p-cymene

Endpoint summary

Description of key information

Hydrolysis

In accordance with column 2 of Annex VIII of the REACH regulation, testing for this endpoint is scientifically not necessary and does not need to be conducted since the test chemical is readily biodegradable.

Biodegradation in water

Biodegradation study was conducted for 14 days for evaluating the percentage biodegradability of test chemical (from authoritative database and secondary source (2018)). The study was performed in accordance with OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions at a temperature of 25±1°C and pH 7.0, respectively. Activated sludge was used as a test inoculums for the study. Test inoculum was collected from 10 municipal wastewater sewage treatment plants, mixed and adjusted to pH 7.0.Portions of 500 mL each taken from filtrates of sludge samples collected at above sites were mixed with 5 L of filtrate of the old sludge which had been used for testing to make 10 L of a new sludge suspension. This suspension was adjusted to pH of 7.0 ± 1.0 and aerated in an incubation tank. Filtered outdoor air was used for aeration. After stopping the aeration of the incubation tank to let the sludge settle for approximately 30 minutes, about one-third of the supernatant was replaced by equal amount of 0.1% synthetic sewage water before resuming the aeration. This procedure was repeated daily to prepare the activated sludge culture. The incubation temperature was 25 ± 2℃.Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l, respectively. 300 ml culture bottles were used as a test vessel for the study.Basal medium was used as a test medium for the study. Medium was prepared by mixing each of solutions A, B, C and D prescribed in Japanese Industrial Standard "Testing methods for industrial waste water: biochemical oxygen demand" (JIS K 0102-1985 21) and purified water to make a final volume of 1l and then adjusted the pH to 7.0.Test suspensions were prepared in six separate bottles. Those bottles were incubated under the test conditions.These bottles including the test suspension also contains inoculum blank containing mineral, abiotic control system contain test chemical in water at a conc. 100 mg/l and reference control, respectively. Alanine (at 100 mg/l in mineral medium with 30 mg/l suspended solids) was used as a reference substance.After the end of the incubation period, the test substance remaining in the test solution was analyzed. Also in the (sludge + test substance) system and the sludge blank system the test solution was analyzed for remaining dissolved organic carbonusing a total organic carbon (TOC) meter.Besides oxygen consumption, gas chromatography (GC) was used to measure the test substance, and dissolved organic carbon was measured.Reference substance alanine undergoes 53% and 87% degradation based on BOD parameter after 7 and 14 days, respectively.The 10-day window was met for all three replicates based on BOD.There was no oxygen consumption in the abiotic control and very limited oxygen consumption in the inoculum blank amounting to 3.8 mg O2/L after 14 days.The percentage degradation of test chemical was determined to be 88, 89 and 100% by BOD, TOC removal and GC parameter in 14 days. Thus, based on percentage degradation,test chemical is considered to be readily biodegradable in nature.

Biodegradation in water and sediment

In accordance with column 2 of Annex IX of the REACH regulation, testing for this end point is scientifically not necessary and does not need to be conducted since the test chemical is readily biodegradable in water.

Biodegradation in soil

In accordance with column 2 of Annex IX of the REACH regulation, testing for this end point is scientifically not necessary and does not need to be conducted since the test chemical is readily biodegradable in water.

Adsorption / desorption

Adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical (Handbook, 2006). The adsorption coefficient (Koc) value was calculated using a logKow of 4.0. The adsorption coefficient (Koc) value of test chemical was estimated to be 5011.87 (Log Koc = 3.7). This Koc value indicates that the test chemical has a strong sorption tosoil and sediment and therefore have negligible to slow migration potential to ground water.

Additional information

Hydrolysis

In accordance with column 2 of Annex VIII of the REACH regulation, testing for this endpoint is scientifically not necessary and does not need to be conducted since the test chemical is readily biodegradable.

Biodegradation in water

Various experimental key and supporting studies of the test chemical were reviewed for the biodegradation end point which are summarized as below:

 

In an experimental key study from authoritative database and secondary source (2018),biodegradation experiment was conducted for 14 days for evaluating the percentage biodegradability of test chemical. The study was performed in accordance with OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions at a temperature of 25±1°C and pH 7.0, respectively. Activated sludge was used as a test inoculums for the study. Test inoculum was collected from 10 municipal wastewater sewage treatment plants, mixed and adjusted to pH 7.0.Portions of 500 mL each taken from filtrates of sludge samples collected at above sites were mixed with 5 L of filtrate of the old sludge which had been used for testing to make 10 L of a new sludge suspension. This suspension was adjusted to pH of 7.0 ± 1.0 and aerated in an incubation tank. Filtered outdoor air was used for aeration. After stopping the aeration of the incubation tank to let the sludge settle for approximately 30 minutes, about one-third of the supernatant was replaced by equal amount of 0.1% synthetic sewage water before resuming the aeration. This procedure was repeated daily to prepare the activated sludge culture. The incubation temperature was 25 ± 2℃.Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l, respectively. 300 ml culture bottles were used as a test vessel for the study. Basal medium was used as a test medium for the study. Medium was prepared by mixing each of solutions A, B, C and D prescribed in Japanese Industrial Standard "Testing methods for industrial waste water: biochemical oxygen demand" (JIS K 0102-1985 21) and purified water to make a final volume of 1l and then adjusted the pH to 7.0.Test suspensions were prepared in six separate bottles. Those bottles were incubated under the test conditions. These bottles including the test suspension also contains inoculum blank containing mineral, abiotic control system contain test chemical in water at a conc. 100 mg/l and reference control, respectively. Alanine (at 100 mg/l in mineral medium with 30 mg/l suspended solids) was used as a reference substance. After the end of the incubation period, the test substance remaining in the test solution was analyzed. Also in the (sludge + test substance) system and the sludge blank system the test solution was analyzed for remaining dissolved organic carbon using a total organic carbon (TOC) meter. Besides oxygen consumption, gas chromatography (GC) was used to measure the test substance, and dissolved organic carbon was measured. Reference substance alanine undergoes 53% and 87% degradation based on BOD parameter after 7 and 14 days, respectively. The 10-day window was met for all three replicates based on BOD. There was no oxygen consumption in the abiotic control and very limited oxygen consumption in the inoculum blank amounting to 3.8 mg O2/L after 14 days. The percentage degradation of test chemical was determined to be 88, 89 and 100% by BOD, TOC removal and GC parameter in 14 days. Thus, based on percentage degradation, test chemical is considered to be readily biodegradable in nature.

 

Another biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test chemical (from peer reviewed journal GILLES KLOPMAN et. al., 1997 and secondary source, 2018). Evaluation was done using the MultiCASE programs in which the database used for analysis was MITI. Thus, the study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions. MultiCASE is an artificial intelligence computer program that had been trained to identify molecular substructures believed to cause or inhibit biodegradation. It consisted of 200 molecules, all of which containing at least one benzene ring. In this study, test substance (100 mg/L) is inoculated and incubated with 30 mg/L of sludge for 28 days. Final day biological oxygen demand (BOD) was reported as the percentage of ultimate degradation. BOD is measured from day 0 continuously to day 28. In the analysis of the result in this was the cut-off of the biodegradation of 5%, which measure initial biodegradation and means that if a test chemical final day BOD value is greater than 5 (more than 5% was biodegraded), it is treated as biodegradable. In the MITI test evidence of biodegradation was a final day BOD>5%.The percentage degradation of test chemical was determined to be 88% by BOD parameter after a period 28 days. Thus, based on percentage degradation, test chemical is considered to be readily biodegradable in nature.

 

Additional biodegradation study from peer reviewed journal (Koichi Yamada et. al., 1965) was conducted for 7 days for evaluating the percentage biodegradability of test chemical. The study was performed at a temperature of 30°C. Five micro-organisms, i.e, S449B1, B2, B3, B4 and B6 were isolated from soil which was later identified as closely resembling Pseudomonas desmolytica was used as a test inoculum. 500 ml flask was used as a test vessel for the study. Test medium contains, per liter, 4 gm NH4NO3, 1.5 g KH2PO4, 1.5 g Na2HPO4, 0.2 g MgSO4.7H2O, 0.05 g FeSO4.7H2O, 0.002 g MnSO4.4H2O, 0.01 g CaCl2.2H2O, 0.5 g yeast extract. A 500 ml flask containing 50 ml of the medium, was autoclaved at 110°C for 10 mins. Before cultivation, 0.5 ml of sterile test chemical was added to the medium in the flask. When cultural conditions were tested, 1.5 ml of cell suspension, grown on test chemical agar- slant for 2 days, was inoculated into 50 ml of the medium. The medium was incubated at 30°C on reciprocal shaker for 1 to 7 days. Each strain was cultivated on the individual hydrocarbons.After24, 63 and 193 hours, the cultural broth was submitted to the paper chromatography. Paper chromatography was employed for detection of metabolic products. Solvent system used during the analysis involves n-butanol and n-butanol: acetic acid: water (4:1:2). The spots were visualized by ultraviolet-ray irradiation and fo rthe spraying of the developing reagents. Tδyδ filter paper No. 50 was used. From the test chemical, methyl-red positive and ultraviolet-absorbing spot was detected from the broth of all 5 strains (Solvent 1). Cumic acid, produced in cultural broth, was extracted by equal volume of ether. The ether solution was titrated by 1/20 N-NaOH, then amount of the acid produced was calculated from the titration value. The chemical characteristics of the crystal were compared with those of the authentic cumic acid. Product has identical absorption spectra and m. p. 118 to 118.5°C.Test chemical was reported to be biodegradable by all the 5 strains of the test micro-organisms. The transformation product of the test chemical was evaluated to be cumic acid. Thus, based this, test chemical is considered to be biodegradable in water.

 

On the basis of overall results of the test chemical(from peer reviewed journals, authoritative databases and secondary source), it can be concluded that the test chemical can be considered to be readily biodegradable in water.

Biodegradation in water and sediment

In accordance with column 2 of Annex IX of the REACH regulation, testing for this end point is scientifically not necessary and does not need to be conducted since the test chemical is readily biodegradable in water.

Biodegradation in soil

In accordance with column 2 of Annex IX of the REACH regulation, testing for this end point is scientifically not necessary and does not need to be conducted since the test chemical is readily biodegradable in water.

Adsorption / desorption

Experimental study and various predicted data of the test chemical were reviewed for the adsorption end point which are summarized as below:

 

In an experimental study from handbook (2006),adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical. The adsorption coefficient (Koc) value was calculated using a logKow of 4.0. The adsorption coefficient (Koc) value of test chemical was estimated to be 5011.87 (Log Koc = 3.7). This Koc value indicates that the test chemical has a strong sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.

 

Another adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical (HSDB and PubChem, 2017). The adsorption coefficient (Koc) value was calculated using a structure estimation method based on molecular connectivity indices. The adsorption coefficient (Koc) value of test chemical was estimated to be 1120 (Log Koc = 3.049). This Koc value indicates that the test chemical has a moderate sorption to soil and sediment and therefore have slow migration potential to ground water.

 

For the test chemical from authoritative database (2017), adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical. The adsorption coefficient (Koc) value of test chemical was estimated to be 4732 (Log Koc = 3.675), respectively. This Koc value indicates that the test chemical has a strong sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.

 

In a prediction done using the KOCWIN program of Estimation Programs Interface, the soil adsorption coefficient i.e Koc value of test chemical was predicted. The soil adsorption coefficient i.e Koc value of test chemical was estimated to be 1120 L/kg (log Koc=3.049) by means of MCI method (at 25 deg C). This Koc value indicates that the test chemical has a moderate sorption to soil and sediment and therefore have slow migration potential to ground water.

 

On the basis of above results of test chemical (from handbook, authoritative and modelling databases), it can be concluded that the logKoc value of test chemicalwas evaluated to be ranges from 3.049 to 3.7, respectively, indicating that the test chemical has a moderate to strong sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.