Ethyl 9,9-dioctyl-4,7,11-trioxo-3,8,10-trioxa-9-stannatetradeca-5,12-dien-14-oate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

The target substance is a mono-constituent organotin substance that consists of a tin as central metal element with two octyl-ligands. The source substance Dioctyltin oxide (DOTO) (EC Number 212-791-1 and CAS 870-08-6) is also an organotin compound that has the identical structure elements as the target substance in respect of the tin-alkyl moiety.
According to WHO IPCS CIRCAD (2006) organotin compounds are characterized by a tin–carbon bond and have the general formula RxSn(L)(4−x), where R is an organic alkyl or aryl group and L is an organic (or sometimes inorganic) ligand. The organotin moiety is significant toxicologically. The anionic ligand influences physicochemical properties but generally has little or no effect on the toxicology.
Since the target substance and the source substances share the identical organotin moiety, and the organotin moiety is generally recognized as the relevant toxophore of organotins and the toxicity estimates (AE) respectively toxicity limits for organotins are expressed as tin, the overall ecotoxicity/systemic toxicity of the target can be interpolated by assessing the (eco-)toxicity of the source (WHO IPCS CIRCAD, 2006, BAUA AGS TRGS 900, 2014, Summer KH, Klein D and Greim H, 2003).
The purity of the source and target substance are expected to be similar, based on the manufacturing method. The impurity profile is not expected to have strong effects on substance properties and any impurity of (eco-)toxicological relevance of the source substances is expected to be present in the target substance. Consequently, the hazard profiles of the source substances, including those of their impurities, are intrinsically covered. Differences in impurities are not expected and thus do not have an impact on the (eco-)toxic properties.

References
BAUA (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institute for Occupational Safety and Health)) AGS (Ausschuss für Gefahrstoffe (Committee on Hazardous Substances)) TRGS (Technical Rules for Hazardous Substances) 900 (2014). Begründung zu n-Octylzinnverbindungen, April 2014.
Summer KH, Klein D, Griem H (2003). Ecological and toxicological aspects of mono- and disubstituted methyl-, butyl-, octyl-, and dodecyltin compounds - Update 2002. GSF National Research Center for Environment and Health, Neuherberg, for the Organotin Environmental Programme (ORTEP) Association.
World Health Organization (WHO) International Programme on Chemical Safety (IPCS) Concise International Chemical Assessment Document (CICAD) 73 Mono- and disubstituted methyltin, butyltin, and octyltin compounds (2006). Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (O2 consumption)

Value:

1.5

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

1.9

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

1.9

Sampling time:

31 d

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

6 December 2002 to 15 January 2003

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study was performed to GLP and in line with the standardised guidelines OECD 301-F and EU Method C.4-D with no deficiencies thought to influence the accuracy of the presented results. The study was reported to a high standard. Since the test material DOTO (di-n-octyltin oxide) is in the same category of substance as the registration substance, it is considered acceptable to use a read-across approach to address this endpoint.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

yes

Remarks:

(100 mg (dry weight) of suspended solids, as no biodegradation occurred, this was not considered to affect the results)

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

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:
PHYSICO-CHEMICAL PROPERTIES
- Melting point: melting with decomposition from approximately 282 °C
- Vapour pressure: 0.00042 Pa at 25 °C
- Water solubility (under test conditions): <0.0000152 g/L at 20 °C
- Log Pow: Calculated estimate of 9.26 (method not validated for this class of material)

OTHER PROPERTIES (if relevant for this endpoint)
- Results of short-term toxicity testing on invertebrates (Daphnia magna): 48 hour EC50 >water solubility under the conditions of the study (between 0.09 and 0.54 mg/L); EC50 >0.21 mg/L (geometric mean of the solubility of the test material).
- Results of short-term toxicity testing on fish (Brachydanio rerio): 96 hour LC50 >water solubility under the conditions of the study (between 0.05 and 0.18 mg/L); LC50 >0.09 mg/L (geometric mean of the solubility of the test material).
- Results of growth inhibition study on algae (Desmodesmus subspicatus): 72 hours ErC50 >0.0018 mg/L; the test material exhibited little or no difference on the growth rate of the algae, the ErC50 of the test material is considered to be greater than the water solubility.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: The activated sludge was obtained from an oxidation ditch situated in the municipality of Hazerswoude, the Netherlands (3 Dec 2002)
- Preparation of inoculum for exposure: 8 mL of sludge was added to 300 mL of mineral medium
- Concentration of sludge: 100 mg of solids per litre

Duration of test (contact time):

755 h

Initial conc.:

27.3 mg/L

Based on:

test mat.

Initial conc.:

50.5 mg/L

Based on:

ThOD/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

PREPARATION OF THE TEST MATERIAL
The test material was thoroughly mixed (homogenisation was not possible). Portions with and average weight of 0.00712 g of the test material (average of all bottles containing test material, including the toxicity control bottles) were dosed directly on glass fibre filters. The filters were placed into the test flask containing 300 mL of the medium.

TEST CONDITIONS
- Composition of medium: 1 mL of the following nutrient stock solutions were added to ultrapure water with a final volume
Stock solution a) Dissolved in and made up to 1000 mL ultrapure water: 8.5 g KH2PO4, 21.8 g K2HPO4, 33.4 g Na2HPO4.7H2O, 0.5 g NH4Cl and 100 g NaNO3. (pH 7.4 ± 0.1)
Stock solution b) Dissolved in and made up to 1000 mL ultrapure water: 22.5 g MgSO4.7H20
Stock solution c) Dissolved in and made up to 1000 mL ultrapure water: 36.4 g CaCL2.2H2O
Stock solution d) 0.25 g FeCl3.6H2O
To prevent nitrogen limitation, additional NaNO3 was added to the mineral medium.
- Test temperature: 20 ± 2 °C
- pH: 7.3-7.4
- pH adjusted: no
- Suspended solids concentration: 100 mg/L

TEST SYSTEM
- Number of culture flasks/concentration: 3 flasks containing test material and 3 flasks containing a blank filter
- Measuring equipment: A Micro-Oxymax respirometer. The respirometer measured the percentage oxygen in the air of the respective flasks and calculated, based on the earlier measurement, the resulting oxygen consumption in a certain time period. Based on these values the oxygen consumption per flask was derived. Oxygen concentration was determined every 5 hours.

CONTROL AND BLANK SYSTEM
- Inoculum activity control: 3 flasks containing mineral medium only and 2 flasks containing 100 mg/L sodium acetate
- Toxicity control: 2 flasks containing 100 mg/L of sodium acetate and 23.7 mg/L test material

STATISTICAL METHODS: The oxygen consumption in each flask was calculated based on the respiration rate (mg O2/flask/hour). The oxygen consumption due to the test or control substance at each time was calculated by subtracting the mean cumulative oxygen consumption in the blanks from that in the flask under consideration. These crude values were then converted to values per mg substance (BOD). The percentage biodegradation of the test substance was calculated as BOD/ThOD x 100.
Based on the empirical formula, the Theoretical Oxygen Demand (ThOD) without nitrification (ThODNH3) value of the test material was calculated to be 2.13 mg O2/mg. The degree of biodegradation was calculated with this ThODNH3 value, assuming a purity of 100 %.

Reference substance:

acetic acid, sodium salt

Test performance:

The pH of the test medium was fairly constant during the test with the final values in the range of 7.2-7.8 after 39 days incubation. The higher pH values were found in the activity and toxicity control vessels were CO2 production was highest.
The temperature during the test was recorded as between 20.1-22.3 °C.
On day 32, oxygen measurements were stopped for a short period to allow recalibration. In a later stage all data after day 31 were considered unreliable and were not reported. Between 661 and 675 h a data point was missing as it was out of range.
Very low negative values of oxygen consumption and high values that are not part of a peak are attributed to possible leakages of the system. These occurred mainly after 755 h and between 581 and 675 h and are related to a technical failure of the oxygen sensor, these results were therefore disregarded.

Parameter:

% degradation (O2 consumption)

Value:

1.5

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

1.9

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

1.9

Sampling time:

31 d

Details on results:

The average percent degradation of the test material after 28 days was approximately 2 % with a concentration of 23.7 mg/L. In two flasks, negligible biodegradation occurred, in the third approximately 8 % biodegradation was observed.
The oxygen consumption in the blanks (with and without filter) was 1.21 to 2.96 mg per flasks after 28 days incubation, equivalent to 4.0-9.9 mg/L.
Figure 1 depicts the oxygen consumption in the control and test flasks over time
Figure 2 depicts the biological oxygen demand (BOD)
Figure 3 depicts the percentage biodegradation based on the ThODNH3

Results with reference substance:

>25 % biodegradation was observed in the toxicity controls, demonstrating the the test material is not toxic to the inoculum.
The reference substance was sufficiently degraded within 14 days of incubation (>60%).

Table 1: Results with test material

Time (days)	BOD mg O2/mg	Biodegradation ThODNH3%
14	1.4	1.7
28	1.8	2.1
31	1.7	2.0

 

Table 2: Results with control vessels

Time (days)	Inoculum blank (mg O2/flask)	Inoculum blank with filter (mg O2/flask(	Inoculum activity control		Toxicity control
			mg O2/flask	Biodegradation ThOD %^1	mg O2/flask	Biodegradation ThOD %^1
14	1.4	1.7	21.6	99	21.5	56.0
28	1.8	2.1	23.1	105	23.2	56.6
31	1.7	2.0	23.0	105	23.1	59.6
All values are expressed as the mean of all the replicates in that test series ^1Corrected for corresponding blank

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The average percentage degradation of the test substance after 28 days was approximately 2 % under the conditions of the test. In two of the three flasks containing the test material, no significant biodegradation was observed. In the third flask approximately 8 % biodegradation was observed. The test substance was not toxic to the inoculum.

Executive summary:

The ready biodegradability of the test material was assessed in a Manometric Respirometry test conducted in accordance with OECD guideline 301F and EU Method C.4 -D and to GLP. Under the conditions of the study, the test material degraded approximately 2 % within 28 days of incubation with activated sludge. Two of the flasks performed with the test material gave negligible oxygen consumption, whilst the third gave 8 % within 28 days. All controls performed as part of the test were demonstrated that the test system was operating correctly and the test material exhibited no toxic effect on the inoculum. All validity criteria of the guideline were met. Therefore, under the conditions of the study, the test material can be categorised as 'not readily biodegradable'.

Description of key information

Not readily biodegradable, dioctyltin oxide, OECD 301-F, EU Method C.4-D, Hanstveit 2003

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The ready biodegradability of the test material was assessed in a Manometric Respirometry test conducted in accordance with OECD guideline 301-F and EU Method C.4 -D and to GLP. Under the conditions of the study, the test material degraded approximately 2 % within 28 days of incubation with activated sludge. Two of the flasks performed with the test material gave negligible oxygen consumption, whilst the third gave 8 % within 28 days. All controls performed as part of the test demonstrated that the test system was operating correctly and the test material exhibited no toxic effect on the inoculum. All validity criteria of the guideline were met. Therefore, under the conditions of the study, the test material can be categorised as 'not readily biodegradable'.

 

As the study was performed on a read-across substance in the same category as the registered substance (di-n-octyltin oxide), it was assigned a reliability score of 2 (reliable with acceptable restrictions) in accordance with the criteria for assessing data quality as outlined in Klimisch (1997) and considered suitable for assessment as an accurate reflection of the test material.