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Ecotoxicological information

Toxicity to aquatic plants other than algae

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Reference
Endpoint:
toxicity to aquatic plants other than algae
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Read-across from the alternative salt form of the registered substance is justified as per the document attached in section 13.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Deviations:
no
Guideline:
other: Commission Regulation (EU) 2016/266
Deviations:
no
Test organisms (species):
Lemna gibba
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Nominal and measured concentrations:
Nominal: 0 (control), 10, 22, 46, 100, 220 mg/L
Initial measured: 0 (control), 2.517, 6.892, 16.225, 36.043, 91.817 mg/L
Key result
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
EC20
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
>= 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
7 d
Dose descriptor:
EC20
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
>= 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
> 91.817 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
Signs of phytotoxicity were observed in the treatment groups 10 mg/L and higher on day 5 and in treatment groups 22 mg/L and higher on day 7.
The toxicity results of the main study are consistent with the results from preliminary tests.
Results with reference substance (positive control):
The EC50(7d) of the reference substance 3,5 Dichlorphenol was 7.10 mg/L.

Table 1: Effect concentrations based on nominal concentration (mg/L) after

7 days for the response variable average specific growth rate

Effect concentration [mg/L] Average specific growth rate
based on frond number
[mg/L]
Average specific growth rate
based on dry weight
[mg/L]
ErC10
(95% CL)
>220
-
>220
-
ErC20
(95% CL)
>220
-
>220
-
ErC50
(95% CL)
>220
-
>220
-
NOErC ≥220 ≥220
LOErC >220 >220

– insufficient data for calculation

Table 2: Effect concentrations based on initial measured concentration (mg/L) after

7 days for the response variable average specific growth rate

Effect concentration [mg/L] Average specific growth rate
based on frond number
[mg/L]
Average specific growth rate
based on dry weight
[mg/L]
ErC10
(95% CL)
>91.817
-
>91.817
-
ErC20
(95% CL)
>91.817
-
>91.817
-
ErC50
(95% CL)
>91.817
-
>91.817
-
NOErC ≥91.817 ≥91.817
LOErC >91.817 >91.817

– insufficient data for calculation

Table 3: Effect concentrations based on nominal concentration (mg/L) after 7 days for the response variable yield

Effect concentration [mg/L] Yield based on frond number
[mg/L]
Yield based on dry weight
[mg/L]
ErC10
(95% CL)
>220
-
>220
-
ErC20
(95% CL)
>220
-
>220
-
ErC50
(95% CL)
>220
-
>220
-
NOErC ≥220 ≥220
LOErC >220 >220

Table 4: Effect concentrations based on initial measured concentration

(mg/L) after 7 days for the response variable yield

Effect concentration [mg/L] Yield based on frond number
[mg/L]
Yield based on dry weight
[mg/L]
EyC10
(95% CL)
>91.817
-
>91.817
-
EyC20
(95% CL)
>91.817
-
>91.817
-
EyC50
(95% CL)
>91.817
-
>91.817
-
NOEyC ≥91.817 ≥91.817
LOEyC >91.817 >91.817

– insufficient data for calculation

Table 5: Signs of phytotoxicity were observed in the treatment groups 10 mg/L

and higher on day 5 and in treatment groups 22 mg/L and higher on day 7

Nominal concentration [mg/L] Vessel No. Morphological changes, signs of phytotoxicity
Day 2 Day 5 Day 7
o (control) 1-6 0 0 0
10 7-9 0 8 0
22 10-12 0 8 9(++)
46 13-15 0 8 6(+)
100 16-18 0 8 3, 6(++)
220 19-21 0 8 6

Explanation of abbreviations:

0: No findings

1: frond or root yellowing (chlorosis)

2: fronds humped or swollen (gibbosity)

3: small fronds

4: shortened roots

5: no roots

6: plants fragmented (fronds and/or roots)

7: dead white plant tissue (necrosis)

8: plants colored by test substance (roots are yellowish)

9: plants increased (fronds and/or roots)

(+): slight effects

(++): medium effects

(+++): strong effects

Conclusions:
The growth inhibition test on Lemna Gibba on the source substance showed signs of phytotoxicity in the treatment groups >10 mg/L on day 5 and in treatment groups >22 mg/L on day 7. The EC10 for the registered substance is 91.817 mg/L based on initial measured concentration.

Description of key information

In an OECD 221 Lemna growth inhibition study on the read-across substance, 7 day ErC50 values for the growth rate based on initial concentrations were >91.817 mg/L. The EyC50 for the yield was determined to be >91.817 mg/L.

Key value for chemical safety assessment

EC50 for freshwater plants:
91.817 mg/L
EC10 or NOEC for freshwater plants:
91.817 mg/L

Additional information