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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
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 isophthalic acid, has a reliability of 1 (reliable without restriction).
Justification for type of information:
The test substance rapidly hydrolyses to isophthalic acid (IPA). Therefore, the study with IPA is being used to fulfil this data requirement. Additional documentation, provided within the IUCLID Assessment Reports section, supports the read-across approach.
Reason / purpose:
read-across: supporting information
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Remarks:
Conducted according to guideline in effect at the time of study conduct
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: Samples were collected from the test solutions containing 0, 62.5, 250 and 1000 mg/L of the test substance at 0 hours and 96 hours.
- Sampling method: High Performance Thin-Layer Chromatography
- Sample storage conditions before analysis: less than 20ºC
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION: The stock solution was prepared once before the beginning of the test. The amount of test material used was 1112.82 mg. The test material was dissolved in 1 L twice glass distilled water and stirred continuously during preparation and storage. The nominal concentration of the stock solution was 1112.82 mg/L. The stock solution was diluted with water to prepare the individual test concentrations.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Strain: Chodat, SAG 86.81
- Age of inoculum (at test initiation): 13 days

ACCLIMATION PERIOD: 4 days
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
22.5 - 22.7°C
pH:
8.0 - 10.2
Salinity:
freshwater
Nominal and measured concentrations:
Nominal Concentrations: 0, 62.5, 125.0, 250.0, 500, and 1000 mg/L
Measured Concentrations at 0 hours: 0, 67.7, 294, 1015 mg/L and 0, 68.5, 301, 1030 mg/L
Measured Concentrations at 96 hours: 0, 60.5, 212, 1028 mg/L and 0, 51.8, 240, 910 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 300 mL Erlenmeyer flasks containing 100 mL test solution covered with a cotton plug
- Initial cells density: 6.7x 10e6 cells per mL in pre-culture before inoculation; volume of pre-culture used: 0.150 mL
- Control end cells density: range of 280 to 380 x 10e4
- No. of organisms per vessel: 10e4
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

GROWTH MEDIUM
- Standard medium used: no
- Detailed composition if non-standard medium was used:
To obtain 1 L of concentrated algal medium, 500 mg NaHCO3 were dissolved in 100 mL of solution A, then 10 mL of solution B, C, D and E, respectively, were added; sterilised deionised water was used to fill up to 1 L. Before measuring the pH the medium was aerated for 30 min.

Stock solution A: NH4CI - 1500 mg/L
MgCl2 * 6 H2O - 1200 mg/L
CaCI,2 * 2 H20 - 1800 mg/L
MgSO4 * 7 H2O - 1500 mg/L
KH2P04 - 160 mg/L
Stock solution B: FeCI3 * 6 H2O - 80 mg/L
Na EDTA * 2 H2O - 100 mg/L
Stock solution C: MnCl2 4 H2O - 415 mg/L
H3B04 - 185 mg/L
Stock solution D: Na Mo04 * 2 H2O - 7 mg/L
ZnCI2 - 3 mg/L
CoCI2, * 6 H2O - 1.5 mg/L
Stock solution E: CuCl2 * 2 H2O - 0.01 mg/L

OTHER TEST CONDITIONS
- Sterile test conditions: yes, twice glass distilled water was used, flasks covered with a cotton plug
- Adjustment of pH: stock test solution adjusted to approximately 8.0
- Photoperiod: light/dark (24/0 h) OSRAM L36W/25 (universal white)
- Light intensity and quality: 120 ± 10 1µE x sec e-1 x m e-2 (400 - 700 nm)
- Salinity: freshwater

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: THOMA Counting Chamber with Microscope Metalux II,


TEST CONCENTRATIONS
- Range finding study data: The highest concentration tested causing no obvious inhibition of growth within the period of the range-finding-test relative to. the control: 100.0 mg/L.
In none of the concentration levels tested within the period of the range-finding test an effect relative to the control could be determined.
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
> 996 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks:
ErC50
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
> 996 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
cell number
Remarks:
EbC50
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
996 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
other: growth rate and cell number
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): After 72 hours till the end of the test in all replicates of the concentration levels 250, 500 and 1000 mg/L the cells were remarkably smaller than in the controls and the lower concentration levels, but the cell number was higher.
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no
Reported statistics and error estimates:
Oneway Analysis of Variance (ANOVA with Bonferroni multiple range test) was used to calculate whether there were significant differences between the growth of algae in the control group and the algae exposed to the various test substance concentrations.

It is thought that Isophthalic Acid was hydrolysed under test conditions. As a result it is believed that under test conditions and after pH adjustment to the required physiological value. Isophthalic Acid and Isophthalic Sodium Salt, respectively, were the test materials investigated in this study.

 

Effects on the Growth of Desmodesmus subspicatus following 96-hour Exposure

Nominal IPA conc., (mg/L)

Mean algal density
(cells
×104/mL)

Integrated biomass (AUGC)

Specific growth rate (0-96 h)

24 h

48 h

72 h

96 h

mean

% inhib.

mean

% inhib.

0 (control)

5.5

12.0

93.3

330.0

6535.2

-

0.056866

-

62.5

3.8

14.3

90.3

252.5

5547.6

15

0.058283

‑2

125

6.0

12.8

92.0

320.0

6415.2

2

0.055230

3

250

4.3

10.8

105.0

305.0

6458.4

1

0.059190

‑4

500

5.3

13.0

112.0

417.5

8053.2

‑23

0.060647

‑7

1000

6.3

13.8

102.8

347.5

7035.6

‑8

0.055697

2

 * Negative inhibition values signify enhanced growth, relative to the untreated control.

--

Measured Concentrations

 

Initial

96 hours

Nominal Conc. (mg/L)

Measured mg IPA/L

% of Nominal

Measured mg IPA/L

% of Nominal

62.5

67.2

108

60.5

97

62.5

68.5

110

51.8

83

250

294

118

212

85

250

301

121

240

96

1000

1015

102

1028

103

1000

1030

103

910

91

-

In the report, the endpoint is given as >969 mg/L, apparently the mean measured value at the highest concentration, but based on the 96-h data only, i.e. (1028 + 910)/2. This is incorrect; the mean should include the 0-h data as well,i.e. (1015 + 1030 + 1028 + 910)/4 = 996 mg/L.

-

Validity criteria fulfilled:
yes
Conclusions:
This study and the conclusions which are drawn from it fulfill the quality criteria (validity, reliability, repeatability).

The static 96-hour EbC50 and ErC50 of isophthalic acid (converted to its sodium salt prior to exposure) to Desmodesmus subspicatus were both >996 mg/L, based on the mean measured concentrations at the maximum treatment applied. The NOEC was 996 mg/L (mean measured).

Executive summary:

In accordance with OECD Guideline 201 under GLP, Desmodesmus subspicatus (formerly known as Scenedesmus subspicatus) was exposed in a static test system over a period of 96 hours to isophthalic acid (IPA) after conversion to its sodium salt(s). Each test vessel was initially inoculated with 10000 algal cells/mL.

 

The nominal concentrations to which the test organisms were exposed were 62.5, 125, 250, 500 and 1000 mg/L. The analytically determined actual concentrations of the test material at the beginning of the study were found to be within the range of 102% and 121% with an average of 110.3%. After 96-hours of exposure, analysed concentrations of the test material were relatively unchanged from measurements at 0 hours. They were found to be within the range of 83% and 103% of the nominal values with an average of 92.5%.

 

The EbC50 (96 h) and ErC50 (96 h) endpoints both exceeded 996 mg/L isophthalic acid (as sodium isophthalate), based on the mean measured exposure concentration at the highest treatment. Based on the absence of statistically significant effects on algal growth at all of the applied treatments, the NOEC was 996 mg/L (mean measured).

 

It is thought that Isophthalic Acid was hydrolysed under test conditions. As a result it is believed that under test conditions and after pH adjustment to the required physiological value. Isophthalic Acid and Isophthalic Sodium Salt, respectively, were the test materials investigated in this study.

Description of key information

The study was conducted using isophthalic acid, the primary degradate of isophthaloyl dichloride. In an OECD 201 Guideline study under GLP, Desmodesmus subspicatus (formerly known as Scenedesmus subspicatus) were exposed in a static test system over a period of 96 hours to the test substance after conversion to its sodium salt. The nominal exposure concentrations were 62.5, 125, 250, 500 and 1000 mg/L with each vessel initially inoculated with 10000 algal cells/mL. The analytically determined actual concentrations of the test material at the beginning of the study were found to be within the range of 102% and 121% with an average of 110.3%. After 96-hours of exposure, analysed concentrations of the test material were relatively unchanged from measurements at 0 hours. They were found to be within the range of 83% and 103% of the nominal values with an average of 92.5%. The EbC50 (96 h) and ErC50 (96 h) endpoints both exceeded 996 mg/L (converted to its sodium salt prior to exposure), based on the mean measured exposure concentration at the highest treatment. Based on the absence of statistically significant effects on algal growth at all of the applied treatments, the NOEC was 996 mg/L (mean measured).

Key value for chemical safety assessment

EC50 for freshwater algae:
996 mg/L
EC10 or NOEC for freshwater algae:
996 mg/L

Additional information