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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
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 211 (Daphnia magna Reproduction Test)
Version / remarks:
1998
Deviations:
yes
Remarks:
Medium: ADaM; feed: S. dimorphus 8x10^5 cells/mL
GLP compliance:
not specified
Specific details on test material used for the study:
Sulfaguanidine (minimum purity: 99%) was purchased from Sigma–Aldrich.
Analytical monitoring:
yes
Details on sampling:
Sublethal effects on growth were determined as follows. Sixty haphazardly selected juveniles (<24 h old) were transferred in clean ADaM, fixed by progressively adding ethanol to a 70% concentration, and their length measured (from the top of the eye to the base of the tail spine) by means of a DMD108 digital microimaging device (Leica Microsystems, Milano, Italy). The same procedure was repeated on the surviving daphnids at the end of tests and the average daily growth rate calculated over the 21-days period.
Vehicle:
yes
Remarks:
ADaM medium
Details on test solutions:
Fresh stock solutions were prepared just before each experiment by diluting in the proper medium (ADaM) 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):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia magna, <24-h old
- Strain/clone: Straus
- Source:from a single clone, cultured and maintained in ADaM medium and obtained from the second to fifth brood

FEEDING DURING TEST:
- Food type: S. dimorphus
- Amount: 8 x 10^5 cells mL-1
- Frequency: every other day
Test type:
semi-static
Water media type:
other: ADaM medium
Total exposure duration:
21 d
Hardness:
193 mg CaCO3 L-1
Test temperature:
20 ± 1°C
pH:
8.0–8.3
Dissolved oxygen:
6.2–6.8 mg/L
Salinity:
not specified
Conductivity:
1016–1170 µS/cm
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. The nominal values were: control, 0.098, 0.195, 0.395, 0.781 and 1.562 mg/L.
Details on test conditions:
The ADaM medium was used for the controls and the dilution of test solutions. For each of the five concentration tested and for the control, 10 young daphnids were allocated individually in 50 mL of solution and incubated at the same conditions (light, temperature) used for culturing. During the tests, solutions were renewed every other day, the neonates removed and counted, and the feed (S. dimorphus, 8 x 10^5 cells/mL) supplied. Old (48-h) solutions from each concentration level were then pooled and monitored for pH, conductivity and dissolved oxygen using YSI 85 multiparameter instrument (YSI Incorporated, Yellow Springs, OH, USA).
Reference substance (positive control):
no
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.395 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
0.781 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
other: EC20
Effect conc.:
0.322 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
0.869 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
reproduction
Details on results:
Statistically significant effects were observed on reproduction at concentrations of sulfaguanidine (SGD) equal or above 0.781 mg L-1 and these were concentration dependent. At concentration of 1.562 mg/L significant effects on growth were also observed. No mortality was observed in the control, with an average of 97 neonates per survived female.

CONFIDENCE INTERVALS (95% confidence level):
EC20: 0.152 - 0.559 mg/L
EC50: 0.630 - 1.097 mg/L
Results with reference substance (positive control):
None

Nominal

concentration (mg L-1)

Survival

rate (%)

Average daily

growth (length, µm)

Total

number of neonates

Neonates per

female (mean ± sd)

1.562

20

125.2 a

17

8.50 a

0.781

90

147.7 ± 13.8

499

55.44 ± 31.70 a

0.395

80

145.5 ± 10.3

603

75.38 ± 36.79

0.195

100

154.3 ± 6.5

806

80.60 ± 30.63

0.098

100

152.9 ± 11.2

928

96.90 ± 16.86

Control

100

156.6 ± 10.6

974

97.40 ± 14.23

a Significantly different from the control (p< 0.05).

Validity criteria fulfilled:
yes
Conclusions:
The acute toxicity of the test item sulfaguanidine (SGD) to Daphnia magna was determined in a 21-day test, resulting in a 21-day 0.395 mg/L NOEC and 0.781 mg/L LOEC.
EC20 was calculated to be 0.3217 mg/L while EC50 was calculated to be 0.869 mg/L.
Executive summary:

The aquatic toxicity of sulfaguanidine (SGD) was evaluated on Daphnia magna reproduction in general accordance with OECD guideline 211 of 1998. Statistically significant effects were observed on reproduction at concentrations equal or above 0.781 mg/L and these were concentration dependent. At concentration of 1.562 mg/L significant effects on growth were also observed. Based on results from statistical analysis, 0.781 mg/L was taken as the LOEC and 0.395 mg/L was taken as the NOEC. The estimated EC50 of SGD for D. magna reproduction was 0.87 mg/L.

Description of key information

The aquatic toxicity of sulfaguanidine (SGD) was evaluated on Daphnia magna reproduction in general accordance with OECD guideline 211 of 1998. Statistically significant effects were observed on reproduction at concentrations equal or above 0.781 mg/L and these were concentration dependent. At concentration of 1.562 mg/L significant effects on growth were also observed. Based on results from statistical analysis, 0.781 mg/L was taken as the LOEC and 0.395 mg/L was taken as the NOEC. The estimated EC50 of SGD for D. magna reproduction was 0.87 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.395 mg/L

Additional information