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

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

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

Lipid content:

6 %

Time point:

end of exposure

Remarks on result:

other: Control and treated fish

Lipid content:

4 %

Time point:

start of exposure

Remarks on result:

other: Control fish only

Type:

BCF

Value:

> 100 dimensionless

Basis:

whole body w.w.

Remarks on result:

other: Conc.in environment / dose:2.5 µg/L

Reference 2

Endpoint:

bioaccumulation: aquatic / sediment

Type of information:

(Q)SAR

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

Not reported

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Original report not available, information obtained from a summary within a dossier created for the harmonisation of the classification of the read across substance n-dioctyltin oxide under directive 67/548/EEC. The value was estimated by a QSAR, which is not validated for organometallics.

Justification for type of information:

QSAR prediction.

Qualifier:

according to guideline

Guideline:

other: Other guideline: REACH guidance on QSARs R.6

Principles of method if other than guideline:

Estimated by QSAR software, BCFWIN, v. 2.15, limited information available in the summary reported.

USEPA. 2000. BCFWIN. Version 2.15. BCF Estimate from Log Kow. EPIWIN (Estimation Program Interface for Windows). Version 3.12. Office of Pollution Prevention Toxics (OPPTS) and Syracuse Research Corporation (personal communication from C. Staples, Assessment Technologies, Inc., 1/29/05).

GLP compliance:

no

Type:

BCF

Value:

100 L/kg

Remarks on result:

other: No further details reported

Type:

other: Log BCF

Value:

2

Remarks on result:

other: No further details reported

Conclusions:

The BCF of the registered substance was estimated to be 100 L/kg, derived using an estimated Log Kow of 9.26.

Executive summary:

The data was obtained from a summary within a dossier created for the proposal for a harmonised classification under directive 67/548/EEC, the value was estimated by a QSAR, which is not validated for organometallics. The BCF of the registered substance was estimated to be 100 L/kg, derived using an estimated Log Kow of 9.26.

Reference 3

Endpoint:

bioaccumulation: aquatic / sediment

Type of information:

(Q)SAR

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

Not reported

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Original report not available, information obtained from a summary within an IUCLID dataset with brief details. The value was estimated on the read across substance n-dioctyltin oxide by a QSAR, which is not validated for organometallics.

Justification for type of information:

QSAR prediction

Qualifier:

according to guideline

Guideline:

other: Other guideline: REACH guidance on QSARs R.6

Principles of method if other than guideline:

Estimated by QSAR software, BCFWIN, v. 2.15, limited information available in the summary reported.

USEPA. 2000. BCFWIN. Version 2.15. BCF Estimate from Log Kow. EPIWIN (Estimation Program Interface for Windows). Version 3.12. Office of Pollution Prevention Toxics (OPPTS) and Syracuse Research Corporation (personal communication from C. Staples, Assessment Technologies, Inc., 1/29/05).

GLP compliance:

no

Type:

BCF

Value:

100 L/kg

Remarks on result:

other: No further details reported

Type:

other: Log BCF

Value:

2

Remarks on result:

other: No further details reported

Conclusions:

The BCF of the registered substance was estimated to be 100 L/kg, derived using an estimated Log Kow of 9.26.

Executive summary:

The data was obtained from a summary within an IUCLID dataset with brief details, the value was estimated by a QSAR, which is not validated for organometallics. The BCF of the registered substance was estimated to be 100 L/kg, derived using an estimated Log Kow of 9.26.

Reference 4

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 April 2009 to 15 May 2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study was conducted in line with GLP and in accordance with standardised testing guidelines. The study was performed on a surrogate substance dioctyltin bis(2-ethylhexyl thioglycate) which like all octyltin compounds is anticipated to hydrolyse to dioctyltin oxide very rapidly in water. The fish in the study are therefore expected to have been exposed to the same organotin species that would occur if the test had been performed using the registration substance.

Qualifier:

according to guideline

Guideline:

OECD Guideline 305 (Bioconcentration: Flow-through Fish Test)

Deviations:

yes

Remarks:

(the validity criteria state that the concentrations must be maintained with ± 20 % of the mean measured concentrations during the uptake phase. Due to limitations concerning the analytical methods, this could not be verified for the lowest concentration)

Qualifier:

according to guideline

Guideline:

EU Method C.13 (Bioconcentration: Flow-through fish test)

Deviations:

yes

Remarks:

(the validity criteria state that the concentrations must be maintained with ± 20 % of the mean measured concentrations during the uptake phase. Due to limitations concerning the analytical methods, this could not be verified for the lowest concentration)

GLP compliance:

yes

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
PHYSICO-CHEMICAL PROPERTIES
- Water solubility: <0.1 mg/L (insoluble)

Radiolabelling:

no

Details on sampling:

- Sampling intervals/frequency for test organisms: Fish were sampled on test days 1, 3, 7, 14, 21, 28 and 30 for analysis of dioctyltin and monooctyltin concentrations (fish sampled on day 30 were also analysed for total tin concentration). Fish were also sampled on test days 0 and 30 for lipid extraction.
- Sampling intervals/frequency for test medium samples: Water samples were taken on test days -1, 0, 1, 3, 7, 14, 21, and 28 for analysis of dioctyltin and monooctyltin concentrations.
- Sample storage conditions before analysis: Water samples were analysed freshly. On sample days 1 to 28, fish samples taken for analysis of test material concentration were analysed fresh, samples from day 30 were stored in a deep freezer until analysis. Fish samples taken for lipid extraction were stored in a deep freezer until analysis.
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods): 25 mL water samples were taken from a central point in the test chamber. The first water samples were taken from the control and both concentrations and analysed before the introduction of the fish to check the concentration of the test material. Fish were sampled using a small net, rinsed with untreated water, blotted dry and killed instantly and then weighed. Fish samples taken for test material concentration and tin content analysis were homogenised using a scalpel. No distinction was made between filets, guts and skin. Fish samples taken for lipid analysis were homogenised in a food processor in dry ice.

Vehicle:

yes

Details on preparation of test solutions, spiked fish food or sediment:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Test solutions were prepared from standard stock solutions. Stock solutions were prepared in acetone at a factor of 10,000 higher than the desired test concentrations.
- Controls: vehicle control
- Chemical name of vehicle : acetone
- Concentration of vehicle in test medium : 0.1 mL/L (treated solutions)

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Length at study initiation : 4.5 ± 0.3 cm
- Weight at study initiation : 1.74 ± 0.33 g
- Health status: Healthy (supplied with a health certificate)
- Description of housing/holding area: 64 L (40 x 40 x 40 cm) stainless steel test vessels covered by a removable Perspex plate
- Feeding during test: Pelleted fish food
- Amount: 2 % of body weight
- Frequency: Daily. Recalculation of the feeding rate was performed after each sampling point.

ACCLIMATION
- Acclimation period: A minimum of 12 days
- Acclimation conditions: Adjusted ISO medium formulated using RO water
- Feeding frequency: Daily
- Health during acclimation: During the 7 days prior to the start of the test, the mortality was less than 5 %

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

30 d

Hardness:

180 mg as CaCO3
11-12 °DH

Test temperature:

13.0-15.3 °C

pH:

7.7 ± 0.3

Dissolved oxygen:

8.5-9.8 mg/L

TOC:

23.86-36.45 mgC/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Aquarium
- Type : closed (covered by a removable perspex plate)
- Type of flow-through: proportional diluter
- Material, size, headspace, fill volume: 64 litres (40 x 40 x 40 cm) consisting of stainless steel
- Aeration: Continuous
- Renewal rate of test solution: flow rate 10 L/h, equivalent to 4 volume replacements per day
- No. of organisms per concentration: 42 fish for the vehicle control, 58 fish for each of the test concentrations
- Biomass loading rate: 0.42 g fish/L/day

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Adjusted ISO medium
- Conductance: 547-562 µs/cm

OTHER TEST CONDITIONS
- Photoperiod: 16 hours photoperiod daily

RANGE-FINDING / PRELIMINARY STUDY
- Results used to determine the conditions for the definitive study: Test concentrations were selected based on the solubility of the test material in water and the detection limits of the analytical methods employed in the study.

Nominal and measured concentrations:

Nominal: 0.25 µg/L
Mean measured concentrations: 0.14-0.26 µg/L (a mean concentration of 0.62 µg/L was recorded for the measurement on day 7, this was considered to be an outlier).
Nominal: 2.5 µg/L
Mean measured concentrations: 2.1-3.0 µg/L

Reference substance (positive control):

no

Lipid content:

4 %

Time point:

start of exposure

Remarks on result:

other: control fish only

Lipid content:

6 %

Time point:

end of exposure

Remarks on result:

other: control and treated fish

Type:

BCF

Value:

< 100 dimensionless

Basis:

whole body w.w.

Remarks on result:

other: Conc.in environment / dose:2.5 µg/L

Details on results:

WATER CONCENTRATIONS:
Results were based on DOT only as MOT was below the LOQ in the 0.25 µg/L concentration. MOT concentrations were also below the LOQ at 2.5 µg/L for three out of seven samples. Procedural recoveries were very low on test day 0 (0.25 µg/L: 2.1 and 1.8 %; 2.5 µg/L: 6.3 and 5.9 %). The actual test concentrations were therefore corrected with the means of these low recoveries. The outlying high value obtained for the lowest treatment group on day 7 was not expected to represent the actual test conditions and was therefore excluded from mean calculations.
The mean concentrations of DOT were 0.19 ± 0.048 µg/L and 2.6 ± 0.35 µg/L at 0.25 and 2.5 µg/L respectively. The measured concentrations varied within the ± 20 % window of the mean concentration at the target concentration of 2.5 µg/L but not at the target concentration of 0.25 µg/L.
FISH CONCENTRATIONS
Analyses of the concentrations of both DOT and MOT during the test demonstrated that the concentrations were always below the LOQ.

BIOCONCENTRATION FACTORS
Based on a worst-case-scenario, the LOQ for 0.25 mg/kg was used as the concentration in fish in order to calculate the BCF at each sampling point. Subsequently the mean BCFs of DOT at target concentrations of 0.25 and 2.5 µg/L were calculated to be 1294 and 99 respectively.
As 0.25 mg/kg of DOT was the LOQ of the analytical method, a bioaccumulation factor of 100 for the highest concentration tested was the lowest that could be measured. Measured concentrations in fish samples were always below the LOQ resulting in BCFs close to 1300 and 100 for the 0.25 and 2.5 µg/L test concentrations, respectively.
The concentrations in fish exposed to the lower target concentration were expected to have been lower than the concentrations in fish exposed to the highest target concentration. The high BCF value derived (1294) was considered to be due to the limitations of the sensitivity analytical methodology. It is anticipated that with the an analytical method capable of measuring lower concentrations, BCFs of less than 100 would have been derived.

TOTAL TIN CONCENTRATIONS
Total tin concentrations were analysed in fish samples to confirm that the BCF values were in fact below the cut off criteria of 2000.
After 30 days, the concentrations of total tin in fish samples were 0.27 and 0.054 mg/kg for the 0.25 and 2.5 µg/L groups, respectively.
Total tin concentrations in water samples of day 30 were not analysed. Based on the known concentrations of DOT and MOT (29.5 and 37.3 %, respectively) total tin concentrations in water could be calculated. Mean measured concentrations of DOT and MOT in water were corrected for the respective percentages of tin and then summed. The MOT concentrations in water were below the LOQ, in this situation the LOQ was used as to represent the MOT concentration. Mean concentrations of total tin in water were calculated to be 0.15 and 0.92 µg/L at target concentrations of 0.25 and 2.5 µg/L of the test substance, respectively.
The BCFs of total tin at 0.25 and 2.5 µg/L of the test substance were 178 and 58, respectively.

LIPID EXTRACTION
Lipid extraction was performed using the control group (exposed to acetone only) on day 0 and all groups on day 30. The lipid concentration of the fish at the start of the study was 4 %. This percentage was in agreement with previous lipid extractions during previous bioconcentration studies by the same performing laboratory.
At the end of the uptake phase (day 30), the percentage of lipids found in all groups was 6 %. Based on these results, the lipid content increased slightly during the uptake phase.

DEPURATION
Depuration was not performed as the concentration of both DOT and MOT were below the LOQ throughout the uptake phase, a depuration phase was not performed. The study was terminated after 30 days of exposure.

TEST CONDITION
- Mortality of test organisms: There was no mortality or sub-lethal effects in the two treatment groups.
- Behavioural abnormalities: No effects observed.
- Mortality and/or behavioural abnormalities of control: Two fish died unexpectedly in the control group. The fish exhibited no clinical signs before death. The mortality in the control was less than 10 % at the end of the study.

ANALOGUE APPROACH JUSTIFICATION:
The study was performed on a surrogate substance dioctyltin bis(2-ethylhexyl thioglycate) which like all octyltin compounds is anticipated to hydrolyse to dioctyltin oxide very rapidly in water. The fish in the study are therefore expected to have been exposed to the same organotin species that would occur if the test had been performed using the registration substance.

Reported statistics:

An uptake curve was plotted using the measured concentrations in/on fish against time on arithmetic scales. As all measured concentrations based on both DOT and MOT were below the limit of quantification, a “plateau” could not be determined. A mean BCF based on DOT was calculated using the following equation:
BCFmean = Cfmean/Cwmean
Where:
Cfmean = mean concentration in fish
Cwmean = mean concentration in water

Table 1: Measured concentration of DOT in water

Time of measurement (days)	Measured concentration (µg/L)
	Target concentration 0.25 µg/L	Target concentration 2.5 µg/L
0	0.14^1	3.0^1
1	0.18	2.9
3	0.16	2.1
7	0.62^2	3.0
14	0.17	2.5
21	0.24	2.7
28	0.26	2.3
^1Corrected concentrations ^2Value was omitted (outlier)

 

Table 2: Measured concentrations of DOT in fish

Time (days)		Target concentration: 0.25 µg/L		Target concentration: 2.5 µg/L
		Concentration (mg/kg fish)	BCF^1	Concentration (mg/kg fish)	BCF^1
Uptake phase	1	< 0.25	1389	< 0.25	88
	3	< 0.25	1592	< 0.25	119
	7	< 0.25	401^2	< 0.25	84
	14	< 0.25	1479	< 0.25	100
	21	< 0.25	1046	< 0.25	93
	28	< 0.25	965	< 0.25	109
^1The LOQ of 0.25 mg/kg was used as the concentration in fish in order to calculate the BCF ^2Value was omitted from calculations as an outlier

Table 3: Lipid extraction

Target concentration (µg/L)	Day	Weighed amount (g)	Weight vessel (g)	Weight vessel + Lipid (g)	Lipid (g)	Lipid (%)
Control	0	10.02	60.08	60.52	0.44	4 %
Control	30	10.21	61.32	61.91	0.59	6 %
0.25	30	13.09	63.84	64.42	0.58	6 %
2.5	30	13.25	65.01	65.59	0.58	6 %

 

Table 4: Validation of the analytical methods

Analytical method/media		LOQ	Accuracy (%)		Repeatability (%)
			High level (2.5 µg/L)	LOQ Level (0.25 µg/L)	High level (2.5 µg/L)	LOQ Level (0.25 µg/L)
GCMS/Water	MOT	0.25 µg/L	102	99	5.8	6.2
	DOT	0.25 µg/L	99	98	5.7	3.4
GCMS/Fish	MOT	0.25 mg/kg	94	106	2.8	6.9
	DOT	0.25 mg/kg	101	109	8.2	5.8
ICPMS/Fish	Total tin	0.025 mg/kg	86	100	1.1	1.5

 

Validity criteria fulfilled:

yes

Remarks:

All validity criteria were met with the exception of the maintenance of the low test concentration. This was limited by the analytical methods and could not be further improved.

Conclusions:

The biococnentration of dioctytin bis(2-ethylhexyl thioglycolate) in rainbow trout exposed to 0.25 and 2.5 µg/L of dioctytin bis(2-ethylhexyl thioglycolate) for 30 days in a flow-through system was determined to be 1294 and 99 respectively based on measured dioctyltin.
The high BCF value found at the 0.25 µg/L concentration was due to the limitations in the sensitivity of the analytical methods employed in the study and could not be further improved.
Based on the result found at the highest concentration tested, the BCF is at least less than 100 and therefore the substance is not expected to bioconcentrate.

Executive summary:

The study was performed to GLP and in line with the OECD guideline No. 305, 1996.In addition; the procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.13, 2008.

The study was performed on a surrogate substance dioctyltin bis(2-ethylhexyl thioglycate) which like all octyltin compounds is anticipated to hydrolyse to dioctyltin oxide very rapidly in water. The fish in the study are therefore expected to have been exposed to the same organotin species that would occur if the test had been performed using the registration substance.

The batch of Dioctyltin bis(2-ethylhexyl thioglycolate) used was a colourless liquid with a purity of 97.5 area %. Water solubility was indicated to be below 0.1 mg/L. Stock solutions for the bioconcentration test were prepared in acetone and dosed via a computer-controlled system consisting of micro-dispensers into a mixing flask separately from the medium supply. Medium was supplied via a flow meter at a flow rate of 10 L/h. In the mixing flask the dosed stock volume and the dilution water were mixed under continuous stirring at a ratio of 1:10,000. The final target concentrations were 0.25 and 2.5 µg/L (based on water solubility and detection limits of the analytical methods used).

At the start of the bioconcentration test 58 fish per concentration were exposed to the target concentrations of 0.25 and 2.5 µg Dioctyltin bis(2-ethylhexyl thioglycolate) per litre and 42 fish were exposed to a control. The uptake phase lasted for 30 days, during which samples were taken from the test medium and from the fish.

Analyses were based on both dioctyltin (DOT) and monooctyltin (MOT). Results were based on DOT, due to the fact that MOT-concentrations were below the Limit Of Quantification (LOQ) for the target concentration of 0.25 µg/L. The mean concentrations of DOT were 0.19 ± 0.048 µg/L and 2.6 ± 0.35 µg/L at target concentrations of 0.25 and 2.5 µg/L, respectively. The measured concentrations varied within the ± 20 % window of the mean concentration at the target concentration of 2.5 µg/L but not at the target concentration of 0.25 µg/L.

Analyses of the concentrations of both DOT and MOT in fish tissues during the 30-day uptake phase showed measured concentrations that were always below the Limit of Quantification, i.e. < 0.25 mg/kg.

Since the concentrations of both DOT and MOT in fish were constantly below the LOQ during the uptake phase, a depuration phase was not considered to be significant. Therefore, the bioconcentration test was terminated after 30 days of exposure. In addition to the analytical work already performed on tin species, fish samples taken after 30 days of exposure were analysed on total tin.

The mean BCF-values based on dioctyltin at target concentrations of 0.25 and 2.5 µg/L were1294 and 99, respectively. The mean BCF-values based on total tin at target concentrations of 0.25 and 2.5 µg/L were 178 and 58, respectively.

The high value found at the target concentration of 0.25 µg/L was in fact due to the analytical methodology limit, which could not be further improved.

Based on the result found for the highest target concentration of 2.5 µg/L, the BCF is at least less than 100 and therefore the substance does not bioconcentrate.

Description of key information

BCF <100, dioctytin bis(2-ethylhexyl thioglycolate), OECD 305, EU Method C.13, Bouwman 2010

Key value for chemical safety assessment

BCF (aquatic species):

100 dimensionless

Additional information

The key study was performed in line with GLP and in accordance with standardised guidelines OECD 305 and EU Method C.13. The study was performed on the surrogate substance dioctyltin bis(2-ethylhexyl thioglycate); like all octyltin compounds, this is anticipated to hydrolyse very rapidly in water. The fish in the study are therefore expected to have been exposed to the same organotin species that would occur if the test had been performed using the registration substance as the test essentially measures the dioctyltin species.

The bioconcentration of the test material in rainbow trout exposed to 0.25 and 2.5 µg/L for 30 days in a flow-through system was determined to be 1294 and 99 respectively based on measured dioctyltin. The high BCF value found at the 0.25 µg/L concentration was due to the limitations in the sensitivity of the analytical methods employed in the study and could not be further improved. Based on the result found at the highest concentration tested, the BCF is at least less than 100 and therefore the substance is not expected to bioconcentrate.

The study was performed to a good standard with a sufficient level of detail to assess the quality of the results. As such it was assigned a reliability score of 2 due to being used in a read across capacity using the principles for assessing data quality as set out in Klimisch (1997) and considered suitable as an accurate reflection of the test material.

Two disregarded studies, Recommendation for classification dossier (2005) and IUCLID Dataset (2006), on the read across material n-dioctyltin oxide were included for completeness as both are in the public domain. The studies were deemed unsuitable as the result was derived using calculation software not validated for organometallic substances and reported in a secondary source.