Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Abiotic degradation: DT50 in water and air are > 1 year and < 2 days, respectively.

Biotic degradation

Biotic degradation: Not readily biodegradable;

Biotic degradation: in river water : DT50<1day;

Biotic degradation in sediment: DT50 of parent < 10 days;

Biotic degradation in sludge amended soil and agricultural soil: DT50 is < 6 days;

Environmental fate and distribution:

Log Koc: 4.1

Henry coefficient: 11.3 Pa.m3/m3 (25oC)

Log BCF in fish: 2.6

Additional information

- Abiotic degradation:

Air: Based on a study conducted by Aschmann et al. (2001), OTNE undergoes in air rapid degradation after reaction with hydroxyl radicals and NO3 radicals. The atmospheric DT50 value after reaction with hydroxyl radicals and NO3 radicals is 1 hour and 1.4 minutes respectively. The half-life time of the substance is < 2 days. The substance will not reach the stratosphere and is therefore not considered to be a long-range transported chemical in air (http: //www.unece.org/fileadmin/DAM/env/documents/2000/ece/eb/ece%20eb%20air.60.e.pdf).

The substance does not have an ozone depletion potential because it does not contain halogens and does not have the potential to reach the stratosphere (CLP, 2008, Part 5).

Water: It can be reliably predicted that it is hydrolytically stable. It does not contain hydrolysable groups in its chemical structure such as esters, carbamates, epoxides, halomethanes, acylhalides (see Hydrowin, EpiSuite for all hydrolysable groups). The half-life at 20°C is therefore expected to be > 1 year.

- Biotic degradation:

In the key screening study according to OECD TG 301C 11% biodegradation (based on analysed material concentration) was found after 28 days. This study shows that the substance is not readily biodegradable under the conditions of this test. This result is supported by an additional ready biodegradability test and an inherent biodegradability 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 be rapidly degraded under natural conditions.

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 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.

Thus 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.

 - Environmental fate and distribution:

Adsorption/Desorption: The substance is a lipophilic substance with log Kow 5.65. The sorption to organic matter, log Koc, has been determined using measurements in samples of sludge and effluent in sewage treatment plants in southern and northern Europe and is 4.12. This indicates that the substance will have a moderate potential to adsorb to sediment/soil.

Volatility: To assess the volatilisation potential of the substance a Henry's law constant was calculated using EUSES, which gave a result of 23.6 Pa. m3/mol at 25°C and 11.3 Pa. m3/mol at environmental temperature (12°C). From the distribution modelling results it can be concluded that volatilisation is of some importance in the environmental behaviour of the substance.

Bioaccumulation: The BCF value for fish (lipid content 5%) was determined to be 391. It can be concluded that the substance has a relatively low bioaccumulation potential.

The BCF in earthworms was estimated to be 5361 l/kg ww with the equation from EUSES (Jager, 1998), indicating that the potential for bioaccumulation in terrestrial organisms will be moderate.

Distribution modelling:

Based on Level III distribution modelling using EPISUITE (assuming equal and continuous releases to air, water and soil) using the CAS number 54464-57-2 and the measured physico-chemical parameters as input, it is estimated that the majority of the substance released to the environment will partition mainly into soil (89.1%) with smaller amounts to water (8.84%) and sediment (2.08%) and a negligible amount to air (0.02%).

The SimpleTreat model, which is incorporated in EUSES, simulated the distribution of the substance in a Sewage Treatment Plant based on vapour pressure, water solubility, log Koc and biodegradability. The model predicts that 0% of the substance will biodegrade, 37.2% of the substance will partition to water, 56.8% to sewage sludge and 6.03% to air at 12°C.

Experimental simulation data show that the removal from the STP ranges from >50% to far more than 90%.