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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
Remarks:
In-vivo study performed to meet the requirements of a new substance notification in Japan.
Adequacy of study:
key study
Study period:
2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliance study with detailed report
Qualifier:
according to
Guideline:
OECD Guideline 305 E (Bioaccumulation: Flow-through Fish Test)
Qualifier:
according to
Guideline:
other: Test Method Relating to New Chemical Substances (Yakushokuhatsu No. 1121002, Heisei 15.11.13 Seikyoku No. 2, Kanpokihatsu No. 031121002, Novermber 21, 2003; the latest revision)
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Vehicle:
yes
Details on preparation of test solutions, spiked fish food or sediment:
Vehicle used was dimethyl sulfoxide at 25 ppm (v/v)

The dilution water was prepared by treating Yokohama municipal tap water with activated charcoal and adding sodium thiosulfate solution to neutralize trace free chlorine. Water quality parameters of the dilution have been checked half-yearly by Mitsubishi Chemical Analytech Co., Ltd. Measured values generally met the Water Quality Criteria fro the Protection of Aquatic Living Resources 2005 and were comparable to previous data from the laboratory. Thus, this water was considered acceptable for dilution water.
Test organisms (species):
Cyprinus carpio
Details on test organisms:
- Source: Niikura Fish Farm, 1217, SHimoya, Isehara-city, Kanagawa, Japan
- Date of purchase: July 21, 2009
- Lot number: 09-K-0271
- Total length: 5 +- 3 cm
- Body weight: ca. 4 g
- Age: ca. 1 year after hatching
- Acclimation: yes. At the start of acclimation, abnormal fish were removed upon visual inspection. The remaining normal fish were then reared in an aquarium with flowing water. No medication was provided during the acclimation period.
- Water temperature: 24 +- 2°C
- Food: Babygold from Kyorin
- Feeding: the food was given daily in an amount equivalent to 1.5% of the fish body weight
- Mortality during the 1 week before testing < 5%
Route of exposure:
aqueous
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
ca. 61 d
Total depuration duration:
ca. 3 d
Hardness:
53-57 mg CaCo3/L during exposure
58-59 mg CaCo3/L during depuration
Test temperature:
24.1 - 24.9 °C
pH:
7.5 - 8.5
Dissolved oxygen:
7.6 - 8.5 mg/L
TOC:
8.74 - 8.89 mg/L before the start of exposure
7.12 - 9.28 mg/L during exposure period
0 mg/L during depuration
Details on test conditions:
Fish were kept in the flow-through bioconcentration test system set up in a series of two (high and low) concentrations of the test substance and a control without the test substance, with no replicates. During the exposure period, concentrations of the test substance in water and fish were measured periodically. The bioconcentration factors calculated based on the comparison fo the measured values in fish and water were used to evaluate bioconcentration potential of the test substance in fish. As the BCFs exceeded 10, depuration test was performed after exposure period to calculate biological half lives.

- Supply of dilution water: 800 L/day
- Supply of feed solution: 20 mL/day
- Number of fish (at the start of the exposure period):
- High concentration level: 44 fish in 50L test water (>1L/day/g)
- Low concentration level: 44 fish in 50L test water (>1L/day/g)
- Control: 44 fish in 50L test water (>1L/day/g)
- Continuous aeration
Nominal and measured concentrations:
Nominal concentrations: 0 mg/L, 0.005 mg/L, 0.05 mg/L
Measured concentrations: 0 mg/L, 0.00566, 0.0502 mg/L
Reference substance (positive control):
no
Lipid content:
ca. 3.7 %
Time point:
other: end of depuration
Lipid content:
ca. 3.1 %
Time point:
start of exposure
Type:
BCF
Value:
ca. 35 dimensionless
Basis:
other: whole body
Calculation basis:
steady state
Remarks on result:
other: Conc.in environment / dose:0.05 mg/L
Type:
BCF
Value:
>= 20 - <= 54 dimensionless
Basis:
other: whole body
Remarks on result:
other: The BCFs at low concentration level are considered to be within the range of 20-54 regardless of the variation of the test substance concentration in the test water
Remarks:
Conc.in environment / dose:0.005 mg/L
Elimination:
yes
Parameter:
DT50
Depuration time (DT):
0.17 d
Elimination:
yes
Parameter:
DT50
Depuration time (DT):
0.89 d
Details on results:
The biological half lives determined during the test were dependent on the concentration tested as the BHLs were calculated to be 0.17 and 0.89 days for the high and the low concentrations respectively.
Validity criteria fulfilled:
no
Remarks:
At the low concentration level, one of the validity criteria was not met since variation of the test substance concentrations in test water was not within +-20% of the average measured value. All other validity criteria were met.
Conclusions:
The current test results indicate that the substance has a very low bioaccumulative potential in fish under the evaluated test conditions.
Executive summary:

A bioconcentration study of DBPP with Carp was conducted according to OECD 305E guideline 'Bioconcentration: Flow-Through Fish Test'. Nominal test concentrations in the water were 0 mg/L (control), 0.005 mg/L (low concentration) and 0.05 mg/L (high concentration).

At the high concentration level, variation of mean BCFs from three consecutive measurements at over 48 -hour intervals were within +-20% and it was considered that steady state was reached. The BCF at steady state was calculated to be 35.

At the low concentration level, variation of mean BCFs from three consecutive measurements at over 48 -hour intervals were not within +-20%.Therefore, a steady state was not considered to have been reached, and the BCF at steady state was not calculated. Instead, the BCF at this concentration is presented as a range (20 -54).

Although it is indicated that one of the validity criteria is not met for the low concencentrations, the results from this bioconcentration assay can still be regarded as valid and sufficient to draw a conclusion related to the bioaccumulative potential of DBPP.

Based on the results of this test it can be concluded that DBPP does not have the potential to bioaccumulate in aquatic organisms.

Description of key information

A bioconcentration study of DBPP (multi-constituent) with Carp was conducted according to OECD 305E guideline 'Bioconcentration: Flow-Through Fish Test' (Kobayashi, 2010). The BCF for DBPP (mono-constituent) at steady state was calculated to be 35. From the results of this key study it can be concluded that DBPP does not have the potential to bioaccumulate. 

Key value for chemical safety assessment

BCF (aquatic species):
35 dimensionless

Additional information

The available key study (Koboyashi, 2010) is a bioconcentration study with Carp which was conducted according to OECD 305E guideline. Nominal test concentrations in the water were 0 mg/L, 0.005 mg/L and 0.050 mg/L (respectively control, low and high concentration). At the high concentration level, the BCF at steady state for the mono-constituent DBPP was calculated to be 35. At the low concentration level, variation of mean BCFs from three consecutive measurements at over 48 -hour intervals were not within the specified range (+-20%). Therefore, at the low concentration a steady state was not considered to have been reached. Therefore, the BCF at this concentration is presented as a range (20 -54). Based on the results of this test it could be concluded that the substance (DBPP) does not have the potential to bioaccumulate.

Additional supporting studies were conducted, based on a QSAR approach for all three constituents DiButyl Phenyl Phosphate (DBPP), TriButyl Phosphate (TBP) and Butyl DiPhenyl Phosphate (BDPP):

compound              log BCF

DBPP                     1.54 (key study)

DBPP                     1.66

TBP                      1.48

BDPP                     1.75

The QSAR is well described with a clear regression model, a clear endpoint and all three compounds fall well within the applicability domain of the QSAR. The QSAR result of DBPP is in good agreement with the result of the key study and confirms that DBPP has no bio-accumulation potential. Also TBP and BDPP have no bio-accumulation potential.

The low bio-accumulation potential for DBPP was also confirmed by a supporting (older) study (Saeger et al., 1979), in which the bioconcentration factor of DBPP was estimated using a different QSAR (based on the log Pow). This study did not contain sufficient information for assessment and was consequently ranged K4 (no indication of the applicability domain nor error estimates were given). Nevertheless, also in this study it was indicated that the substance has a low potential for bioaccumulation (estimated BCF of 270, log BCF 2.43).