Cetrimonium chloride

Bioaccumulation: terrestrial

Administrative data

Endpoint:

bioaccumulation: terrestrial

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

The vapour pressure of the test substance was determined using the isothermal thermogravimetric effusion method according to OECD Guideline 104, EU Method A.4 and US EPA OPPTS 830.7950 (Brekelmans, 2012).

Vapour pressure:

0.006 Pa

at the temperature of:

25 °C

Vapour pressure was <0.0015 Pa at 20°C.

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Based on the results of the read across study, a similar complete removal of the test substance from the domestic wastewater treatment plants can be expected.

Further, based on the results of the 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.

Sewage treatment simulation testing

A continuous activated sludge (CAS) study was conducted to determine the biodegradation of the read across 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 read across substance, by spiking at a nominal influent concentration of 49 mg/L (36 mg/L carbon) for a period of 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 toxicity of the read across substance. The activated sludge acclimatised to the read across substance within a few days, resulting in a decrease of 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 read across 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 read across substance was removed from wastewater at a very high percentage (approximately 99.998%) in the continuous activated sludge test. Removal of the read across substance from the influent through adsorption onto sludge was only 0.016 to 0.023% at two sampling times, demonstrating that the read across substance was removed almost completely and biodegraded. This suggests that the read across substance biodegrades almost completely in conventional biological wastewater treatment plants (Ginkel, 2007). Based on the results of the read across study, a similar complete removal of the test substance from the domestic wastewater treatment plants can be expected.  

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 has been considered further for 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 with the read across substance, C12-16 ADBAC, the transformation of the 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 (x2)compared to the SFO model was used further for 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 read across 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 read across 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. Read across 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 read across 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 read across 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 read across 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 read across 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 table below:

	Soil 2.2	Soil 2.3	Soil 2.4	Soil 5M	Geo. Mean	Adj. to 12° C
SFO DT50s
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
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 errorwas used further for risk assessment.

Based on the results of the read across study, similar degradation potential and half-life is considered for the test substance.

 

Study 2:A study was conducted to determine the aerobic biodegradation of the read across 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 read across 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 read across 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 read across 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 read across substance after 70 days. This percentage of the theoretical carbon dioxide production presumes complete mineralization. The DT50 was estimated to be 40 days (Ginkel, 1994). Based on the results of the read across study, similar degradation potential and half-life is considered for the test substance.  ​

Based on the most recent and radiolabelled aerobic biodegradation study in soil with the read across substance, C12-16 ADBAC, the transformation of the C12 and C14 carbon chains of the 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 (x2)compared to the SFO model was used further for risk assessment. Therefore, in line with the biocides dossier, the DT50 of 17.1 days at 12°C derived for the read across substance based on the biphasic model (FOMC) also has been considered further for hazard/risk assessment of the test substance.  

Cross-reference 4

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

The results of the read across study, supported with the estimated BCF value for the test substance together with its ionic nature indicates a low bioaccumulation and biomagnification potential. The higher experimental BCF value of 79 L/kg wt-wt from the read across study with C12-16 ADBAC and the growth corrected kinetic biomagnification factor (BMFkg) value of 0.0463 based on read across to C18 TMAC, has been considered further for hazard/risk assessment. 

BCF (aquatic species):

79 L/kg ww

BMF in fish (dimensionless):

0.046

Study 1: A study was conducted to determine the aquatic bioaccumulation of the read across 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 read across 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 read across 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 conditions of the study, the whole body BCF of the read across substance was determined to be 79, indicating low potential to bioaccumulate (Fackler, 1989).

 

Study 2:A study was conducted to determine the tissue distribution of two cationic surfactants mixtures in Rainbow Trout (Oncorhynchus mykiss) following exposure via water for seven days and analysis of different fish tissues. The test chemicals were grouped into two mixtures of six containing 10 alkyl amines and 2 quaternary alkylammonium surfactants: C10 TMAB (as part of MIX 2) and C14 TMAC (as part of MIX 1). Studying chemical mixtures has the advantage that differences in behavior between chemicals are not obscured by biological variability or experimental variables. Bioconcentration studies with mixtures have been shown to provide similar results to studies with single chemicals.The experiments were conducted in 300 L fiberglass aquaria with a water renewal rate of 1.3 L min−1 (MIX 1) and 1.45 L min−1 (MIX 2). A solution of the test chemical mixture in methanol was infused continuously (3.5 and 3.8 μL min−1 for MIX 1 and MIX 2, respectively) into the water inflow using a syringe pump. The intended concentrations of C10 TMAB and C14 TMAC were 59 and 1.3 μg/L (measured). The water temperature was 10 °C and the pH 7.5. The water hardness was estimated to be 1.1 mM Ca2+. For each mixture, the syringe pump was started in an aquarium containing no fish. After 16 h, to allow the concentrations to stabilize, 12 rainbow trout were added. After 7 d of exposure, the fish in the exposure aquaria as well as several unexposed (control) fish were sacrificed followed by blood collection.The surface of the fish posterior of the gills was rinsed with 100% methanol to remove read across substance residues adsorbed to the outer surface of the skin and absorbed in the skin mucus.The fish were then dissected and the liver, the kidney, the gills, and the remaining contents of the abdominal cavity were taken and weighed. Skin and muscle samples were prepared from the upper dorsal region on semi-frozen fish after the methanol rinse had removed the mucus. For 6 fish from each aquarium and 3 control fish, samples of muscle, skin, liver, and gills were homogenized in a bullet blender (muscle and liver) or in a cryo-mill (skin and gill). A sub-sample of 0.5−1.2 g of the homogenate was extracted twice in methanol, employing centrifugation at 4000 rpm for phase separation. Isotope labeled standards of C10 TMAB and C14 TMAC were added to a portion of the extract corresponding to 12−75 mg of the sample. Whole blood was analyzed rather than plasma because of the small quantity of sample available and the anticipated low concentrations.The test chemical concentrations generally increased in the order muscle <blood < skin < gills < liver. Because the mass of extracted mucus was not determined, the concentrations in mucus were normalized to the estimated fish’s total surface area excluding the head, which was not rinsed. The concentration in mucus was on average 3.9 (range 0.9−11.6) times lower than the surface area-normalized concentration in gills. To calculate the quantity of the test chemical in the different tissues, the amount of each tissue in the fish was estimated and multiplied by the concentration in that tissue. The test chemical quantities in the different tissues were then summed to give the body burden in each fish. The apparent BCFs (BCFapp) values at the end of the 7-day exposure were calculated by dividing the surfactant body burden (blood, muscles, liver, gills, skin, mucus) by the fish mass, and dividing this by the average measured concentration in water samples taken during the exposure phase. Under the study conditions, the BCFapp for the two quaternary substances C10 TMAB and C14 TMAC were determined to be 0.1 and 31 L/kg ww, respectively. Mucus, skin, gills, liver, and muscle each contributed at least 10% of body burden for the majority of the test chemicals. In contrast to the analogue alkylamine bases, the permanently charged quaternary ammonium compounds accumulated mostly in the gills and were nearly absent in internal tissues, indicating that systemic uptake of the charged form of cationic surfactants is very slow (Kierkegaard, 2020).

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. 

Study 4: The Bioconcentration factor (BCF) value of test substance, C16 TMAC 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 values using this method is considered to be more realistic or accurate. Therefore, except for ionic, pigments and dyes, perfluorinated substances, for which it is not recommended (as of now), the Arnot-Gobas method is used preferentially used for BCF predictions. Considering that test substance is a monoconstituent containing ionic main constituents (e.g., the quaternary ammonium salts) and few non-ionic impurities (e.g., amines), the BCF values were predicted using regression-based and Arnot-Gobas BAF-BCF models respectively and using SMILES codes as the input parameter. The BCF values for the constituents ranged from 70.80 to 164.2 L/kg ww (log BCF: 1.85 to 2.21), indicating a low bioaccumulation potential. On comparing with domain descriptors, all constituents were found to meet the MW, log Kow and/or maximum number of correction factor instances domain criteria as defined in the BCFBAF user guide of EPISuite. Further, given that the major constituents or impurities are overall structurally similar and vary mostly 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 71.30 L/Kg ww (Log BCF = 1.85). 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.

This is further supported by the no 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 TMAC’s assessment ((ECHA biocides assessment report, 2015, 2016). The report concluded the following in the Coco TMAC assessment report: “Coco alkyltrimethylammonium chloride is readily biodegradable, is rapidly excreted and does not accumulate in mammals, and it adsorbs onto the fish surface where its irritating action is expressed (therefore accumulation is more related to the concentration of the administered solution). Based on these properties’ bioaccumulation is not expected to be of concern for ATMAC/TMAC. An experimental BCFwhole body of 81 L/kg was determined in a flow-through test with Lepomis machrochirus and the read across substance DDAC (Lonza Cologne GmbH and Akzo Nobel Surface Chemistry AB, same study). A very similar result was obtained for the other quaternary ammonium compound benzyl-C12-16-alkyldimethyl ammonium chloride (C12-16-BKC/ADBAC) in a fish bioconcentration test, which gave a BCFwhole body = 79 L/kg (Akzo Nobel Surface Chemistry AB, access to Lonza Cologne GmbH study). Being both studies equally reliable, the BCFwhole body = 81 L/kg is chosen because related to the lead read across substance (DDAC) and it is slightly higher than the C12-16 BKC/ADBAC endpoint.”   

Overall, the results of the read across study, supported with the estimated BCF value for the test substance together with its ionic nature indicates a low bioaccumulation and biomagnification potential. The higher experimental BCF value of 79 L/kg wt-wt from the read across study with C12-16 ADBAC and the growth corrected kinetic biomagnification factor (BMFkg) value of 0.0463 based on read across to C18 TMAC, has been considered further for hazard/risk assessment. 

Cross-reference 5

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Based on the available weight of evidence and the cationic nature, the test substance, C16 TMAC, is expected to have a low absorption potential followed by excretion primarily via feces. Based on QSAR predictions and data on read across substance, it is likely to undergo aliphatic hydroxylation as the first metabolic reaction. Further, based on its ionic nature, molecular weight and key physico-chemical properties it is likely to have no or very bioaccumulation potential. 

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

10

Absorption rate - dermal (%):

10

Absorption rate - inhalation (%):

50

ABSORPTION:   

Oral absorption   

Based on physicochemical properties:   

According to REACH guidance document R7.C (May 2014), oral absorption is maximal for substances with molecular weight (MW) below 500. Water-soluble substances will readily dissolve into the gastrointestinal fluids; however, absorption of hydrophilic substances via passive diffusion may be limited by the rate at which the substance partitions out of the gastrointestinal fluid. Further, absorption by passive diffusion is higher at moderate log Kow values (between -1 and 4). If signs of systemic toxicity are seen after oral administration (other than those indicative of discomfort or lack of palatability of the test substance), then absorption has occurred.  

The test substance, C16 TMAC is an alkyl trimethyl ammonium chloride (TMAC) and a cationic surfactant. It is a mono-constituent with majorly C16 alkyl chain length and molecular weight of 320 g/mol. The purified form of the substance is solid powder but it is placed on the market in the solution form. It has a moderate water solubility of 240 mg/L at 25°C (based on CMC) and a low log Kow of 3.08 value, which was determined using estimation method based on solubility ratios.  

Based on the R7.C indicative criteria, together with the fact that the test substance is cationic with a strong adherence potential to the negatively charged surfaces of the membranes, suggests that, it is not expected to easily pass biological membranes.

Based on experimental data on read across substances:   

A study was conducted to determine the absorption, distribution and excretion of orally administered radiolabelled read across substance, [14C] C16 TMAB (99% radiolabelled purity), in female rats. Approximately 80% of the dose of radioactivity was found in the gastro-intestinal tract 8 h after administration, only small amounts were found in the blood plasma and about 2% of the administered radioactivity was excreted in the bile during the first 12 h after treatment. The low levels of radioactivity in the serum and bile, together with the large amounts of radioactivity found in the gastro-intestinal tract, indicated poor intestinal absorption of the read across substance. Only small amounts of radioactivity were found in the liver, kidneys, spleen, heart, lungs and skeletal muscle, and the tissue radioactivity declined rapidly, only traces being found in the examined tissues 4 d after [14C] read across substance administration. Within 3 d of ingestion, 92% of the administered radioactivity had been excreted in the faeces and 1% in the urine. No radioactivity was found in the expired CO2 collected during day 1 after administration of [14C] read across substance, indicating that no complete oxidation of the cetyl group occurred. The results of thin-layer chromatography of bile and urine samples indicated that the read across substance was metabolized to some extent in the rat. Under the study conditions, the read across substance can be assumed to have very low absorption (i.e., <10%), distributed mainly in GIT and excreted in faeces (Isomaa, 1975). 

A study was conducted to determine the basic toxicokinetics of the read across substance, C12-16 ADBAC (49.9% active in water with 99.4% radiolabelled purity), according to OECD Guideline 417, in compliance with GLP. In this study, Sprague-Dawley rats were treated with single and repeated oral doses (50 or 200 mg/kg bw) as well as a single dermal dose (1.5 or 15 mg/kg bw) of the radiolabelled read across substance. Following single and/or repeated oral doses, the plasma, blood and organ radioactivity levels were essentially non-quantifiable, indicating a low oral bioavailability. The actual fraction of the oral dose absorbed was around 8% (urine and bile fractions). This was eliminated rapidly, essentially within a 48 to 72 h period. The majority of the oral dose was excreted in the faeces. At the high oral dose level only, quantifiable levels of radioactivity (2,386 to 23,442 ηg equivalent/g) were found in some central organs at 8 h post-dosing; otherwise, the vast majority of the dose was confined to the intestines, where their levels decreased over time and were all non-quantifiable by 168 h (i.e., 7 d). Only about 4% of the oral dose was eliminated in the bile in a 24 h period, of which about 30% during the first 3 h. Under the conditions of the study and following oral administration the read across substance was found to have limited absorption (ca. 10%), low distribution (below quantification limits within 4-7 d) and majorly excreted via faeces (ca. 80%) (Appelqvist, 2006). Further, a biocides assessment report available on the read across substance by RMS Italy, concluded that the read across substance“is highly ionic and, therefore, it is expected not to be readily absorbed from the gastrointestinal tract or skin. The vast majority of the oral dose was excreted in the faeces (80%) as unabsorbed material (only about 4% of the oral dose was eliminated in the bile in a 24-hour period). The actual fraction of the oral dose absorbed was about 10%, based on the urinary mean value 3-4% (with a single peak value of 8.3%) and biliary excretion values (3.7-4.6%), as well as on the absence of residues in the carcass, as measured at 168 h. Excretion was rapid (within a 48 to 72-hour period). The radioactivity excreted in the urine was not associated with the parent compound, but with more polar metabolites which were not identified”(ECHA biocides assessment report, 2015).

In another study conducted according to EPA OPP 85-1, Sprague-Dawley rats (10 animals per sex per group) were treated with radiolabelled read across substance, C12-16 ADBAC (30% active in water with 99.4% radiolabelled purity). The study was conducted in four phases: a single low dose (10 mg/kg); a single high dose (50 mg/kg); a 14 d repeated dietary exposure with non-radiolabelled read across substance (100 ppm) and single low dose of radiolabelled (14C) read across substance (10 mg/kg); and single intravenous dose (10 mg/kg). Following the single doses or the last dietary dose, urine and faeces were collected for 7 d. A preliminary study had indicated that insignificant 14CO2 was generated. Tissues, urine and faeces were collected and analysed for radioactivity and faeces were analysed by TLC, HPLC and MS for metabolites and parent compound. Following oral administration, radiolabelled read across substance was rapidly absorbed, although in very limited amounts, consistent with its highly ionic nature. Residual 14C in tissues was negligible after administration by gavage both after single and repeated dosing, indicating low potential for bioaccumulation. After i.v. administration a higher amount of radioactivity (30−35%) was found as residue in the tissues. About 6−8% of orally administered read across substance is excreted in the urine whereas, 87−98% was found in the faeces. Since no data on bile duct-cannulated rats are available, it was not possible to conclude if this radioactivity accounts exclusively for unabsorbed read across substance or not. However, the i.v. experiment showed that 20−30% was excreted in the urine and 44-55% in the faeces, suggesting that both the kidney and liver are capable of excreting read across substance once absorbed and that absorption is higher than the % found in the urine after oral administration. Based on the urinary mean value 3-4% (with a single peak value of 8.3%) and biliary excretion values (3.7-4.6%), as well as on the absence of residues in the carcass, as measured at 168 h, it can be expected that the read across substance absorption through the g.i. tract is about 10% (conclusion not included in the study report; as assessed by the Italian Rapporteur Member state in the biocides dossier; ECHA biocides assessment report, 2015). Less than 50% of the orally administered read across substance was found to be metabolised to side-chain oxidation products. In view of the limited absorption of the read across substance, the four major metabolites identified were expected to be at least partially formed in the gut of rats, apparently by microflora. No significant difference in metabolism between male and female rats or among the dosing regimens was observed. Repeated dosing did not alter the uptake, distribution or metabolism of read across substance. Under the conditions of the study, the read across substance was found to have limited absorption (ca. 10%; due to its ionic nature), negligible distribution (no bioaccumulation), and majorly excreted majorly via faeces (87-98%) following oral administration. However, following i.v. administration, it was found to be widely distributed (30-35%) in tissues and excreted both via faeces (40-55%) and urine (20-30%). Four major metabolites were identified, formed via oxidation of the alkyl chain (Selim, 1987). Further, the biocides assessment report concluded that“the oral absorption can be considered to be approximately 10%, based on the 5-8% of the C12-16-ADBAC administered dose eliminated via urine and tissue residues (less than 1% of the administered dose 7 days after single and repeated oral dosing). More than 90% is excreted in the faeces and the pattern did not change after repeated doses. Although it was not possible to discriminate between unabsorbed/absorbed material, based on the chemical nature of the test substance, it can be anticipated that about 90% is present in faeces as unabsorbed material. The majority of C12-16-ADBAC metabolism is expected to be carried out by intestinal flora; the metabolites, which account for less than 60% of the administered dose, include hydroxyl- and hydroxyketo- derivatives of the dodecyl, tetradecyl and hexadecyl chains. No metabolite accounted for more than 10% of the total administered dose”(ECHA biocides assessment report, 2015).  

Assessment from biocides assessment report available on read across substances:  

As indicated above the biocides assessment reports available on the read across substance C12-16 ADBAC indicated that given its ionic nature, C12-16 ADBAC was not expected to be readily absorbed from the gastrointestinal tract or skin. And based on the results from thein vivostudies with rats andin vitrostudies with human skin, an oral and dermal absorption value of 10% could be considered at non-corrosive concentrations. Another biocides assessment report by RMS Italy , on the read across substance Coco TMAC, additionally reported two supportingin vivostudies on rats from literature, apart from the studies with C12-16 ADBAC and didecyldimethylammonium chloride (DDAC), which indicated an oral uptake of C16 TMAC of about 3.3 % (1.22 excreted by urine and around 2% in bile; 92% found back in faeces on day 3); and a dermal uptake of about 3.15% (in two days: 1.76% excreted in urine, 0.28% in faeces, organs 1.11%) (ECHA biocides assessment report, 2015, 2016). 

Conclusion:Overall, based on the available weight of evidence information, the test substance can be expected to overall have low absorption potential through the oral route at non-corrosive concentrations. Therefore, in line with the biocide assessment report and as a conservative approach a maximum oral absorption value of 10% can be considered for risk assessment.   

Dermal absorption   

Based on physicochemical properties:   

The two well-known parameters often used to characterise percutaneous penetration potential of substances are the dermal permeability coefficient (Kp[1]) and maximum flux (Jmax). Kp reflects the speed with which a chemical penetrates across SC and Jmax represents the rate of penetration at steady state of an amount of permeant after application over a given area of SC. Out of the two, although Kp is more widely used in percutaneous absorption studies as a measure of solute penetration into the skin. However, it is not a practical parameter because for a given solute, the value of Kp depends on the vehicle used to deliver the solute. Hence, Jmax i.e., the flux attained at the solubility of the solute in the vehicle is considered as the more useful parameter to assess dermal penetration potential as it is vehicle independent (Robert and Walters, 2007).  

The test substance is a solid paste, with an MW exceeding 100 g/mol, moderate water solubility and an estimated log Kow exceeding slightly above 3.This together with the fact that the test substance is cationic with a strong adherence potential to the negatively charged surfaces, suggests that the test substance at non-corrosive concentrations is likely to have a low penetration potential through the skin.  

At higher corrosive concentrations although there is a likelihood of exposure to the test substance due to disruption of the barrier properties of the skin, the likelihood of occurrence of these cases is expected to be minimal due to the required risk management measures and self-limiting nature of the hazard. Therefore, this scenario has not been considered further for toxicokinetic assessment. 

Based on QSAR prediction:   

The two well-known parameters often used to characterise percutaneous penetration potential of substances are the dermal permeability coefficient (Kp[1]) and maximum flux (Jmax). Kp reflects the speed with which a chemical penetrates across SC and Jmax represents the rate of penetration at steady state of an amount of permeant after application over a given area of SC. Out of the two, although Kp is more widely used in percutaneous absorption studies as a measure of solute penetration into the skin. However, it is not a practical parameter because for a given solute, the value of Kp depends on the vehicle used to deliver the solute. Hence, Jmax i.e., the flux attained at the solubility of the solute in the vehicle is considered as the more useful parameter to assess dermal penetration potential as it is vehicle independent (Robert and Walters, 2007).   

In the absence of experimental data, Jmax can be calculated by multiplying the estimated water solubility (using WATERNT v.1.02) with the Kp value from DERMWIN v2.02 application of EPI Suite v4.11. The calculated Jmax values for the mono-constituent substance was determined to be 2.52E-5 μg/cm2/h. As per Kroeset al.,2004 and Shenet al.2014, the default dermal absorption for substances with Jmax ≤0.1 μg/cm2/h can be considered to be less than 10%. Based on this, the test substance can be predicted to have low absorption potential through the dermal route.   

Based on experimental data on read across substances:  

A study was conducted to determine the percutaneous absorption of the radiolabelled read across substance, [C14] C12 TMAB, under occlusive conditions on rat skin. The test substance was applied to the intact clipped skin of 3 rats under three scenarios: at 1% and 3% in aqueous solution followed by subsequent with and without rinsing respectively and 0.5% hair-rinse formulation of test substance. Application in a cream hair-rinse preparation under user conditions resulted in the absorption of about 0.1% of the administered radioactivity after 48 h. No measurable radioactivity was present in the blood. However, application of the test substance at 1% and 3% aqueous without subsequent rinsing solution gave a somewhat higher absorption (0.6% after 72 h and 3.15% after 48 h respectively), whereas, some radioactivity was found in the blood after application of the test substance to the skin without subsequent rinsing. Overall, the percutaneous absorption of the test substance was low. Under study conditions, percutaneous absorption of the radiolabelled test substance was found to be 0.6% with rinsing and 3.15% without rinsing (Bartnik 1979). 

A study was conducted to determine thein vitrodermal absorption of the read across substance, C16 TMAC contained in a hair care formulation (14% formulation containing 25% C16 TMAC aqueous solution) using pig skin, according to OECD Guideline 428, in compliance with GLP. Preparations of dermatomed pig skin (from back and flank of castrated male pig) measuring 1000 μm in thickness with stratum corneum, epidermis and parts of the dermis were used. Six skin samples were mounted in parallel in Teflon diffusion chambers (static diffusion cell) which were continuously rinsed with receptor fluid (0.9% sodium chloride in distilled water). The test formulation containing 0.875 mg/cm2 of the read across substance was applied to the skin disks at an area dose of 25 mg/cm² (100 mg on 4 cm²) for an exposure period of 30 minutes and subsequently rinsed off with a neutral shampoo and water. Concentrations of the read across substance in receptor fluid were determined at the start of the experiment (0 h) and after 16, 24, 40, 48, 64 and 72 h by HPLC/ESI/MS detection. In addition, the read across substance was analysed in different skin layers and in the rinsing fluid in order to enable calculation of total recovery. Based on the analysis, at any of the different sampling times, small quantities of the read across substance could be detected in the horny layer (1.25-14.25 μg/cm²) and in residual skin (0.75-7.25 μg/cm², corresponding to 0.086-0.83%, with a mean of 0.27±0.28%). The total recovery was about 108%. As per the SCCS opinion, for the purposes of the risk assessment, a conservative value (limit of quantification, LOQ) for the receptor fluid may be taken as a worse case value with the assumption that the amounts in the receptor fluid were at the respective LOQ value. For the duration of 24 h, a mean value of about 3.3 μg/cm² (range 2.4-3.7 μg/cm²) can be calculated from the data in the table in Appendix III of the study. Adding the amount of the read across substance in dermis would result in 10.6 μg/cm² as a worst-case value. Under the study conditions, the worst-case dermal absorption value for risk assessment of the read across substance was assumed to be 10.6 μg/cm2 (SCCS, 2012) (i.e., equivalent to 1.2% of the applied dose). 

Following a single dermal application of the read across substance, C12-16 ADBAC in the Appelqvist (2006) study, the plasma and blood radioactivity levels were non-quantifiable at nearly all time-points. For the 1.5 mg/kg bw group, around 2 and 43% of the dose was eliminated in the urine and faeces, respectively, mostly within a 48-h period, suggesting that the dermal dose was highly absorbed via the skin. However, this apparent high absorption via the skin may have been due to the animal licking the test site. This was also supported with the finding that, after oral dosing, only about 4% was excreted via bile back to the intestine and 4% excreted via urine. If similar routes of excretion are expected for dermally absorbed doses, it would not be possible to find levels of 50% of applied doses in intestine with only 2% excreted via urine. This indicates that about 50% of the dermally applied dose was taken up orally after all. Excretion in urine (2%) following dermal exposure was similar to that following oral exposure. At 24 h post-dosing, most of the radioactivity was in the “stripped” skin (dermis/epidermis) application site (15.02/8.74% [male/female] and 33.8/24.2% of the dose for the high and low dose groups respectively) and intestines for both dose levels (5.76/8.32% and 5.61/7.79% of the dose for the high and low dose groups respectively), though some radioactivity was in the skin adjacent to the application site and minor traces were in the eyes (both most likely from cross-contamination due to grooming). At 168 h, levels in the application site of the individual animals of the low dose were 5.19 to 9.21% of the radioactive dose, suggesting the skin acted as a drug reservoir. In the stratum corneum of the application site, the levels of radioactivity were of similar magnitude in the different layers at each time-point. For all tissues/organs, the radioactivity levels decreased over time. All data showed generally a low inter-animal variability. In addition, there was no evidence of gender differences (Appelqvist, 2006). Further, the biocides assessment report concluded that “The available data on BKC dermal absorption do not allow to quantify exactly the % of the dose which was absorbed after dermal application. However, due to the radioactivity recovered at the skin application site after removal of the stratum corneum layers (6.5-8.7% of the dose) and the ionic nature of the test item, it can be anticipated that the dermal absorption is not different from the oral one (10% at non corrosive concentration)”(ECHA biocides assessment report, 2015).  

Anin vitrostudy was conducted to determine the rate and extent of dermal absorption of the read across substance, C12-16 ADBAC (80.5% active; >99% radiolabelled purity), according to OECD Guideline 428, in compliance with GLP. The study was conducted with radiolabelled read across substance at 0.03% and 0.3% concentrations, which was topically applied over split-thickness human skin membranes mounted into flow-through diffusion cells. Receptor fluid was pumped underneath the skin at a flow rate of 1.5 mL/hour. The skin surface temperature was maintained at approximately 32°C. A barrier integrity test using tritiated water was performed and any skin sample exhibiting a permeability coefficient (kp) greater than 2.5 x 10-3 cm/h was excluded from subsequent absorption measurements. The 14C- radiolabelled read across substance was applied at an application rate of 10 mg/cm2. Absorption was assessed by collecting receptor fluid in hourly intervals from 0-6 h post dose and then in 2-hourly intervals from 6-24 h post dose. At 24 h post dose, the exposure was terminated by washing and drying the skin. The stratum corneum was then removed from the skin by 20 successive tape strips. All samples were analysed by liquid scintillation counting. Under the conditions of the study, the mean absorbed dose and mean dermal deliveries were determined to be 0.05% (0.01 ηg equiv. /cm2) and 2.22% (0.07 ηg equivalent/cm2) of the applied dose for the low concentration test preparation, respectively, and 0.03% (0.01 ηg equivalent /cm2) and 2.16% (0.67 ηg equivalent/cm2) of the applied dose for the high concentration test preparation, respectively. The stratum corneum acted as a barrier to absorption, with the mean total unabsorbed doses (recovered in skin wash, tissue swabs, pipette tips, cell wash, stratum corneum and unexposed skin) of 96.80 and 94.68% of the applied dose for the low and high concentration test preparations, respectively. The maximum fluxes for the low and high doses were 0.12 ηg equivalent /cm2/h and 0.74 ηg equivalent /cm2/h, respectively, at 2 h (Roper, 2006). Based on literature evidence, substances with Jmax ≤ 0.1μg/cm2/h, can be expected to have low skin penetration potential and can be assigned a default skin absorption of <10% (Shenet al., 2014, Kroeset al.,2004). Further, the dermal absorption of the read across substance was concluded in its biocides assessment report (by RMS Italy) to be 8.3%, which was obtained by summing up the radioactivity present in the receptor fluid (0.05%), at the application site (after 20 consecutive tape stripping procedures) and the one present in tape strips (n°6-20) (ECHA biocides assessment report, 2015). 

Assessment from biocides assessment report available on read across substances: 

As indicated above the biocides assessment reports available on the read across substance C12-16 ADBAC indicated that given its ionic nature, C12-16 ADBAC was not expected to be readily absorbed from the gastrointestinal tract or skin. And based on the results from thein vivostudies with rats andin vitrostudies with human skin, an oral and dermal absorption value of 10% could be considered at non-corrosive concentrations (ECHA biocides assessment report, 2015). 

Conclusion:Overall, based on all the weight of evidence information, the test substance at non-corrosive concentrations can be expected to have a low absorption potential absorption through the dermal route. While the studies with C16 TMAC/C12 TMAB support a lower absorption potential (<5%), as a conservative approach and in line with the biocide assessment report a maximum dermal absorption value of 10% can be considered for risk assessment.  

Inhalation absorption   

Based on physicochemical properties:   

According to REACH guidance document R7.C (ECHA, 2017), inhalation absorption is maximal for substances with VP >25 KPa, particle size (<100 μm), low water solubility and moderate log Kow values (between -1 and 4). Very hydrophilic substances may be retained within the mucus and not available for absorption. 

The test substance, because of its relatively low vapour pressure of 0.0058 Pa at 25°C, will not be available as vapours for inhalation under ambient conditions. In the case of spraying applications, coarse droplets would be formed which typically settle on the ground and result in a very lower inhalable or respirable fraction. Of the inhalable fraction, due to the droplet size and the moderate water solubility, almost all droplets are likely to be retained in the mucus and will not be available to reach the deeper lungs. The deposited droplets in the upper respiratory tract are expected to be absorbed in a relatively slower rate compared to the deeper lungs due to differences in vascularity. Some amounts of these deposited droplets are also expected to be transported to the pharynx and swallowed via the ciliary mucosal escalator. Therefore, the systemic uptake of the test substance via the respiratory route can be considered to be similar to the oral route.  

Conclusion:Based on all the available weight of evidence information, together with the fact that the test substance is cationic with an adherence potential to the negatively charged surfaces, the test substance can be expected to have low to moderate absorption potential through the inhalation route, depending on the droplet size. Therefore, a value of 50% can be considered for the risk assessment as a conservative approach.   

METABOLISM:    

Based on experimental data on read across substances:   

As discussed in the Selim, 1987 study, less than 50% of the orally administered C12-16 ADBAC is metabolised to side-chain oxidation products. In view of the limited absorption of the test substance, the four major metabolites identified may be at least partially formed in the gut of rats, apparently by microflora. The metabolites, which account for less than 60% of the administered dose, include hydroxyl- and hydroxyketo- derivatives of the dodecyl, tetradecyl and hexadecyl chains. No metabolite accounted for more than 10% of the total administered dose. No significant difference in metabolism between male and female rats or among the dosing regimens was observed. Repeated dosing did not alter the uptake, distribution or metabolism of the test substance (Selim, 1987).  

In addition, the even-carbon chain alkyl trimethylammonium chloride is suggested to follow degradation by a common pathway involving ω-oxidation of the alkyl chain followed by β-oxidation, to give rise to metabolites with chain lengths of C2 and C4 (SSC, 2012). Based onin vitrometabolism data identified for a cetrimonium bromide, other minor metabolic pathways, which are expected for the TMACs, involve the dealkylation of the trimethylamine and dimethylamine (Maduagwu, 1985, 1988). However, the velocity of metabolism and the formation of tertiary and secondary amines were considered to be dependent on the length and structure of the alkyl or aryl moiety of the molecule (SCCS, 2012). 

Based on QSAR modelling:  

The OECD Toolbox (v.4.4.1) and FAME 3 were used to predict the first metabolic reaction, since the rat liver S9 metabolism simulator performs predictions for salts, while SMARTCyp and MetaPrint2D are not powered enough for this type of substances. The second simulator of the OECD Toolbox (in vivorat metabolism simulator) was not used as it does not consistently perform predictions for salts. As per the rat liver S9 metabolism simulator, the major constituents are primarily predicted to undergo ω or ω-1 aliphatic hydroxylation reactions. Similar results were found with FAME 3 metabolism simulation tool (which currently covers only CYP metabolism). See the below table for the reaction sites. For further details, refer to the read across justification.

 

Major constituents (major chains >=10%)		Rat liver S9 metabolism simulator / Fame 3
Cetrimonium chloride (C16)		ω or ω-1 aliphatic hydroxylation

Overall, similar reactive sites were predicted for other TMACs and ADBACs from the category.  

Conclusion:Based on all the available weight of evidence information, the test substance is considered to be primarily metabolised by alkyl chain hydroxylation, which is carried out by the intestinal flora.   

DISTRIBUTION  

Based on physico-chemical properties:  

According to REACH guidance document R7.C (ECHA, 2017), the smaller the molecule, the wider the distribution. Small water-soluble molecules and ions will diffuse through aqueous channels and pores, although the rate of diffusion for very hydrophilic molecules will be limited. Further, if the molecule is lipophilic (log P >0), it is likely to distribute into cells and the intracellular concentration may be higher than extracellular concentration particularly in fatty tissues. Identification of the target organs in repeated dose studies are also indicative of the extent of distribution.  

Generally given the ionic nature of the test substance, the test substance is not likely to readily partition across the blood membranes into the different organs, leading to an overall low distribution potential. Moreover, even if the test substance distributes to a certain extent, it is not expected to bioaccumulate based on the read across experimental BCF values of C14 TMAC or C12-16 ADBAC or the predicted BCF values generated for the test substance using ionic BCF regression-based equation from BCFBAF v. 3.02 program of EPISuite^TM(see section 4.3 of the CSR).  

Based on experimental data on read across substances:  

As discussed above, in the Isomaa, 1975 study, only small amounts of radioactivity were found in the liver, kidneys, spleen, heart, lungs and skeletal muscle, and the tissue radioactivity declined rapidly; only traces being found in the examined tissues 4 d after [14C] oral administration of the read across substance in rats. In the Appelqvist, 2006 study, quantifiable levels of radioactivity (2,386 to 23,442 ηg equivalent/g) were found in some central organs at 8 h post-dosing at 200 mg/kg bw; otherwise, the vast majority of the dose was confined to the intestines, where their levels decreased over time and were all non-quantifiable by 168 h (i.e., 7 d). In the Selim, 1987 study, residual 14C in tissues was negligible after administration by gavage both after single and repeated dosing, indicating low potential for bioaccumulation. However, following i.v. administration, it was found to be widely distributed (30-35%) in tissues (Selim, 1987).  

Conclusion:Based on all the available weight of evidence information, the test substance is expected to have a low distribution and bioaccumulation potential.   

EXCRETION:  

Based on physicochemical properties:  

Given the expected low absorption potential of the test substance due to its ionic nature and physico-chemical properties, it can be expected to be primarily excreted through faeces.  

Based on experimental data on read across substances:  

Based on the evidence from the available oral studies (Isomaa, 1975; Appelqvist, 2006; and Selim, 1987), the test substance is primarily expected in faeces (>90%) and less via urine (<10%).Further, in the Isomaa, 1975 study, no radioactivity was found in the expired CO2 collected during Day 1 after administration of [14C] C16 TMAB, indicating that no complete oxidation of the cetyl group occurred.  

Conclusion:Based on all the available weight of evidence information, the test substance is expected to be primarily excreted via faeces.  

[1] Log Kp = -2.80 + 0.66 log kow – 0.0056 MW