5-potassium hydrogen L-glutamate

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Report date:

2022

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

23 March 2006

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

1

Reference substance name:

5-potassium hydrogen L-glutamate

EC Number:

243-094-0

EC Name:

5-potassium hydrogen L-glutamate

Cas Number:

19473-49-5

Molecular formula:

C5H9NO4.K

IUPAC Name:

potassium 5-oxido-5-oxo-L-norvaline

Test material form:

solid

Specific details on test material used for the study:

3.1. TEST ITEM
Information supplied by the Sponsor:
Name: L-Glutamic acid potassium salt monohydrate*
Lot number1: VG29748063
CAS number: 6382-01-0
Description: White powder
Expiry date: 01 December 2022
Purity: 100 %
Storage conditions: Room temperature (15-25 ºC, below 70% relative humidity)
Safety precautions: Routine safety precautions (lab coat, gloves, safety glasses, face
mask) for unknown materials will be applied to assure personnel
health and safety.
The certificate of analysis is presented in Appendix 4.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

For determination of the test item concentration, samples were taken from the test solutions and the controls at the start, at 24, 48 hours
and at the end of the experiment. Samples were transferred immediately after collection for
concentration measurement to the Test Facility.
The concentration analyses were conducted under the control of the Analyst, based on the analytical
method validation and in compliance with the relevant SOPs of the Test Facility. The results are
included in the Study Report as Appendix 3.

Test solutions

Vehicle:

no

Details on test solutions:

The stock solution was prepared by dissolving the appropriate amount of test material in Z8 medium, then divided into 7 parts to get the test solutions with six parallel and an additional flask to measure the temperature during the study.

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

Raphidocelis subcapitata

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test conditions

Test temperature:

22 +-1 °C.

pH:

The pH was measured in the control(s) and in the used test concentration in each test vessel at the start and at the end of the experiment. The pH varied by not more than 1.5 units of the tests.

Details on test conditions:

The vessels were held for the duration of the study in a climate chamber, the test temperature was
22  1 °C. The water temperature was determined at least daily in one extra vessel and continuously
with a min/max thermometer in the climate chamber.
The pH was measured in the control(s) and in the used test concentration in each test vessel at the start
and at the end of the experiment. The pH varied by not more than 1.5 units of the tests.
Illumination: fluorescent lamps were used with continuous lighting with light intensity of
~7000 lux at the liquid surface.

Reference substance (positive control):

yes

Remarks:

For the evaluation of the quality of the algal cultures and the experimental conditions, potassium dichromate is tested at least twice a year to demonstrate satisfactory test conditions.

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC100

Effect conc.:

> 29.73 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

ca. 29.73 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 29.73 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

In the 72-h algal growth inhibition test on Raphidocelis subcapitata, the 72-h EC50
value based on growth rate was determined to be higher than 29.73 mg/L and
based on yield was calculated to be higher than 29.73 mg/L. The NOEC related to
growth rates was determined to be 29.73 mg/L and related to yield it was
determined to be 29.73 mg/L.
The results are based on the geometric mean of the measured concentrations.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

In the 72-h algal growth inhibition test on Raphidocelis subcapitata, the 72-h EC50
value based on growth rate was determined to be higher than 29.73 mg/L and
based on yield was calculated to be higher than 29.73 mg/L. The NOEC related to
growth rates was determined to be 29.73 mg/L and related to yield it was
determined to be 29.73 mg/L.
The results are based on the geometric mean of the measured concentrations.

Executive summary:

The purpose of this study was to determine the effect of the test item on the growth of a unicellular
green algal species Raphidocelis subcapitata. Exponentially growing cultures of Raphidocelis
subcapitata were exposed to the test item over several generations under defined conditions.
As no inhibition was seen in the highest concentration in the preliminary study, a limit test with 100
mg/L dose level was carried out. The test design included six replicates of the test concentration and
six replicates for the untreated control.
Based on the analytical measurements at the beginning, at 24, 48 hours and at the end of the
experimental phase, the concentration of the item decreased during the study. Therefore a geometric
mean of the data was calculated, referring to the final amount as 1 mg/L instead of 0. The geometric
mean concentration of the test item in the test solution was 29.73 mg/L.
All biological results are based on this geometric mean of the measured concentrations.
The initial biomass in the test cultures was set to 104 cells/mL.
Glass flasks with total capacity of ~250 mL were used as test vessels. The volume of the test liquid in
the vessels was 100 mL. The test vessels were covered with air-permeable stoppers.

Conclusion: In the 72-h algal growth inhibition test on Raphidocelis subcapitata, the 72-h EC50
value based on growth rate was determined to be higher than 29.73 mg/L and
based on yield was calculated to be higher than 29.73 mg/L. The NOEC related to
growth rates was determined to be 29.73 mg/L and related to yield it was
determined to be 29.73 mg/L.
The results are based on the geometric mean of the measured concentrations.