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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:
1996-07-26 - 1996-10-16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 305 C (Bioaccumulation: Test for the Degree of Bioconcentration in Fish)
Version / remarks:
May 12, 1981
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: "Bioaccumulation test of a chemical substance in fish or shellfish" provided in "the Notice on the Test Method Concerning New Chemical Substances"
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Purity: 99.9 %
Radiolabelling:
no
Details on sampling:
Feeding was stopped the day before the test fish were collected.

Test substance analysis in test water was performed twice a week (12 times in total) during the exposure period for both concentrations tested.
Test substance in fish was analysed 4 times at week 2,3,4 and 6 after the start of exposure for both concentrations tested .
Control was analysed at the start and the end of exposure.
Vehicle:
yes
Remarks:
HCO-40
Details on preparation of test solutions, spiked fish food or sediment:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Concentration 1: Dissolving the test substance and 10 times the amount of HCO-40 in acetone and adding ion-exchanged water. Then, evaporate the solvent (acetone) on rotary evaporator, then on nitrogen purge
- Controls: HCO-40 dissolved in water, 40 mg/L
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): HCO-40
- Concentration of vehicle in test medium (stock solution and final test solution(s) at different concentrations and in control(s)): 1st Concentration area: 100 µg/L, 2nd Concentration area: 10 µg/L
Test organisms (species):
Cyprinus carpio
Details on test organisms:
TEST ORGANISM
- Common name:common carp
Strain: Carp (Cyprinus carpio)
- Source: Sugishima fish farm
- Condition for fish cultivation : The fishes were receipt at May 16, 1996 and were macroscopically examined on recipt. Those demonstrating abnormalities were removed. Then, the fishes were cultivated for 3 days under the condition of flow-through water following a dipping to prevent of infection and exterminate parasite in the received tank.
- Length at study initiation (length definition, mean, range and SD): 9.3 cm on average
- Weight at study initiation (mean and range, SD): 20.4 g on average
- Lipid content at test initiation (mean and range, SD): 3.8 %
- Health status: good
- Feeding during test
- Food type: pelleted food (Japan Haigo Shiryo K.K.),
- Amount: about 2 % of body weight
- Frequency: twice a day; On the day of before sampling, however, feeding was suspended.

ACCLIMATION
- Acclimation period: 28 days
- Acclimation conditions (same as test or not): same
After external desinfection under static conditions with 50 mg/L terramycin and 7 g/L sodium chloride, the fish were reared ina flow through system for about 37 d. During acclimatization period, fishes demostrating abnormalities were eliminated. Fish were reared in an acclimatization tank (flow through system) for another 46 d at 25 +/- 2 °C.
- Type and amount of food: pelleted food (Japan Haigo Shiryo K.K.), about 2 % of body weight
- Feeding frequency: twice a day
- Health during acclimation (any mortality observed): no
Route of exposure:
aqueous
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
6 wk
Hardness:
measured every 6 months
Test temperature:
continuously measured (once a day)
25 ± 2 °C
pH:
continuously measured
Dissolved oxygen:
continuously measured (twice a week)
Concentration 1 area: 7.6 - 8.0 mg/L
Concentration 2 area: 7.6 - 8.2 mg/L
Control area : 7.9 - 8.2 mg/L
TOC:
COD measured every 6 months
Salinity:
not applicable
Details on test conditions:
TEST SYSTEM
- Test vessel: glass tanks
- fill volume: 100 L
- Type of flow-through (e.g. peristaltic or proportional diluter): A running water system assembled by this testing facility was used.
- Renewal rate of test solution (frequency/flow rate): The test material second stock solution and the dilution water were supplied to the test aquarium in an amount of 1155 L/ day, at a rate of 2 mL/min of undiluted solution and 800 mL/min of test wate, respectively
- No. of organisms per vessel: 15 - 20
- No. of fish per concentration (replicates): 11
- No. offish per control / vehicle control (replicates): 5
- Observation of fish: twice a day

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: undergroundwater from the Kurume Research Laboratories
- Water quality assessment : The water sample was obtained at August 07, 1996. The frequency of analysis was periodically once per six months. It was confirmed that following parameters such as total hardness, suspended solid, pH, total organic carbon, chemical oxygen demand, residual chlorine, ammonium nitrogen, together with hazardous substances such as total cyan, organic phosphorus, heavy metals etc. in this Laboratory were not larger than the concentration value described in the " Water Quality Standards based on Water Works Law " (Health and Welfare Ministry Ordinance No. 69, amended on Dec. 21, 1992), " OECD Guideline for Testing Chemical, " Fish, Early-life Stage Toxicity Test (Guideline 210, July 17, 1992 " or " Water Quality Criteria for Fisheries " (Japan Marine Resource Protection Association, March 1983).


RANGE-FINDING / PRELIMINARY STUDY
Acute toxicity test:
- Test conditions: semi-static, 48h, vehicle: HCO-40
- Results used to determine the conditions for the definitive study: LC50(48h) 9.35 mg/L, Rice fish (Oryzias latipes)

RATIONAL OF THE TEST MATERIAL CONCENTRATION FOR DEFINITIVE TEST ;
Based on the preliminary test result for 48-hr LC50 and the analytical sensitivity of test material, the test material concentrations for definitive test were determined as follow ;
Concentration 1 area ; 0.1 mg/L
Concentration 2 area ; 0.01 mg/L
It was confirmed that the test item was stable under the test conditions.
Nominal and measured concentrations:
nominal: 10 µg/L (1st concentrataion) and 1 µg/L (2nd concentration)
vehicle control nominal: 1 mg/L
Reference substance (positive control):
no
Details on estimation of bioconcentration:
not specified
Lipid content:
3.8 %
Time point:
start of exposure
Conc. / dose:
1 µg/L
Type:
BCF
Value:
<= 48 L/kg
Basis:
whole body w.w.
Calculation basis:
other: Calculation was performed on 2, 4 and 6 week.
Conc. / dose:
10 µg/L
Type:
BCF
Value:
>= 7.8 - <= 19 L/kg
Basis:
whole body w.w.
Calculation basis:
other: Calculation was performed on 2, 4 and 6 week.
Details on kinetic parameters:
Steady state was reached within 7 days. Due to the low uptake, no depuration phase was necessary.
Metabolites:
none
Results with reference substance (positive control):
no use of reference substance
Details on results:
Concentration: The mean test substance concentration in the test water was maintained at or above 85 % of the nominal concentration.
Mortality of test organisms: No death was observed during test period.
Abnormalities of test fish: No abnormalities were observed during test period.

Table1 Mean concentration values of the test substances in the test water

Nominal Concentration (µg/L)

Measured Concentration (µg/L)

Week 2

Week 3

Week 4

Week 6

10

8.93

8.78

8.74

8.68

1

0.950

0.954

0.952

0.955

  The mean test substance concentration in the test water was maintained at or above 85 % of the nominal concentration.

Table 2 Bioconcentration Factors

Nominal Concentration (µg/L)

BCF

Week 2

Week 3

Week 4

Week 6

10

11

12

11

11

9.3

19

7.8

15

1

below 48

below 48

below 48

below 48

below 48

below 48

below 48

below 48

The BCF in the 10 µg/L test group in carp was 7.8 - 19. For the 1 µg/L test group the BCF was below 48.

Validity criteria fulfilled:
yes
Conclusions:
The test material showed no relevant bioaccumulation at concentrations at or above the water solubility. The steady state BCF values were at 7.8 - 19 at a concentration of 10 µg/L and below 48 at a concentration of 1 µg/L, respectively. The test material showed no relevant bioaccumulation (BCF < 500).
Executive summary:

A bioaccumulation study was carried out to evaluate the bioaccumulation potential of the test material thymol. The study was conducted in accordance with the Japanese guideline “Bioconcentration test of chemical substances in fish and shellfish” specified in ‘The test method relating to new chemical substances’ and OECD Guideline 305C following GLP.

Subsequent to an acute toxicity investigation in Oryzias latipes (LC50 (48h) 9.35 mg) the BCF in Cyprinus carpio was determined over a 6 week exposure period at concentrations of 1 µg/L and 10 µg/L thymol, respectively. The exposure method was a continuous flow-through system.The test material showed no relevant bioaccumulation at concentrations at or above the water solubility. The steady state BCF values were 7.8 - 19 at a concentration of 10 µg/L and ≤ 48 at a concentration of 1 µg/L, respectively. The measured BCF is far below 500; and hence thymol has no significant bioaccumulation potential.

Description of key information

Bioaccumulation test, OECD Guideline 305C, GLP, 1 µg/L and 10 µg/L, Cyprinus carpio, flow-through, 6 weeks: BCF 7.8 - 48 (MITI 1996).

The measured BCF is far below 500; and hence thymol has no significant bioaccumulation potential.

Key value for chemical safety assessment

BCF (aquatic species):
48 dimensionless

Additional information

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