Sodium 2-sulphonatoethyl laurate

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

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

Reference 2

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-07-20 to 2009-11-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study has been conducted according to OECD Guideline 303A; however, no claim for GLP compliance is made for this study. However, the study was carried out in the spirit of GLP. Read-across is based upon a commonality of functional groups, constituents, breakdown products and metabolic pathways. A detailed justification is appended in Section 13.

Qualifier:

according to guideline

Guideline:

OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units)

Deviations:

yes

Remarks:

In this continuous activated sludge test, the protocol was modified accordingly so that the fate of the test items could be assessed at environmentally realistic concentrations using radiolabelled test items along with un-labelled test item at a nominal c

GLP compliance:

yes

Remarks:

No claim for GLP compliance is made for this study; however, the study was conducted according to the principles of GLP

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not Applicable

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on source and properties of surface water:

Not applicable - liquid influent was primary settled sewage

Details on source and properties of sediment:

Not applicable for this guideline

Details on inoculum:

The mixed liquor suspended solids of the return activated sludge was determined prior to addition to the aeration vessel. The volume of sludge required was calculated so that the aeration vessel contained nominally 2.5 g/L mixed liquor suspended solids suspended. The aeration vessel was filled with sufficient return activated sludge obtained from the return activated sludge line at Broardholme waste water treatment plant. The final separator was filled with effluent (both obtained from Anglia Water Broardholme sewage works, Ditchford, Rushden, UK).

Duration of test (contact time):

ca. 72 d

Initial conc.:

ca. 2 other: uCi/L

Based on:

other: scintillation counting (radioactivity)

Initial conc.:

ca. 0.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

radiochem. meas.

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: 3L aeration vessel
- Composition of medium: settled sewage
- Additional substrate: not applicable
- Solubilising agent (type and concentration if used): SLI (76) Stripped was used as a solubilising agent for Sodium [14C] Stearoyl Isethionate; no solubilising agent was used for any of the other test items. Sodium Lauryl Isethionate was used as a carrier but not as a solubilising.
- Solvent: Dimethyl formamide
- Test temperature: 18-25 degrees C
- pH: 7-8
- pH adjusted: no
- Aeration of dilution water: not applicable
- Suspended solids concentration: initial 2.5g/L (sludge retention time controlled at 6 days)
- Continuous darkness: no
- Any indication of the test material adsorbing to the walls of the test apparatus: no

TEST SYSTEM
- Method used to create aerobic conditions: Carbon dioxide free air
- Method used to create anaerobic conditions: not applicable
- Test performed in closed vessels due to significant volatility of test substance: used close vessels but not due to volatility of test substance but to obtain a mass balance CO2
- Test performed in open system: no
- Details of trap for CO2: sodium hydroxide 1M

SAMPLING
- Sampling frequency: daily
- Sampling method: traps/effluent/waste sludge changed daily (aliquots taken for counting)
- Sterility check if applicable: not applicable
- Sample storage before analysis: scintillation counting conducted immediately. Specific sample analysis preserved with 40% methanol in a refridgerated container

CONTROL AND BLANK SYSTEM
- Inoculum blank: see below
- Abiotic sterile control: see below
- Toxicity control: see below
- Other: Carbon mass balance control

STATISTICAL METHODS: mean, 95% confidence limits (Student's T-test)
- Results calculated over a 32 day calculation period (days 40-72)

Reference substance:

other: Dimethyl formamide added at same application rate as test vessels so that equal amount of carbon was added to control vessel.

Test performance:

Throughout the study, conditions were maintained in the test system that best represent a waste water sewage treatment plant but at a laboratory scale i.e. OECD303A Guideline (Husmann units). The test was carried out with the hydraulic and sludge retention times controlled at 6 hours and 6 days respectively. After the acclimation period (<6 weeks), the test was run for 32 days with samples collected daily and analysed for radioactivity remaining in effluent, sludge and traps. Concentrations of the test items obtained by scintillation counting in the sludge and effluent were determined daily between 40 and 72 days after a period of 40 days acclimatisation. All concentrations (sludge, effluent and mineralisation) were corrected for mass balance. In addition, HPLC analysis was conducted on samples collected at the conclusion of the calculation period (Day 72) to ascertain the concentration of parent material remaining in effluent and sludge and the percentage primary degradation that had occurred.

Compartment:

other: water / sediment, material (mass) balance

Remarks on result:

other: see "% Recovery" column in Table 1 below

% Degr.:

99.77

Parameter:

radiochem. meas.

Sampling time:

1 d

Remarks on result:

other: Range, every day from day 40 - day 72. Sodium Lauryl [14C] Isethionate

% Degr.:

99.61

Parameter:

radiochem. meas.

Sampling time:

1 d

Remarks on result:

other: Range, every day from day 40 - day 72. %parent in effluent is 0.11%. % parent in sludge is 2.74%. Sodium [14C] Stearyl Isethionate

% Degr.:

99.99

Parameter:

radiochem. meas.

Sampling time:

1 d

Remarks on result:

other: Range, every day from day 40 - day 72. Sodium [14C] Lauryl Isethionate.

Transformation products:

not measured

Details on transformation products:

Not applicable

Evaporation of parent compound:

not measured

Volatile metabolites:

not measured

Residues:

not measured

Details on results:

The mixed liquor temperatures for all test and control plants ranged between 22 and 23 degrees C, which are within OECD guideline range of 18 - 25 degrees C.

The pH of the test and control units were, with few exceptions, within the accepted range for the growth of bacteria (i.e. between pH 6 to 8).

The dissolved oxygen [DO] levels remained above the critical concentration of 2 mg/L.

The hydraulic retention time [HRT] was calculated from the influent flow rates as determined by the mass of effluent collected per 24 hours. The HRT data remained largely within 6 ± 1 hours.

The sludge return flow rates for each plant remained largely within 8.5 ± 1 mL/min.

The sludge retention time [SRT] was calculated from the volume of sludge wasted per day. The SRT data remained largely within 6 ± 1 days.

Mixed liquor suspended solids: Initially concentrations were variable and often lower than anticipated (<2.5 g/L) during the acclimatisation period. However, throughout the calculation period the solids levels had increased to a normal level (~2.5 g/L) and appeared to be stable. Throughout the calculation period similar concentrations were observed between the test and control plants.

Throughout the calculation period similar organic carbon removal levels/concentrations were observed between the test and control plants.

Throughout the calculation period similar ammonia removal levels/concentrations were observed between the test and control plants.

Variable levels of solids concentration and ammonia removal efficiency observed during the acclimatisation phase of this study were probably attributable to the addition of dimethylformamide to the test system. Dimethylformamide is known to be biodegradable, however it also known to inhibit biological activity. These data suggests that the test system acclimatised to the solvent and it did not inhibit biological activity.

Throughout the test all of the above parameters were consistent with properly operated sewage treatment systems.

Results with reference substance:

not applicable

Table 1: Distribution of test items in Continuous Activated Sludge system

Test Item	% parent^#			% Recovery
	degraded	in effluent	in sludge
Sodium Lauryl [14C] Isethionate	99.77 (90.7)	0.02 (2.4)	0.21 (6.9)	94.2
Sodium [1-14C] Lauryl Isethionate	99.99 (94.5)	0.01 (1.8)	0.00 (3.7)	87.0
Sodium [1-14C] Stearyl Isethionate	99.61 (94.5)	0.11 (2.2)	0.28 (3.3)	78.0

Figures in parentheses relate to total 14C (parent, metabolites or biomass) remaining

^#All values corrected for recovery

Validity criteria fulfilled:

yes

Conclusions:

Degradation of parent material was extensive with 99.61 to 99.99% removed in the CAS systems. The concentrations of parent in the effluent ranged from 0.01 to 0.11% and the concentration of the parent in the sludge ranged from 0.21 to 0.28% of applied test item. The observed distribution of the sodium [1-14C] lauryl isethionate and the sodium [1-14C] stearyl isethionate was similar suggesting that all chain lengths would behave in a similar manner in a CAS system.

Executive summary:

The purpose of this study was to assess the environmental distribution (percent degradation and concentrations in sludge and effluent) of radio-labelled Defi test items in a continuous activated sludge (CAS) system. It was not practical to assess the fate of a commercial sample of DEFI, as it is a mixture of different chain lengths of alkyl isethionates. Therefore, the items tested (labelled in the alkyl chain) in this study were selected to represent the shortest (lauryl isethionate)and longest (stearyl isethionate)significant chain length present in the commercial mixture. In addition, the lauryl isethionate(labelled in the isethionate group) was included in the study. 

 

The CAS systems were operated in accordance with EU L133/106 and OECD Guideline 303A. The test was carried out at the recommended temperature range (18-25 °C) with the hydraulic and sludge retention times controlled at 6 hours and 6 days respectively. The study deviated from the OECD 303A guideline in that the test items used were radio-labelled. As a consequence the apparatuswas modified to accommodate capture of¹⁴CO_2. No other modifications were made.

 

Concentrations of the test items obtained by scintillation counting in the sludge and effluent were determined daily between 40 and 72 days after a period of 40 days acclimatisation. All concentrations (sludge, effluent and mineralisation) were corrected for mass balance (see below table). In addition, HPLC analysis was conducted on samples collected at the conclusion of the calculation period (Day 72) to ascertain the concentration of parent material remaining in effluent and sludge and the percentage primary degradation that had occurred.

 

Degradation of parent material was extensive with 99.61 to 99.99% removed in the CAS systems. The concentrations of parent in the effluent ranged from 0.01 to 0.11% and the concentration of the parent in the sludge ranged from 0.21 to 0.28% of applied test item. The observed distribution of the sodium [1-14C] lauryl isethionate and the sodium [1-14C] stearyl isethionate was similar suggesting that all chain lengths would behave in a similar manner in a CAS system.

Distribution of test items in Continuous Activated Sludge system

Test Item	% parent^#			% Recovery
	degraded	in effluent	in sludge
Sodium Lauryl [14C] Isethionate	99.77 (90.7)	0.02 (2.4)	0.21 (6.9)	94.2
Sodium [1-14C] Lauryl Isethionate	99.99 (94.5)	0.01 (1.8)	0.00 (3.7)	87.0
Sodium [1-14C] Stearyl Isethionate	99.61 (94.5)	0.11 (2.2)	0.28 (3.3)	78.0

Figures in parentheses relate to total 14C (parent, metabolites or biomass) remaining

^#All values corrected for recovery

Reference 3

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted according to OECD guidelines and GLP principles.

Qualifier:

according to guideline

Guideline:

other: OECD guideline 314D (Simulation tests to assess the biodegradability of chemical discharged in wastewater - Biodegradation in treated effluent-surface water mixing zone)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: Effluent-surface water mixing zone

Details on inoculum:

Sludge and effluent were collected from the wastewater treatment plant (WWTP) RWZI 's-Hertogenbosch (Waterschap AA en Maas). The sludge was sampled from the well mixed region of the aeration basin. The effluent was collected from the discharge point of the WWTP:
Location: RWZI 's-Hertogenbosch, The Netherlands
Type of plant: Municipal
Origin of wastewater: Mixed industrial and domestic
Treatment system: Aerobic
Sludge:
- Temperature: 21.2 Degrees C
- pH: 7.2
-O2 concentration: 1.2mg/L
- Redox potential: 222mV
Effluent:
- Temperature: 23.0 degrees C
- pH: 7.4
- O2 concentration 6.5mg/L
- Redox potential: 203mV
Sampling date: 28 June 2010
Storage: 20 +/- 2 degrees C, continuous aeration

Surface water was sampled from natural surface water upstream of the WWTP from the river Dieze:
Location: Dieze, near A59
Water temperature: 23.6 degrees C
pH: 8.3
O2 concentration: 10.7mg/L
Redox potential: 214mV
Sampling date: 28 June 2010
Storage: 20 +/- 2 degrees C, continuous aeration

Within one day after sampling, the water was sieved through a 150um sieve and the sludge was sieved over a 2mm screen. Mixed liquor suspended solids (MLSS) in the sludge were allowed to settle and the clear liquid was removed. The total suspended solids (TSS) in effluent, surface water and MLSS was measured.

Approximately 2250mL surface water and 250mL effluent were weighed into 5L metabolism flasks. A volume of 0.86mL sludge was added to obtain a biosolids concentration of 3.0mg/L. The effluent-surface water mixture was used in the biotic experiment, abiotic and reference controls. Abiotic controls were obtained via chemical (0.1g/L mercuric chloride) and heat treatment (autoclaving 90 minutes at 121 degrees C and 15psi (1.034bar)).

Duration of test (contact time):

28 d

Initial conc.:

51.4 other: ug Sodium [14C]Lauryl Isethionate/L

Initial conc.:

62 other: ug Sodium [14C]Stearyl Isethionate/L

Based on:

other:

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

test mat. analysis

Details on study design:

TEST CONDITIONS
The incubation lasted 28 days and took place in the dark at 20 +/- 2 degrees C. The temperature in the climatised room was continuously onitored. The treated effluent-surface water mixtures were gently stirred and the headspace was continuously purged with CO2-free humidified air. During incubation, dissolved oxygen, pH, and redox potential were determined twice a week in two untreated metabolism flasks (one biotic system and one abiotic control).

TEST SYSTEM
See section "Details on inoculum"

SAMPLING
Each flask was sampled after 1, 2, 4, 6, 8 hours and 1, 2, 4, 7, 14, 21, and 28 days of incubation. The EGME traps and NaOH traps were sampled after 2, 7, 14, 21 and 28 days. The biotic test systems were also sampled after 6 hours and 1 day. At the sampling points, the traps were removed and replaced by fresh ones.

STATISTICAL METHODS:
The DT50 and DT90 values were calculated using the amounts of parent (not averaged) as determined by HPLC. The single first order kinetics (SFO) model was fitted to the data. Optimisations were performed using the program ModelMaker (AP Benson, Wallingford, Oxfordshire, UK).

Reference substance:

benzoic acid, sodium salt

Test performance:

During incubation (main study), the pH values ranged from 8.5 to 8.9 (biotic systems) and 8.6 to 9.0 (abiotic controls) indicating slightly alkaline condition. The dissolved oxygen concentrations fluctuated between 7.8 and 8.7mg/L (biotic system) and 7.5 and 8.6mg/L (abiotic control). Together with the positive redox potentials (142 to 381mV in biotic systems and 143 to 307mV in abiotic controls), the measurements indicate aerobic conditions in the water layer thrughout the incubation period.

Compartment:

other: water, material (mass) balance

% Recovery:

70.5

% Degr.:

64.2

St. dev.:

5

Parameter:

CO2 evolution

Sampling time:

28 d

Remarks on result:

other: Sodium [14C]Lauryl Isethionate - biotic test system

% Degr.:

69.6

St. dev.:

3

Parameter:

CO2 evolution

Sampling time:

28 d

Remarks on result:

other: Sodium [14C]Stearyl Isethionate - biotic test system

% Degr.:

100

Parameter:

test mat. analysis

Sampling time:

2 h

Remarks on result:

other: Sodium [14C]Lauryl Isethionate - biotic test system

% Degr.:

100

Parameter:

test mat. analysis

Sampling time:

6 h

Remarks on result:

other: Sodium [14C]Stearyl Isethionate - biotic test system

Compartment:

water

DT50:

0.21 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: r2 = 0.314; chi squared: 32.6; DT90 = 0.69hours; Sodium [14C]lauryl isethionate

Compartment:

water

DT50:

0.36 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: r2=0.758; chi squared = 74.8; DT90 = 1.2 hours; sodium [14]stearyl isethionate

Transformation products:

no

Details on transformation products:

Both test substances degraded to one major metabolite each. These metabolites, which were more apolar than the parent compound (based on their retention on the HPLC column) exceeded 10% of applied activity. In the biotic test system spiked with Sodium [14C]Lauryl lsethionate, maximum was reached after 2 hours of incubation (71% of applied) and after 6 hours the metabolite was no longer apparent. In the biotic test system spiked with Sodium [14C]Stearyl isetlhionate, maximum concentrations were reached after 2 hours of incubation (97% of applied) and after 48 hours the metabolite was no longer apparent. Transformation products were not identified.

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

not specified

Details on results:

Both test substances degraded to one major metabolite each. These metabolites, which were more apolar than the parent compound (based on their retention on the HPLC column) exceeded 10% of applied activity. In the biotic test system spiked with Sodium [14C]Lauryl Isethionate, maximum was reached after 2 hours of incubation (71% of applied) and after 6 hours the metabolite was no longer apparent. In the abiotic control maximum was reached at the end of incubation (45% of applied). In the biotic test system spiked with Sodium [14C]Stearyl Isethionate, maximum concentrations were reached after 2 hours of incubation (97% of applied) and after 48 hours the metabolite was no longer apparent. In the abiotic control maximum was reached after 21 days of incubation (24% of applied).

In the biotic test systems significant amounts of CO2 were formed upon degradation of the metabolites, i.e. up to 64% for the systems spiked with Sodium [14C]Lauryl Isethionate and 70% for the systems spiked with Sodium [14C]Stearyl Isethionate. Additional CO2 was detected as dissolved CO2 in the aqueous phase. Mineralisation was therefore the main degradation route in treated non-sterilised effluent/surface water mixing zones. Formation of organic volatiles was negligible in all test systems (≤ 0.2% of applied).

Based on single first order (SFO) kinetics, the following DT50 and DT90 values of Sodium [14C]Lauryl Isethionate and Sodium [14C]Stearyl Isethionate in effluent/surface water mixing zones (biotic and abiotic control) were calculated:

Sodium [14C]Lauryl Isethionate - biotic test system DT50: 0.21 hours, DT90: 0.69 hours
Sodium [14C]Stearyl Isethionate - biotic test system DT50: 0.36 hours, DT90: 1.2 hours
Sodium [14C]Lauryl Isethionate - abiotic control DT50: 30 days, DT90: 100 days
Sodium [14C]Stearyl Isethionate - abiotic control DT50: 23 days, DT90: 76 days

From Material (mass) balance: Incomplete mass balances for the biotic systems were partially due to the fact that not at all sampling points activity in the NaOH traps was measured. Because a lot of CO, was formed in the biotic systems, not only recovered in the NaOH traps but also dissolved in the aqueous phase, it can be expected that some activity was lost during sampling. In the test systems treated with Sodium [14~]~tealrsyetlh ionate, part of the activity was adsorbed to sludge particles.

Conclusions:

Upon addition of Sodium [14C]Lauryl Isethionate and Sodium [14C]Stearyl Isethionate to the test systems (effluent/surface water mixing zones) the test substances rapidly degraded. In the biotic systems, no test substance could be recovered anymore after 2 or 6 hours, respectively. The decrease in the abiotic controls was less; at the end of the incubation period approximately half of the initially spiked substance was recovered.

Both test substances degraded to one major metabolite each. These metabolites, which were more apolar than the parent compound (based on their retention on the HPLC column) exceeded 10% of applied activity. In the biotic test system spiked with Sodium [14C]Lauryl Isethionate, maximum was reached after 2 hours of incubation (71% of applied) and after 6 hours the metabolite was no longer apparent. In the abiotic control maximum was reached at the end of incubation (45% of applied). In the biotic test system spiked with Sodium [14C]Stearyl Isethionate, maximum concentrations were reached after 2 hours of incubation (97% of applied) and after 48 hours the metabolite was no longer apparent. In the abiotic control maximum was reached after 21 days of incubation (24% of applied).

In the biotic test systems significant amounts of CO2 were formed upon degradation of the metabolites, i.e. up to 64% for the systems spiked with Sodium [14C]Lauryl Isethionate and 70% for the systems spiked with Sodium [14C]Stearyl Isethionate. Additional CO2 was detected as dissolved CO2 in the aqueous phase. Mineralisation was therefore the main degradation route in treated non-sterilised effluent/surface water mixing zones. Formation of organic volatiles was negligible in all test systems (≤ 0.2% of applied).

Based on single first order (SFO) kinetics, the following DT50 and DT90 values of Sodium [14C]Lauryl Isethionate and Sodium [14C]Stearyl Isethionate in effluent/surface water mixing zones (biotic and abiotic control) were calculated:

Sodium [14C]Lauryl Isethionate - biotic test system DT50: 0.21 hours, DT90: 0.69 hours
Sodium [14C]Stearyl Isethionate - biotic test system DT50: 0.36 hours, DT90: 1.2 hours
Sodium [14C]Lauryl Isethionate - abiotic control DT50: 30 days, DT90: 100 days
Sodium [14C]Stearyl Isethionate - abiotic control DT50: 23 days, DT90: 76 days

Executive summary:

Upon addition of Sodium [14C]Lauryl Isethionate and Sodium [14C]Stearyl Isethionate to the test systems (effluent/surface water mixing zones) the test substances rapidly degraded. In the biotic systems, no test substance could be recovered anymore after 2 or 6 hours, respectively. The decrease in the abiotic controls was less; at the end of the incubation period approximately half of the initially spiked substance was recovered. Both test substances degraded to one major metabolite each. These metabolites, which were more apolar than the parent compound (based on their retention on the HPLC column) exceeded 10% of applied activity. In the biotic test system spiked with Sodium [14C]Lauryl Isethionate, maximum was reached after 2 hours of incubation (71% of applied) and after 6 hours the metabolite was no longer apparent. In the abiotic control maximum was reached at the end of incubation (45% of applied). In the biotic test system spiked with Sodium [14C]Stearyl Isethionate, maximum concentrations were reached after 2 hours of incubation (97% of applied) and after 48 hours the metabolite was no longer apparent. In the abiotic control maximum was reached after 21 days of incubation (24% of applied). In the biotic test systems significant amounts of CO2 were formed upon degradation of the metabolites, i.e. up to 64% for the systems spiked with Sodium [14C]Lauryl Isethionate and 70% for the systems spiked with Sodium [14C]Stearyl Isethionate. Additional CO2 was detected as dissolved CO2 in the aqueous phase. Mineralisation was therefore the main degradation route in treated non-sterilised effluent/surface water mixing zones. Formation of organic volatiles was negligible in all test systems (≤ 0.2% of applied). Based on single first order (SFO) kinetics, the following DT50 and DT90 values of Sodium [14C]Lauryl Isethionate and Sodium [14C]Stearyl Isethionate in effluent/surface water mixing zones (biotic and abiotic control) were calculated: Sodium [14C]Lauryl Isethionate - biotic test system DT50: 0.21 hours, DT90: 0.69 hours Sodium [14C]Stearyl Isethionate - biotic test system DT50: 0.36 hours, DT90: 1.2 hours Sodium [14C]Lauryl Isethionate - abiotic control DT50: 30 days, DT90: 100 days Sodium [14C]Stearyl Isethionate - abiotic control DT50: 23 days, DT90: 76 days

Description of key information

The removal of both short (Lauryl, C12) and the longest (Stearyl, C18) chained fatty acid isethionates was extensive with 99.8% and even greater for the short chain lauryl, C12 at 99.88%.  The concentrations of parent substance in the sludge for both short (Lauryl, C12) and the longest (Stearyl, C18) chained fatty acid isethionates was 0.16% and for the short chain lauryl, C12 was 0.02%. The DT50s in river water of C12 lauryl sodium isethionates was 0.21 h at 20 C. Therefore the biodegrdation of for lauric acid 2-sulfoethyl ester, sodium salt (sodium lauroyl isethionate) CAS No 7381-01-3 is demonstrated to be rapid and extensive.

The value (99.8%) for the short (Lauryl, C12) and the longest (Stearyl, C18) chained fatty acid isethionates were used for the risk assessment demonstrating a conservative, worst case scenario, as the removal rates for the lauric acid 2-sulfoethyl ester, sodium salt (shorter C12) are better at 99.88%. However, the observed distribution of the sodium [1-14C] lauryl isethionate and the sodium [1-14C] stearyl isethionate was similar suggesting that all chain lengths would behave in a similar manner in a CAS system.

Key value for chemical safety assessment

Half-life in freshwater:

0.21 h

at the temperature of:

20 °C

Additional information

There is no biodegradation simulation study available for lauric acid 2-sulfoethyl ester, sodium salt (sodium lauroyl isethionate) CAS No 7381 -01 -3. There are however studies on the source chemical,Fatty acids, C12-18 and C18-unsatd., 2-sulfoethyl esters, sodium salts CAS No 85408 -62 -4

which are rated Klimisch 2 and was carried out as described below.

The partitioning and biodegradation of C12 and C18 fatty acid isethionates in activated sludge systems was estimated in an OECD 303A study (Gore, 2010). A continuous activated sludge (CAS) test was performed with 14C- lauryl sulfoethyl ester, sodium salt according to guideline OECD 303A, under the spirit of GLP conditions under slightly adapted conditions. The protocol was modified so that the fate of the test substance could be assessed at environmentally realistic concentrations using radiolabelled test substance along with un-labelled test substance. The test substance was exposed to non-adapted micro-organisms maintained by addition of domestic wastewater. The wastewater was spiked at a nominal influent concentration of ~0.5 mg/L for a period of 72 days. Extensive primary biodegradation of both short (Lauryl, C12) and the longest (Stearyl, C18) chained fatty acid isethionates was observed (99.8%), partitioning to effluent was minimal (0.16%) and the percentage parent material remaining in sludge was 0.05%. Degradation of the shortest chain-C12 lauryl sodium isethionates is even greater calculated at average of 99.88%, average % parent material in effluent of 0.02% and average % parent in sludge of 0.11%.

The biodegradation of lauryl and stearyl isethionate in river water (OECD 314d) was shown to be extremely rapid with degradation half-life < 4 hours. DT50s in river water of C12 lauryl sodium isethionates was 0.21 h at 20 C and 0.36 h in water of sodium [14] stearyl isethionate. (Brands, 2010)

Therefore the biodegradation of for lauric acid 2-sulfoethyl ester, sodium salt (sodium lauroyl isethionate) CAS No 7381-01-3 is demonstrated to be rapid and extensive with the DT50s in river water of C12 lauryl sodium isethionates was 0.21 h at 20 C and removal of 99.88%. These results demonstrate a near complete removal of parent compound at stringent STP conditions (SRT of 6 ± 1 day), removal of the test substance from the influent through adsorption onto sludge and primarily removed by biodegradation of the test substance (Gore, 2010 and Brand, 2010). Read-across from the source chemical,

Fatty acids, C12-18 and C18-unsatd., 2-sulfoethyl esters, sodium salts CAS No 85408 -62 -4

to the target chemical is considered to be justified based upon a commonality of functional groups, constituents, breakdown products and metabolic pathways.Therefore we consider these study endpoint results as sufficiently conservative to be taken account of in the risk assessment of lauric acid 2-sulfoethyl ester, sodium salt (sodium lauroyl isethionate) CAS No 7381-01-3.