Glyoxylic acid

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes

Remarks:

Huntingdon Life Sciences, Wooley Road, Alconbury, Huntingdon, Cambridgeshire, PE284HS, England

Analytical monitoring:

yes

Details on sampling:

The test concentrations were not verfied as part of this study. Samples taken during the definitive test were returned to the Sponsor for analysis (see Clariant study 1114).

Vehicle:

no

Details on test solutions:

The test substance (200 mg) was added directly to sterile culture medium (2 L). This aqueous solution was either used directly at the highest test concentration or was serially diluted with sterile culture medium to provide the media at the lower test concentrations.
In addition a portion (800 mL) of the medium prepared at 100 mg/L was adjusted using sodium hydroxide (0.1 M) from pH 4.6 to 7.6 before use.

Test organisms (species):

Scenedesmus capricornutum

Details on test organisms:

TEST ORGANISM
- Common name: Selenastrum capricornutum
- Strain: No CCAP 278/4
- Source (laboratory, culture collection): Axenic, uni-cellular, liquid slope cultures of algae were obtained frmom the Culture Collection of Algae and Protozoa, Institute of Freshwater Ecology, Cumbria, UK

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

23.5 - 24.2°

pH:

pH 7.6 at the beginning of the test and 6.9 at 72 h
As a marked pH drop (4.36 -4.71) of the algal medium (pH 7.52 -9.96) was observed after addition of the highest test substance concentration (100 mg/L), the test at 100 mg/L was also done with pH-adjustment of the test medium with NaOH (pH value remained between 7.64 and 6.90).

Nominal and measured concentrations:

nominal concentrations: 0, 4.27, 9.39, 20.7, 45.5 or 100 mg/L.

Details on test conditions:

The effect of Glyoxylic acid 50 on the growth of the unicellular green alga Selenastrum capricornutum was assessed under non-axenic conditions.


Triplicate algal cultures, with an initial cell density of 1 x 10E4/mL, were exposed to Glyoxylic acid 50 dispersed in algal nutrient medium at nominal concentration of 0, 4.27, 9.39, 20.7, 45.5 and 100 mg/L.
At 100 mg/L, the culture medium became acidic (pH 4.4 at the beginning of the test and 4.7 at 72 h) after the addition of the test substance, so algae were exposed to test medium with and without pH adjustment at 100 mg/L (pH 7.6 at the beginning of the test and 6.9 at 72 h); at 4.27 to 45.5 mg/L, no adjustment of pH was conducted.
The cultures were incubated in an orbital incubator under continuous illumination at temperatures ranging from 23.5 to 24.2°C for 72 hours.

pH of control cultures were 7.52 at the beginning of the test and 9.96 at 72 hours.

Cell numbers were counted daily to monitor growth. The test result are expressed in terms of the area under the growth curve and rowth rate using nominal exposure concentrations.

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

65.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks:

without pH adjustment

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

67.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

without pH adjustment

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

65 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks:

without pH adjustment

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

69.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

without pH adjustment

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

with pH adjustment

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

with pH adjustment

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

37.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Growth curve

Details on results:

The results of the chemical analysis performed by the Sponsor confirmed that the intended exposure cocentrations were achieved, ranging between 83 to 96 % of their nominal values at the start of the algal test. After 72 hours, the concentrations measured in samples of expired media containing algal cells had decreased, ranging between 58 and 91 % of their nominal values (between 63 and 97 % of their starting values), with the greatest losses occurring where algal growth was not inhibited. Based on a geometirc mean, the overall measured concentrations were 3.05, 7.57, 17.7, 37.1 and 92.4 mg/L for media in which the pH had not been adjusted.

Since the concentrations measured at some of the exposure levels decreased by more than 20 % during the test, the results from the algal test have been re-calculated using the geometric means of the concentrations measured at the start and end of the test.

The following values were derived from the data:
Area under the growth curve
EbC50 (0-72 h) Nominal concentrations:
No pH adjustment: 67.5 (45.5 - 100) mg/L , pH adjustment at 100 mg/L: > 100 mg/L (no inhibition)

EbC50 (0-72 h) Measured concentrations:
No pH adjustment: 65.4 (42.4 - 76.9) mg/L

Average specific growth rate:
ErC50 (0-72 h) Nominal concentrations:
No pH adjustment: 69.5 (45.5 - 100) mg/L , pH adjustment at 100 mg/L: > 100 mg/L (no inhibition)

ErC50 (0-72 h) Measured concentrations
No pH adjustment: 65.0 (47.4 - 88.0) mg/L

No Observed effect concentration (NOEC)
Nominal concentrations, no pH adjustment: 45.5 mg/L
Measured concentrations, no pH adjustment: 37.1 mg/L
pH adjustment at 100 mg/L: >= 100 mg/L.

Results with reference substance (positive control):

The results of the most recent laboratory reference tets using potassium dichromate indicated that its 72-hour EbC50 to Selenastrum capricornutum was 0.86 mg/L, this was in the range typically obtained in this laboratory (0.3 to 1 mg/L).

When the pH of the algal medium was adjusted after the addition of the test substance at 100 mg/l, algal growth was not inhibited.

Validity criteria fulfilled:

yes

Executive summary:

To assess the effect of Glyoxylic Acid a toxicity study on the growth of Selenastrum capricornutum was conducted in accordance with OECD TG 201 (1984). Growth inhibition was observed over 72 hours of exposure employing nominal concentrations of 0, 4.27, 9.39, 20.7, 45.5 or 100 mg/L of Glyoxylic Acid. As a marked pH drop (4.36 -4.71) of the algal medium (pH 7.52 -9.96) was observed after addition of the highest test substance concentration (100 mg/L), the test at 100 mg/L was also done with pH-adjustment of the test medium with NaOH (pH value remained between 7.64 and 6.90). Since the concentrations measured at some of the exposure levels decreased by more than 20 % during the test without pH-adjustment, results were re-calculated using the geometric means of the concentrations measured at the start and end of the test.Without pH-adjustment of the medium the EbC50 and ErC50 were 67.5 mg/L nominal (65.4 mg/L mean measured) and 69.5 mg/L nominal (65.0 mg/L mean measured), respectively. With pH-adjustment of the medium both the EbC50 and ErC50 were >100 mg/L nominal. The NOEC for both area under the growth curve and growth rate was calculated to be 37.1 mg/L nominal (45.5 mg/L mean measured).

Description of key information

To assess the effect of Glyoxylic Acid 50% a toxicity study on the growth ofSelenastrum capricornutumwas conducted in accordance with OECD TG 201 (1984). Growth inhibition was observed over 72 hours of exposure employing nominal concentrations of 0, 4.27, 9.39, 20.7, 45.5 or 100 mg/L of Glyoxylic Acid 50%. As a marked pH drop (4.36 -4.71) of the algal medium (pH 7.52 -9.96) was observed after addition of the highest test substance concentration (100 mg/L), the test at 100 mg/L was also done with pH-adjustment of the test medium with NaOH (pH value remained between 7.64 and 6.90). Since the concentrations measured at some of the exposure levels decreased by more than 20 % during the test without pH-adjustment, results were re-calculated using the geometric means of the concentrations measured at the start and end of the test.Without pH-adjustment of the medium the EbC50 and ErC50 were 67.5 mg/L nominal (65.4 mg/L mean measured) and 69.5 mg/L nominal (65.0 mg/L mean measured), respectively. With pH-adjustment of the medium both the EbC50 and ErC50 were >100 mg/L nominal. The NOEC for both area under the growth curve and growth rate was calculated to be 37.1 mg/L nominal (45.5 mg/L mean measured).