Pyrasulfotole

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 Oct - 25 Oct 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPP 72-2 (Aquatic Invertebrate Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Samples were taken from all test chambers on Day 0 (prior to the introduction of the test organisms to the test chambers) and on Day 2 (test termination).
- Sampling method: Samples at each time point were taken at mid-depth and did not include any extraneous materials.
- Sample storage conditions before analysis: Samples were analyzed on the same day.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution of the technical in dilution water (i.e., blended well water) was prepared at a nominal concentration of 100.0 mg/L by adding the test substance to 1-Liter of dilution water. This was then stirred for ~70 minutes at test temperature.
- Controls: dilution water control
- Eluate: no
- Differential loading: yes

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Source: parental stock (Lot #D-7) was purchased from Aquatic Research Organisms, Hampton, NH
- Age of parental stock: 17 day old
- Feeding during test: none
- Age at study initiation: <24 h

ACCLIMATION
- Acclimation period: <24 h
- Acclimation conditions (same as test or not): not reported
- Type and amount of food: unicellular green algae, Pseudokirchneriella subcapitata supplemented with TetraFin fish food suspension or fed with Pseudokirchneriella subcapitata only without supplement.
- Feeding frequency: twice daily with supplement every Monday, Wednesday, and Friday
- Health during acclimation (any mortality observed): The parental culture had a cumulative adult survival of 100%, no behavioral signs of stress, and no ephippia. Neonate mortality did not exceed 10% in the parental culture from which organisms were obtained for use in the study.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

164 mg/L

Test temperature:

19.3 to 19.9 °C

pH:

7.3 to 8.3

Dissolved oxygen:

97 to 102% saturation

Conductivity:

1100 to 1200 μmhos/cm

Nominal and measured concentrations:

control and 100 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
Test vessel
- Type (delete if not applicable): closed (covered to prevent evaporation and addition of extraneous material).
- Material, size, headspace, fill volume: 250 mL Pyrex beaker (6.5 cm diameter, 8.6 cm high) containing 200 mL of test solution with a test solution depth of approximately 6.5 cm. Headspace: 50 mL.
- Aeration: none
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: well water blended with softened well water to lower the hardness and filtered to remove iron, trace organics, and suspended particulates (including microbes)
- Total organic carbon: - Particulate matter: - Metals: - Pesticides: - Alkalinity: 308 mg/L
- Ca/mg ratio: 3.58
- Conductivity: 1100 to 1200 μmhos/cm
- Intervals of water quality measurement: Semi-annual

OTHER TEST CONDITIONS
- Photoperiod: 16:8 hours, light:dark
- Light intensity: 400 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mobility, behavior and appearance.

VEHICLE CONTROL PERFORMED: no vehicle was used

RANGE-FINDING STUDY
- Test concentrations: 0.1, 1.0, 10, and 100 mg/L
- Results used to determine the conditions for the definitive study: No mortality was observed in any treatment. Thus, a limit test was selected for the definitive study.

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Behavioural abnormalities: none
- Mortality of control: none
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no precipitates observed
- Effect concentrations exceeding solubility of substance in test medium: no

For details on measured concentrations, study observation data and study water quality data see attachment.

No immobilisation or sub-lethal effects were observed in the control or concentration of 100 mg/L during the study.

Table 1: Measured test substance concentrations.

	Measured Test Substance Concentrations (mg/L)
Sample Name (mg/L)	23 OCT. 02	25 OCT. 02	Mean Recovery (mg/L)	Mean Percent Recovery(%)
Control solvent	<LOQ^b	<LOQ^b	<LOQ^b	<LOQ^b
Dilution water	<LOQ^b	<LOQ^b	<LOQ^b	<LOQ^b
100-1^a	97.0772	89.8985	93	93
100-2^a	97.0405	99.0549	98	98
Statistics	Overall Mean = 96% n=4 Overall Std. Dev. = 4.02%

^aThis sample injected twice and presented as 100-1 and 100-2.

^bLOQ = 1.0 mg/L

Table 2: Validity criteria for OECD 202 (2004)

Criterion from the guideline	Outcome	Validity criterion fulfilled
In the control, including the control containing the solubilising agent, not more than 10% of the daphnids should have been immobilized.	In the controls 0% of the daphnids were immobilized.	yes
The dissolved oxygen concentration at the end of the test should be ≥ 3 mg/L in control and test vessels.	The dissolved oxygen concentration at the end of the test was 9.1 mg/L in control and 9.1 mg/L in the test vessels	yes

 

Validity criteria fulfilled:

yes

Remarks:

See Table 2 in "Any other information on results incl. tables".

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

4 Jun - 8 Jun 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-3 (Estuarine/Marine Fish, Mollusk, or Shrimp Acute Toxicity Test)

Version / remarks:

1985

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Samples were taken from all test chambers on Day 0 (prior to the introduction of the test organisms to the test chambers) and on Day 4 (test termination).
- Sampling method: samples at each time point were taken at mid-depth.
- Sample storage conditions before analysis: Samples were tested immediately after sampling.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The stock solution was prepared by stirring 0.0541 g of test substance for 1 hour on a magnetic stir plate with 4.0 L of dilution seawater, followed by sonication for 10 minutes. Exposure solutions were prepared by appropriate dilution of the stock solution.
- Eluate: no
- Differential loading: no
- Controls: yes, test medium control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): No
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): No; The primary stock solution was observed to be slightly beige in color with no visible undissolved test substance.

Test organisms (species):

Americamysis bahia (previous name: Mysidopsis bahia)

Details on test organisms:

TEST ORGANISM
- Common name: mysid
- Source: Brood stock was originally obtained from Aquatic BioSystems, Inc., a commercial supplier located in Fort Collins, Colorado, USA (Lot: 04A07).

- Feeding during test
- Food type: live brine shrimp (Artemia salina) nauplii
- Frequency: once daily
- Age at study initiation: ≤ 24 h
- Holding conditions: Cultured in glass aquaria with a closed-loop recirculating filtration system providing artificial seawater to the aquaria (salinity: 28 - 31 ‰). The photoperiod was 16 h light/8 h dark. Mysids were fed live brine shrimp (Artemia salina) nauplii once daily.

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES: Method reported by Reitsema, L.A. and J.M. Neff. 1980. A recirculating artificial seawater system for the laboratory culture of (Crustacea; Pericaridae). Estuaries 3: 321-323

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

24 to 26 °C

pH:

7.9 to 8.1

Dissolved oxygen:

5.5 to 7.5 mg/L

Salinity:

32 to 34‰

Nominal and measured concentrations:

0.10, 0.20, 0.40, 0.80, 1.6, 3.2, 6.4 and 13 mg a.i./L (nominal)
0.093, 0.20, 0.37, 0.75, 1.5, 2.9, 6.2 and 12 mg a.i./L (measured)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: Glass, 1 L, headspace: 100 mL, fill volume: 900 mL
- Aeration: No
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates):2
- No. of vessels per control (replicates) :2:


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Cape Cod Canal seawater
- Total organic carbon: < 2.0 mg/L
- Metals, Pesticides and PCBs were analyzed but no data was reported:
- Salinity: 32 to 34 ‰
- Intervals of water quality measurement: periodically

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light and 8 hours of darkness
- Light intensity: 58 to 80 footcandles

EFFECT PARAMETERS MEASURED (with observation intervals if applicable)
- Mortality was assessed by the absence of mobility and failure to respond to gentle prodding daily. Moreover, physical and behavioral abnormalities were recorded.

VEHICLE CONTROL PERFORMED: no; no vehicle was used

RANGE-FINDING STUDY
- Test concentrations: 0.10, 1.0, 10.0 and 100 mg/L
- Results used to determine the conditions for the definitive study: At test termination (96 hours), 40, 95 and 100% mortality was observed among mysids exposed to the 1.0, 10 and 100 mg a.i./L treatment levels, respectively. No mortality or adverse effects were observed among mysids exposed to the remaining treatment level tested (0.10 mg a.i./L) or the control. Based on these results nominal concentrations of 0.10, 0.20, 0.40, 0.80, 1.6, 3.2, 6.4 and 13 mg a.i./L were selected for the definitive exposure.

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

1.1 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Basis for effect:

mortality

Remarks on result:

other: 95% CI of 0.84 - 1.5 mg a.i./L

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.37 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

act. ingr.

Basis for effect:

mortality

Details on results:

- Behavioural abnormalities: No adverse effects (e.g. lethargy) were observed among the surviving mysids at these treatment levels.
- Mortality of control: None
- Effect concentrations exceeding solubility of substance in test medium: no precpitates were recorded

Reported statistics and error estimates:

The 96-hour LC50 value was determined by probit analysis.

Concentrations of test substance measured in the exposure solutions during the 96-hour exposure of mysids (Americamysis bahia).

Table 1: Measured concentrations.

Nominal Concentration (mg a.i./L)	Measured Concentration (mg a.i./L)			Percent of Nominal^a
	0 Hour	96 Hour	Mean^a
Control	<0.0099	<0.0099	NA^b	NA
0.10	0.093	0.094	0.093	93
0.20	0.21	0.19	0.20	99
0.40	0.39	0.35	0.37	93
0.80	0.76	0.74	0.75	94
1.6	1.5	1.5	1.5	95
3.2	2.9	3.0	2.9	92
6.4	6.4	6.0	6.2	97
13	13	12	12	96
QC^c#1 0.0500	0.00493 (9.86)^d	0.0430 (85.9)
QC#2 1.00	0.904 (90.4)	0.858 (85.8)
QC#3 15.0	13.2 (88.1)	13.2 (88.2)

^aMean measured concentrations and percent of nominal were calculated using the actual analytical (unrounded) results and not the rounded (two significant figures) values presented in this table.

^bNA = Not Applicable

^cQC = Quality Control sample with percent of recovery presented in parentheses.

^dThe percent recovery for this QC sample is outside of the established acceptance range (70.0 to 120%).

Mean measured concentrations tested, corresponding cumulative mortality, and observations made during the 96-hour static toxicity test exposing mysids (Americamysis bahia) to test substance.

Table 2: Cumulative mortality.

Mean Measured Concentration (mg a.i./L)	Cumulative Mortality^a(%)
	24 Hour			48 Hour			72 Hour			96 Hour
	A	B	Mean	A	B	Mean	A	B	Mean	A	B	Mean
Control	0 (0)	0 (0)	0	0 (0)	0 (0)	0	0 (0)	0 (0)	0	0 (0)	0 (0)	0
0.093	0 (0)	0 (0)	0	10 (1)	0 (0)	5	10 (1)	0 (0)	5	10 (1)	0 (0)	5
0.20	0 (0)	0 (0)	0	0 (0)	10 (1)	5	0 (0)	10 (1)	5	0 (0)	10 (1)	5
0.37	0 (0)	0 (0)	0	0 (0)	0 (0)	0	0 (0)	10 (1)	5	0 (0)	10 (1)	5
0.75	0 (0)	0 (0)	0	0 (0)	0 (0)	0	30 (3)	50 (5)	40	30 (3)	50 (5)	40
1.5	0 (0)	0 (0)	0^b	0 (0)	20 (2)	10^e	50 (5)	50 (5)	50	50 (5)	50 (5)	50
2.9	0 (0)	0 (0)	0^c	0 (0)	30 (3)	15	80 (8)	70 (7)	75	90 (9)	90 (9)	90
6.2	0 (0)	0 (0)	0^cd	40 (4)	10 (1)	25^c	70 (7)	70 (7)	70	90 (9)	100 (10)	95
12	0 (0)	0 (0)	0^d	40 (4)	20 (2)	30^f	80 (8)	100 (10)	90	100 (10)	100 (10)	100

^aThe actual number of mortalities is presented in parentheses.

^bTwo mysids were observed to be lethargic.

^cSeveral mysids were observed to be lethargic.

^dSeveral mysids were observed to be swimming erratically.

^eOne mysid was observed to be lethargic and on the bottom of the test vessel.

^fAll surviving mysids were observed to be swimming erratically.

Table 3: Validity criteria for OECD 202 (2004)

Criterion from the guideline	Outcome	Validity criterion fulfilled
In the control, including the control containing the solubilising agent, not more than 10% of the daphnids should have been immobilized.	In the control 0% of the daphnids were immobilized.	yes
The dissolved oxygen concentration at the end of the test should be ≥ 3 mg/L in control and test vessels.	The dissolved oxygen concentration at the end of the test ranged from 5.6 to 7.5 mg/L in control and test vessels.	yes

 

Validity criteria fulfilled:

yes

Remarks:

See Table 3 in "Any other information on results incl. tables".

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

28 May - 1 Jun 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-3 (Estuarine/Marine Fish, Mollusk, or Shrimp Acute Toxicity Test)

Version / remarks:

1984 and emended 1990

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1025 (Bivalve Acute Toxicity (shell deposition test))

Version / remarks:

1996

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Samples were taken from all test chambers on Day 0 (prior to the introduction of the test organisms to the test chambers) and on Day 4 (test termination).
- Sampling method: samples at each time point were taken at mid-depth.
- Sample storage conditions before analysis: ambient temperature until analysis

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A 100 mg a.i./L test solution was prepared by adding the test substance to 220 L of dilution water (natural seawater). The solution was prepared by first adding the test substance to approximately 3 L of dilution water and ultrasonicating for 45 minutes. The 3-L solution was then combined with 217 L of seawater in a 600 L fiberglass tank and was further mixed for two hours before flowing to the test aquaria.
- Eluate: no
- Differential loading: yes
- Controls: yes, test medium control
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): no

Test organisms (species):

other aquatic mollusc: Crassostrea virginica

Details on test organisms:

TEST ORGANISM
- Common name: Eastern oyster
- Justification for species other than prescribed by test guideline: selected because of the availability of the species
- Source: Circle C Oysters, Ridge, Maryland, USA
- Feeding during test: yes
- Food type: algae (Tetraselmus maculata)
- Amount: 180 mL, approximately 10E+07 cells/mL
- Frequency: three times daily

ACCLIMATION
- Acclimation period: 14 days
- Acclimation conditions (same as test or not): comparable to test; During the acclimation period, the salinity was gradually increased from 15 to 32‰.
- Type and amount of food: algal diet of Tetraselmus maculata prepared in seawater from a concentrate
- Feeding frequency: three times daily
- Health during acclimation (any mortality observed): no mortality

Test type:

flow-through

Water media type:

saltwater

Limit test:

yes

Total exposure duration:

96 h

Test temperature:

19 to 22 °C

pH:

7.4 to 8.0

Dissolved oxygen:

7.0 to 7.3 mg/L

Salinity:

32 to 34‰

Nominal and measured concentrations:

control, 100 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: glass aquaria measuring 49.5 x 25.5 x 29 cm equipped with an overflow side drain positioned at a height of 14 cm.
- Aeration: no
- Type of flow-through (e.g. peristaltic or proportional diluter): Circulation was provided by pumping the exposure solution with a magnetic drive pump from one end of the aquarium and returning it to the opposite end.
- Renewal rate of test solution (frequency/flow rate): 1.75 L/minute or about 5.25 L per oyster per hour
- No. of organisms per vessel: 20
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Seawater was pumped from the Cape Cod Canal, Bourne, Massachusetts from about 1 to 4 meters offshore at a depth of approximately 0.5 meters. The seawater was transferred by pump and pipe to the laboratory where it was filtered and analysed.
- Metals/Pesticides: Representative samples of the dilution water source were analysed periodically for the presence of pesticides, PCBs and toxic metals by GeoLabs, Inc., Braintree, Massachusetts; however, none of these compounds were detected in any of the water samples analysed.
- Salinity: 32 to 34‰
- Intervals of water quality measurement: pH and salinity were checked daily during test

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light and 8 hours darkness

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality, shell growth and visible abnormalities (such as excessive mucous production or a failure to siphon and feed, as evidenced by a lack of fecal and pseudofecal production)

VEHICLE CONTROL PERFORMED: no vehicle was used

RANGE-FINDING STUDY
Selection of the nominal concentration for the 96-hour definitive toxicity test with Eastern oysters was based on toxicity and solubility information during preliminary testing. Eastern oysters were exposed to a nominal test substance concentration of 100 mg a.i./L and a dilution water control. Two aquaria containing 20 oysters each was established for the test concentration and the control. Following 96 hours of exposure, shell growth of 2.8 mm was observed among oysters exposed to the nominal concentration, 100 mg a.i./L, and 2.9 mm among oysters exposed to the control. Based on this and the sponsor-reported limit of solubility in seawater (<100 mg/L), a limit test was selected for the definitive testing.

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: shell growth

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: shell growth

Details on results:

- Behavioural abnormalities: none
- Mortality of control: none

Reported statistics and error estimates:

The No-Observed-Effect Concentration (NOEC) for the 96-hour exposure period was statistically determined by using a t-Test to compare the treatment and control responses (shell growth).

Mean shell growth for oysters exposed to the 100 mg a.i./L treatment level was 2.5 mm, which was 17% less than the control oyster growth (3.0 mm). However, this difference was not statistically significant, based on a t-Test of the control and treatment responses.

Validity criteria fulfilled:

not applicable

Description of key information

Freshwater:

EC50 (48 h) > 100 mg /L (nominal, Daphnia magna, OECD 202)

Marine water:

EC50 (96 h) = 1.1 mg a.s./L (mean measured,

Americamysis bahia, EPA OPP 72-3, key study)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

> 100 mg/L

Marine water invertebrates

Marine water invertebrates

Dose descriptor:

EC50

Effect concentration:

1.1 mg/L

Additional information

Three experimental studies are available on the short-term toxicity to aquatic invertebrates of the test item (M-103462-02-2, M-122206-01-1, M-122204-01-1). One study was conducted with the freshwater species Daphnia magna and two with the marine species Americamysis bahia and Crassostrea virginica, respectively. The studies were performed according to OECD guideline 202 (in case of Daphnia magna), according to EPA OPP 72-3 (in case of Americamysis bahia) and additionally according to OPPTS 850.1035 (in case of Crassostrea virginica). The nominal concentrations were verified by analytical monitoring. All studies were performed according to GLP.

The key study for freshwater (M-103462-02-2) was conducted with Daphnia magna. The test organism was exposed over a period of 48 h to nominal concentrations of 0 and 100 mg/L designed as a limit test without feeding in a static system. Juvenile daphnids (less than 24 hours old), from parents 17 days old, were exposed to nominal concentrations of 0 (control) and 100 mg/L of the test substance for a 48 hour period. All treatments were in triplicate with 10 daphnids per test vessel. Samples of the freshly prepared test solutions were taken for analysis of the test item at test start 0 hour and at test end after 48 hours (pooled replicates) were analyzed. The mean measured test item concentration was 96 mg/L over the course of the study, representing 96% of the nominal concentration. Test solutions at 0 hour were 97% of nominal concentration, and at 48 hours, they were at 94% of nominal concentration. Therefore, all toxicity values were based on the nominal concentrations of the test item during the study. No mortality or sub-lethal effects were observed in the control or 100 mg/L treatments during the study. The 48-hour EC50 was derived to be > 100 mg/L.

The key study for the marine compartment (M-122206-01-1) was conducted with Americamysis bahia. The test species was exposed over a period of 96 h to the nominal (mean measured) concentrations of 0 (control). 0.10 (0.093), 0.20 (0.20), 0.40 (0.37), 0.80 (0.75), 1.6 (1.5), 3.2 (2.9), 6.4 (6.2) and 13 (12) mg a.i./L in natural filtered seawater (pH at 7.9-8.0, salinity at 32‰) for a 96 hour period. All treatments were assayed in duplicates with 10 mysids per test vessel. In the definitive study at test termination (96 hours), 40, 50, 90, 95 and 100% mortality was observed among mysids exposed to the 0.75, 1.5, 2.9, 6.2 and 12 mg a.i./L treatment levels, respectively. Mortality of 5% was observed among mysids exposed to the 0.093, 0.20 and 0.37 mg a.i./L treatment levels. No adverse effects (e.g. lethargy) were observed among the surviving mysids at these treatment levels. ASTM (2002) recognizes the limitations of acute toxicity testing, i.e., response less than or equal to 10% is allowable in a control population and is considered within the expected range of naturally occurring variability. Therefore, the mortality (5%) observed in the lower treatment levels (0.093, 0.20 and 0.37 mg a.i./L) was not considered an adverse response from exposure to the test substance. No mortality or adverse effects were observed among mysids exposed to the control. The 96-hour LC50 value was determined by probit analysis to be 1.1 mg a.i./L (95% confidence interval: 0.84 - 1.5 mg a.i./L). The NOEC was determined to be 0.37 mg a.i./L.

The second study for the marine compartment (M-122204-01-1) was conducted with eastern oysters (Crassostrea virginica) under flow-through conditions. The test species was exposed to nominal concentrations of 0 (control) and 100 mg a.i./L (functional limit of solubility in natural seawater) for 96 h. The dilution water was natural filtered sea water with a salinity of 32‰ and a pH of 8.0. Reduction of shell deposition was used as the indicator of toxicity. The mean measured exposure concentration was 100 mg a.i./L, which averaged 100% of the nominal concentration. Growth among dilution water control oysters at test termination averaged 3.0 mm. The growth of the control group during this study was within the historical range (0.5 to 4.5 mm) compiled at the laboratory. Based on these data, the amount of shell deposition observed during this study is considered representative for this species and acceptable for establishing the relative toxicity of the test item to Eastern oysters. No mortality was observed among oysters at the treatment level tested or the control. Furthermore, no sublethal effects were observed among any of the exposed oysters. Mean shell growth for oysters exposed to the 100 mg a.i./L treatment level was 2.5 mm, which was 17% less than the control oyster growth (3.0 mm). However, this difference was not statistically significant, based on a t-test of the control and treatment responses. Since the concentration tested did not produce 50% reduction in growth, the 96-hour EC50 was empirically estimated to be greater than 100 mg a.i./L, the highest mean measured concentration tested. The No-Observed-Effect Concentration (NOEC) was statistically determined to be 100 mg a.i./L.