Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

In water n-octyl methacrylate (n-OMA) will be rapidly biodegraded, abiotic degradation by hydrolysis is not of major concern. From the water surface the test substance has a high volatility. After exposure to air it will be rapidly degraded by photochemical processes (half life 4.5 h). Based on a logPow of 5.24, n-OMA would be expected to have a significant bioaccumulation potential. In an actual bioaccumulation test with 2 -Ethylhexyl methacrylate structurally analogue substance to n-octyl methacrylate with fish, however, only a bioaccumulation rate of 37 was observed, most likely due to rapid metabolism. Soil adsorption/desorption studies have been performed with MAA, MMA and iBMA. Koc values for EMA, n-Butyl methacrylate (nBMA) and 2-Ethylhexyl methacrylate (2 –EHMA) were estimated by regression from the measured data (Staples, 2009).

Adsorption of the structural related substance isobutyl methacrylate ( iBMA) to soil was measured in three types of soil and the Koc ranged from 1480 to 3920 with a mean of 2760. It should be recognised that when interpreting the measured data of Christensen that they had assumed binding to soil since they could not detect iBMA in the aqueous desorption phase. However, failed to use sterilised soil and therefore rapid biodegradation by soil microflora may have contributed to the disappearance of iBMA from the aqueous phase and the true Koc is likely to be lower than that assumed. On this basis the estimates made by Staples for 2-EHMA with a value of 6400 may also be too high.

A low bioaccumulation potential of 2-EHMA was demonstrated in a bioaccumulation study in fish (cf above).

Furthermore, based on a Mackay Level 1 calculation the substance 2 -EHMA will mainly partition to air (ca. 90.7 %) in this equilibrium model, and to a much lesser degree to soil (4.5 %) and sediment (4.2 %). In the Mackay Level III model, which additionally takes into account transport and degradation processes 2-EHMA and n-OMA, when released to air or water, will predominantly remain in the environmental compartment into which it was released (2 -EHMA: air: 98.6 %; water: 95.5 % and n-OMA: air: 97.2 %; water: 96.0 %).REACH annex VIII (9.3.1) states that an adsorption/desorption study does not need to be conducted if:

    based on the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient), or

    the substance and its relevant degradation products decompose rapidly.

Hence, testing is not required.