Phenethyl propionate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of Phenethyl propionate for effects in the environment:

 

The chemical Phenethyl propionate (CAS no. 122-70-3) is used as intermediate in chemical synthesis and pharmaceutical industry. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for Phenethyl propionate. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.

 

 

Persistence assessment

The tested substance does not fulfil the P criterion within Annex XIII based on the assessment that here follows:

 

Biotic degradation

In an experimental key study from peer reviewed journal (Dingfue Hu and Joel Coats, 2008) and review article (Dingfue Hu, 2007), biodegradation experiment was conducted for 30 days for evaluating the percentage biodegradability of test substance 2 -phenylethyl propanoate (CAS no. 122-70-3). 3H-phenethyl propionate were purchased from PerkinElmer Life Sciences and Analytical Sciences. (Boston, MA, USA). Analytical standards of phenethyl propionate, 2-phenylethanol, 2-(4-hydroxyphenyl) ethanol were purchased from Lancaster Synthesis, Inc. Methanol was purchased from Fisher Scientific Solvents used for extraction and chromatographic analysis were analytical reagent grade or better. Monophase® S scintillation cocktails were purchased from PerkinElmer Life and Analytical Sciences. Pond water was used as a test inoculum collected from the Iowa State University Horticulture Farm pond (Ames, IA, USA). Initial test substance conc. used for the study was 10μg/g. The pH of the water was 7.3, the alkalinity was 91 mg/ml, and the total hardness was 182 mg/ml. Pond water (100 ml) was kept in French square bottles and spiked with 3H-PEP in 300 μl of acetone carrier solvent to result in a concentration of 10 μg/ml in the pond water. The samples were incubated in dark and in light separately, and were maintained at a constant temperature of 25 ± 2°C throughout the study in the environmental chamber. Aluminum foil wrapping was used to prevent “dark” incubations from having exposure to light. Samples were taken at days 0, 0.25, 0.5, 1, 3, 7, 14, 21 and 30 post-treatment.Quantitative analysis of PEP was performed using a Hewlett-Packard (Palo Alto, CA, USA) series 1100 HPLC system with a quaternary pump, an autosampler, a thermostatted column compartment, and a Spectroflow 757 absorbance detector (ABI Analytical, Kratos Division, Ramsey, NJ, USA). Data were collected and analyzed using HP Chemstation system software (REV. A.04.01). An Alltech Adsorbosphere® (Deerfield, IL, USA) C18 column (4.6×250 mm, 5-μm particle size) was used. Detection was conducted at 270 nm with a flow rate of 1.0 ml/min at room temperature. The mobile phase was methanol/distilled water (70:30, v/v).Dissipation rates of PEP were calculated using first-order open models. A student’st-test was used to compare dissipation rates of PEP in light and in dark from the water dissipation studies. Dissipation of PEP in water was very rapid with a DT 50 of 5 days. Volatility loss was negligible in one month with mass balance from 96% to 100%. The primary degradation product was 2-phenylethanol, which was produced from ester hydrolysis of phenethyl propionate; another degradation product was 2-(4-hydroxyphenyl) ethanol, which was probably a biotransformation product of 2-phenylethanol in microbes. The percentage degradation of test substance2-phenylethyl propanoate was determined to be50% in 5 days. Thus, based on percentage degradation,2-phenylethyl propanoate is considered to be readily biodegradable in nature.

 

In a prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compound2-phenylethyl propanoate(CAS No. 122-70-3) in the presence of mixed populations of environmental microorganisms was estimated.The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical 2-phenylethyl propanoate is expected to be readily biodegradable.

 

Further, experimental studies for the read across substances (CAS: 103-37-7 and 60-12-8) also indicate that they are readily biodegradable.

 

Environmental fate

Biodegradation study was conducted for 30 days for evaluating the percentage biodegradability of test substance 2-phenylethyl propanoate (Dingfue Hu and Joel Coats, 2008 & Dingfue Hu, 2007).

Initial test substance conc. used for the study was 10μg/g. The soil contained 1.6% organic matter, 60% sand, 22% silt, 18% clay, and pH 7.0. Soil (50g) was kept in a 250-ml French square bottle, and soil moisture content was adjusted to 75% of 1/3 bar moisture. The temperature was maintained at 25 ± 2°C. Soil samples were treated with 3HPEP in methanol at 10 μg/g. Bottles were sealed with Teflon® caps. Polyurethane foam was suspended above the treated soils inside each bottle to capture volatile compounds. Soil sampling times were at pre-treatment, at 1, 3, 7, 14, and 30 days post-treatment.

Quantitative analysis of PEP was performed using a Hewlett-Packard (Palo Alto, CA, USA) series 1100 HPLC system with a quaternary pump, an autosampler, a thermostatted column compartment, and a Spectroflow 757 absorbance detector (ABI Analytical, Kratos Division, Ramsey, NJ, USA). Detection was conducted at 270 nm with a flow rate of 1.0 ml/min at room temperature. The mobile phase was methanol/distilled water (70:30, v/v). Soil samples (50 g) were extracted with methanol/distilled water (95:5) three times, and the resulting extracts were pooled. Filtered samples were directly injected for HPLC analysis. HPLC fractions were collected for liquid scintillation counting (LSC). Drierite and polyurethane foam were thoroughly extracted with methanol, and the resulting extracts were subjected to LSC to measure trapped radioactivity. Non-extractable radioactive residues in soil were measured by soil combustion using a Packard sample oxidizer. A 0.5-g soil sample was incorporated into a cellulose pellet, and three replications were performed for each treatment. Dissipation rates of PEP were calculated using first-order open models. A student’s t-test was used to compare dissipation rates of PEP in light and in dark from the water dissipation studies. The half-life of test substance2-phenylethyl propanoate was determined to be 4 days. The degradation product of chemical 2-phenylethyl propanoate were 2-Phenylethanol and 2-(4-hydroxyphenyl) ethanol, respectively. 2-Phenylethanol reached the maximal concentration in 1 week both in water and in soil; however, the peak in soil was 36% of total radioactivity compared to 74% of total radioactivity in water. The formation of 2-(4-hydroxyphenyl) ethanol was also less in soil than in water. The average radioactivity as bound residues remained below 6%, and mineralization was less than 3%.Based on this half-life value of test chemical 2-phenylethyl propanoate (i.e. 4 days), it is concluded that the chemical 2-phenylethyl propanoate is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

 

If released in to the environment, 24.9 % of the chemical will partition into water according to the Mackay fugacity model level III in EPI suite version 4.1 (2017). However, the half-life (15 days estimated by EPI suite) indicates that the exposure risk to aquatic animals is moderate to low.

 

Moreover, its persistent characteristic is only observed in the sediment compartment but Fugacity modelling shows that sediment is not an important environmental fate (less than 1% when estimated by EPI Suite version 4.1).

 

Hence it has been concluded that Phenethyl propionate is not persistent in nature.

 

 

Bioaccumulation assessment

The tested substance does not fulfil the B criterion within Annex XIII based on the assessment that here follows:

 

Theestimated BCF value from various databases was determined to be in the range 46 – 83.4 and theoctanol water partition coefficient of the test chemical is 3.06 which is less than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a low risk for the chemical to bioaccumulate in fish and food chains.

 

Toxicity assessment

The tested substance does not fulfil the T criterion within Annex XIII based on the assessment that here follows:

 

Mammals

The tested chemical is regarded to be not classified for carcinogenicity, mutagenicity and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1(oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).

 

Aquatic organisms

All of the available short-term eco-toxicity estimations for fish, invertebrates and algae for the substance indicates the LC50/EC50 value to be in the range 10 - 296 mg/L. These value suggest that the substance is likely to be hazardous to Aquatic organisms at environmentally relevant concentrations but since the substance is readily biodegradable, it can be considered to be not classified as per the CLP regulation.

 

There are no available long-term toxicity evaluations for Phenethyl propionate. By speculation, long-term NOEC for aquatic organisms were not expected for the substance at concentration below 0.01 mg/L based on the data mentioned above.

 

The chemical was therefore not considered as hazardous to aquatic environments as per the criteria set out in Annex XIII.

 

Conclusion

Based on critical, independent and collective evaluation of information summarized herein, the tested compound does not fulfil the P, B and T criterion and has therefore not been classified as a PBT compound within Annex XIII.