Dimethyl sulphone

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 evaluating the percentage biodegradability of test chemical (NTRL report, 1991). The study was performedunder aerobic conditions at a pH range 6.9 to 7.2.1 lt cylinder with bottom diffusers was used as a test vessel for the study. Activated sludge taken from the bench-scale completely mixed activated sludge system (CMAS) was used as test inoculums for the study. Test inoculum was further settled, decanted, washed with 20 mM pH 7.0 phosphate buffer, and resuspended in the same buffer solution. Initial test substance conc. used in the study was 100 mg/l. The removal of the test chemical and TOC were analyzed over several days.Alltheoxygen uptake tests were done with a 250-m1 BOO bottle and an Orbisphere oxygen probe equipped with an adapter. Endogenous rates were taken after 30-min aeration without feed. When substrate was included, the sludge was washed twice with 10 or 20mM pH7 phosphate buffer. The BOD5 and COO (dichromate) analyses were done according to the Standard Methods. TOC was analyzed with a Beckman TOCAMASTER Model 915-B. Sulfate was determined by ion exchange chromatography (Dionexl.Inorganic sulfate has been identified as a degradation product of test chemical. The percentage degradation of test chemical was determined to 87-100% by using test material analysis & TOC removal parameter in 48 hrs. Thus, based on percentage degradation, test chemical is considered to be readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (2018) prediction model was run to predict the half-life in water and sediment for the test chemical. If released in to the environment, 43.7% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of test chemical in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.0838%), indicates that test chemical is not persistent in sediment.

 

Biodegradation in soil

The half-life period of test chemical in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (2018). If released into the environment, 49.9% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical in soil is estimated to be 30 days (720 hrs). Based on this half-life value of test chemical, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2018). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 4 mg of test item and diluted with Methanol up to 10 ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 7.1. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to structural similarity with the test substance and calibration graph was prepared. The reference substances were Benzamide, Nitrobenzene, 4 -Nitrobenz amide, N,N-dimethylbenzamide, N-methylbenzamide, 2 - nitrophenol having Koc value ranging from 1.239 to 2.47. The Log Koc value of test chemical was determined to be 1.809 ± 0.001 dimensionless at 25°C.This log Koc value indicates that the substance has a low sorption to soil and sediment and therefore have moderate 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

Experiment study of the test chemical and various supporting weight of evidence studies for its read across chemical were reviewed for the biodegradation end point which are summarized as below:

 

In an experimental key study from NTRL report (1991),biodegradation study was conducted for evaluating the percentage biodegradability of test chemical. The study was performed under aerobic conditions at a pH range 6.9 to 7.2.1 lt cylinder with bottom diffusers was used as a test vessel for the study. Activated sludge taken from the bench-scale completely mixed activated sludge system (CMAS) was used as test inoculums for the study. Test inoculum was further settled, decanted, washed with 20 mM pH 7.0 phosphate buffer, and resuspended in the same buffer solution. Initial test substance conc. used in the study was 100 mg/l. The removal of the test chemical and TOC were analyzed over several days. All the oxygen uptake tests were done with a 250-m1 BOO bottle and an Orbisphere oxygen probe equipped with an adapter. Endogenous rates were taken after 30-min aeration without feed. When substrate was included, the sludge was washed twice with 10 or 20mM pH7 phosphate buffer. The BOD5 and COO (dichromate) analyses were done according to the Standard Methods. TOC was analyzed with a Beckman TOCAMASTER Model 915-B. Sulfate was determined by ion exchange chromatography (Dionexl.Inorganic sulfate has been identified as a degradation product of test chemical. The percentage degradation of test chemical was determined to 87-100% by using test material analysis & TOC removal parameter in 48 hrs. Thus, based on percentage degradation, test chemical is considered to be readily biodegradable in nature.

In a supporting weight of evidence study from authoritative databases (2018) for the test chemical,biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test chemical. The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions. Activated sludge was used as a test inoculums for the study. 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. The percentage degradation of test chemical was determined to 106 and 89% by BOD, TOC removal and CE parameter in 28 days Thus, based on percentage degradation, test chemical is considered to be readily biodegradable in nature.

For the test chemical, biodegradation study was conducted for 27 days for evaluating the percentage biodegradability of test chemical (from HSDB and PubChem authoritative databases and secondary source, 2017). The study was performed in accordance with the IS0 7827 "Evaluation in an aqueous medium of the 'ultimate' aerobic biodegradability of organic compounds -method by anlaysis of dissolved organic carbon (DOC)"under aerobic conditions. Initial test substance conc. used in the study was 162 mg/l. Acetic acid, sodium saltwas used as a reference substance for the study. The percentage degradation of test chemical was determined to 99% by Test material analysis parameter after a period of 27 days. Thus, based on percentage degradation, test chemical is considered to be readily biodegradable in nature.

On the basis of above results of the test chemical, it can be concluded that the test chemicalcan be considered to be readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (2018) prediction model was run to predict the half-life in water and sediment for the test chemical. If released in to the environment, 43.7% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 15 days (360 hrs). The half-life (15 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of test chemical in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.0838%), indicates that test chemical is not persistent in sediment.

 

Biodegradation in soil

The half-life period of test chemical in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (2018). If released into the environment, 49.9% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical in soil is estimated to be 30 days (720 hrs). Based on this half-life value of test chemical, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

On the basis of available information, the test chemical can be considered to be readily biodegradable in nature.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2018). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 4 mg of test item and diluted with Methanol up to 10 ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 7.1. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to structural similarity with the test substance and calibration graph was prepared. The reference substances were Benzamide, Nitrobenzene, 4 -Nitrobenz amide, N,N-dimethylbenzamide, N-methylbenzamide, 2 - nitrophenol having Koc value ranging from 1.239 to 2.47. The Log Koc value of test chemical was determined to be 1.809 ± 0.001 dimensionless at 25°C.This log Koc value indicates that the substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.