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Ecotoxicological information

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C4 fluorinated isonitrile is a gas. The maximum attainable water concentration in a water solubility test conducted under a pure substance headspace was 272 µg/L, however the substance itself is hydrolytically unstable. In tests conducted using aquatic test media under conditions similar to a toxicity test (shaking for algae medium, still for daphnid medium), small volumes of gas were injected into sealed containers completely filled with medium, and then held for 48 hours. Analyses were completed as soon as possible after test vessel assembly, at 24 hours, and at 48 hours. The parent was analyzed in the limited headspace and in solution, and the hydrolysis product was measured in solution only. Average mass balances during these tests were 98-108%, indicating that all parent and degradation product were recovered. In the daphnia medium experiment (unshaken), ca. 75% of the parent gas remained in the headspace. The aqueous concentration of parent declined from 200 µg/L to 30 µg/L within 48 hours, while the concentration of hydrolysis product increased from 700 µg/L at time zero to 40,000 µg/L at 48 hours. The total process (entry into the aquatic phase and hydrolysis) showed first-order kinetics, indicating that the process was limited by transport into the dissolved phase. In the test of algae medium (with shaking), ca. 80% of parent was lost from the headspace within 24 hours and 90% within 48 hours. The initial and 24-hour parent aqueous concentrations were similar (ca. 600 and 800 µg/L) but declined at 48 hours (ca. 200 µg/L). The remaining mass of parent had been converted to dissolved hydrolysis product (ca. 90 % by 48 hours, >100 mg/L). The overall process did not follow first-order kinetics, which is expected since the flasks were shaken and limitation by transport was at least partially mitigated. The extent of increase in the hydrolysis product's concentration indicates that the parent can only be maintained in solution by replacement from an adequately large headspace, while concentration of the hydrolysis product would increase throughout the test. Consistent test concentrations of the parent and its hydrolysis product cannot be maintained even in a closed container. For these reasons, and due to the inherent difficulties of toxicity testing on a gas, the amide hydrolysis product was tested directly. In these tests of the amide hydrolysis product, concentrations were stably maintained, and the EC50s were >100 mg/L. In the key study with Daphnia magna, no immobilization was observed after 48-hours up to the highest concentration. In the key study with the alga Pseudokirchneriella subcapitata, a 6% reduction in growth rate was observed at the highest concentration. Because this effect was statistically significant, the 72-hour EC50 was >100 mg/L, and the NOEC was 10 mg/L.