Short-term oral toxicity study of FAVOR PAC in rats.

A short-term rat feeding study was conducted to evaluate the oral toxicity of FAVOR PAC (CAS Registry No. 9003-04-7), one member of a family of cross-linked sodium polyacrylate polymers developed by Stockhausen GmbH & Co KG (Krefeld, Germany). FAVOR polymers are classified as superabsorbent polymers because of their ability to absorb and retain large volumes of fluid. In this short-term study, three groups of 10 male and 10 female Sprague-Dawley rats were administered 0 (control), 1, or 5% FAVOR PAC in the diet daily for up to 32 days. No significant changes in clinical signs, body weight and food consumption, functional observation battery results, ophthalmoscopy, hematology and clinical chemistries, or absolute and relative organ weights were observed. Significant differences between treated and control animals were limited to increases in water consumption and modifications in urinary ionic excretion. Both findings were likely the result of the relatively high concentration of sodium in the test article, and thus consistent with adaptive physiologic changes, not overt toxicity. In conclusion, levels of up to 5% FAVOR PAC in the diet produced no treatment-related toxicity in rats under the conditions of this short-term test (i.e., a NOAEL of 5% FAVOR PAC in the diet was identified).

Mutagenicity studies of FAVOR PAC.

A series of in vitro and in vivo assays have been conducted using FAVOR PAC (CAS Registry No. 9003-04-7), a cross-linked sodium polyacrylate polymer, to test its ability to induce mutations. FAVOR PAC is a member of the FAVOR family of superabsorbent polymers (SAPs) developed by Stockhausen GmbH & Co KG (Krefeld, Germany). These SAPs are known for their ability to retain large volumes of fluid, even against pressure. The genotoxic potential of FAVOR PAC and its extracts was examined in the following five standard mutagenicity assays: the Salmonella typhimurium and Escherichia coli reverse mutation assay, the mouse lymphoma fluctuation assay, the mouse lymphoma forward mutation assay, the in vivo mouse micronucleus assay, and an in vitro rat DNA synthesis assay. Based on the results of these assays, it was concluded that FAVOR PAC was clearly not genotoxic under any of the conditions of the mutagenicity assays performed.

Disposition of radiolabeled FAVOR PAC in rats.

FAVOR is the name for a family of superabsorbent cross-linked sodium polyacrylate polymers developed by Stockhausen GmbH & Co KG (Krefeld, Germany) that are known for their ability to absorb and retain large volumes of fluid. The absorption, distribution, rates and routes of excretion of radiolabeled FAVOR PAC (CAS Registry No. 9003-04-7; [14C]FAVOR PAC), one member of the FAVOR family, were evaluated following a single oral administration of the compound. Male Sprague-Dawley rats were administered single doses of 26 to 39 mg/kg [14C]FAVOR PAC by gavage. Approximately 98.8% (normalized mean) of the total administered dose was excreted in the feces within 5 days, and the majority ( approximately 88%) was excreted within the first 24 h. Urinary excretion accounted for 0.69% (normalized mean) of the total administered dose. Recovery of radioactivity in the organs, tissues, and carcass was generally less than 0.5% of the dose administered. Levels of total radioactivity in whole blood ranged from 0.75 to 1.20 microg equiv/g. Biliary elimination of total radioactivity accounted for less than 0.1% of the dose administered. The results indicate that FAVOR PAC is poorly absorbed and rapidly eliminated in feces following oral administration.

Single-dose oral toxicity study of a cross-linked sodium polyacrylate/polyvinyl alcohol copolymer in chickens (Gallus domesticus).

A single-dose oral toxicity study of a grafted copolymer of cross-linked sodium polyacrylate with polyvinyl alcohol was conducted in chickens (Gallus domesticus) to demonstrate this copolymer's safety for use as a hydration medium in recently hatched poultry chicks. Three experimental groups, each composed of 25 male and 25 female 1-day-old chicks, were administered a one-time dose of 0, 3, or 6 g of the hydrated test article by gavage. All chicks were monitored daily for mortality and morbidity during their typical grow-out period of approximately 8 weeks. Interim sacrifices of one animal of each sex from each treatment group were made at 1, 2, 4, and 6 weeks. All surviving animals were necropsied at the end of the study. A single dose of up to 6 g of hydrated copolymer did not adversely affect these animals during their grow-out period. Mortality was comparable across all experimental groups, as no statistically significant survival differences were found. Body weights were also comparable across the three experimental groups at all time points during the study, and no statistically significant differences were detected in mean terminal body weights among the groups. Finally, lesion frequencies were similar across the three experimental groups, with none of the lesions deemed related to administration of the test article. Thus, the safety of this cross-linked sodium polyacrylate/polyvinyl alcohol copolymer has been demonstrated for its intended use.

Biodegradation of superabsorbent polymers in soil.

Biodegradation of two superabsorbent polymers, a crosslinked, insoluble polyacrylate and an insoluble polyacrylate/ polyacrylamide copolymer, in soil by the white-rot fungus, Phanerochaete chrysosporium was investigated. The polymers were both solubilized and mineralized by the fungus but solubilization and mineralization of the copolymer was much more rapid than of the polyacrylate. Soil microbes poorly solublized the polymers and were unable to mineralize either intact polymer. However, soil microbes cooperated with the fungus during polymer degradation in soil, with the fungus solubilizing the polymers and the soil microbes stimulating mineralization. Further, soil microbes were able to significantly mineralize both polymers after solubilization by P. chrysosporium grown under conditions that produced fungal peroxidases or cellobiose dehydrogenase, or after solubilization by photochemically generated Fenton reagent. The results suggest that biodegradation of these polymers in soil is best under conditions that maximize solubilization.

Cellobiose dehydrogenase-dependent biodegradation of polyacrylate polymers by Phanerochaete chrysosporium.

When Phanerochaete chrysosporium was cultured using conditions which promote the expression of cellobiose dehydrogenase (CDH), but not the ligninolytic peroxidases, the fungus effectively solubilized and mineralized an insoluble, crosslinked polyacrylate and an insoluble polyacrylate/polyacrylamide copolymer. Addition of iron to the cultures increased CDH activity in the cultures and the rate and extent of solubilization and mineralization of both polymers. Solubilization of both polymers was observed when incubated with purified CDH, ferric iron and hydrogen peroxide.

Biodegradation of crosslinked acrylic polymers by a white-rot fungus.

Two synthetic superabsorbent crosslinked acrylic polymers were mineralized by the white-rot fungus Phanerochaete chrysosporium. The amount of polymer converted to CO(2) increased as the amount of polymer added to the cultures increased. In the presence of sufficiently large amounts of the superabsorbents, such that all of the culture fluid was absorbed and a gelatinous matrix was formed, the fungus still grew and mineralization was observed. Neither the polymers, nor their degradation products were toxic to the fungus. While the rates of mineralization were low, all of the polymers incubated in the liquid fungal cultures were completely depolymerized to water soluble products within 15-18 days. The depolymerization of the polymers was observed only in nitrogen limited cultures of the fungus which secrete the lignin degradation system, however, the water soluble products of depolymerization were mineralized in both nutrient limited and sufficient cultures of the fungus. The rate of mineralization of the depolymerized metabolites was more than two times greater in nutrient sufficient cultures. Following longer incubation periods, most (> 80 %) of the radioactivity was recovered in the fungal mycelial mat suggesting that carbon of the polymer had been converted to fungal metabolites.