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Environmental fate & pathways

Endpoint summary

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A test for ready biodegradability conducted according to the Modified MITI (OECD Test Guideline 301C) indicated that the chemical only very slowly degraded under the conditions of the test (Iwami S, 1994). The result of this test indicates that the BDP is not readily biodegradable.

The compound has a large Koc (log Koc > 4.53), indicating strong affinity for the organic component of soils and sediments, and low mobility in these media. The log of the adsorption coefficient (Koc) of BDP was also determined to be higher than 6.87 using batch equilibrium method (OECD TG 106).

The high log Pow (> 6), relatively low molecular weight (693 g/mol) and low water solubility (0.4 mg/L), which were all used to estimate the BCFs of BDP, indicates that the BCFs were lower than 250, and BDP was not likely to cause bioaccumulation.

Furthermore, BCF was determined via a Bioconcentration Test (Semi-Static System) to Zebra-fish (Brachydanio rerio) in accordance with OECD Test Guideline 305.The study was conducted under semi-static conditions with the nominal concentration of 0.4 mg/L and solvent control for a period of 33 days. 250 test fish were used for each treatment and equally divided into 10 test containers. The test solution was renewed once every two days. During the exposure time, the mortality, number of abnormal fish and abnormal behavior of fish was observed and recorded once a day. The water sample and fish sample were taken to analyze the concentration of the test substance (BDP). The bioconcentration factor (BCF) value was calculated as the ratio (as BCFss) of concentration in the fish (Cf) and in the water (Cw) at the apparent steady-state. BDP was stable under test condition.During the test, based on the nominal concentration of 0.4 mg/L, the mean measured concentration of BDP test solution was 0.37 mg/Land standard deviation was 0.04.The steady state bioconcentration factorBCFsswas determined to be 5, which therefore showed BDP is not bioaccumulative in Zebra fish (Brachydanio rerio).

Hydrolytic degradation of the compound was studied as a function of pH by incubating stoppered flasks containing (nominally) 0.25 mg/L in buffer solutions at pH 4, 7 and 9 for 5 days. The concentration of the compound in the solutions was determined using HPLC at various times over the 5 day (120 hour) test period. Very little degradation was observed in any of the buffers over the 5 day test period, with the maximum loss of 5% of initial concentration observed in the pH 9 buffer. These data indicate that the phosphate ester linkages within the molecules are stable to hydrolysis at 50°C. The small extent of observed degradation extrapolated to 25 °C indicates a half life of greater than 1 year at environmental pH 4-9.