Registration Dossier

Ecotoxicological information

Toxicity to aquatic plants other than algae

Currently viewing:

Administrative data

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:
other: well performed and documented study according to OECD guideline
Qualifier:
according to
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
GLP compliance:
no
Analytical monitoring:
yes
Details on sampling:
- samples for dissolved Pb analysis were taken at test initiation, after 4/5 days and at test termination (after 7 days)
Vehicle:
no
Details on test solutions:
- Filtered natural water with a dilute aliquot of modified APHA medium (Environment Canada, 1999) if deemed necessary
Test organisms (species):
Lemna minor
Details on test organisms:
CULTURING AND PREPARATION
- Plants used for the preliminary and definitive investigations were cultured axenically as per method outlined by Environment Canada, with minor modifications regarding the type of culture vessels

TEST ORGANISM
- Plants used for each of the treatments were of equal size and frond number
- Plants with 3 fronds
- Common name: duckweed
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Hardness:
between 8 - 266 mg/L CaCO3
Test temperature:
25 +/- 2°C
pH:
pH was measured and adjusted as needed using trace metal 0,1M HNO3
Nominal and measured concentrations:
Average dissolved Pb concentrations (µg/L) are:
* Santiam River: 2.0; 9.3; 18.7; 45.5; 92.3; 216.7; 490; 950; 1600
* Upper Peninsula: 11.8; 310; 543.3; 893.3; 1533.3; 2266.7; 3566.7; 5600
* Lake texoma: 0.9; 73.7; 143.3; 270; 550; 936.7; 836.7; 1766.7
* Calapooia watershed: 1.1; 21.7; 78.7; 143.3; 266.7; 463.3; 816.7
* Soap creek: 4.1; 9.2; 16; 37.0; 97.0; 250; 676.7; 1433.3
* Pinelands: 2.9; 12.7; 33.7; 87; 243.3; 533.3; 1600; 4033.3
* McKay Creek: 1.6; 20.7; 46; 112.3; 263.3; 623.3; 1200; 1700
Details on test conditions:
TEST SYSTEM
- min. 6 conc + control
- 3 replicates
- 100 mL test solution and 2 Lemna minor plants having three fronds each were added to a 250 ml erlenmeyer flask
- flask was covered with foam stopper. To ensure a proper air-tight seal, a layer of silicon was placed between the aquaria frame and the fitted lid, which was held in place with removable sealant tape. A small hole drilled in the lid pumped CO2 in to the aquarium.
- 24h light cycle with light intensity 4080-5220 lux
- solutions were completely replaced daily by decanting


TEST MEDIUM / WATER PARAMETERS
- Natural waters were field-collected from different sites within the US by Paramatrix Environmental Research Laboratory. For each site 40 l of water were collected in sample bladder filled to the top, packed in coolers, and couriered to aquatox. The temperature of all incomping splaes was between 3 and 9°C. All natural waters were immediately placed in a walk-in coller at approx 4°C. Prior to use of the natural waters for toxicity testing, all samples were subjected to vaccuum filtration using a 47 mm, 1µm glass fiber to minimize the risk of algal contamination. Any chemical modifications made to the waters, such as the addition of a lead spike, were perfomred at least 24h prior to test initiation to allow for adequate chemical equilibration.
- Waters were gently aerated for min 2 hrs, suing acid-washed glass pipettes placed on the end of the plastic tubing that was used to deliver the air from the pump to the sample. Each test water was then pH adjusted if deemed necessary from results of the preliminary testing, divided among 8 4L low density plyethylene containers. All test waters were left for min 24hrs prior to test initiation to allow for chemical equilibration.
- APHA media (Environment Canada, 1999) was added to the medium if deemed necessary
- Changes in DOC were not quantified because previous 7d tests showed that DOC is stable and remains within 90% of the value at test initiation


OTHER TEST CONDITIONS
- preliminary tests were performed to ensure the success of the definitive test (richness of natural waters in nutrients, concentration APHA medium required, concentration range of Pb, the flow rate of CO2 needed)
Duration:
7 d
Dose descriptor:
IC10
Effect conc.:
85 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Remarks:
Pb
Basis for effect:
other: root growth rate
Remarks on result:
other: Santiam river water; Hardness: 29 mg/L; pH: 7.9; confidence limits: 64-111 µg/L
Duration:
7 d
Dose descriptor:
IC10
Effect conc.:
1 025 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Remarks:
Pb
Basis for effect:
other: root growth rate
Remarks on result:
other: Upper peninsula water; Hardness: 56 mg/L; pH: 7.2; confidence limts: 919-1143 µg/L
Duration:
7 d
Dose descriptor:
IC10
Effect conc.:
255 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Remarks:
Pb
Basis for effect:
other: root growth rate
Remarks on result:
other: Lake texoma water; Hardness: 266 mg/L; pH: 8.3; confidence limts: 137-473 µg/L
Duration:
7 d
Dose descriptor:
IC10
Effect conc.:
172 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Remarks:
Pb
Basis for effect:
other: root growth rate
Remarks on result:
other: Calapooia watershed water; Hardness: 172 mg/L; pH: 8.5; confidence limts: 85-349 µg/L
Duration:
7 d
Dose descriptor:
IC10
Effect conc.:
186 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Remarks:
Pb
Basis for effect:
other: root growth rate
Remarks on result:
other: Pinelands water; Hardness: 8 mg/L; pH: 5.7; confidence limts: 65-532 µg/L
Duration:
7 d
Dose descriptor:
IC10
Effect conc.:
348 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Remarks:
Pb
Basis for effect:
other: root growth rate
Remarks on result:
other: Mackay creek water; Hardness: 33 mg/L; pH: 8.0; confidence limts: 214-568 µg/L
Reported statistics and error estimates:
Data were plotted using Sigma plot software.NOEC and LOEC values were determined with Dunnett's Multiple Comparison test using statistical program CETIS. Assumptions of equal variance and normal distribution of the sample populations with the Bartlett Equality of Variance test and Shapiro-Wilk normality test values are calculated from measurements obtianed at test termination. The effects concentrations IC10 were recalculated using log-logistic curve fitting on individual measurements. Calculations of average specific growth rate were made according to the OECD guidelines. IC10 on root growth rate were calculated by the University of Ghent in 2012.
Validity criteria fulfilled:
yes
Remarks:
> 7 times increase in biomass in 7 days (OECD, 2002)

Description of key information

Both data stems from accepted high quality long term Pb toxicity studies for freshwater and marine aquatic plants, conducted at relevant pH and water hardness conditions.

Key value for chemical safety assessment

EC10 or NOEC for freshwater plants:
1 025 µg/L
EC10 or NOEC for marine water plants:
11.9 µg/L

Additional information