only 3 tumours were seen in 31 rats after SOPP and NH4C1. The oncogenic effects of OPP were promoted in alkaline urine and those of SOPP were inhibited in acid urine (Fujii et al., 1987). COMMENTS Previous concerns about 2-phenylphenol and its sodium salt have focused on the urothelial carcinogenicity of the compound in the rat. The many carcinogenicity and metabolic studies now available have provided data which are reassuring with regard to this effect. The ADI was based on the study in rats in which a clear no-effect level for proliferative effects in the urothelium was observed. Because the rat is clearly an extremely sensitive species for this effect, a hundred-fold safety factor was considered to be appropriate. The available data now make previous requirements for additional information unnecessary. No further carcinogenicity/ long-term toxicity studies in rats are needed and metabolic studies in other species are of less significance than the qualitative and quantitative monitoring data of the urinary excretion of 2-phenylphenol and its metabolites by those regularly exposed to 2-phenylphenol or sodium 2- phenylphenate. There were no significant findings in the rat reproduction study apart from the urothelial lesions. The ADI was established on the basis of the NOAEL in the rat long-term study. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Rat: 40 ppm in the diet (equivalent to 2 mg/kg bw/day) Dog: 300 mg/kg bw/day Estimate of acceptable daily intake for humans 0 - 0.02 mg/kg bw Studies which will provide information valuable in the continued evaluation of the compound Further observations in humans. REFERENCES Eigenberg, D.A. (1989). Two-Generation dietary reproduction study in rats using Orthophenylphenol. Unpublished report number 85-671-02 from Health, Environment and Safety, Corporate Toxicology Department, Mobay Corporation. Submitted to WHO by Bayer AG, Leverkusen, Germany. Fukushima, S., Shibata, M.A., Kurata, Y., Tamano, S., and Masui, T. (1986). Changes in the urine and scanning electron microscopically observed appearance of the rat bladder following treatment with tumour promoters. Jpn. J. Cancer Res. 77:1074-1082. Fujii, T., Nakamura, K., and Hiraga, K. (1987). Effects of pH on the carcinogenicity of o-phenylphenate in the rat urinary bladder. Fd. Chem. Toxic. 25:259-362.
See Also: Toxicological Abbreviations Phenylphenol, 2- (FAO/PL:1969/M/17/1) Phenylphenol, 2- (WHO Pesticide Residues Series 5)