Sulfaguanidine

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Version / remarks:

2006

Deviations:

yes

Remarks:

culture media: M-Hoagland nutrient medium

GLP compliance:

not specified

Specific details on test material used for the study:

Sulfaguanidine was purchased from Sigma–Aldrich with minimum purity of 99%.

Details on sampling:

To check for the stability of the compounds, samples of 7 days old test solution (with/without test organisms) was collected. As the media did not interfere with the analysis, extraction and purification were unnecessary. Samples were simply filtered through Phenex- PTFE 0.45 lm (Phenomenex, Castelmaggiore, Italy) and then analyzed by means of HPLC, with UV detector set at 268 nm.

Vehicle:

no

Details on test solutions:

For the preparation of the M-Hoagland medium all the ingredients used were of analytical quality and purchased from Sigma–Aldrich (Milano, Italy). Fresh stock solutions of sulfaguanidine were prepared just before each experiment by diluting in the proper medium (M-Hoagland) the compound to be tested. Where necessary, the solubilization was achieved by bringing back the pH of the medium to the original value using 1 M NaOH. The pH was measured using a BASIC 20 pH meter (CRISON, Carpi, Italy). All working solutions used in tests were prepared by appropriately diluting the stock solution with medium to the requested concentration.

Test organisms (species):

Lemna gibba

Details on test organisms:

Axenic stock cultures of the duckweed L. gibba were grown in 0.5 L Erlenmeyer flasks containing 250 mL of M-Hoagland nutrient medium (Cowgill and Milazzo, 1989 (The culturing and testing of two species of duckweed. In: Cowgill, U.M., Williams, L.R. (Eds.), In aquatic toxicology and hazard assessment: 12th volume, ASTM STP 1027. American Society for Testing and materials, Philadelphia, pp. 379–391.)). They were maintained in a climatic chamber (25 ± 2°C) at a light intensity of 150 µE/s/m² provided by fluorescent tubes (OSRAM Lumilux L 58W/940). From a single isolated plant, randomly selected from the culturing flask, a stock culture was grown for 3 weeks before the beginning of the tests.

Test type:

static

Water media type:

other: M-Hoagland nutrient medium

Total exposure duration:

7 d

pH:

No significant pH variations were recorded during the 7-days incubation period.

Nominal and measured concentrations:

As the concentration of all the tested substances was maintained within ±20% of the initial concentration, test results were based on nominal values.

Details on test conditions:

The tests were performed in general accordance with the OECD Guideline 221 (OECD, 2006). Glass beakers (150 mL) were filled with 75 mL of either M-Hoagland nutrient medium alone (controls) or M-Hoagland and sulfaguanidine. Based on preliminary experiments, five concentrations of sulfaguanidine (SGD) (2.5, 5, 10, 20, 40 mg/L) were tested, in triplicate. The test started by introducing 12 L. gibba fronds into each beaker. The beakers were covered with a glass cap during the tests and incubated at the same conditions (light, temperature) used for culturing. Colonies were inspected with a dissecting microscope for changes in frond number at the beginning (day 0), on days 3, 5, and at the end of the exposure period (day 7). The increase in frond number was calculated by subtracting the initial number of fronds from the final number of fronds in each beaker. Concentration response curves were obtained by plotting the mean of increase in frond number against the logarithm of concentration. On day 7, after counting, the fronds were dried in an oven at 60 °C for 24 h and their dry weight for each exposition level, including control, was also determined.

Reference substance (positive control):

no

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

5 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

LOEC

Effect conc.:

10 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

EC20

Effect conc.:

6.058 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

30.304 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

CONFIDENCE INTERVALS (95% confidence level):
EC20: 3.375 - 8.024 mg/L
EC50: No data

Results with reference substance (positive control):

none

Validity criteria fulfilled:

not specified

Conclusions:

The toxicity of the test item sulfaguanidine to Lemna gibba was determined in a 7-day static test, resulting in a 7-day NOEC of 5 mg/ and LOEC of 10 mg/L.
EC20 was calculated to be 6.058 mg/L while EC50 was calculated to be 30.304 mg/L.

Executive summary:

The aquatic toxicity of sulfaguanidine (SGD) was evaluated on the Lemna gibba in general accordance to the OECD guideline 221 of 2006 (Lemna sp. growth inhibition test). The toxicity of the test item sulfaguanidine to Lemna gibba was determined in a 7-day static test, resulting in a 7-day NOEC of 5 mg/ and LOEC of 10 mg/L.

EC20 was calculated to be 6.058 mg/L while EC50 was calculated to be 30.304 mg/L.

Description of key information

The aquatic toxicity of sulfaguanidine (SGD) was evaluated on the Lemna gibba in general accordance to the OECD guideline 221 of 2006 (Lemna sp. growth inhibition test). The toxicity of sulfaguanidine to Lemna gibba in a 7-day static test resulted in a 7-day NOEC of 5 mg/ and LOEC of 10 mg/L.

EC20 was calculated to be 6.058 mg/L while EC50 was calculated to be 30.304 mg/L.

Key value for chemical safety assessment

EC50 for freshwater plants:

30.304 mg/L

EC10 or NOEC for freshwater plants:

5 mg/L