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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
96 hours
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Conducted in accordance with current testing guidelines and GLP-compliant.
Qualifier:
according to
Guideline:
OECD Guideline 203 (Fish, Acute Toxicity Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Details on test solutions:
A brown liquid, was received in an amber, glass jar and stored at room temperature until use .
Test organisms (species):
Cyprinodon variegatus
Details on test organisms:
The sheepshead minnows, Cyprinodon variegatus, used for this study were obtained from AQUATOX,Hot Springs, Arkansas. Upon arrival at the ESG facility, sheepshead minnows were placed in tanks containing synthetic seawater. Test fish were held in a recirculating, 110 liter, glass aquarium for at least twelve days prior to testing. During holding, fish were fed a dry commercial fish food or live Artemia napulii 5 to 7 days a week. In order to assess test fish suitability, a reference standard test (as outlined by OSPAR~) using 3, 5-dichlorophenol was conducted on this particular batch of sheepshead minnows. Fish were semi-statically exposed to 2.3 mg/L 3, 5-dichlorophenol. Percent mortality after 96 hours was determined to be 20 %: the acceptability range is 20 - 80%. Sheepshead minnows used for the MK92K study appeared in good health and mortalities during the 72 hours immediately preceding the test was less than 1%. Twenty-four hours before initiating the test, fish were taken off feed. Ten fish were introduced at random into the control and each exposure vessel (one vessel per concentration). The control fish had a mean (10 organisms) total length of 1.56 cm and a mean weight of 0.037 grams. Biological loading was 0.12 g/L.
Test type:
other: Semi-static renewable at 48 hours
Water media type:
saltwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
Temperature in the test water was 19.4 to 20.8°C
pH:
8.0
Salinity:
32-33 parts per thousand
Nominal and measured concentrations:
5, 10, 20, 40 and 80 mg/L nominal concentration.
Details on test conditions:
Environmental control was achieved through the use of a Heinicke HC 982M walk-in environmental chamber. Thermostatic controls were adjusted to achieve a nominal chamber test temperature of 20 ± 2°C. Temperature range in the test water was 19.4 to 20.8°C, while the photoperiod consisted of a 16-hour daylight regime. During the course of the study, salinity was 32 - 33 parts per thousand.

The test was started by preparing a 25 mg/ml stock solution of MK92K in distilled water. This sheepshead minnow bioassay was conducted in one gallon glass, widemouth jars fitted with plastic screw caps. Appropriate test volumes of the toxicant stock were added to a 1 liter volumetric flask and brought up to volume with synthetic seawater. This one liter of seawater solution was poured into a 4-liter, glass beaker followed by 2.0 liters of seawater bringing the total volume up to 3 liters. This solution was vigorously stirred and subsequently poured into the respective jars. Fish used in this test were selected from the acclimation tank and randomly introduced into each jar. Five concentrations and a control were used to determine the toxicity of MK92K to the sheepshead minnow.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
14.1 mg/L
Basis for effect:
mortality
Remarks on result:
other: Confidence limits unavailable
Duration:
24 h
Dose descriptor:
LC50
Effect conc.:
28.3 mg/L
Basis for effect:
mortality
Remarks on result:
other: Confidence limits unavailable
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
23 mg/L
Basis for effect:
mortality
Remarks on result:
other: 95% confidence limits, 18.8 to 28.1 mg/L
Duration:
72 h
Dose descriptor:
LC50
Effect conc.:
14.1 mg/L
Basis for effect:
mortality
Remarks on result:
other: Confidence limits unavailable
Details on results:
Refer to any other information on results section

The substance was readily soluble; no cloudiness or signs of insoluble material were observed throughout the 96-hour duration of the study. The 96-hour LC50to the sheepshead minnow was determined to be 14.1 mg/L. The 96 hour maximum concentration causing 0% mortality was determined to be 10 mg/L; the minimum concentration causing 100% mortality was 20 mg/L. The 96-hour No Observed Effect Concentration (NOEC) is less than 5 mg/L. Mortality, LC50values and associated 95% confidence limits are presented in Table 1 and 2. Behaviour monitored throughout the study is detailed in Table 3. Chemical and physical parameters were monitored during the test.

 

Table 1: Mortality Observations (# dead out of 10)

 

 

Control

5

10

20

40

80

24 Hour

0

0

0

0

10

10

48 Hour

0

0

0

3

10

10

72 Hour

0

0

0

10

10

10

98 Hour

0

0

0

10

10

10

 

Table 2: LC50 Calculations

 

Observation Time

LC50(mg/L)

95% Confidence Limits (mg/L)

Calculation Method

24 Hour

28.3

(Unavailable)

Spearman-Karber

48 Hour

23.0

(18.8 – 28.1)

Spearman-Karber

72 Hour

14.1

(Unavailable)

Spearman-Karber

96 Hour

14.1

(Unavailable)

Spearman-Karber

 

Table 3: Behavioural Observations

 

 

Control

5

10

20

40

80

24 Hour

Normal

Normal

Quiescent

Quiescent, surfacing and twitching. Swimming ceased and on side.

Respiration ceased.

Respiration ceased.

48 Hour

Normal

Quiescent

Quiescent

Quiescent, surfacing and twitching. Swimming ceased and on side.

Respiration ceased.

Respiration ceased.

72 Hour

Normal

Quiescent

Quiescent and surfacing. Swimming erratic

Respiration ceased.

Respiration ceased.

Respiration ceased.

96 Hour

Normal

Quiescent

Quiescent, surfacing and twitching. Swimming erratic.

Respiration ceased.

Respiration ceased.

Respiration ceased.

Validity criteria fulfilled:
yes
Conclusions:
The 96 hour LC50 is 14.1 mg/L.
Executive summary:

The static acute, 96 hour LC50 to the sheepshead minnow, Cyprinodon variegatus, in synthetic seawater is 14.1 mg/L. This value is based upon nominal concentrations in seawater, with a renewal of test concentrations at 48 hours.

Description of key information

Key value for chemical safety assessment

LC50 for marine water fish:
14.1 mg/L

Additional information

The acute toxicity to the sheepshead minnow was determined according to OECD guideline 203 (Fish, Acute Toxicity Test) under semi-static conditions.