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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1991
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1991
Report Date:
1991

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Version / remarks:
EU Method C2
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline
Details on test material:
PCMX powder at ambient conditions.
Specific details on test material used for the study:
Test substance

Identification:

para chlor meta xylenol
Supplied by: Date of receipt: Thomas Swan & Co Limited 30.08.1991
Shelf life: Storage: Appearance: Odour:
Relative density (quoted): not stated
ambient conditions cream powder phenolic
Relative density (measured): Solubility in water:
250 mg/litre (quoted)

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:


The tests were carried out in accordance wi th the experimental procedure detailed in Annex, f-'.eneral Test PnK:edures. There were no reasons to deviate from these procedures, which follow the OECD Guideline for the Testing of Chemicals Ref. 202.(l)


Test solutions

Vehicle:
yes
Details on test solutions:
A stock solution of 100 mg PCMX per litre dechlorinated mains water was prepared by continuotL'i magnetic stirring for a period of twelve hours. This was then diluted to 10 mg/li tre so tha t suitable vol umes were used in the 100 ml test volumes for the selected concentrations.

Test organisms

Test organisms (species):
Daphnia sp.
Details on test organisms:

Juvenile Daphnia are selected for the test by passing the stock through a stainless steel mesh wi th apertures of 0.8mm. The population obtained from the supplier is mixed, but those used for the test arc of the same ki nd

Study design

Test type:
static
Water media type:
other: De-chlorinated
Total exposure duration:
24 h
Remarks on exposure duration:
The jars are placed in an incubator and maintained at 20°C for 24 hours
Post exposure observation period:
At the end of 24 hours the tcmperatue is recorded, and the pH value and dissolved oxygen concentration are measured for each jar. The number of Daphnia immobilised is determined by examination. A Daphnia is considered to be immobilised if on gentle agitation of the jar it is unable to swim.

Test conditions

Hardness:
The hardness is confirmed analytically by titration with standard Wanklyn's soap solution
Test temperature:
20
pH:

5.0
2.8
1.6
0.9
0.5
Dissolved oxygen:
95%
Salinity:
N/A
Conductivity:
N/A
Nominal and measured concentrations:
Suitable test concentrations are established by carrying out a series of range finding tests prior to the main test. The objective is to determine a suitable range of concentrations such that the main test will give meaningful resu lts. Concentrations tested are in a geometric series, and the highest concentration tested is less than l g/litre
Details on test conditions:
In cases where the test substance is soluble in water, each test solution is prepared by direct addition of the required amount of test substance to the dilution water. In cases where the substance has limited solubility then one of the following methods is used in order to maintain an adequate level of dispersion throughout the test period:

(i) acetone/methanol is used to disperse the test substance

(ii) a benign dispersing/emulsifying agent is used
Reference substance (positive control):
yes

Results and discussion

Effect concentrations
Key result
Duration:
24 h
Dose descriptor:
LC50
Effect conc.:
ca. 1 g/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
mobility
Details on results:
At a concentration of 5 mg/litre PCMX the Daphnia were almost completely immobilised (5% active). The three lowest concentrations tested all resulted in similar immobilisation (15%). However when the results of the two lowest concentration were omitted from the estimation of the EC50, the value obtained was similar (2.8
mg/litre), and the 95% confidence limits overlapped.

The results of this test suggest that concentrations of PCMX greater than 2 mg/litre are likely to immobilise at least 50% of a population of Daphnia sp.
Results with reference substance (positive control):
Numbers of Da phnia sp. immobilised after 24 hours exposure

Test sample: para chlor meta xylenol



Concentration mg/l i tre
5.0
A I
2.8
A I
1.6
A I
0.9
A I
0.5
A I
control A I
Time 24 h jar 1 1 4 5 0 4 I 4# 1 4 1 5 0
jar 2 0 5 3 2 4 1 4 1 3 2 5 0
jar 3 0 5 2 3 5 0 4 1 5 0 5 0
jar 4 0 5 4 1 4 1 5 0 5 0 4 I
I % IMMOBILISATION I 95 I 30 I 15 I 13.3 I 15 I 5 I

A = ACTIVE
I = IMMOBILISED

# This result was omitted from the calculation due to the low dissolved oxygen recorded at the end of the test.
Reported statistics and error estimates:
When the results of the two lowest concentration were omitted from the estimation of the EC50, the value obtained was similar (2.8
mg/litre), and the 95% confidence limits overlapped.

Any other information on results incl. tables

·Table  1.       Toxicity of para chlormetaxylenol to Daphnia sp.

Per cent Immobilisation after 24 hours exposure

Concentration mg/li tre       

lmmobilisation after 24

hours       (%)

5.0       95

2.8       30

1.6       15

0.9       1}3

0.5       15

control       5

From these results the EC50  value is estimated to be 2.0 mg/litre para chlormetaxylenol as shown in Graph No.I.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
At a concentration of 5 mg/litre PCMX the Daphnia were almost completely immobilised (5% active). The three lowest concentrations tested all resulted in similar immobilisation (15%). However when the results of the two lowest concentration were omitted from the estimation of the EC50, the value obtained was similar (2.8
mg/litre), and the 95% confidence limits overlapped.

The resul ts of this test suggest that concentrations of PCMX greater than 2 mg/litre are likely to immobilise at least 50% of a population of Daphnia sp.