5-chloro-2-(4-chlorophenoxy)phenol;[DCPP]

Toxicity to aquatic plants other than algae

Administrative data

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

migrated 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:

other: GLP guideline study on Triclosan, suitable for read-across.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Reference 2

Reference Type:

other: Amendment

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: EPA, TSCA Environmental Effects Testing Guidelines, Subpart B, Section 797.1050, Federal Register, Vol. 52, No. 97 May 20, 1987;

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: ASTM, 1991, Standard guide for conducting static toxicity tests with Lemna gibba G3, E1415-91.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Triclosan

EC Number:

222-182-2

EC Name:

Triclosan

Cas Number:

3380-34-5

IUPAC Name:

5-chloro-2-(2,4-dichlorophenoxy)phenol

Details on test material:

- Name of test material (as cited in study report): Triclosan
- Lot/batch No.: EN:275927.26
- Analytical purity: 99.5 %

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
To begin each test, a fresh primary stock solution was prepared by weighing an appropriate amount of Triclosan and diluting with the solvent acetone. The primary stock solution was mixed by inversion or by sonication for five minutes, resulting in a clear liquid. Secondary stock solutions for each test were prepared, in acetone, by serial dilution at concentrations such that an equivalent amount of solvent was used in each test treatment. The nominal concentration for the primary stock solution was as follows: 1330 µg/mL.
For each toxicity test, the test treatments were prepared by quantitatively diluting aliquots of the appropriate stock solutions, with medium in volumetric flasks, to yield nominal test solution concentrations. Actual nominal concentrations for each definitive test were as follows: 0.500, 2.50, 12.5, and 62.5 µg/L. The no-treatment controls contained medium only. The solvent controls contained an amount of solvent equivalent to the amount present in each test treatment, i.e., 0.5 mL/L. After thorough mixing of the test substance treatments, appropriate volumes of the no-treatment control, solvent control, and each test substance treatment were added to each of the replicate test vessels.

Test organisms

Test organisms (species):

Lemna gibba

Details on test organisms:

- Common name: Duckweed
- Source: in-house culture
- Age of inoculum (at test initiation): inoculum was taken from healthy 12-d old stock cultures.
- Breeding method: stock cultures were maintained according to facility SOPs. Transfers were made regularly into fresh medium to provide cultures in the logarithmic phase of growth for toxicity test inoculations.
- Culturing conditions: 25±2°C; permanent illumination of 5000 ± 750 lux (warm white lights).

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Test conditions

Test temperature:

24.10 - 24.76 °C

pH:

start: 7.71 - 7.76
termination: 7.58 - 8.92

Nominal and measured concentrations:

The nominal concentrations were 0.5, 2.5, 12.5 and 62.5 µg a.s./L

Details on test conditions:

TEST SYSTEM
- Incubation chamber used: yes pH Environmental Incubator, Model CEC-32TC
- Test vessel: 500-mL Erlenmeyer flasks
- Fill volume: 200 ml
- No. of colonies per vessel: Three plants, consisting of four fronds each (total of 12 fronds) per vessel were used
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Medium was prepared by adding, for each litre, aliquots of the 20X-AAP media stock solution to ASTM Type 1 reagent grade water. The pH was adjusted to 7.5 ± 0.1 with 0.1 N or 1.0 N sodium hydroxide or hydrochloric acid as necessary and the volume brought to one liter. Medium was then filtered through a 0.22 µ filter into a sterile container.

OTHER TEST CONDITIONS
- Photoperiod: Continuous illumination
- Light intensity and quality: 5000 ± 1 5% lux

EFFECT PARAMETERS MEASURED
- Determination of frond number: manual counting

Results and discussion

Effect concentrations

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

> 62.5 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: reduction in growth (frond number)

Details on results:

Exposure of L. gibba to Triclosan resulted in effects ranging from 16.2 % stimulation to 20.9 % inhibition.
Since no test concentration resulted in inhibition > 25 %, the EC50 could not be determined and is reported to be > 62.5 µg/L.

Any other information on results incl. tables

Effects of Triclosan on the growth of Lemna gibba:

Nominal concentration [µg/L]	Frond counts on day 7 (Mean ± Standard deviation)	% inhibition relative to mean in combined controls
Combined controls	163 ± 12	-
0.5	178 ± 12	- 10.3
2.5	172 ± 11	- 6.08
12.5	187 ± 5	- 16.2
62.5	131 ± 17	20.9

A negative percent inhibition indicates stimulation