Hydrogen peroxide-urea

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1978

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Principles of method if other than guideline:

Cell multiplication inhibition test

GLP compliance:

no

Analytical monitoring:

not specified

Vehicle:

no

Details on test solutions:

The test substance was dissolved in double distilled water and neutralised to pH 7.0.

Test organisms (species):

Scenedesmus quadricauda

Details on test organisms:

Scenedesmus quadricauda; green algae. The algae were maintained in 100 mL Erlenmeyer flasks with metal caps. They were kept on a white surface under continuous illumination under two parallel fluorescent tubes (Osram L 40/30) at 27 °C and 50 % relative humidity. The algae were kept in 20 mL culture medium.
- Culture medium:
NaNO3, K2HPO4 (water-free, pure), MgSO4.7H2O, CaCl2.2H2O, Na2SiO3, Na2CO3 (water-free), citric acid C6H8O7.H2O, Iron(III)-citrat C6H5FeO7.5H2O and 1,2-cyclohexanediaminetetraacetic acid. All dissolved in 1 L bidest water.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

192 h

Test temperature:

27 °C

pH:

7

Nominal and measured concentrations:

1 part test item in 2^0 to 2^14 part mixture with bidest water. A dilution series was performed to prepare the next lower test concentration.

Details on test conditions:

The tests were carried out in 300 mL Erlenmeyer flasks with 80 mL test solution, maintained under the same conditions as the stock cultures. The algae were exposed to the test substance for 192 hours to determine the toxicity threshold. The inhibition of cell multiplication was assessed at the end of the test period by photometric measurements. The test flasks were shaken once every day through the exposure period.

Reference substance (positive control):

no

Key result

Duration:

192 h

Dose descriptor:

NOEC

Remarks:

toxicity threshold

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

biomass

Validity criteria fulfilled:

not applicable

Conclusions:

The 192-hour NOEC (toxicity threshold) of the green algae Scenedesmus quadricauda to urea is > 10000 mg/L. Therefore, urea is not considered toxic to algae.

Executive summary:

An experiment with several test urea solutions was performed in order to determine the toxicity threshold of urea to green algae Scenedesmus quadricauda. The algae were exposed to the test solution for 192 hours under constant illumination at 27 °C. At the end of the experiment the cell multiplication inhibition effect of urea was measured photometrically. The 192-h NOEC (toxicity threshold) was determined to be >10000 mg/L.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1978

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Principles of method if other than guideline:

Cell multiplication inhibition test

GLP compliance:

no

Specific details on test material used for the study:

Urea
CAS 57-13-6

Analytical monitoring:

not specified

Vehicle:

no

Details on test solutions:

The test substance was dissolved in double distilled water and neutralised to pH 7.0.

Test organisms (species):

Microcystis aeruginosa

Details on test organisms:

Blue-green algae; Microcystis aeruginosa. The algae were maintained in 100 mL Erlenmeyer flasks with metal caps. They were kept on a white surface under continuous illumination under two parallel fluorescent tubes (Osram L 40/30) at 27 °C and 50 % relative humidity. The algae were kept in 20 mL culture medium.
- Culture medium:
NaNO3, K2HPO4 (water-free, pure), MgSO4.7H2O, CaCl2.2H2O, Na2SiO3, Na2CO3 (water-free), citric acid C6H8O7.H2O, Iron(III)-citrat C6H5FeO7.5H2O and 1,2-cyclohexanediaminetetraacetic acid. All dissolved in 1 L bidest water.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

192 h

Test temperature:

27 °C

pH:

7

Nominal and measured concentrations:

1 part test item in 2^0 to 2^14 part mixture with bidest water. A dilution series was performed to prepare the next lower test concentration.

Details on test conditions:

The tests were carried out in 300 mL Erlenmeyer flasks with 80 mL test solution, maintained under the same conditions as the stock cultures. The algae were exposed to the test substance for 192 hours to determine the toxicity threshold. The inhibition of cell multiplication was assessed at the end of the test period by photometric measurements. The test flasks were shaken once every day through the exposure period.

Reference substance (positive control):

no

Key result

Duration:

192 h

Dose descriptor:

NOEC

Remarks:

toxicity threshold

Effect conc.:

47 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

biomass

Validity criteria fulfilled:

not applicable

Conclusions:

The 192-hour NOEC (toxicity threshold) of the blue-green algae Microcystis aeruginosa to urea is 47 mg/L. Therefore, urea is not considered toxic to algae.

Executive summary:

An experiment with several test urea solutions was performed in order to determine the toxicity threshold of urea to blue-green algae Microcystis aeruginosa. The algae were exposed to the test solution for 192 hours under constant illumination at 27 °C. At the end of the experiment the cell multiplication inhibition effect of urea was measured photometrically. The 192-h NOEC (toxicity threshold) was determined to be 47 mg/L.

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1980

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

As a method the cell multiplication inhibition test following Bringmann was applied to the model organisms.

GLP compliance:

no

Vehicle:

yes

Remarks:

double distilled water

Details on test solutions:

Test solutions were prepared in double distilled water in 300 mL Erlenmeyer flasks, stoppered with cotton-lined plastic caps. The first solution in each dilution series contained 80 mL solution. Subsequent dilutions were prepared from this one by consistently mixing 40 mL of the test solution and 40 mL double distilled water.

Test organisms (species):

Scenedesmus quadricauda

Details on test organisms:

Stock cultures were stored in 20 mL nutrient solution in 100 mL Erlenmeyer flasks stoppered with metal caps, on a white surface protected from daylight and exposed to constant lighting by luminescent worm white tubes at 60 cm distance from each other, at 27 °C and a relative humidity 50 %.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Test temperature:

27 °C

Nominal and measured concentrations:

Dilutions containing 1 part v/v of the test substance in 2^0 to 2^14 parts v/v of mixture, up to 10000 mg/L

Details on test conditions:

Test solutions were incubated with the algal cultures in 100 mL Erlenmeyer flasks stoppered with metal caps, on a white surface protected from daylight and exposed to constant lighting by luminescent worm white tubes at 60 cm distance from each other, at 27 °C and a relative humidity 50 %. At the end of the study period the extinction of the monochromatic radiation was determined.

Reference substance (positive control):

no

Key result

Duration:

7 d

Dose descriptor:

NOEC

Remarks:

toxicity threshold

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

The 7 day toxicity threshold / NOEC of urea to Scenedesmus quadricauda was > 10000 mg/L.

Validity criteria fulfilled:

not applicable

Conclusions:

The toxicity threshold (NOEC) was determined after 7 d to be >10000 mg/L.

Executive summary:

A study testing the toxicity of an array of pollutants on different bacteria and algae was performed using Bringmann method of cell multiplication inhibition test. Scenedesmus quadricauda (green algae) were exposed for 7 days to the test item - urea at concentration levels up to 10000 mg/L. No toxic effects on the bacteria were observed. The toxicity threshold (NOEC) was determined after 7 d to be >10000 mg/L.

Reference 4

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Please refer to section 13 for "Read-Across justification".

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

7 d

Dose descriptor:

NOEC

Remarks:

threshold toxicity

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: species: Scenedesmus quadricauda

Key result

Duration:

192 h

Dose descriptor:

NOEC

Remarks:

threshold toxicity

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

biomass

Remarks on result:

other: species: Scenedesmus quadricauda

Key result

Duration:

192 h

Dose descriptor:

NOEC

Remarks:

threshold toxicity

Effect conc.:

47 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

biomass

Remarks on result:

other: species: Microcystis aeruginosa

Reference 5

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Please refer to section 13 for "Read-Across justification".

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

NOEC

Remarks:

threshold toxicity

Effect conc.:

>= 6.8 - <= 10.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: optical density

Reference 6

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Principles of method if other than guideline:

Algae species were exposed to H2O2 and after an exposure period the chlorophyll was extracted and determined photometrically. The optical density at 665 nm was used to determined the toxicity effects of the test item.

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Ankistrodesmus sp.

Details on test organisms:

Obtained from Carolina Biological Supply. Cultured in Carolina Alga-Gro® medium prepared with Carolina Spring Water® in an incubator under fluorescent lighting at 25 °C and with a 12 hour photoperiod..

Test type:

static

Water media type:

freshwater

Test temperature:

25 °C

Nominal and measured concentrations:

Nominal concentrations: 0 to 34 mg/L (0 to 1 mM)
No measured concentrations.

Details on test conditions:

A 100 mL aliquot of an unialgal suspension was placed in each of several 250 mL Erlenmeyer flasks and was treated with H2O2 at concentrations varied from 0 to 1 mM (0 to 34 mg/L). Each treatment was tested in triplicates. Flasks were placed in a growth chamber under combined incandescent and fluorescent lighting with a 14-h photoperiod and a 25/20 °C day/night temperature regime. Flasks were illuminated at a quantum flux density of app. 500 µE.m-2.s-1.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

NOEC

Remarks:

threshold toxicity

Effect conc.:

>= 6.8 - <= 10.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: optical density

Details on results:

Ankistrodesmus sp. showed to be very sensitive to H2O2 when evaluated under laboratory conditions. Using regression analysis the treshold toxicity / NOEC was determined be between 6.8 and 10.2 mg/L (0.2 and 0.3 mM). The optical densities of chlorophyll extracts were reduced to about 5 % of the controls after only 24 h by treatment of 0.5 mM (17 mg/L) H2O2, but no further reduction occurred by treatment with higher concentrations.

Validity criteria fulfilled:

not applicable

Conclusions:

The toxicity threshold / NOEC of H2O2 to Ankistrodesmus sp. was determinedto be in the range of 6.8 - 10.2 mg/L.

Executive summary:

An array of experiments with hydrogen peroxide and different aquatic species were performed. Different fish, invertebrate and algae species were tested to determine the threshold toxicity / NOEC of H2O2. For algae Ankistrodesmus sp. were exposed to H2O2 concentrations between 0 and 34 mg/L. After the exposure period aliquots were collected and the chlorophyll was determined photometrically to obtain the optical desnsity. Based on the difference in the optical density between the treated samples and controls the toxicity of H2O2 was determined. The threshold toxicity / NOEC of H2O2 was determined to be in the range of 6.8 - 10.2 mg/L. These experiments showed that the tested algae species were very sensitive towards H2O2.

Description of key information

The toxicity threshold (NOEC) of H2O2, the degradation product of the test item, was determined to be between 6.8 and 10.2 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

6.8 mg/L

Additional information

The toxicity to aquatic algae of the test item was addressed with a read-across approach to its degradation products - urea and hydrogen peroxide. The test item is not stable and decomposes rapidly to urea and H2O2, therefore, the read-across to both substances is considered acceptable.

Publications reporting the toxicity to aquatic algae of urea and hydrogen peroxide were used in a read-across weight of evidence approach.

Urea

An experiment with several test urea solutions was performed in order to determine the toxicity threshold of urea to green algae Scenedesmus quadricauda. The algae were exposed to the test solution for 192 hours under constant illumination at 27 °C. At the end of the experiment the cell multiplication inhibition effect of urea was measured photometrically. The 192-h NOEC (toxicity threshold) was determined to be >10000 mg/L.

In the same experiment, the toxicity threshold of urea to blue-green algae Microcystis aeruginosa was also determined. The algae were exposed to the test solution for 192 hours under constant illumination at 27 °C. At the end of the experiment the cell multiplication inhibition effect of urea was measured photometrically. The 192-h NOEC (toxicity threshold) was determined to be 47 mg/L.

A study testing the toxicity of an array of pollutants on different bacteria and algae was performed using Bringmann method of cell multiplication inhibition test. Scenedesmus quadricauda (green algae) were exposed for 7 days to the test item - urea at concentration levels up to 10000 mg/L. No toxic effects on the bacteria were observed. The toxicity threshold (NOEC) was determined after 7 d to be >10000 mg/L.

Hydrogen peroxide (H2O2)

An array of experiments with hydrogen peroxide and different aquatic species were performed. Different fish, invertebrate and algae species were tested to determine the threshold toxicity / NOEC of H2O2. For algae Ankistrodesmus sp. were exposed to H2O2 concentrations between 0 and 34 mg/L. After the exposure period aliquots were collected and the chlorophyll was determined photometrically to obtain the optical desnsity. Based on the difference in the optical density between the treated samples and controls the toxicity of H2O2 was determined. The threshold toxicity / NOEC of H2O2 was determined to be in the range of 6.8 - 10.2 mg/L. These experiments showed that the tested algae species were very sensitive towards H2O2.

Based on the results obtained for urea for the different tested species and endpoints, the relevant endpoint - growth rate, is taken into account, therefore, urea is considered to not ihibit the growth of algae. Thereafter, the toxicity to algae of hydrogen peroxide-urea (1:1) is based on the toxicity of H2O2. The NOEC (threshold toxicity) for H2O2 was determined to be in the range of 6.8 to 10.2 mg/L. In conclusion, the test item hydrogen peroxide-urea (1:1) is expected to have a NOEC in the same range.