Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

A key ready biodegradability study is available for OTNE. The biodegradability of OTNE was tested in a Modified MITI test (OECD TG 301C). The validity criteria for the test were met. The concentration of the test substance added was 100 mg/l, with an activated sludge concentration of 30 mg/l suspended solids. The mean percentage biodegradation found was 0% based on BOD and 11% based on analysed test material concentration. In conclusion, OTNE was not readily biodegradable under the conditions of this test.

Although OTNE does not readily mineralize in standard tests, studies in natural sediment and soils as well as the river water die-away study show that OTNE will rapidly be degraded under natural conditions as can be derived from the following tests.

Die-away studies were carried out with radio-labelled C14 -OTNE in river water, in sediment as well as in soils. All tests confirm that OTNE degrades rapidly and that metabolites are formed that are transformed to polar metabolites and to CO2.

The river water test mimics the conditions in the mixing zone after the STP. After 28 days 10% mineralisation to CO2 was detected. The DT50 (Disappearance 50) for primary degradation is circa 1 days. The kinetic assessment showed an initial first-order loss rate of 1.83/h and a second first-order loss rate of 0.022/h.

In sediment, circa 50% was recovered as CO2 after 8 weeks and < 1% remained of the parent material.The half-life of the parent substance was estimated at 9.5 days.

In agricultural soils OTNE in soil is almost completely degraded after 6 weeks. After 6 weeks the mineralisation (CO2 evolution) is circa 50%. After a lag time of approx. 7 days the initial rate of CO2 production was 1.4 - 1.8% /day in the sludge amended soil and in the agricultural soil, respectively. The half-life of the parent substance was estimated at 6.0 and 4.2 days in the sludge amended soil and in the agricultural soil, respectively.

Overall summary: It is concluded that OTNE will be rapidly biodegraded under natural conditions in river water, in sediment as well as in soils, with a half-life time of 1 day in water, 10 days in sediment and 6 days in soil.