Reaction mass of 2,4,6-tris(1-phenylethyl)phenol and bis(1-phenylethyl)phenol and o-(1-phenylethyl)phenol

Bioaccumulation: aquatic / sediment

Description of key information

TSP has a BMF < 1, therefore, it has a low potential for biomagnification.
DSP is not considered as bioaccumulable.

Additional information

In total 3 studies are available that address the bioaccumulative potential of the constituents of the reaction mass of 2,4,6-tris(1-phenylethyl)phenol and bis(1-phenylethyl)phenol.

Study 1:

As TSP and DSP have low water solubility (< 1 mg/L) and logKow values above 6, a dietary study was used as replacement to OECD TG 305 in accordance with the ECHA Guidance on information requirements and chemical safety assessment (Chapter R.7c: Endpoint specific guidance, May 2008). This study is considered to be the key study.

The dietary bioaccumulation study was conducted on a mixture of TSP / DSP (60% / 40%) to determine the half-life time (t_1/2, from the elimination rate constant, k_depuration), the assimilation efficiency (alpha), the biomagnification factor (BMF) and the lipid-normalised biomagnification factor (BMFL), with rainbow trout (Oncorhynchus mykiss). The test items were administered to the test system via the diet. The study was performed according to the principles of the Basic Protocol (2004) and GLP.

 

A flow-through test with 3 tested groups was carried out. Fish were fed with spiked food during an uptake phase of 10 days followed by a depuration phase of 42 days. An untreated control group was tested. The test item Mixtureof DSP / TSP was tested with a concentration of 1000 µg/g food and hexachlorobenzene (HCB) was used as benchmark substance (= positive control) with a concentration of 250 µg/g food. The study was conducted over 52 days. All validity criteria required in the guideline were fulfilled.

 

Analytical verification:

The concentrations of distyrenated phenol (DSP) and tristyrenated phenol (TSP) were determined via LC-MS/MS, concentrations of HCB via GC-MS. 10 fish samples were taken from each tank at test start (day 0, only control fish) and on days 1, 5 and 10 of the uptake phase and on days 1, 2, 4, 7, 14, 28 and 42 of the depuration phase. Additionally, guts of 10 fish from day 10 (uptake phase) were analysed to investigate if the analytes remained in the gut after feeding.

Furthermore water samples, collected during uptake phase, were analysed to investigate if the analytes were present either by release from the fish via excretion or by release from the food during feeding.

DSP was not observed to bioaccumulate when applied via the diet. There was no bioconcentration measured for DSP. No bioconcentration factors were assessed. Furthermore analyses of the water samples demonstrated that DSP was absent conclusively ruling out that DSP was excreted by fish or released from the diet during feeding. Additionally, DSP was not detected in the gut samples.

 

TSP accumulated in rainbow trout when applied via the diet. The uptake rate was determined to be 0.1052 *d-1 derived by the intercept of the linear regression. During the depuration phase, the slope of depuration was -0.0590 * d-1, the intercept (= day 0 of depuration) was 2.725. The calculated concentration in fish was 15.3 µg TSP / g fish. The mean measured concentration of TSP in fish on day 10 of the uptake phase was 21.6 µg TSP / g fish. The growth corrected depuration rate (kdepuration) was 0.038 d-1 and the half life time (t½) was 18.4 days.

The biomagnification factor BMF was 0.110. The lipid based biomagnification factor was 0.355.TSP was present only in traces in the water samples and all determined concentrations were < LOQ. Analyses of guts revealed that TSP was absent.

HCB, being measured as a positive control, bioaccumulated as expected. The biomagnification factor BMF was 1.35. The lipid based biomagnification factor was 4.42.

 

Study 2:

 

Furthermore, a flow-through bioaccumulation study with rainbow trout (Oncorhynchus mykiss) was conducted to determine the bioconcentration potential of tristyrylphenol (TSP). In this test, the fish were exposed via TSP in the water rather than the diet. The study consisted of 2 phases: the exposure (uptake) phase and post-exposure (depuration) phase. A flow-through test with 2 groups was carried out: an untreated control group, and the test item with a nominal concentration of 2 µg/L was tested. The study was conducted over 111 days; the uptake phase lasted 52 days and the depuration phase lasted 58 days.

 

The concentrations of tristyrylphenol in the aqueous phase were measured via two different methods: the enrichment method and the standard addition method. The first method resulted in an overestimation of the BCF and therefore this has to be taken into account in the interpretation of the results. 

 

The bioconcentration factors (at any time) have been calculated based on the fish body weight. No other bioconcentration factors (i.e. BCF kinetic and BCF steady state) have been calculated since the conditions for these calculations were not suitable. The uptake did not follow a first-order kinetic and a steady state was not observed.

 

Due to observed mortality in the control group this study is considered invalid. However, the data obtained in this study are of scientific use and have been ascertained without any influence of the control group.

 

With TSP water concentrations determined via standard addition method, BCF values were lower the maximum BCF at any time was 6116 (body weight based, reached on day 35 of the uptake phase) and a BCF lipid normalized of 5106.

Lipid normalized BCF have been calculated on base of 5% lipid per fish.

 

Study 3:

 

Thirdly, the bioaccumulation of individual constituents of the reaction mass of 2,4,6-tris(1-phenylethyl)phenol and bis(1-phenylethylphenol) is further examined by way of the BCF base-line model. This model takes into account both lipophilicity as well as metabolic pathways.

 

For TSP, 2,6 -DSP and 2,4 -DSP the model estimates a large contribution of metabolism in reducing the calculated logBCFmax. The predicted metabolism in fish for TSP, 2,6 -DSP and 2,4 -DSP is supported by documented metabolism for similar chemicals.