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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
This study is used for read-across and therefore has been assigned a reliability of 2 (reliable with restrictions). The study, if used in support of terephthalic acid, has a reliability of 1 (reliable without restriction).
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
A sample of the test solution was taken at the beginning of the test (0 h) and at the end (48 h) and the concentration was determined.
Vehicle:
no
Details on test solutions:
Reconstituted water was used to prepare the stock solution of the test substance, to dilute the test substance and to keep the daphnids in the stock cultures before and during the period of the test. The final concentrations of the salts in the reconstituted water were:
i) CaCl2.2H2O = 294.00 mg/L
ii) MgSO4.7H2O = 123.00 mg/L
iii) NaHCO3 = 65.00 mg/L
iv) KCl = 5.75 mg/L

For the range-finding test, the stock solution was prepared before starting the test. The test material (100.2 mg) was added to 1.0 L of reconstituted water and it was allowed to dissolve after addition of NaOH for pH adjustment. The nominal concentration of the stock solution was 100.2 mg/L. In the definitive test the stock solution was prepared by the same method, however, this time a concentration of 1000 mg/L was obtained.
Test organisms (species):
Daphnia magna
Details on test organisms:
Daphnia magna (Straus) from Hoechst AG, D-6230 Frankfurt. Purchased in Oct 1989. In deviation to the protocol, the daphnids were not kept in reconstituted water supplemented with vitamin B12 and sodium selenate but in Elendt M7 medium. Furthermore, in deviation to the protocol the daphnids were not fed with specially prepared fish food but only with algae. The daphnia were fed twice a week. For the test only daphnids more than six hours and less than 24 h old were used.

During the test, the daphnids were not fed and were transferred to reconstituted water.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
Mean = 232.64 mg/L CaCO3
Test temperature:
Mean = 22.07°C

pH:
Mean = 7.79
Dissolved oxygen:
Mean = 92.38%

Salinity:
freshwater
Nominal and measured concentrations:
Nominal: 80, 130, 220, 350, 600 and 1000 mg TS/L

Details on test conditions:
In the range-finding test the exposure conditions were as follows;
- Test vessel:
- covered by glass lids
- made of glass, 300 mL; height: 5 cm; diameter: 9 cm
- Amount of test solution per test vessel = 250 mL
- No renewal of test solution.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates):2

In the definitive test the exposure conditions were as follows;
- Test vessel:
- covered by glass lids
- made of glass, 300 mL; height: 5 cm; diameter: 9 cm
- Amount of test solution per test vessel = 200 mL
- No renewal of test solution.
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates):4

In both the definitive test and range finding test ;
- Adjustment of pH was made using NaOH to pH 7.8
- Photoperiod: 24 h in light
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 967 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
967 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
The range finding study showed that there was no immobilisation of daphnids at 100 mg/L. Therefore the lowest concentration causing 100% immobilisation within the period of the range finding test was >100 mg/L.

Based on the range finding study results, concentrations were selected for a definitive assay. From the results obtained, the highest test concentration which caused no immobilisation within the period (EC0) of the test was 600 mg/L. The lowest concentration causing 100% immobilization within the period of the test (EC100) was > 1000 mg/L.

The actual concentration of the test solution was taken and found not to be 100% of the nominal concentration. At the beginning of the test the measured concentrations were 92.7% of the nominal concentration. The average at the end of the test (48 h) was 85.7%. Based on the measured average concentration (85.7%) of all concentration levels analysed the result of the study was EC0 (48 h): 514 mg/L terephthalic acid and terephthalic sodium salt. Based on the measured average concentration (98.2%) of the highest concentration level tested (nominally 1000 mg/L) the result of the study was; EC50 (48 h) >982 mg/L terephthalic acid and terephthalic sodium salt.

In the report, the endpoint is given as >982 mg/L, apparently the mean measured value at the highest concentration, but based on the 48-h data only, i.e. (970 + 994)/2. The mean should include the 0-h data as well, i.e. (958 + 945 + 970 + 994)/4 = 967 mg/L.
Results with reference substance (positive control):
Results with reference substance not reported.
Reported statistics and error estimates:
None reported

Tabulated below are the results from the range finding test. The highest concentration (100.0 mg/L) caused no immobilization within the period of the range finding test.

 

Table 1

Range Finding Test Results (no immobilised/no per treatment, replicates combined) for Daphnia exposed to terephthalic acid (sodium terephthalate) 

Conc

"Salinity Control"*

Control

1

3

10

30

100

R

Time

1

0

0/10

0/10

0/10

0/10

0/10

0/10

0/10

2

0

0/10

0/10

0/10

0/10

0/10

0/10

0/10

1

24

0/10

0/10

0/10

0/10

0/10

0/10

0/10

2

24

0/10

0/10

0/10

0/10

0/10

0/10

0/10

1

48

0/10

0/10

0/10

0/10

0/10

0/10

0/10

2

48

0/10

0/10

0/10

0/10

0/10

0/10

0/10

* The "salinity control" consisted of test medium amended with NaOH solution only.

 

Tabulated below are the results obtained for the definitive test. The selection of the test substance concentrations for the definitive assay were based upon results of the range finding test.

 

Table 2

Definitive test results; Effects of terephthalic acid (sodium terephthalate) on Daphnia in a 48 -hour, acute toxicity test under static conditions (no. immobilised/no. per treatment, replicates combined) 

Conc

Salinity Control

Control

80

130

220

350

600

1000

Time

0

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

24

5% (1/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

48

5% (1/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

0% (0/20)

5% (1/20)

 

Maximum immobilisation in the nominal 1000 mg TPA/L treatment after 48 h (5%) was identical to the level of immobilisation observed in the salinity control (reconstituted water medium amended with NaOH). The effect seen at 1000 mg/L (nominal) is therefore considered not to be related to treatment.

 

Table 3

Measured concentrations of terephthalic acid during a 48 hour, static acute toxicity test with Daphnia.

Exposure Period (h)

Terephthalic Acid Nominal mg/L

Measured Terephthalic Acid mg/L

Percentage of nominal %

0

80

71.8

68.6

90

86

0

350

338

321

97

92

0

1000

958

945

96

95

48

80

63.0

72.8

79

91

48

350

263

256

75

73

48

1000

970

994

97

99

In the report, the endpoint is given as >982 mg/L, apparently the mean measured value at the highest concentration, but based on the 48-h data only, i.e. (970 + 994)/2. This is incorrect; the mean should include the 0-h data as well, i.e. (958 + 945 + 970 + 994)/4 = 967 mg/L.

 

 

Validity criteria fulfilled:
yes
Conclusions:
The static 48-h EC50 of the test substance (converted to its sodium salt prior to exposure) to Daphnia magna was >967 mg/L, based on the mean measured concentration at the maximum treatment applied. The 48-h NOEC is 967 mg/L.
Executive summary:

Daphnia magna (Straus) were exposed in a static test system over a period of 48 hours to the test substance (TS) after conversion to its sodium salt. The nominal concentrations to which the test organisms were exposed were 80, 130, 220, 350, 600 and 1000 mg TS/L. There were 4 replicate test vessels per treatment, each containing 5 daphnids. Exposure concentrations were verified analytically at the start and end of the test in three of the treatments. The analytically determined initial concentrations of the test substance were between 86% and 97% of nominals. Residual concentrations at test-end were between 73% and 99% of nominals in all three treatments that were analysed and 97% to 99% of nominal at the maximum concentration which defined the endpoint of the study.

The EC50 (48 h) was >967 mg/L test substance (as sodium terephthalate), based on the mean measured exposure concentration at the highest treatment. Based on the absence of treatment-related immobilisation exceeding that observed in the "salinity control", the NOEC was 967 mg TS/L.

Description of key information

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
967 mg/L

Additional information

The study was conducted using terephthalic acid, the primary degradate of terephthaloyl dichloride, according to OECD 202 under GLP. Daphnia magna were exposed in a static test system over a period of 48 hours to the test substance after conversion to its sodium salt. The nominal concentrations to which the test organisms were exposed were 80, 130, 220, 350, 600 and 1000 mg/L. Exposure concentrations were verified analytically at the start and end of the test and were between 73% and 99% of the nominal values.

The static 48-h EC50 of the test substance (converted to its sodium salt prior to exposure) to Daphnia magna was >967 mg/L, based on the mean measured concentration at the maximum treatment applied. Based on the absence of treatment-related immobilisation exceeding that observed in the control, the NOEC was 967 mg/L.