Metabolic behaviour of water-soluble fluorescent whitening agents in the rat and bean plant

The behaviour of three representative water-soluble fluorescent whitening agents (FWAs) was studied in rats and bean plants using 14C-labelled compounds. Following oral doses of 5 mg/kg of each of the FWAs to rats, rapid and complete excretion of radioactive material was observed, with an excretion half life ranging from 7-13 hours. Faeces were practically the only route of excretion, indicating, in combination with the short half life times, that no significant amounts of whitener were absorbed from the digestive tract. No radioactive residues were found in blood, liver, kidney, brain, muscle, or fat 96 hours after dosing (limit of quantitative determination 0.005-0.01 ppm Fwa equivalents). Whereas, after application of compound (1) and compound (3), radioactive material was completely extractable from faeces in the form of unchanged parent compounds, that in the compound (2) experiments was not extractable. When bean plants (Phaseolus vulgaris) were grown in the presence of 14C-labelled compound (3) in nutrient solution (11.5 ppm) and in soil (,7.5 ppm), approximately 55% and 2% of the applied radioactive material, respectively, was absorbed by the plants. More than 90% of thie material was bound to the roots in both experiments 40 days after the application. Eight percent of the radioactive material absorbed in the soil experiment was translocated mainly into the stems whereas only trace amounts of the order of less than 0.1 ppm reached the leaves and bean pods. It is concluded from these experiments with extremely high concentrations of compound (3) that under the conditions which may occur in practice residues of water-soluble FWAs do not appear in substantial amounts in edible parts of crops.