2-tetradecyloxirane, reaction products with boric acid

Endpoint summary

Description of key information

Abiotic degradation; Hydrolysis

The main functional groups in the components of the test item are hydroxyl and borate esters. The hydroxyl group would be unlikely to hydrolyse. However, the borate esters have the potential to be hydrolysed due to the empty p-orbital of boron which is susceptible to interactions with electron donors. Under real environmental alkaline or acidic conditions, hydrolysis of borate esters could be initiated by water molecules attacking the boron p-orbital, especially from the less sterically hindered side. Although the test item is hydrophobic and has low water solubility, water molecules could cause hydrolysis and result in the loss of parent compound

Biodegradation in water

The results for the test item were an average of 26.7% degradation over a 28-day test period. The test substance is not readily biodegradable under the conditions of the study (OECD TG 301 B).

Simulation testing on ultimate degradation in surface water

The test item degraded rapidly in surface water with an estimated DT50 value of 4.9 hours (at 0.325 μg/mL) and 3.4 hours (at 0.065 μg/mL) and an estimated DT90 value of 16.4 hours (at 0.325 μg/mL) and 11.3 hours (at 0.065 μg/mL) (OECD TG 309).

Sediment simulation testing

The test item degraded rapidly in two aquatic sediment systems. The estimated DT50 values in sediment were determined to be 10.8 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond). The estimated DT90 values in sediment were 35.9 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond) (OECD TG 308).

Soil simulation testing

Following incubation in four different soil types under aerobic conditions at 20 ± 2 °C and at a moisture content equivalent to that at pF 2, the test item degraded with DT50 values of 25.0 h (Calke; sandy loam), 28.5 h (Brierlow; silt clay loam), 24.9 h (South Witham; clay) and 59.6 h (Ingleby; loamy sand). The DT90 values determined under aerobic conditions were 82.9 h (Calke; sandy loam), 94.7 h (Brierlow; silt clay loam), 82.6 h (South Witham; clay) and 198 h (Ingleby; loamy sand). Following incubation in one soil type (Ingleby; loamy sand) under anaerobic conditions at 20 ± 2 °C the test item degraded with a DT50 value of 13 hours and a DT90 value of 981 hours (OECD 307).

Bioaccumulation

The substance will not bioaccumulate. The experimentally derived Log Pow value for the substance has been identified as > 9.4.

Adsorption coefficient

The adsorption coefficient (Koc) of the test item has been determined to be > 4.27E05, Log Koc > 5.63.

Henry’s law constant

Henry's law constant was calculated to be less than or equal to 2.125E01 Pa.m3/mol at 25 °C. A low rate of volatilisation from surface water is expected.

Distribution modelling

The substance is predicted to partition mainly to soil (37.6 - 83.0%) and sediment (44.2 - 55.7%)

Additional information

Abiotic degradation: Hydrolysis

The test item is a complex mixture for which the test guideline for hydrolysis is not recommended. This is not only because the components could have different hydrolytic rates but also hydrolysis products can be analytically indistinguishable from their starting material. Although the test item was determined to have a water solubility value of less than 0.17 mg/L, it had been considered that this was a significant over estimation. Therefore, the test solution concentration required for the test would be impractically low to perform the test and a sufficiently sensitive analytical method was not available.

Biodegradation in water

In a key study performed in accordance with OECD TG 301 B (Ready Biodegradability: CO2 Evolution Test) the inoculated test medium is dosed with a known amount of test item, as the nominal sole source of organic carbon and aerated with CO2-free air. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2 -free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced from the biodegradation of the test substance (corrected for that evolved by the blank inoculum) was expressed as a percentage of the theoretical amount of CO2 (TCO2). The reference group was dosed with canola oil, a substance known to be biodegradable, at a nominal concentration of 10 mg C/L. The treatment group test chambers were used to evaluate the test item at a nominal concentration of 10 mg C/L.

The viability of the inoculum and validity of the test were supported by the reference substance, canola oil, degrading an average of approximately 88.3%. The amount of CO2 evolved by the control chambers did not exceed the 17 mg/L value considered the acceptable limit for CO2 evolution tests. The results for the test substance were an average of 26.7% degradation over a 28-day test period. The test substance is not readily biodegradable under the conditions of the study.

Simulation testing on ultimate degradation in surface water

The key study was performed in compliance with OECD TG 309: Aerobic Mineralisation in Surface Water – Simulation Biodegradation Test (April 2004), Commission Regulation (EU) No 283/2013 in accordance with Regulation (EC) No 1107/2009 and SANCO/3029/99 (Rev.4).

The rate of degradation (DT50, DT90) of test item was studied in surface water under aerobic conditions in the laboratory. Surface water vessels were set up and allowed to acclimatise at 12 ± 2 °C in the dark overnight before being treated with test item (in duplicate at each concentration) at nominal application rates of 0.325 μg/mL and 0.065 μg/mL. The surface water samples were incubated with continuous stirring to maintain aerobic conditions at 12 ± 2 °C in darkness for periods of up to 24 hours. At each sampling occasion, the amounts of test item in the surface water vessels were determined using validated analytical methodology. Aliquots of surface water samples were taken for analysis immediately after test item application and at intervals up to 24 hours.

The concentration of test item declined at both concentrations. For a concentration 0.325 μg/mL, the mean test item detected declined from 0.300 μg/mL at zero-time to 0.0215 μg/mL at 24 hours. For a concentration 0.065 μg/mL, the mean test item detected declined from 0.0538 μg/mL at zero-time to <LOQ at 24 hours.

DT50 and DT90 values for the decline of the test item in surface water were calculated using Single First Order (SFO) kinetic models. The test item degraded rapidly in surface water with an estimated DT50 value of 4.9 hours (at 0.325 μg/mL) and 3.4 hours (at 0.065 μg/mL) and an estimated DT90 value of 16.4 hours (at 0.325 μg/mL) and 11.3 hours (at 0.065 μg/mL).

Sediment simulation testing

The key study was performed in compliance with OECD TG 308: Aerobic and Anaerobic Transformation in Aquatic Sediment Systems (April 2002) (aerobic part) and SANTE/2020/12830, Rev.1 of 24 February 2021: Guidance Document on Pesticide Analytical Methods for Risk Assessment and Post-approval Control and Monitoring Purposes.

The rate of degradation (DT50, DT90) of test item was studied in two aquatic sediment systems incubated under aerobic conditions in the laboratory. The sediment from Calwich Abbey Lake was a silt loam with a higher organic carbon content while that from Lumsdale Middle Pond was a sand with a lower organic carbon content. Samples of each aquatic sediment system were allowed to acclimatise before being treated with test item at a nominal rate of 0.325 μg/mL based on the amount of water in the test vessel including that present within the sediment. The samples were incubated under aerobic conditions at about 12 °C in darkness for periods of up to 50 hours. At each sampling occasion, the amounts of test item in the sediment/water samples were determined using validated analytical methodologies. Duplicate samples from each aquatic sediment system were taken for analysis immediately after test item application and at intervals of up to 50 hours.

In Calwich Abbey Lake aquatic sediment, the concentration in the water layer declined from a mean of 0.342 μg/mL at time zero to < LOQ after 38 hours of incubation. In sediment, the concentration increased to a mean of 0.447 μg/g after 12 hours and then decreased to < LOQ after 38 hours of incubation.

In Lumsdale Middle Pond aquatic sediment, the concentration in the water layer declined from a mean of 0.319 μg/mL at time zero to 0.0152 μg/mL after 50 hours of incubation. In sediment, the concentration remained at < LOQ, therefore no decline was observed.

DT50 and DT90 values for the decline of test item from the water, the sediment and from the total aquatic sediment system were calculated on the results obtained using Single First Order (SFO) kinetic models are shown below.

Assessment	Calwich Abbey Lake DT50 (hours)	Calwich Abbey Lake DT90 (hours)	Lumsdale Middle Pond DT50 (hours)	Lumsdale Middle Pond DT90 (hours)
Water	13.3	44.3	15	49.9
Sediment	10.8	35.9	No decline (< LOQ)	ND
Total system	14.5	48.3	15	49.9

The test item degraded rapidly in both aquatic sediment systems. The estimated DT50 values in sediment were determined to be 10.8 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond). The estimated DT90 values in sediment were 35.9 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond).

Soil simulation testing

The key study was performed in compliance with OECD TG 307: Aerobic and Anaerobic Transformation in Soil (April 2002).

The rate of degradation (DT50, DT90) of the test item was studied in four soils incubated under aerobic conditions and one soil under anaerobic conditions in the laboratory.

For the rate of degradation tests under aerobic conditions, soil samples were set up and allowed to acclimatise before being treated with test item at a nominal application rate of 10 mg/kg (on a dry weight basis). The soil samples were incubated under aerobic conditions in the dark at approximately 20°C at a moisture content equivalent to pF 2. At each sampling occasion, the amounts of test item in the soil samples were determined using the validated analytical methodology. Duplicate soil samples from each soil type were taken for analysis immediately after test item application and at intervals of up to 146 hours after treatment in Calke, Brierlow and South Witham soil and up to 169 hours in Ingleby soil.

For the rate of degradation test under anaerobic conditions, soil samples were set up and allowed to acclimatise before being treated with test item at a nominal application rate of 10 mg/kg (on a dry weight basis), as per the aerobic test. The period of the aerobic phase was DT50 (60 hours). At the end of this period, the soil in each vessel (apart from the T0 samples) was flooded with high purity degassed water. Duplicate soil samples were taken for analysis at zero-time (soil samples only), before the vessels were flooded. Subsequent duplicate samples were taken for analysis (soil and water samples were analysed separately) at intervals of up to 336 hours post flooding.

The analytical method was validated at 0.5 and 10 mg/kg in soil. The analytical method comprised of an extraction with acidified methanol prior to quantitation using liquid chromatography with tandem mass spectrometric detection (LC-MS/MS).

The analytical method was validated at 0.025 μg/mL and 2.5 μg/mL in water (equivalent to 2.5 μg/100 mL and 250 μg/100 mL). The analytical method comprised of an extraction with acetonitrile, followed by the addition of a QuEChERS citrate extraction mix and subsequent shaking and centrifuge. The acetonitrile phase was transferred to an auto-sampler vial prior to quantitation using liquid chromatography with tandem mass spectrometric detection (LC-MS/MS).

The concentration of test item declined in each soil type during investigation of degradation under aerobic conditions. The decline information is summarised below:

(a) Calke (sandy loam):the mean test item detected declined from 9.10 mg/kg at zero-time to <LOQ (less than the limit of quantitation of 0.5 mg//kg) at 146 hours.

(b) Brierlow (silt clay loam):the mean test item detected declined from 8.63 mg/kg at zero-time to <LOQ (less than the limit of quantitation of 0.5 mg//kg) at 146 hours.

(c) South Witham (clay):the mean test item detected declined from 9.05 mg/kg at zero-time to <LOQ (less than the limit of quantitation of 0.5 mg//kg) at 146 hours.

(d) Ingleby (loamy sand):the mean test item detected declined from 10.2 mg/kg at zero-time to <LOQ (less than the limit of quantitation of 0.5 mg//kg) at 169 hours.

 The DT50 and DT90 values for Calke, Brierlow, South Witham and Ingleby soil were calculated on the results obtained using Single First Order (SFO) kinetic models and values are shown in the table below:

Soil	Soil type (USDA classification)	DT50 (hours)	DT90 (hours)
Calke	Sandy loam	25.0	82.9
Brierlow	Silt clay loam	28.5	94.7
South Witham	Clay	24.9	82.6
Ingleby	Loamy sand	59.6	198

 

The concentration of test item declined during investigation of degradation under anaerobic conditions. The decline information is summarised asIngleby (loamy sand):the mean test item detected declined from 4.08 mg/kg (pre-flood) to <LOQ (less than the limit of quantitation of 0.5 mg//kg) at 336 hours (post-flood).

The DT50 and DT90 values for Ingleby soil were calculated on the results obtained using First Order Multi Compartment (FOMC) kinetic model and values are shown in the table below:

Soil	Soil type (USDA classification)	DT50 (hours)	DT90 (hours)
Ingleby	Loamy sand	13.0	981

 

The mean recoveries for the analytical method validation in soil were within the acceptable range of 70 to 110 %, demonstrating accuracy (recovery) of the method. The relative standard deviation (RSD) obtained at each fortification level was within the acceptable range of≤20 %, demonstrating precision of the method.

The mean recoveries for the analytical method validation in water were within the acceptable range of 70 to 110 %, demonstrating accuracy (recovery) of the method. The relative standard deviation (RSD) obtained at each fortification level was within the acceptable range of≤20 %, demonstrating precision of the method.

Following incubation in four different soil types under aerobic conditions at 20 ± 2 °C and at a moisture content equivalent to that at pF 2, the test item degraded with DT50 values of 25.0 h (Calke; sandy loam), 28.5 h (Brierlow; silt clay loam), 24.9 h (South Witham; clay) and 59.6 h (Ingleby; loamy sand). The DT90 values determined under aerobic conditions were 82.9 h (Calke; sandy loam), 94.7 h (Brierlow; silt clay loam), 82.6 h (South Witham; clay) and 198 h (Ingleby; loamy sand). Following incubation in one soil type (Ingleby; loamy sand) under anaerobic conditions at 20 ± 2 °C the test item degraded with a DT50 value of 13 hours and a DT90 value of 981 hours.

Identification of degradation products

The main constituents of EC 701-392-2 follow similar degradation pathways leading to the formation of boric acid and hexadecane-1,2-diol. The latter is mineralised to carbon dioxide and water by beta-oxidation.

Bioaccumulation

The substance will not bioaccumulate. The experimentally derived Log Pow value for the substance has been identified as > 9.4. QSAR calculations of Log Pow for the components determined that Log Pow >10 for the majority of the components. ECHA Guidance on Information requirements and chemical safety assessment Chapter R11: PBT assessment (Version 3.0; June 2017) on determination of bioaccumulation potential states: The aquatic BCF of a substance is probably lower than 2000 L/kg if the calculated log Kow is higher than 10. QSAR calculation of the BCF values for the components of the substance using EPIWIN indicate that the BCF of the majority of the substance are less than 500.

Adsorption/desorption

The adsorption coefficient was performed using the HPLC screening method according to OECD Guideline 121 and EC Method C.19.

The test item had no dissociation constants within the environmentally relevant pH range and therefore was tested in an unadjusted mobile phase. The sample was prepared in tetrahydrofuran that had been shaken with anhydrous sodium sulphate in an attempt to remove residual water and reduce any potential hydrolysis that may occur while in solution prior to analysis.

The adsorption coefficient (Koc) of the test item has been determined to be > 4.27E05, Log Koc > 5.63.

Henry’s Law Constant

Henry's law constant was calculated to be less than or equal to 2.125E01 Pa.m3/mol at 25 °C. A low rate of volatilisation from surface water is expected.

Environmental distribution

The substance is predicted to partition mainly to soil (37.6 - 83.0%) and sediment (44.2 - 55.7%).