Phosphorodithioic acid, O,O-di-C1-14-alkyl esters, zinc salts

Endpoint summary

Description of key information

Biodegradation in water

Biodegradability of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt (CAS no. 68649 -42 -3) is predicted using OECD QSAR toolbox version 3.3 (2017) with logKow as the primary descriptor. Test substance undergoes 18% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical Dialkyl(C1-C14)dithiophosphoric acid, zinc salt was estimated to be not readily biodegradable in water.

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound Dialkyl(C1-C14)dithiophosphoric acid, zinc salt (CAS No. 68649 -42 -3). If released in to the environment, 13.5% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt in water is estimated to be 60 days (1440 hrs). The half-life (60 days estimated by EPI suite) indicates that the chemical is persistent in water and the exposure risk to aquatic animals is moderate to high whereas the half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt in sediment is estimated to be 541.66 days (13000 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.00412%), indicates that Dialkyl(C1-C14)dithiophos phoric acid, zinc salt is not persistent in sediment.

 

Biodegradation in soil

The half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt (CAS No. 68649 -42 -3) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 86.4% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt in soil is estimated to be 120 days (2880 hrs). Based on this half-life value of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt, 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.

Additional information

Biodegradation in water

Various predicted data for the target compound Dialkyl(C1-C14)dithiophosphoric acid, zinc salt (CAS No. 68649-42-3) and supporting weight of evidence studies for its read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done by SSS (2017) using OECD QSAR toolbox version 3.3 with logKow as the primary descriptor, percentage biodegradability of test chemical Dialkyl(C1 -C14)dithio phosphoric acid, zinc salt(CAS No. 68649-42-3) was estimated.Test substance undergoes 18% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical Dialkyl(C1-C14)dithiophosphoric acid, zinc salt was estimated to be not readily biodegradable in water.

 

In another prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compoundDialkyl(C1-C14)dithiophosphoric acid, zinc salt(CAS No. 68649-42-3) 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 Dialkyl(C1-C14)dithiophosphoric acid, zinc salt is expected to be not readily biodegradable.

 

In a supporting weight of evidence study from secondary source (HPVIS, 2017) for the read across chemical zinc bis[bis(dodecylphenyl)] bis(dithiophosphate) (CAS no. 54261-67-5), biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of read across substance zinc bis[bis(dodecylphenyl)] bis(dithiophosphate). The study was performed according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) under aerobic conditions at a temperature of 20 ± 1°C. A preadapted activated sludge inoculum was used for the biodegradation test obtained from domestic wastewater treatment plant. The sludge was homogenized in a blender at medium speed for approximately 2 minutes and allowed to settle for approximately 30 minutes. The supernatant was used for inoculum preadaptation. The activated sludge supernatant was combined and supplemented with vitamin free casamino acids and 25 mg/L yeast extract. The supernatant from the homogenized activated sludge was used as inoculum. Bacterial counts in the inocula were 1 x 105to 2 x 106cells/mL. 100 ml of the supplemented inoculum was combined with 900 ml of test medium within each 2-L erlenmeyer flask. The solutions were aerated with CO2 free air and test substances added incrementally at concentrations equivalent to 4, 4, and 8 mg C/L on days 0, 7, and 12, respectively. On day 14, each adapted culture was homogenized in a blender and a composite culture prepared by mixing equal volumes of the homogenized cultures. The mixture was continuously stirred in a closed flask at a constant temperature for up to 28 days. Each reactor flask is equipped with an electrolytic cell assembly, which generates oxygen to replace the amount consumed by the test mixture in the flask. The oxygen uptake in all flasks were monitored continuously and recorded automatically every 4 hours throughout the test period using the BI Data Acquisition software. The percentage degradation of test substance zinc bis[bis(dodecylphenyl)] bis(dithiophosphate) was determined to be4.2% by O2 consumption parameter in 28 days.  Thus, based on percentage degradation, zinc bis[bis(dodecylphenyl)] bis(dithiophosphate) is considered to be not readily biodegradable in nature.

 

Another biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of the same read across substance zinc bis[bis(dodecylphenyl)] bis(dithio phosphate) (CAS no. 54261-67-5) (HPVIS, 2017). The study was performed according to OECD Guideline 310 B (Ready Biodegradability: CO2 in the sealed vessels (Headspace Test) and E PA OTS 796.3260 (Ready Biodegradability: Modified Sturm Test), respectively under aerobic conditions at a temperature of20 ± 3°C.A preadapted activated sludge supernatant from domestic wastewater treatment plant and soil filtrate was used as a test inoculum for the study. Soil was collected from a wooded lot to a depth of 20 cm (surface soil was not included). Prior to use, 200 gm (wet weight) of soil was suspended in 2 L of water, allowed to settle for 30 min and filtered through glass wool. Filtrate was aerated until use. Activated sludge from domestic wastewater treatment plant was sieved through a 2 mm screen, aerated for 4 hours and homogenized in a blender. The sludge was allowed to settle for 30 minutes and supernatant was removed for use. Sufficient amount of test material was added to each flask, giving 10 mg C/L in the test flasks. 100 ml of the supplemented inoculum was combined with 900 ml of test medium within each 2-L erlenmeyer flask. The solutions were aerated with CO2 free air and test substances added incrementally at concentrations equivalent to 4, 8, and 8 mg C/L on days 0, 7, and 11, respectively. On day 14, an equal volume of each culture was combined and composite inoculum screened using glass wool and homogenized in a blender. CO2 traps were removed for analysis on Days 2, 5, 11, 13, 16, 18, 23, and 29. On day 28, the test was terminated by the acidification of the test chamber to release dissolved CO2.The CO2 generated within each test chamber was trapped as K2C03 in the KOH solution and measured using a carbon analyzer.Inoculum blank and positive controls was included in the study. Abiotic and toxicity controls were not. Canola oil was used as the reference substance in the positive controls. The reference substance, canola oil, degraded 92% (2 - 5day lag period) in 28 days.The percentage degradation of test substance zinc bis[bis(dodecylphenyl)] bis(dithiophosphate) was determined to be 5.9% by CO2 evolution parameter in 28 days.  Thus, based on percentage degradation, zinc bis[bis(dodecylphenyl)] bis(dithio phosphate) is considered to be not readily biodegradable in nature.

 

For the read across chemical Dibutylbis((1-oxododecyl)-oxy) stannane (CAS no. 77-58-7), biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of read across substance Dibutylbis((1-oxododecyl)-oxy) stannane (OECD SIDS, 2006). The study was performed according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) and EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test), respectively under aerobic conditions at a temperature of 20.5°C and pH 7.2. Activated sludge was used as a test inoculum obtained from an oxidation ditch, which is used to treat domestic waste water. The activated sludge was kept in a plastic flask and aerated until use. Conc. of inoculum and initial test substance concentration used in the study was 30 and 22.2 mg/l, respectively. Test medium used for the study as that specified in OECD Guideline 301. NaNO3 was added to prevent nitrogen limitation. 500 ml glass flasks was used as a test vessel for the study. 0.2666 g of the test substance was dissolved in 10 ml ethanol (Stock I). An aliquot of 250 µl of Stock I was applied to glass fibre filters (Whatman GF/C, diameter 47 mm). After being air-dried, a glass fibre filter was placed in each flask that were filled with 300 ml mineral medium. The oxygen consumption (mg O2/L) was calculated based on the respiration rate (mg O2/flask/h) as measured by an Micro-Oxymax respirometer. The oxygen consumption due to test or control substance was calculated by subtracting the mean cumulative oxygen consumption in the blanks from that of the flask under consideration. These values were then converted to the Biological Oxygen Demand (BOD) which is expressed in mg O2/mg test substance. The percentage biodegradation of the test substance was calculated as BOD/ThOD x 100 (ThOD: Theoretical Oxygen Demand). Sodium acetate, anhydrous (100 mg/l) was used as a reference substance for the study. The cumulative oxygen consumption in the toxicity control (sodium acetate and test substance) after 14 days was slightly higher than that of the inoculum activity control (sodium acetate) alone. This indicated that the test substance did not inhibit the degradation of sodium acetate at the concentration tested. Based on the combined ThOD of both substances a biodegradtion of >25% was reached which, according to the guidelines, means that the test substance is considered not toxic to the inoculum. The percentage degradation of substance Dibutylbis((1-oxododecyl)-oxy) stannane was determined to be 20, 22, 23 and 33% by using O2 consumption parameter in 14, 28 and 39 days, respectively. Thus, based on percentage degradation, Dibutylbis((1-oxododecyl)-oxy) stannane is considered to be not readily biodegradable in nature.

 

In a supporting weight of evidence study from authoritative database (J-CHECK, 2017) for the read across chemical 1-Decanaminium, N-decyl-N,N-dimethyl-, chloride (CAS no. 7173-51-5), biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of read across substance 1-Decanaminium, N-decyl-N,N- dimethyl-, chloride. The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) and other guideline "Biodegradation test of a chemical substance using a microorganism etc." provided in "the Notice on the Test Method Concerning New Chemical Substances", respectively. 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 substance 1-Decanaminium, N-decyl-N,N-dimethyl-, chloride was determined to be 0% by O2 consumption, BOD, Test mat. analysis and LC-MS parameter in 28 days.Thus, based on percentage degradation,1-Decanaminium, N-decyl-N,N-dimethyl-, chloride is considered to be not readily biodegradable in nature.

 

On the basis of above results for target chemical Dialkyl(C1-C14)dithiophosphoric acid, zinc salt (from OECD QSAR toolbox version 3.3 and EPI suite, 2017) and for its read across substance (from authoritative database J-CHECK and secondary source), it can be concluded that the test substance Dialkyl(C1-C14)dithiophosphoric acid, zinc salt can be expected to be not readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound Dialkyl(C1-C14)dithiophosphoric acid, zinc salt (CAS No. 68649 -42 -3). If released in to the environment, 13.5% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt in water is estimated to be 60 days (1440 hrs). The half-life (60 days estimated by EPI suite) indicates that the chemical is persistent in water and the exposure risk to aquatic animals is moderate to high whereas the half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt in sediment is estimated to be 541.66 days (13000 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.00412%), indicates that Dialkyl(C1-C14)dithiophos phoric acid, zinc salt is not persistent in sediment.

 

Biodegradation in soil

The half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt (CAS No. 68649 -42 -3) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 86.4% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt in soil is estimated to be 120 days (2880 hrs). Based on this half-life value of Dialkyl(C1-C14)dithiophosphoric acid, zinc salt, 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 substance Dialkyl(C1-C14)dithiophosphoric acid, zinc salt can be considered to be not readily biodegradable in nature.