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Environmental fate & pathways

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There is no concern for bioaccumulation in aquatic, sediment and terrestrial organisms for Dodecyl methacrylate and the long-chain alkyl methacrylate esters (C12 – C22) as the substances are readily biodegradable and not bioaccumulative.

No study exists for the bioaccumulation of Dodecyl methacrylate but there exists a fish bioconcentration study (OECD 305) with ethylhexyl methacrylate (EHMA). This study was conducted with nominal concentrations of 0.06 and 0.3 mg EHMA/l under flow through conditions. An untreated control was run in parallel. Based on a range-finding experiment which indicated rapid metabolism, the uptake phase was scheduled for 56 hours, the depuration phase for 30 hours. Samples of fish (LOQ 0.05 mg/kg) and water (LOQ 0.001 mg/L) were taken at the same time and analysed for 2-Ethylhexyl methacrylate by GC-MS/MS in order to derive the uptake and depuration constants as well as the bioconcentration factor at equilibrium between uptake and elimination. No mortality was observed in the study. During the uptake phase, all concentrations in water and fish were above the LOQ. In the low treatment group, water concentrations rapidly decreased to 50% of nominal during the first 2 h of exposure.

They remained sufficiently constant thereafter. In the high treatment group, water concentrations rapidly decreased to 30% of nominal during the first 4 h of exposure. They remained sufficiently constant thereafter. For steady state calculations the mean of the concentrations in the water of the last five respectively four samplings were used (low 4 – 56 h, high 8 -56 h).

Concentrations in fish increased fast within the first hours and declined later when concentrations in water remained constant. For a worst case estimation, the last two measurements of the concentrations in fish in the low treatment group were not considered further. The steady state BCF was calculated to be 35 and 34 for the low and the high test concentration, respectively. In the depuration phase concentrations in the fish were below LOQ after 16 h. The depuration rates were calculated to be 0.51/h and 0.47/h for the low and the high treatment, respectively.

The depuration half-life is approximately 1.5 h, 95 % is depurated within approximately 6 h. The equilibrium between uptake and depuration (steady state) is already reached after 2 h of exposure. After 12 h, the concentration factor decreased, particularly in the low treatment group and thus was not used for fitting the uptake rate. Uptake rates were calculated to be 19.2/h and 17.4/h for the low and the high test concentration.

From the kinetic rates the BCF of ethylhexyl methacrylate was calculated to be 37 for both test concentrations.

 

Bioavailability of ethylhexyl methacrylate is expected to be higher than dodecyl methacrylate due to the lower log Pow, lower molecular weight and higher water solublity of ethylhexyl methacrylater (EHMA, C12H22O2: log Pow. 5.59; MW 198.31 g/mol; water solubility: 3.07 mg/l; Dodecyl methacrylate , C16H30O2: log Pow 6.68, MW 254.42 g/mol, water solubility. < 1 µg/l). EHMA and Dodecyl methacrylate are both alkyl methacrylates and the same way of rapid metabolism is expected. Metabolism of EHMA is indeed faster than dodecyl methacrylate, but the concentration of dodecyl methacrylate in organisms is much lower than EHMA due to the lower bioavailability so that bioaccumulation in organisms is also negligible. An exact BCF cannot be estimated but it will also be in the same order of magnitude like EHMA and definitively lower than the criteria for classification and labelling of BCF ≥ 500.