Registration Dossier

Ecotoxicological information

Toxicity to aquatic plants other than algae

Administrative data

Endpoint:
toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Not specified
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Impacts of structural photomodification on the toxicity of environmental contaminants: anthracene photooxidation products
Author:
Mallakin, A., McConkey, B.J., Miao, G., McKibben, B., Snieckus, V., Dixon, G.D, Greenberg, B.M.
Year:
1999
Bibliographic source:
Ecotoxicology and environmental safety 43, 204-212 (1999)

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition test)
Version / remarks:
Toxicity after photomodification was also assessed.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Eluate: 0.1 % DMSO
- Controls: 0.1 % DMSO
--> DMSO was found to have no impact on L. gibba growth.

Test organisms

Test organisms (species):
Lemna gibba
Details on test organisms:
TEST ORGANISM
- Common name: Duckweed
- Strain: Lemna gibba L. G-3

ACCLIMATION
- Culturing media and conditions (same as test or not): Lemna was transferred from sucrose-containing growth medium to sucrose-free medium, 2 weeks prior test

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d

Test conditions

Nominal and measured concentrations:
Nominal concentrations ranged from 0.01 to 10 µg/mL in a logarithmic series
Details on test conditions:
TEST SYSTEM
- Incubation chamber used: yes
- Test vessel: 5-cm petridish
- Type: open
- Renewal rate of test solution: static renewal every 48h
- No. of colonies per vessel: 2
- No. of fronds per colony: 8 leaves

GROWTH MEDIUM
- Standard medium used: fresh half-strength Hunter's medium

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Light intensity and quality: PAR (photosynthetically active radiation), cool-white fluorescent, 400-700 nm and SSR (simulated solar radiation)
- Light saturation: 100 µmol m-2 s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of frond number: manual counting
Reference substance (positive control):
no
Remarks:
no reference substance mentioned in the publication

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
5.5 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
frond number
Remarks on result:
other: EC50 measured in PAR light
Key result
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.05 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
frond number
Remarks on result:
other: LOEC measured in PAR light
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
2.8 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
frond number
Remarks on result:
other: EC50 measured in SSR light
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.09 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
frond number
Remarks on result:
other: LOEC measured in SSR light
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
1.5 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
frond number
Remarks on result:
other: after full photomodification
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.01 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
frond number
Remarks on result:
other: after full photomodification
Details on results:
The effect level EC50 was highest in PAR light (5.5 mg/L), followed by SSR light (2.8 mg/L). After full photomodification, the effect value was 1.5 mg/L. This indicates that due to photomodification a more toxic mixture is formed than the intact substance.
Results with reference substance (positive control):
Not available
Reported statistics and error estimates:
Toxicity data were fit to a sigmoidal function (McConkey et al. 1997). Standard errors were calculated for all EC50 values.

Any other information on results incl. tables

Effect concentrations according to the different experiments:

Effect levels Toxicity in PAR light Toxicity in SSR light Toxicity after photomodification
EC50 LOEC EC50 LOEC EC50 LOEC
mg/L 5.5 ±0.14 0.05 2.8 ±0.57 0.09 1.5 ±0.28 0.01

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
Conclusions:
The effect levels were assessed in a 7d Lemna study, semi-static study. The effect level EC50 was highest in PAR light (5.5 mg/L), followed by SSR light (2.8 mg/L). After full photomodification, the effect value was 1.5 mg/L. This indicates that due to photomodification a more toxic mixture is formed than the intact substance.
Executive summary:

The toxicity of the test substance to Lemna gibba was assessed in a study similar to OECD 221. The growth inhibition was determined under photosynthetically active radiation (PAR) and simulated solar radiation (SSR). Additionally, as the test substance is known to undergo photomodification (half-life measured to be 3h in SSR), a study was also ran after full photomodification (test substance kept 7days in SSR light).

The study was conducted as a semi-static study with renewal of test medium every 48h. The effect concentrations that were assessed are EC50 and LOEC values. In PAR light, the EC50 was found to be 5.5 mg/L and the LOEC 0.05 mg/L. In SSR light, the EC50 was determined to be 2.8 mg/L and LOEC 0.09 mg/L. The lowest effect concentrations were observed after full photomodification: EC50 = 1.5 mg/L and LOEC=0.01 mg/L.

The results indicate that due to photomodification a more toxic mixture is formed.