Docosyl methacrylate

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

2005-11-02 - 2005-11-06

Justification for type of information:

For "read across justification" please refer to chapter 13.

Reason / purpose for cross-reference:

read-across source

Key result

Type:

BCF

Value:

37 dimensionless

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

1.5 h

Elimination:

yes

Parameter:

other: DT95

Depuration time (DT):

6 h

Description of key information

The bioconcentration factor of the substance is ca. 37. Thus, the substance does not accumulate in organisms.

Key value for chemical safety assessment

BCF (aquatic species):

37 dimensionless

Additional information

Discussion

No study exists for the bioaccumulation of docosyl methacrylate (CAS 16669-27-5). The octanol/water partition coefficient of the substance, 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 log Kow used. On the contrary, an experimental study (MPA, UNTER 04-033, 2006) has been carried out on the close structural analogue 2-ethylhexyl methacrylate (CAS 688-84-6, 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 2 -ethylhexyl methacrylate (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. 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 the structural analogue ethylhexyl methacrylate (CAS 688-84-6) is expected to be higher than for docosyl methacrylate (CAS 16669-27-5) due to the lower log Pow, lower molecular weight and higher water solublity of ethylhexyl methacrylate (EHMA, C₁₂H₂₂O₂,: log Pow 5.59, MW: 198.31 g/mol, water solubility: 3.07 mg/l; docosyl methacrylate, C₂₆H₅₀O₂: log Pow 11.6, MW 394.6 g/mol, water solubility < 1 µg/l). The structural analogue EHMA and docosyl methacrylate are both alkyl methacrylates and the same way of rapid metabolism is expected. Metabolism of EHMA is indeed faster than docosyl methacrylate, but the concentration of docosyl methacrylate in organisms is much lower than EHMA due to the lower bioavailability so that bioaccumulation in organisms is also negligible.

Overall conclusion

An exact BCF for docosyl methacrylate cannot be estimated but it will also be in the same order of magnitude like the structural analogue EHMA (CAS 688-84-6) and definitively lower than the criteria for classification and labeling, laid down in Regulation (EC) 1272/2008 (CLP), of BCF ≥ 500. Thus, the bioconcentration factor of docosyl methacrylate is considered to be BCF ≈ 37. It can be concluded, that docosyl methacrylate does not accumulate in organisms. Hence, taking into account account the provisions laid down in Regulation (EC) 1227/2008 (CLP), the docosyl methacrylate does not have to be classified with respect to bioaccumulation in aquatic environments/sediment.