Registration Dossier

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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study was conducted in accordance with EC Methods for Determination of Ecotoxicity, Annex to Directive 92/69/EEC (O.J. No L383A, 1992) Part C, Method 3 "Algal Inhibition Test" and the OECD guidelines for testing of chemicals No 201 "Alga, Growth Inhibition Test" (1984).

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes
Remarks:
Huntingdon Life Sciences, Wooley Road, Alconbury, Huntingdon, Cambridgeshire, PE284HS, England

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Glyoxylic acid 50; Glyoxylic acid 50 % aqueous solution
- Apperance: liquid
- Storage conditions: ambient
- Expiry date: 1 year
- Lot/batch No.: SCA200104-2
- Purity/Assay (aldehyde group titration): 50.5 %
- total acid: 7.01 Eq/kg
- Glyoxal: 0.3 %

Sampling and analysis

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).

Test solutions

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

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

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h

Test conditions

Test temperature:
23.5 - 24.2°
pH:
pH 7.6 at the beginning of the test and 6.9 at 72 h
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.

Results and discussion

Effect concentrationsopen allclose all
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 meausred 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).

Any other information on results incl. tables

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.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Executive summary:

To assess the effect of Glyoxylic Acid 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. 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).