Phosphoric acid, mono- and di-C16-18 (even numbered) alkyl esters, salts with 2,2'-iminodiethanol

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

See the Justification of Read Across attached

Adequacy of study:

key study

Study period:

2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

See the Read Across justification

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name: Phosphoric acid, mixed decyl and octyl esters, compds. with diethanolamine
CAS No.: 68425-57-0
Physical state: white solid at 20 °C (turbid, non-pourable paste)
Batch No.: PU61810016
Re-certification date of batch: 16 June 2018
Purity: 100 % (UVCB)
Moisture, % (KF) 1,2
pH, 10% in dW 7,2
Stability: stable under test conditions
Storage condition of test material: Room temperature, protected from light

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Activated sludge from the municipal wastewater treatment plant Breisgauer Bucht was used as inoculum with a concentration corresponding to 30 mg dry solids per litre. The treatment plant clarifies predominantly domestic wastewater and has a capacity of 600.000 inhabitant equivalents. Sampling date of activated sludge was on 03 April 2017. The dry solid content of the activated sludge was 5.09 g/L. It was determined by weight measurements after drying at 105°C for 4 hours (mean of triplicate measurements). The activated sludge was washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

92.4

Sampling time:

29 d

Results with reference substance:

The reference compound sodium benzoate reached the pass levels for ready biodegradability within 4 days.

Results

Test item

The degradation extent of the test item at the end of the test was 92.4% (28 d after acidification, mean of two replicates). On day 11, the degradation was for the first time higher than 60%. Since begin of the 10-d window is not before day 1, the mean degradation of >60% was reached within a 10-d window. Therefore the test item reached the criteria for ready biodegradability (60% of ThCO2 within a 10-d window). In one of the three test vessels (vessel 13) significantly lower degradation values were measured, probably due to an error in the addition of the test item. The replicate was therefore regarded as an outlier and not considered in the evaluation.

Blank

The mean CO2-evolution of the blank flasks was 29.5 mg/L on day 28 after acidification.

Test parameters

- Before adding the test item, the IC in the reactor was determined, but only insignificant amounts of IC (0.22 mg/L) were found.

- The IC-concentration of the NaOH in the second CO2-absorber flasks in line, used as protective flasks, was below 7 ppm and was not considered in the data processing, because CO2 absorption from room air was its source.

- The temperature was 21.1 – 23.3°C throughout the whole study.

- The aeration rate was in the tolerated range of 1.6 – 5.5 bubbles/second (counted bubbles: 2.0 – 4.1 bubbles/second).

Criteria of validity

- The IC content in the test vessel was less than 5% of the TOC introduced with the test item.

- The CO2 evolution in the inoculum blank at the end of the test was below 40 mg/L.

- The difference of extremes of replicate values of the test item at the end of the 10-d window and at the end of the test was less than 20%.

- The biodegradation of the reference compound reached the pass level of 60% ThCO2 by day 4.

- The degradation extent in the toxicity control was above 25% in 14 days based on ThCO2.

Table 1: Ultimate biodegradation after x days [% ThCO2]

Reactor	day	0	4	7	11	14	21	28	29
11	test flask	0	28.5	49.8	65.1	69.8	75.8	86.4	89.4
12	test flask	0	25.6	52.0	65.0	68.9	80.9	93.7	95.3
13*	test flask	0	11 .1	25.8	31.3	34.3	37.5	35.1	31.9
4	reference flask	0	71.0	88.0	94.5	96.2	97.1	106.0	107.1
5	reference flask	0	73.0	88.2	97.0	100.3	104.4	113.2	113.2
6	reference flask	0	67.2	82.2	87.5	90.7	91.2	99.0	98.4
14	Toxicity control test item & reference item	0	43.2	67.0	74.7	78.5	79.7	88.4	86.8
Mean CO2 evolution of blank flasks after x days
CO2 evolution [mg/l]		0	7.0	11.5	16.7	19.1	24.4	27.4	29.5

* outlier

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The degradation of the test item at the end of the test was 92.4% (28 d after acidification, mean of two replicates). The test item reached the criteria for ready biodegradability (60% of ThCO2 within a 10-d window).

Executive summary:

In a GLP OECD 301 B study the degradation of the test item at the end of the test was 92.4% (28 d after acidification, mean of two replicates). The test item reached the criteria for ready biodegradability (60% of ThCO2 within a 10-d window). The degradation of the toxicity control after 14 days was 78.5%. The test item had no inhibitory effect on the inoculum according to the criterion of the guideline.

Description of key information

Ready Biodegradable at 92.4% degradation (CO2 evolution).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The biodegradability was tested in Read Across on a Similar substance, according toOECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test) and EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test). See the Justification of read across.

Ready Biodegradable at 92.4% degradation (CO2 evolution).