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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
No standard protocol was used, but the test method was described in enough detail. No chemical analyses on the test concentrations were perfored, only the stock solution was analyzed. From results in chronic tests it can be assumed that the test substance was stable during the test and animals were exposed properly.
Qualifier:
according to guideline
Guideline:
other: protocol developed for EnviroSystems Study Number 90117-DE.
Principles of method if other than guideline:
It is not known if the protocol used is equal to a standard guideline.

Twenty mysids were randomly and equally distributed among two replicates of each treatment. The test was performed in 19.6 liter glass aquaria that contained 15 liters of test solution (water depth was approximately 20 cm). Test vessels were randomly arranged in a water bath during the 96 h test (a random numbers table was used to select the location of each vessel). The test substance was supplied to the test vessels under flow through conditions by an intermittent flow proportional diluter. The diluter, which was constructed at EnviroSystems, allowed test media to contact only glass or Teflon-coated surfaces. The diluter was calibrated before and after the test. During the test the diluter was activated 812 times, resulting in an average of 6.8 media exchanges per 24 hours in each test vessel.

The number of surviving organisms and the occurrence of sublethal effects (loss of equilibrium, erratic swimming, loss of reflex, excitability, discoloration, or change in behavior) were determined visually and recorded after 24, 48, 72, and 96 hours.
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
The concentration of sodium chlorate in test media could not be determined because of naturally occurring interference in the dilution water. The available analytical methods were effective in deionized water used to prepare toxicant stock solutions but not in the dilution water. A subsample of the 600,000 mg/L primary stock solution (prepared in deionized water) was withdrawn from the toxicant reservoir placed into 40 ml VOA vial, and stored in 2-4°C prior to analysis.
Vehicle:
no
Details on test solutions:
- Dilution water: Water used for acclimation of test organisms and for all toxicity testing was unfiltered seawater collected from the Atlantic
Ocean at EnviroSystems in Hampton, New Hampshire. Water, which had a salinity of 11 to 17 ppt (parts per thousand) and a pH of 7.7, was stored in 500-gallon
polyethylene tanks where it was aerated.

- Stock solution: An initial 600,000 mg/L stock solution was prepared by combining 1,200.0 g of test substance and deionized water and adjusting the
volume to approximately 1,800 ml in a 2 liter glass class A volumetric flask. The stock solution was mixed on a magnetic stir plate until the test substance dissolved and the total volume was adjusted to 2.0 L with deionized water. This procedure was repeated twice and all stock solution was transferred to a 6.0 L Erlenmeyer flask.

Test solutions: Appropriate amounts of the stock solution were added directly to dilution water by a proportional diluter (5.0 ml of test substance was combined with 3,000 ml of water during each diluter cycle) and this diluter toxicant cell solution was mixed by a high shear pump equipped with a Teflon
head.
Test organisms (species):
Americamysis bahia (previous name: Mysidopsis bahia)
Details on test organisms:
Juvenile mysids (less than 24 hours old) were identified using an appropriate taxonomic key. They were produced from in-house cultures
at EnviroSystems in Hampton, New Hampshire. Mysids were not treated for disease and they were free of apparent sickness, injuries,and abnormalities at the beginning of the test. Mysids were fed newly hatched Artemia salina nauplii once or twice daily before the test.
Test type:
flow-through
Water media type:
saltwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
21.4 to 23.0 °C
pH:
7.6 to 7.8
Dissolved oxygen:
7.4 to 8.9 mg/L
Salinity:
16 to 17 parts per thousand
Nominal and measured concentrations:
Mean nominal concentrations: 0 (control), 130, 220, 360, 590, and 1,000 mg/L sodium chlorate.
The 600,000 mg/L (nominal) stock solution had a measured concentration of 650,000 mg/L sodium chlorate.
Details on test conditions:
- Photoperiod: A 16 hour light and 8 hour dark photoperiod was automatically maintained
- Light intensity: cool-white fluorescent lights that provided a light intensity of 10 pEs-1/m2
- Aeration: Aeration was not required to maintain dissolved oxygen concentrations above acceptable levels.
- Feeding: Mysids were fed newly hatched Artemia salina nauplii once per day during the test.
Reference substance (positive control):
no
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
One hundred percent survival occurred in the control and no sublethal effects were noted during the exposure period. Control mysids had an average wet weight (blotted dry) of 0.0001 g, resulting in a loading rate during the toxicity test of approximaJely 0.0001 g/L.
One animal died in 590 mg/l and 3 died in 100 mg/l, but this was not significant.
Reported statistics and error estimates:
Results of the toxicity test could not be interpreted by standard statistical techniques (Stephan, 1983) because greater than 50% survival occurred at all tested concentrations.
Validity criteria fulfilled:
not specified
Conclusions:
The test substance did not give significant effects at the highest test concentration of 1000 mg/l, therefore LC50 is greater than 1000 mg/l.
Sodium chlorate is not toxic to Mysid shrimp.
Executive summary:

The acute toxicity of sodium chlorate to the mysid Mysidopsis bahia, is described in this final report. The test was conducted for Albright and Wilson Americas for 96 hours during February 15 to 19, 1991, at the EnviroSystems Division of Resource Analysts Inc. in Hampton, New Hampshire. It was conducted by Peter Kowalski, Ellen Stanford, Jeanne Magazu, Robert Boeri and Timothy Ward according to the protocol developed for EnviroSystems Study Number 90117-DE. The analytical portion of this study was conducted under the supervision of Gloria Switalski. Sodium chlorate (reported purity >99\ active ingredient) was supplied by the sponsor. The test was performed under flow-through conditions with five concentrations of test substance and a dilution water control at a temperature of 22 ± 1°C. The dilution water was unfiltered natural seawater collected at Hampton, New Hampshire. Nominal concentrations of sodium Chlorate were: 0 mg/L (control), 130, 220, 360, 590, and 1,000 mg/L. Nominal concentrations were used for all calculations. Mysids used in the test were less than 24 hours old at the start of the test. They were produced from in-house cultures at EnviroSystems in Hampton, New Hampshire. After 96 hours of exposure the control organisms had an average wet weight (blotted dry) of 0.0001 g. All animals were in good condition at the beginning of the study. Exposure of mysids to the test substance resulted in a 96 hour LC50 greater than 1,000 mg/L sodium chlorate. The 96 hour no observed effect concentration was 1,000 mg/L sodium chlorate, the highest tested concentration.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study generated according to valid , internationally accepted testing guideline and was performed under GLP. No chemical analyses was performed on the test concentrations, only the stock solution could be analyzed. From chronic tests with chemical analyses it can be assumed that the test concentrations were stable and the animals were exposed properly.
Qualifier:
according to guideline
Guideline:
EPA OPP 72-2 (Aquatic Invertebrate Acute Toxicity Test)
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
- Preparation: 600.0 mg/L stock solution was prepared by adding 1200.0 g test substance to 2000 ml deionized water.
Appropriate amounts of stock were added directly to dilution water by a proportional diluter.
Test organisms (species):
Daphnia magna
Details on test organisms:
- Supplier: Aquatic Research Organisms, Hampton, New Hampshire
- Age: less than 24 hours
- Feeding: yeast/trout chow, and/or Selenastrum capricornutum daily
- Pretreatment: acclimatized for 14 days under test conditions.
- Feeding during test: No
Test type:
flow-through
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Test temperature:
19.5-20.9 °C
pH:
7.3-7.7
Dissolved oxygen:
8.5-9.0 mg/L
Nominal and measured concentrations:
Nominal test concentrations: 0, 150, 240, 380, 600, 1000 mg/L
Details on test conditions:
DILUTION WATER:
- Source: groundwater collected from wells in Hampton, New Hampshire
- Aeration: Yes
- pH: 7.6
- Hardness: 180 mg CaCO3/L
- Conductance: 670 µmhos/cm (equal to µS/cm)
- Holding water: same as dilution water
- flow-through, 8.8 media exchanges per 24 hours in each test vessel
- Exposure vessel: 20 liter glass aquaria that contained 15 liter of test solution.
- 20 daphnids were confined in two groups of 10 in cages consisting of glass and Nitex screen.
- Number of replicates, individuals per replicate: 2, 10
- Conductance: 620-1500 µmhos/cm (equal to µS/cm)
- Intensity of irradiation: cool white fluorescent lights with an intensity of 13 µEs/m2
- Photoperiod: 16 hours photoperiod daily
- TEST PARAMETER: immobilization and sublethal effects
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/L
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Details on results:
- 24 hours: 1 organism died in 1000 mg/l
- 48 hours: 1 organism died in 150 mg/l and 1 in 240 mg/l
- No other sublethal effects were observed.
- Control: No affected or immobile organisms were observed
- The replicates mentioned in the report are no true replicates because the two cages were placed in the same aquarium.
Reported statistics and error estimates:
No statistics could be performed because greater than 50% survival occurred in all test con centrations.
Validity criteria fulfilled:
no
Remarks:
the test concentrations were not analyzed, only for the stock concentration chemical analyses was performed.
Conclusions:
Study performed to EPA guidelines under flow through conditions with GLP accreditation. Stocks were analysed but analysis in the test media was not possible to interference. The stock recovery was within specified limits. Due to the test substance stability and the fact that the solution is
continually renewed and providing the automatic diluting system used was working accurately the nominal concentrations can be considered
reliable. The LC50 of >1000mg/l is considered reliable without major restrictions.
Executive summary:

The acute toxicity of sodium chlorate to the daphnid, Daphnia magna, is described in this final report. The test was conducted for Albright and Wilson Americas for 48 hours during March 5 to March 7, 1991, at the EnviroSystems Division of Resource Analysts, Inc. in Hampton, New Hampshire. It was conducted by Peter Kowalski, Ellen Stanford, Jeanne Magazu, Robert Boeri, and Timothy Ward according to the protocol developed for EnviroSystems Study Number 90144-AW. The analytical portion of this study was conducted under the supervision of Gloria Switalski. Sodium chlorate (reported purity >99\ active ingredient) was supplied by the sponsor.

The test was performed under flow-through conditions with five concentrations of test substance and a dilution water control at a temperature of 20 ± 1°C. The dilution water was filtered natural groundwater collected at Hampton, New Hampshire. Nominal concentrations of sodium chlorate were: 0 mg/L (control), iSO, 240, 380, 600, and 1,000 mg/L. Nominal concentrations were used for all calculations.

Organism used in the test were procured from a commercial supplier (Aquatic Research Organisms, Hampton, New Hampshire) and acclimated at EnviroSystems under test conditions for more than 14 days. After 48 hours of exposure the control organisms had an average wet weight (blotted dry) of 0.0006 g. All animals were in good condition at the beginning of the study. to mg/L hQYJ"

Exposure of daphnids LC50 greater than 1,000 concentration. The 48 hour no observed effect concentration was

1,000 mg/L sodium chlorate.

Description of key information

The EC50 for freshwater invertebrates is greater than 1000 mg/l.

The EC50 for marine invertebrates is greater than 1000 mg/l as well.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Dose descriptor:
EC50
Effect concentration:
1 000 mg/L

Marine water invertebrates

Marine water invertebrates
Dose descriptor:
EC50
Effect concentration:
1 000 mg/L

Additional information

Two valid studies with Daphnia magna were found. Both studies were performed under GLP conditions and according to standard protocol. In both studies chemical analyses were carried out, but in the second study (Ward and Boeri (1991d) only analyses on the stock solution were performed. Owusu-Yaw expressed the endpoint in mg chlorate ion per liter, this was transformed to mg sodium chlorate per liter for the purpose of this dossier. The original value was 919.3 mg chlorate/l. The results of the study performed by Owusu-Yaw were heterogeneous and must therefore be considered reliable with restrictions, but nevertheless the results confirm the outcome of Ward and Boeri.


One study valid with restrictions was found for the marine crustacean Mysidopsis bahia (Ward and Boeri, 1991f). This study gave an EC50 greater than 1000 mg/l.


Also, one short-term study valid with restrictions was found for molluscs. From this study (Ward and Boeri, 1991g) it can be seen that marine molluscs are not sensitive to sodium chlorate with an EC­50value based on shell growth and an LC50value both greater than 1000 mg/l sodium chlorate.


The EC50 for fresh water invertebrates is greater than 1000 mg/l even as the LC50 for marine invertebrates.