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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
29.01.2018 - 26.05.2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Remarks:
For the determination of the growth curve not the cell amount was used, but the fluorescence. In a pre-test the correlation of cell amount and fluorescence was confirmed.
GLP compliance:
no
Remarks:
accredited by DAkkS (Deutsche Akkreditierungsstelle)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Sampling and analysis

Analytical monitoring:
no
Details on sampling:
A stock solution was prepared with the test item. Different dilutions with ultrapure water were prepared thereof.
50 mL-test preparations contained 40 ml of the related dilution as well as 5 ml algal medium and 5 ml algal culture (consisting of algal medium and Desmodesmus subspicatus CHODAT). The tests were performed in duplicate over a 72 h period of time.

Test solutions

Vehicle:
yes
Remarks:
water
Details on test solutions:
6 test solutions with 100 mg/l 2,4-dihydroxybenzoic acid,
6 test control solutions

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h

Test conditions

Test temperature:
20 – 22 °C
pH:
in the beginning of the test: 8,3 ± 0,3
at the end of the test: 8,9 ± 0,1.
Nominal and measured concentrations:
100 mg/l
Details on test conditions:
In pre-tests it was found out that a direct correlation of growth rate and measurable fluorescence exists. Hence, the measurement of the fluorescence of all samples was performed using a fluorescence measuring device (Kontron) after 0, 24, 48 and 72 h.
Reference substance (positive control):
yes
Remarks:
potassium dichromate

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: fluorescence
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: fluorescence
Results with reference substance (positive control):
The sensitivity of Desmodesmus subspicatus CHODAT was tested by using potassium dichromate (0,5 mg/l) and determined to be 65% inhibition in average.
Reported statistics and error estimates:
see Table 3 and t-test

Any other information on results incl. tables

Table 2: Fluorescence of all test samples with 2,4-dihydroxybenzoic acid and control (=0 mg/l) in 72 h

test duration

sample

fluorescence

control (0 mg/l)

2,4-Dihydroxybenzoic acid (100 mg/l)

0 h

I

1,7

1,6

II

1,7

1,6

III

1,7

1,6

IV

1,7

1,6

V

1,7

1,6

VI

1,8

1,6

mean

1,7

1,6

24 h

I

2,7

2,9

II

2,5

3,0

III

2,5

2,8

IV

2,6

2,8

V

2,7

3,0

VI

2,7

3,1

mean

2,6

2,9

48 h

I

3,8

4,3

II

3,5

4,2

III

4,3

3,9

IV

4,0

4,1

V

4,1

3,9

VI

3,8

4,1

mean

3,9

4,1

72 h

I

6,5

5,6

II

5,9

5,6

III

6,4

6,2

IV

5,9

5,5

V

6,9

6,3

VI

6,5

6,3

mean

6,4

5,9

Table 3: growth rate in control samples and test samples with 2,4-dihydroxybenzoic acid

 

control

2,4-Dihydroxybenzoic acid

growth rate

I

0,0646

0,0558

II

0,0567

0,0550

III

0,0663

0,0621

IV

0,0583

0,0542

V

0,0708

0,0625

VI

0,0633

0,0629

mean

XK= 0,0633

XD= 0,0588

variance

SK2= 2,26*105

SD2= 1,43*105

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The toxicity of 2,4-dihydroxybenzoic acid to algae was investigated in a limit test acc. to OECD Guideline 201 (Alga, Growth Inhibition Test). The 72 h EC50 and NOEC were determined to be >100 mg/L. According to GHS-criteria, 2,4-dihydroxybenzoic acid is not to be classified as aquatic toxic substance.
Executive summary:

The toxicity of 2,4-dihydroxybenzoic acid on Desmodesmus subspicatus was investigated in a limit test acc. to OECD Guideline 201 (Alga, Growth Inhibition Test).

For the hazard and risk assessment a no-oberved-effect-concentration of >100 mg/l (72 h) should be used.