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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016-2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 305 (Bioaccumulation in Fish: Aqueous and Dietary Exposure) -III: Dietary Exposure Bioaccumulation Fish Test
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Details on sampling:
During the biomagnification test, samples were taken from the food and from the fish for several purposes and at several timepoints.
Analysis of food and lipid extraction: 12 samples
Analysis of fish and lipid extraction: 25 fish.
Due to the analytical method taking 2 days before results became available, fish were transferred to clean vessels on day 14 and fed with untreated food for one day. Fish were sampled on day 15 but not analysed for test item concentration based on the analytical results of fish sampled on day 14.

Food was sampled by weighing the required amount from the batches of treated and untreated food.
Fish were sampled with a small fishing net, rinsed quickly with untreated water, blotted dry and then instantly killed. Subsequently, fish were weighed and measured for total length.

Feeding pellets: the samples were analysed directly after preparation. Samples of approximately 0.5 g of the trial pellets were accurately weighed into glass vessels. The samples were extracted with 20 mL dichloromethane. The shaking time was 30 seconds. Afterwards extract was 10-times diluted with dichloromethane and analysed.

Fish: the test samples were stored in the freezer (= -15°C). Storage stability of samples under these conditions was demonstrated in another project. On the day of analysis, the test samples were defrosted at room temperature. The samples were extracted with 10 mL dichloromethane. Afterwards, samples were ultrasonicated for 5 minutes and shaken for 30 seconds. The QC samples were filtered using Agilent FL filter and diluted at least 10-times with dichloromethane
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
For the preparation of pellets, 375 mL dichloromethane, was spiked with 625 µL of a 1000 mg/L test item solution in duplo and homogenized. Thereafter approximately 125 g pellets were added to get target concentration of 5 µg/g. Dichloromethane was completely evaporated at 30°C using a rotary evaporator. After evaporation, prepared pellets were combined in one container. The trial pellets were dried overnight at room temperature. Before analysis, the clumps were minced and the pellets were homogenized
Test organisms (species):
Cyprinus carpio
Details on test organisms:
Species Male and female carp (Cyprinus carpio, Teleostei Cyprinidae) Linnaeus, 1758
Source Zodiac, proefacc, "De Haar Vissen", Wageningen University and Research Centre, The Netherlands.
Initial fish length 5.9 ± 0.3 cm, based on measurement of all fish used for this test
Initial fish weight 6.43 ± 0.65 g, based on weighing of all fish used for this test
Characteristics F1 from a single parent-pair bred in UV-treated water.
Reason for selection This system has been selected as an internationally accepted species.
Route of exposure:
feed
Justification for method:
dietary exposure method used because stable, measurable water concentrations cannot be maintained
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
14 d
Hardness:
Total hardness ranged from 179 to 196 mg calcium carbonate per litre, which is >140 mg/L as prescribed.
Test temperature:
Temperature remained within the range prescribed by the study plan (20-25°C, constant within ± 2°C).
pH:
The pH ranged from 7.3 to 7.7 during the test period, with an average value of 7.5, which is within the optimum range for carp (6.0-8.5, kept at a variation of not more than ± 0.5 units)
Dissolved oxygen:
Oxygen concentrations ranged from 7.2 to 8.2 mg/L during the test period, which is >60% of saturation as prescribed.
TOC:
During the test period (day 0 - day 14) T(D)OC in ISO medium was <1 mg/L and therefore <2 mg/L as prescribed.
Salinity:
not relevant
Conductivity:
not relevant
Details on test conditions:
1- Edibility test
Preceding the biomagnification test an edibility test was performed during which 10 fish were fed with the spiked fish food (5 µg/g).
Test procedure and conditions were similar to those applied in the bioconcentration test with the following exceptions:
• The mean length of fish was 4.6 ± 0.1 cm;
• The flow-rate of test medium was 5 L/h and test vessels were 24 L;
• No food samples were taken for either concentration analysis or lipid extraction;
• No fish samples were taken for either concentration analysis or lipid extraction;
• No hardness was measured;
• No TOC analysis was performed

2- Biomagnification test
Test duration 14 days, i.e. an uptake phase of 14 days and no depuration phase.
Test vessels 64 litres (40x40x40 cm) consisting of stainless steel and covered by a removable Perspex plate.
Test medium Adjusted ISO medium with a hardness of 180 mg CaCO3 per litre and a pH of 7.7 ± 0.3.
Total number of fish: 85
Number of fish per test group: 45 for the control, 40 for the test concentration
Nominal and measured concentrations:
Nominal concentration of test item in pellets: 5 µg/g
Measured concentrations: one day before the start of exposure the measured food concentrations were in agreement with the treated concentrations (99-102%) and remained stable during the test period, i.e. were 94-107% of treated at the end of the test. The concentration of the test item in fish food before and at the end of the uptake phase was within ± 5%.
Lipid content:
ca. 1.9 %
Time point:
start of exposure
Lipid content:
ca. 2.6 %
Time point:
end of exposure
Conc. / dose:
5 µg/g food
pH:
7.5
Type:
BMF
Value:
< 0.01 dimensionless
Remarks on result:
not determinable
Metabolites:
no absorption
Details on results:
No TPS 32 could be detected in any of the fish at any time point during the 14-day exposure period. This means that the fish did not accumulate TPS 32 from food. Therefore, it was not necessary to perform a depuration phase. The study was terminated after the results of concentration analysis on the samples taken on day 14 became available.
No BMF could be calculated because the measured concentrations in fish were below the limit of detection (LOD = 0.027 µg/g) after 1 day of exposure and remained below the LOD during the entire 14-day exposure period.

Beforehand an edibility study demonstrated that fish fed normally with 5 µg/g treated food.

Analysis of food demonstrated the stability of test item long the 14 day time period of exposure.

No mortality or other clinical effects were observed on the fish exposed to the control and the food concentration of 5 µg/g during the entire test period.

Fish growth during the study was 8%. Since no accumulation was observed and therefore no BMF could be calculated it was not possible to correct the BMF for fish growth.

At the start of exposure the average lipid percentage of the fish sampled from the control was 2%. After 6 and 14 days of exposure the average lipid percentage of the fish sampled from both the control and the treated group was 2 and 3%, respectively. Based on these results lipid concentrations were considered to be similar. Since no accumulation was observed and therefore no BMF could be calculated it was not possible to correct the BMF for lipid.


Validity criteria fulfilled:
yes
Conclusions:
No BMF could be calculated as it was shown from analysis of test substance in fish at the end of exposure phase (14 day), that no absorption and therefore accumulation occured.
In conclusion, polysulfides, di-tert-dodecyl does not bioaccumulate in fish.
Executive summary:

A study on bioaccumulation of polysulfides, di-tert-dodecyl in fish (carp) was carried out according to OECD TG 305, through dietary exposure. This mode of exposure was selected because of the very low water solubility of polysulfides, di-tert-dodecyl, which has been demonstrated to be 0.26 µg/L (OECD 105, slow stirring method, GLP compliant).

Polysulfides, di-tert-dodecyl was incorporated in fish feeding pellets at a concentration of 5 µg/g. It has been shown that this concentration has no impact on edibility, through a preliminary experiment.

According to the guideline, a standard uptake phase took place, at the end of which the fish were transferred to clean vessels and fed during one day with untreated food before that the concentration of polysulfides, di-tert-dodecyl was measured in sampled fish: the measured concentrations were below the limit of detection (LOD = 0.027 µg/g) after 1 day of exposure and remained below the LOD during the entire 14-day exposure period. In consequence the depuration phase was terminated.

No BMF could be calculated because of the absence of absorption in fish flesh. No BCF could be calculated either.

Polysulfides, di-tert-dodecyl does not bioaccumulate in fish.

Description of key information

In order to confirm the lack of potential for bioaccumulation (a calculated logKow > 12 predicts that polysulfide, tert-dodecyl should not be bioavailable) a fish bioaccumulation study has been proposed to ECHA and, further to acceptance, been carried out. The study was carried out according to OECD TG 305, through dietary exposure. This mode of exposure was selected because of the very low water solubility of polysulfides, di-tert-dodecyl, which has been demonstrated to be 0.26 µg/L (OECD 105, slow stirring method, GLP compliant).

Polysulfides, di-tert-dodecyl was incorporated in fish feeding pellets at a concentration of 5 µg/g. It has been shown that this concentration has no impact on edibility, through a preliminary experiment.

According to the guideline, a standard uptake phase took place, at the end of which the fish were transferred to clean vessels and fed during one day with untreated food before that the concentration of polysulfides, di-tert-dodecyl was measured in sampled fish:the measured concentrations were below the limit of detection (LOD = 0.027 µg/g) after 1 day of exposure and remained below the LOD during the entire 14-day exposure period. In consequence the depuration phase was terminated.

No BMF could be calculated because of the absence of absorption in fish flesh. No BCF could be calculated either.

Key value for chemical safety assessment

Additional information