Quaternary ammonium compounds, benzyl C12-C16 (even numbered)-alkyldimethyl chlorides

Sediment toxicity

Administrative data

Endpoint:

sediment toxicity: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

A number of reliable studies have shown that the test substance is readily biodegradable.

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Freshwater:

Study 1: A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (50.1% active in water) in water according to OECD Guideline 301D (closed bottle test), in compliance with GLP. Secondary activated sludge was used in this experiment and the percentage of degradation (O2 consumption) was measured. Since the substance was toxic to microorganisms, it was tested in the presence of silica gel to reduce the concentration in the water phase. During the test period, the substance was released slowly from the silica gel. The validity of the test was demonstrated by an endogenous respiration of 1.3 mg/L at Day 28. Furthermore, the differences between the replicate values at Day 28 were less than 20%. The biodegradation of the reference substance, sodium acetate, at Day 14 was 78%. Finally, the validity of the test was shown by oxygen concentrations being > 0.5 mg/L in the bottles. Under the conditions of the study, the biodegradation of the substance was determined to be 63% at Day 28. The substance was considered readily biodegradable (van Ginkel and Stroo, 1992).

Study 2: A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (80% active in hydroalcoholic solution), in water according to OECD Guideline 301B (CO2 evolution test). Flasks containing inoculum from a household water-treating plant dosed with the equivalent of 5 mg C/L test or 20 mg C/L reference substances were maintained for 28 d. Testing at low concentrations, was required due to the toxicity of the test substance towards the inoculum at higher concentrations. Biodegradability was calculated from the released CO2 over time in the test and reference flasks compared to the blank control (a flask prepared without test or reference substance). CO2 production in the blank (inoculum control) was 39.2 mg. Biodegradability in the reference flask was determined to be 88.9% after 28 d. Under the test conditions, the biodegradation of the test substance in water was determined to be 95.5% after 28 d (CO2 evolution). The test substance was considered to be readily biodegradable (van Dievoet, 2005). This study was also submitted as part of the biocides dossier for product type-8 and was concluded by the authority to be a key and valid study (see below discussions; ECHA assessment report, 2015).

Study 3:A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (49-52% active in water) in water according to OECD Guideline 301D (closed bottle test). Half-lives were determined using inoculum from various aquatic sources. The test substance was added to either seawater or water from the river IJseel, ditch water or mineral medium inoculated with activated sludge such that its concentration was 2 mg/dry weight/L. The oxygen decrease in the bottles as a function of time was measured using a special funnel. This funnel fitted exactly into the bottle and derverd as an overflow reservoir permitting multiple measurements in one bottle. Biochemical oxygen demands (BOD) of the test substances were corrected by subtracting the BOD of the control. The biodegradability was calculated by dividing the corrected BOD by the chemical oxygen demand (COD). The biodegradation of the test substance was 71, 69 and 60% in seawater, ditch water and river water, with half -lives of 0.3, 0.1 and 0.1 d, respectively. Under the study conditions, the biodegradation of the test substance was determined to be >60% within three days in the closed bottle test inoculated with unacclimatized sludge. The test substance was therefore considered readily biodegradable (van Ginkel, 1996).

Study 4: A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (50.15% active in hydroglycolic solution) in water according to OECD Guideline 301D (closed bottle test). The method was adapted according to the recommendations of ECETOC (1985) or Blok et al. (1985). Modifications concerned the inoculum, the composition of the dilution water and the analyses. The inoculum was taken from an activated sludge plan, the municipal wastewater treatment plant in Duiven (NL). The sludge was preconditioned by aeration, to reduce high residual respiration rates. The density of the inoculum in the test was 3 mg s.s./L. On Days 0, 14, 28 and 42, the concentration of oxygen was measured. On Day 28, nitrite and nitrate concentrations were measured. The dilution water was the medium as prescribed by the test guideline without ammonia. This modification was introduced to minimize the consumption of oxygen for the nitrification process. Dark glass bottles of about 280 mL with glass stoppers were filled with a suspension of pre-conditioned activated sludge (3 mg/L) in dilution water and a concentration of the test substance equivalent to about 6 mg ThOD/L (Theoretical Oxygen Demand). The test was carried out in triplicate and at every observation time measurements of oxygen and pH were conducted in a new series of three bottles. The test concentration was 4.3 mg/L, therefore the COD in the test suspension was 5.2 mg O2/L. After 4 weeks, the nitrite and nitrate concentrations were measured to be <0.1 and <1.5 mg/L respectively. The extent of biodegradation, calculated as the BOD related to the COD for test substance is about 65% after 2, 4 and 6 weeks. All validity criteria were fulfilled: i.e., inoculum blank indicated >1.5 mg dissolved oxygen/L after 28 days; the residual concentration of oxygen in the test bottles were >0.5 mg/L; difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or the end of the 10-d window, as appropriate, was less than 20%; and toxicity control showed >25% degradation. Therefore, under the conditions of the study, the test substance was considered readily biodegradable (Balk, 1987).

Study 5: A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (50% active in water) in water according to OECD Guidelines 301D and 302A (closed bottle test / modified SCAS test), in compliance with GLP. The experiment was carried out using a combination of an inherent and a ready biodegradability test. To predict the effects of possible biodegradation products, the toxicity of effluents from semi-continuous activated sludge (SCAS) units was assessed. The test substance caused no reduction of the biodegradation of non-purgeable organic carbon (NPOC) present in primary settled sewage. Therefore, it was considered to be non-inhibitory to activated sludge. During the test period, 99% of the substance was removed from the wastewater by adsorption and/or biodegradation. In a second step, the distinction between biodegradation and adsorption was evaluated in closed bottle tests inoculated with approximately 2 mg/L of activated sludge collected on Days 0 and 28 from the SCAS unit fed with the test substance. With the Day 0 SCAS sample, the test substance was biodegraded by 52% within 28 d and by 62% within 56 d. The biodegradation in the closed bottle tests did increase due to the acclimatisation of the microorganisms in the SCAS test unit. The test substance was biodegraded at 77% on Day 28 in the closed bottle test inoculated with sludge sampled on Day 28. The closed bottle test results demonstrated that the test substance was removed by biodegradation in the SCAS test. Under the study conditions, the test substance was considered to be inherently biodegradable (van Ginkel, 1993). This study was primarily carried out to determine the biodegradation pathway of alkylbenzyldimethylammonium salts and not to assess the ready biodegradability; therefore, the study has been used only as a supporting study.

Study 6: A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (80.8% active in ethanol) in water according to OECD Guideline 301B (CO2 evolution test), in compliance with GLP. Flasks containing acclimated inoculum (at 10 mg/L) from a previous SCAS assay were dosed with 5 and 10 mg a.i./L of the test substance or 20 mg/L of the reference substance (d-glucose) and were maintained for 28 d. Biodegradability was calculated from the CO2 released over time in the test and reference flasks relative to that which was released in the blank control (a flask prepared without test or reference substance). The results indicated that 84.0 and 82.6% CO2 was produced in vessels dosed with 5 and 10 mg/L test substance, respectively, compared to 0% with the control and 80.6% with d-glucose. Final suspended organic carbon (SOC) concentrations were 0.7 mL/L (5 mg/L) and 0.6 mL/L (10 mg/L) compared to 0.4 mL/L with the control and 2.2 mL/L with d-glucose. Under the conditions of the study, the substance was considered to be readily biodegradable (Corby, 1992a).

Study 7: A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (80.8% active in ethanol) in water according to OECD Guideline 302A (Modified SCAS test), in compliance with GLP. Four chambers containing activated sludge were aerated and the suspended solid contents were adjusted to 2500 mg/L. The test substance at 1000 mg a.i./L was added to two test units for a 7-d acclimation period. This consisted of incremental additions until the final test concentration of 10 mg a.i./L was reached. Two additional units did not receive the test substance and served as control. The testing period was an additional 7 d following the acclimation period. Throughout the study, all units were fed synthetic sewage. Effluents withdrawn from each unit were analysed for SOC. Under the conditions of the study, the average percent SOC removal was >100% indicating that the test substance was inherently biodegradable (Corby, 1992b).

A literature review was conducted to determine the biodegradability of the test substance, C12 -16 ADBAC (purity not specified). Van Ginkel et al 2004 and Patrauchan et al 2003 publication were reviewed. Based on the literature data, the test substance is considered readily biodegradable (Van Ginkel, 2004 and Patrauchan, 2003).

The Biocides assessment report on C12-16 ADBAC, published by the Italian authorities in June 2015, reported the above key studies and stated that“The reliability factor of US ISC study (van Dievoet, 2005)is 1. Therefore, the study by US ISC should be considered for the environmental risk assessment at product authorization stage. In conclusion, ADBAC/BKC is ready biodegradable being the 10-day window criterion met (OECD 301B). On the other hand, the EQC study (van Ginkel and Stroo, 1992) has a reliability factor of 2 because it cannot distinguish between the degradation of ADBAC/BKC and Propan-2-ol (solvent). If we follow the argument that Propan-2-ol is readily biodegradable and might contribute more to the oxygen consumption. This results in an overestimation of ADBAC/BKC, and the 14-day window criteria was not met (OECD 301D). Alkyl (C12-16) dimethylbenzyl ammonium chloride is readily biodegradable.”  

Sea water:

A study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (49-52% active in water) in seawater and sediment according to OECD Guideline 306 (biodegradation in seawater). Three bottles containing only seawater and 3 bottles containing seawater and the test substance were used. The test substance was added at a concentration of 2 mg/L. The biodegradability was determined by following the course of the oxygen decrease in the bottles using a special funnel. The funnel fitted exactly in the bottle and served as an overflow reservoir permitting multiple measurements in one bottle. The oxygen concentration was measured on Days 0, 7, 14, 21. 28. 42, 56 and 84. The test substance was toxic to microorganisms and was therefore studied in the presence of silica gel to reduce the concentration in the water phase. During the test period, the substance should be released slowly from the silica gel (0.5 g/bottle). Although no additional oxygen consumption was expected, controls with silica gel were carried out as well. Under the study conditions, the test substance was biodegraded by 38 and 31% on Day 28 in the absence and the presence of silica gel, respectively. Since the test substance was biodegraded at 61% on Day 84 in the prolonged closed bottle test with silica gel, it is expected to be biodegraded in seawater (van Ginkel, 1994).

 

Therefore, based on the available information and in line with the biocides assessment report, the test substance is considered to be readily biodegradable.  

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Given the ionic nature of the test substance and the available experimental and predicted BCF values indicates a low bioaccumulation potential. The experimental BCF value of 79 L/kg ww of the test substance has been considered further for hazard/risk assessment.

BCF (aquatic species):

79 L/kg ww

Study 1: A study was conducted to determine the aquatic bioaccumulation of the test substance, C12 -16 ADBAC (30.64% active; 98.9% radiolabeled purity) in Lepomis macrochirus (bluegill fish) under flow-through conditions, according to EPA OPP 165-4, in compliance with GLP. The blue gill fish were continuously exposed to a nominal concentration of 0.050 mg/L of the test substance (equivalent to a measured concentration of 0.076 mg/L) in well water for 35 days, followed by transfer of 35 fish into flowing uncontaminated water for a 21-d depuration period. Sampling was carried out on Days 0, 1, 3, 7, 9, 10, 14, 21, 23, 28 and 35 for the exposure period and Days 1, 3, 7, 10, 14 and 21 for the depuration period. Water samples were collected on Day 8 of the exposure period and Day 16 of the depuration for analytic determination of the test substance concentration. Radiometric analyses of the water and selected fish tissues revealed that the mean steady state bioconcentration factor (BCF) in the edible, non-edible and whole-body fish tissue during the 35 days of exposure to be 33, 160 and 79 L/kg. The half-life for non-edible tissue was attained between Days 14 and 21, while it could not be reached for the edible and whole-body fish tissues by the end of 21-d depuration period. By Day 21 of the depuration period, the 14C residues present on the last day of exposure in the edible, non-edible and whole-body fish tissues had been eliminated by 29, 60 and 44% respectively. Analysis of skin tissue after 35 d of exposure showed residue levels somewhat higher than those observed for edible tissue at the same sampling period, indicating that there is likely significant binding of 14C-ADBAC to the skins and scales of exposed bluegill, as expected behaviour of cationic surfactants. Under the study conditions, the whole body BCF of the test substance was determined to be 79, indicating low potential to bioaccumulate (Fackler, 1989).

Study 2: The Bioconcentration factor (BCF) value of test substance, C12 -16 ADBAC was predicted using regression-based and Arnot-Gobas BAF-BCF models of BCFBAF v3.02 program (EPI SuiteTMv4.11). The Arnot-Gobas method, takes into account mitigating factors, like growth dilution and metabolic biotransformations, therefore the BCF value using this method is generally considered to be more realistic or accurate. However, ionic, pigments and dyes, perfluorinated substances are currently excluded from the applicability domain of this model. In the case of the test substance, considering that it is a UVCB consisting of a mix of ionic (e.g., the quaternary ammonium salts) and non-ionic constituents (e.g., amines), the BCF values were predicted using the regression-based method for the ionic constituents and the Arnot-Gobas BAF-BCF method for the non-ionic constituents, using SMILES codes as the input parameter. The BCF values for the constituents ranged from 1.55 to 70.8 L/kg ww (log BCF: 0.19 to 1.85), indicating a low bioaccumulation potential. On comparing with domain descriptors, all constituents were found to meet the MW, log Kow and/or the maximum number of correction factor instances domain criteria as defined in the BCFBAF user guide of EPISuite. Further, given that the major constituents are structurally very similar and vary only in the carbon chain length, a weighted average value, which takes into account the percentage of the constituent in the substance, has been considered to dampen the errors in predictions (if any). Therefore, the weighted average BCF value was calculated as 69.62 L/Kg ww (Log BCF = 1.84). Overall, considering either the individual BCF predictions for the constituents or the weighted average values, the test substance is expected to have a low bioaccumulation potential. However, taking into consideration the model’s training set and validation set statistics and the fact that the training set only contains 61 ionic compounds, the BCF predictions for the individual constituents are considered to be reliable with moderate confidence. 

Study 3: A study was conducted to determine the biomagnification (BMF) potential of the read across substance, C18 TMAC (purity 95%), following the principles of OECD TG 305. For the main study rainbow trout (Oncorhynchus mykiss) with an average weight of 5.42 g were fed test diets enriched with read across substance (23.6 mg/kg read across the substance in feed. The resulting treatment and one control group (each 40 animals) were tested simultaneously. The uptake phase of 14 days was followed by a depuration phase lasting 14 days. All animals were fed the non-spiked feed during the depuration phase. The concentrations of the read across substance in fish samples were determined by chemical analysis and all tissue concentrations were calculated based on a wet weight basis. Chemical analysis of the read across substance was performed by liquid chromatography with coupled mass spectrometry (LC-MS/MS). In the main study five animals of each group were sampled randomized on Day 7 and Day 14 of the uptake phase and after 10 h, 24 h, 2 days, 3 days, 7 days and 14 days of depuration. Biomagnification factor (BMF) and distribution factor were calculated based on the tissue concentrations measured at the end of the uptake phase. No mortality or abnormal behaviour of the test animals was observed during the main study. The experimental diets were accepted by the test animals and showed a decent digestibility as confirmed by the texture and appearance of the feces. One fish was euthanized at Day 25 due to injuries. The specific growth rates of the animals ranged from 1.95 to 2.71 %/d over the entire experiment. During the study, the feed conversion ratio (FCR) was 0.69 to 0.95. Fish were measured and weighed at the beginning of the experiment as well as at respective sampling time points to monitor growth and associated growth-dilution effects during the feeding study. Growth rate constants were determined separately for the uptake and depuration phases, for the treatments and the control group, using the ln-transformed weights of the fish. A subsequent parallel line analysis (PLA, as suggested by the OECD Guideline) resulted in no statistical differences between the uptake and the depuration phase among the treated groups with the read across substance. No statistically significant difference was detected with regard to the growth of the treated groups. Hence it was deduced that neither adverse nor toxic effects were caused by the enriched diets. As steady state seemed to be reached after 14 days of exposure, steady state biomagnification factors (BMFss) could be calculated as 0.02709 g/g, which showed that read across substance did not biomagnify after dietary exposure. In general, the GIT and the liver showed the highest values for the BMFk and BMFkg. The kinetic BMF (BMFk) and growth-corrected biomagnification factor (BMFkg) were calculated for the read across substance to be 0.0404 and 0.0463, respectively. Overall, it was concluded from the screening that ionization lowers the tendency of a chemical to bioaccumulate, compared to non-ionized chemicals. Aside from the well-known lipophobicity of ionized groups, fast depuration seems to be a major reason for the observed low biomagnification of ionic compounds, in particular anions. Fast depuration may happen due to rapid metabolism or conjugation of charged compounds, and future studies should test this hypothesis. Under the study conditions, the read across substance BMFss, BMFk and BMFkg values on whole body wet weight basis in rainbow trout were determined to be 0.02709, 0.0404 and 0.0463 g/g, respectively, suggesting low biomagnification potential (Schlechtriem, 2021). Based on the results of the read across study, a similar low biomagnification potential is expected for the test substance. 

This is further supported by the absence of bioaccumulation potential evidence observed in in the two toxicokinetic studies in mammals with the read across substance, C12-16 ADBAC (Selim, 1987 and Appelqvist, 2006). .

Also, the biocides assessment reports available from RMS Italy on Coco TMAC and C12-16 ADBAC, concluded the substances to show low potential for bioaccumulation, based on the results from the above study (Fackler, 1989) and an additional read across to DDAC for the Coco TM AC's assessment ((ECHA biocides assessment report, 2015, 2016).

Overall, given the ionic nature of the test substance and the available experimental and predicted BCF values indicates a low bioaccumulation potential. The experimental BCF value of 79 L/kg ww of the test substance has been considered further for hazard/risk assessment.

Cross-reference 3

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Based on the most recent and radiolabelled aerobic biodegradation study in soil, the transformation of the C12 and C14 carbon chains of the test substance was considered to be rapid with DT50 values ranging from 2.2-28.7 days with the SFO model and 1.6 – 23.3 days with the FOMC model at 20°C.​ Further, in the biocides dossier, a weighted estimate of the DT50 value at 12°C was extrapolated for C12-16 ADBAC by assuming the highest allowable concentrations for the major chains. These calculations resulted in the estimated FOMC DT50 of 17.1 days at 12°C and SOF DT50 of 19.2 days at 12°C. The DT50 of 17.1 days at 12°C based on the biphasic model (FOMC) showing better visual fit and lower error was used further for risk assessment.

Therefore, in line with the biocides dossier, the DT50 of 17.1 days at 12°C based on the biphasic model (FOMC) also has been considered further for hazard/risk assessment.

Half-life in soil:

17.1 d

at the temperature of:

12 °C

Study 1:  

A study was conducted to determine the aerobic transformation/dissipation in the soil of the test substance, C12 -16 ADBAC (radiochemical purity: 98.5%), according to the OECD Guideline 307, in compliance with GLP. Four different standard soils (LUFA 2.2, 2.3, 2.4 and 5M, field fresh sampled), varying in their organic carbon content, pH, clay content, cation exchange capacity and microbial biomass, were treated with [ring-U-14C] Benzalkonium chloride. Soil samples were incubated in the dark under aerobic conditions for up to 128 days under controlled laboratory conditions. After appropriate time intervals, soil samples were extracted, and the extracts were analysed for test substance and transformation products to calculate DT50 and DT90 values. The mineralization was determined by trapping and analysis of the evolved 14CO2. Non-extractable residues (NER) were determined after combustion of the extracted soil samples. The total radioactivity of the soil extracts, the extracted soil (NER) and evolved 14CO2 was determined by LSC. Test substance and transformation products in the soil extracts were analysed by LC-FSA (radio-HPLC). Evaluation of the transformation pathway was done by LC-HRMS. 

Transformation of the C12 chain of the test substance [ring-U-14C]Benzalkonium chloride was rapid in all four soils. The transformation of the C14 chain started after a short adaptation phase but was thereafter rapid as well. Within 7 - 21 days the concentration of the C12 chain decreased from initially 67.2 – 69.6% of applied radioactivity (AR) to < 20 % of AR. The concentration of the C14 chain decreased from initially 23.8 – 24.6 % of AR to < 10 % of AR within 10 – 36 days. Formation of NER started directly after application of the test substance. Further formation of NER increased in parallel to the start of increased mineralisation, indicating that a major amount of NER is comprised by radioactivity incorporated in microbial biomass. At the test end, the biomass concentration was in the range of 1.46 – 2.62 % of soil organic carbon content in all four soils, indicating that viable microbial biomass was present throughout the incubation time. The mass balance was in the range 99.9 – 103.0 % at test start and 90.4 – 94.0 % at test end.

The predominant initial degradation step was the oxidative removal of the alkyl chain. Dimethylbenzylamine was determined as the major metabolite, the highest concentrations of dimethylbenzylamine were determined until Day 22, thereafter the concentrations deceased continuously until test end. Methylbenzylamine was transient and only present in traces. Benzylamine, a suspected metabolite, was not detected. Further metabolites containing partly degraded alkyl chains were all transient and were not detected or only <0.2 % of AR (soil 2.3) at the test end.

With regard to the kinetics, the transformation showed a slight bi-phasic pattern, therefore the ‘Single First Order Model’ (SFO) and the ‘First-Order Multi-Compartment Model’ (FOMC) were compared. Based on the visual fit and x2 error, the transformation of [ring-U-14C]Benzalkonium chloride met the requirements for both models well for all four soils. The calculated DT50 values with the Single-First-Order Model (SFO) for the dissipation of [ring-U-14C]Benzalkonium chloride were 2.2 – 8.7 days (C12 chain) and 6.1 – 28.7 days (C14 chain), the DT90 values were 7.2 – 28.8 (C12 chain) days and 20.2 – 95.4 days (C14 chain). The calculated DT50 values with the FOMC model for the dissipation of [ring-U-14C]Benzalkonium chloride were 1.6 – 7.2 days (C12 chain) and 5.5 – 23.3 days (C14 chain), the DT90 values were 15.0 – 48.8 days (C12 chain) and 35.8 – 164.3 days (C14 chain).

The test substance is predominantly C12-ADBAC and C14-ADBAC, with low to negligible amounts of C16-ADBAC. The chain length distribution is defined as follows:C12 (35-80%), C14 (20-55%), C16 (0-15%). C16-ADBAC was not included in this study because it is present in very low amounts; there are technical difficulties with having sufficient radioactivity for substances present in small amounts relative to other constituents. C16-ADBAC would be expected to degrade by the same route but at a slower rate than its C12 and C14 counterparts, as degradation rate tends to decrease with increasing chain lengths. Under the study conditions, transformations of both C12 and C14 carbon chains of the test substance were determined to be rapid in all four soils and the DT50 values were determined to be 2.2 – 8.7 days [C12 chain] and 6.1 – 28.7 days [C14 chain] with the SFO model and 1.6 – 7.2 days [C12 chain] and 5.5 – 23.3 days [C14 chain] with the FOMC modelat 20°C (Fiebig, 2019).

Further, in the biocides dossier, to account for the potential contribution of C16 ADBAC to the overall DT50 of ADBAC, a geometric mean of SFO and FOMC DT50s for C12 and C14 ADBAC in the four soils (as recommended in BPR Vol IV Part B and C) was calculated and converted to 12° using the following equation (DT50 (12°) = DT50 (20°) * e^{(0.08*(20-12))}. This was followed by linear extrapolation of the geometric mean DT50s for C12 and C14 ADBAC, to estimate the DT50 for C16 ADBAC. See tables below:

SFO DT50s
	Soil	2.2	2.3	2.4	5M	Geo. Mean	Adj. to 12° C
	C12 ADBAC	2.2	3.3	6.2	8.7	4.4	8.4
	C14 ADBAC	6.1	8.9	12.9	28.7	11.9	22.6
	C16 ADBAC	--	--	--	--	--	36.7

 

FOMC DT50s
	Soil	2.2	2.3	2.4	5M	Geo. Mean	Adj. to 12° C
	C12 ADBAC	1.6	3.2	5.8	7.2	3.8	7.3
	C14 ADBAC	5.5	8.3	12.1	23.3	10.7	20.2
	C16 ADBAC	--	--	--	--	--	33.1

 

A weighted estimate of the DT50 of ADBAC (C12-C16) at 12°C was calculated by assuming the highest allowable concentrations of C14- and C16- ADBAC and the balance of C12-ADBAC (i.e., 12% C16, 52% C14 and 36% C12), which resulted in the following estimated DT50s:

SFO DT50 = 19.2d at 12°C; FOMC DT50 = 17.1d at 12°C

However, due to the relatively low levels of C16-ADBAC, the overall estimated DT50s were considered rather insensitive to the assumed DT50 for C16-ADBAC. The DT50 of 17.1 days at 12°C based on the biphasic model (FOMC) showing better visual fit and lower error was used further for risk assessment.

Study 2: A study was conducted to determine the aerobic biodegradation of the test substance, C12-16 ADBAC (50% active in water) in loamy soil, according to the US FDA Environmental Assessment Handbook, Technical Assistance Document 3.12 (1987). The study comprised two treatments: test and chemical blank control group, each with three replicates. The test substance was added into biometers at a concentration of 10 mg carbon per 50 g soil using appropriate amount of deionised water required for bringing the soils to 50-70% of the moisture capacity. Loam was added to the biometers after the test solutions to facilitate uniform moistening of the soils by capillary action. The test was then incubated at 22 ± 3°C and run for approximately 90 d. The side tube of the biometer contained 20 mL 0.2 M KOH for absorbing carbon dioxide produced by the microorganisms. The theoretical CO2 production of the test substance was calculated from its carbon content. The amounts of carbon dioxide were calculated by subtracting the mean carbon dioxide production in the test systems containing the test substance and the mean carbon dioxide production level in the control blank. Biodegradation was calculated as the ratio of experimental carbon dioxide production to theoretical carbon dioxide production [ThCO2P]. Under the study conditions, there was 64% degradation of the test substance after 70 days. This percentage of the theoretical carbon dioxide production presumes complete mineralization. The DT50 was estimated to be 40 days (van Ginkel, 1994).  

Based on the most recent and radiolabelled aerobic biodegradation study in soil, the transformation of the C12 and C14 carbon chains of the test substance was considered to be rapid with DT50 values ranging from 2.2-28.7 days with the SFO model and 1.6 – 23.3 days with the FOMC model at 20°C.​ Further, in the biocides dossier, a weighted estimate of the DT50 value at 12°C was extrapolated for C12-16 ADBAC by assuming the highest allowable concentrations for the major chains. These calculations resulted in the estimated FOMC DT50 of 17.1 days at 12°C and SOF DT50 of 19.2 days at 12°C. The DT50 of 17.1 days at 12°C based on the biphasic model (FOMC) showing better visual fit and lower error was used further for risk assessment.

Therefore, in line with the biocides dossier, the DT50 of 17.1 days at 12°C based on the biphasic model (FOMC) also has been considered further for hazard/risk assessment.

Cross-reference 4

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Based on the results of the study, complete removal of the test substance from the domestic wastewater treatment plants was observed.  Further, based on the results of the soil biodegradation study with the test substance, the DT50 value for degradation in the sediment compartment can be considered to be approximately 171 days.     
    
    

Further, based on the results of the for soil biodegradation study with the read across substance, the DT50 value for degradation in the sediment compartment can be considered to be approximately 171 days. 

Half-life in freshwater sediment:

171 d

at the temperature of:

12 °C

Surface water simulation testing:

The study does not need to be conducted because the substance is readily biodegradable.

Sediment:simulation testing

The study does not need to be conducted because the substance is readily biodegradable.Nevertheless, as per the ECHA E.16 guidance, the half-life in the sediment compartment will be a factor 10 higher than the half-life in soil. Therefore, the sediment half-life value of 171 days at 12°Chas been considered further for risk assessment.

Sewage treatment simulation testing

A continuous activated sludge (CAS) study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (49.2% active in water), in domestic wastewater according to OECD Guideline 303A, in compliance with GLP. In this study, the domestic waste microorganisms were exposed to the test substance, by spiking at a nominal influent concentration of 49 mg/L (36 mg/L carbon) for 58 days. An additional unit fed only with the domestic wastewater was maintained as the control group. All samples were analysed for NPOC. A strong increase in the concentration of NPOC was noted on Day 2 in the test units. This was probably caused by the toxicity of the test substance. The activated sludge acclimatised to the test substance within a few days, resulting in a decrease in the NPOC concentrations. After 3 weeks, very high carbon removal percentages were achieved. The mean removal percentage in the test unit assessed using a HLPC-MS/MS was determined to be 99.998%, indicating ultimate biodegradation. Removal of the test substance from the influent through adsorption onto sludge was only 0.023% on Day 58, showing that the main mechanism of elimination was biodegradation. Based on the results of the study, the test substance was removed from wastewater at a very high percentage (approximately 99.998%) in the continuous activated sludge test. Removal of the test substance from the influent through adsorption onto sludge was only 0.016 to 0.023% at two sampling times, demonstrating that the test substance was removed almost completely and biodegraded. This suggests that the test substance biodegrades almost completely in conventional biological wastewater treatment plants (Ginkel, 2007).