Lack of Carcinogenicity of Sodium Metaphosphate in Fischer 344 Rats.

The carcinogenicity of sodium metaphosphate (SMP) was examined in F344 rats of both sexes. SMP was mixed in basal diet at levels of 0, 1.5 or 3.0%, and groups of 50 male and 50 female rats were administered each of these diets ad libitum. At final sacrifice no statistically significant differences between treated and control groups regarding mean body weight, or total intake were observed in either male or female. The results of urine and serum analysis, or hematological determinations studies show that there was no significant difference between test group and control group. Many tumors developed in all groups including the controls and the organ distribution of neoplasms and their histological characteristics did not differ significantly from those reported to occur spontaneously in this strain of rats. From these findings, it was concluded that sodium metaphosphate does not induce tumours, when given orally at doses of up to 3.0% mixed in basal diet for 108 weeks. With regard to non-neoplastic lesions, there were non-neoplastic lesions in kidneys, mineralization, cast formation and basophilic tubular cell proliferation present in greater proportion in female rats treated with sodium metaphosphate than in non-treated female rats. Mineralization was seen as marked calcium deposition in the pars intermedia of the kidney in female rats treated with 3.0% sodium metaphosphate.