2,4-dihydroxybenzoic acid

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

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

Test material information

Constituent 1

Reference substance name:

2,4-dihydroxybenzoic acid

EC Number:

201-946-9

EC Name:

2,4-dihydroxybenzoic acid

Cas Number:

89-86-1

Molecular formula:

C7H6O4

IUPAC Name:

2,4-dihydroxybenzoic acid

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 concentrations

Effect concentrations 1

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

Effect concentrations 2

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		SK^2= 2,26*10^5	SD^2= 1,43*10^5

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.