Icosyl methacrylate

Bioaccumulation: aquatic / sediment

Description of key information

An experimental study on the structural analogue 2-ethyl hexyl methacrylate (log Kow > 4) (Schäfers, 2006) of bioconcentration of the substance, according to OECD guideline 305 demonstrates that a rapid metabolisation occurs, this depuration prevents any significant accumulation. The measured BCF is 37.

Key value for chemical safety assessment

BCF (aquatic species):

37 dimensionless

Additional information

_{No study exists for the bioaccumulation of Eicosyl methacrylate.}

The octanol/water partition coefficient of the substances, log Kow > 4, predicts a potential for bioaccumulation.

Simple models linking BCF to logKow would give BCF in the range of about > 1000 depending on the model and the logKow used .

On the contrary, an experimental study (Schäfers, 2006) has been carried out on the structural analogue 2-ethylhexyl methacrylate (log Kow > 4) to assess the fish bioconcentration of the substance, according to OECD guideline 305.

_{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 treatmentgroup, 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 eicosyl 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; Eicosyl methacrylate , C24H46O2: log Pow 10.6, MW 366.62 g/mol, water solubility. < 1 µg/l). EHMA and Eicosyl methacrylate are both alkyl methacrylates and the same way of rapid metabolism is expected. Metabolism of EHMA is indeed faster than eicosyl methacrylate, but the concentration of eicosyl 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.}