thiamethoxam (ISO); 3-(2-chloro-thiazol-5-ylmethyl)-5-methyl[1,3,5]oxadiazinan-4-ylidene-N-nitroamine

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

5 Sep 2014 to 8 Oct 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 210 (Fish, Early-Life Stage Toxicity Test)

Version / remarks:

2013 (draft)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1400 (Fish Early-life Stage Toxicity Test)

Version / remarks:

1996 (public draft)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The test concentrations were verified by chemical analysis at days 0 (experimental initiation), 6, 12, 18, 25 and 33 (experimental termination)

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Prior to exposure initiation, an FMI Pump was calibrated to deliver 0.0083 L/cycle of the 2000 mg/L diluter stock solution into the diluter system's chemical mixing chamber, which also received 1.66 L of dilution water per cycle. The solution in the mixing chamber was equivalent to that of the highest nominal test concentration and was proportionally diluted (40%) to produce the remaining nominal test concentrations. A set of negative control aquaria were also established which contained the same dilution water and were maintained under the same conditions as the treatment aquaria, but contained no test substance.

Test organisms (species):

Cyprinodon variegatus

Details on test organisms:

TEST ORGANISM
- Common name: Sheepshead minnow
- Source: Continuous laboratory cultures

POST-HATCH FEEDING
- Start date: On day 6 (day 1 post-hatch)
- Type/source of feed: Brine shrimp nauplii (Artemia salina)
- Amount given: Not reported
- Frequency of feeding: Three times daily. Fish were not fed during the 24 hours prior to study termination.

Test type:

flow-through

Water media type:

saltwater

Limit test:

no

Total exposure duration:

33 d

Remarks on exposure duration:

5 days embryonal period and 28 days post-hatch period

Test temperature:

25.4 - 26.2 °C

pH:

7.3 - 8.3

Dissolved oxygen:

5.02 - 7.30 mg O2/L; 69.5 - 101% saturation

Salinity:

20 - 22 %

Nominal and measured concentrations:

- Nominal concentrations: 0 (control), 0.10, 0.26, 0.64, 1.6, 4.0 and 10 mg/L
- Measured concentrations: An overview of the analytical results is presented in 'Any other information on materials and methods incl. tables'.

Details on test conditions:

TEST SYSTEM
At the start of the exposure, 30 embryos (approximately 24 hours old) were allocated to each replicate aquaria. The exposure was conducted in a temperature-controlled water bath. At the completion of hatch (day 5), the 28-day post-hatch larval exposure was initiated with 20 impartially selected larvae from each incubation cup.
- Test vessel: Glass aquaria with silicone sealing measuring (30 x 14.5 x 20 cm) with a 12.5 cm high side drain that maintained a constant exposure solution volume of approximately 5.5 L.
- Aeration: Not reported
- Type of flow-through: The flow-through exposure was conducted using an exposure system consisting of an intermittent-flow proportional diluter, a temperature-controlled water bath and a set of 28 exposure aquaria. Flow-splitting cells were employed to equally distribute the solutions to the replicate vessels at a rate of 250 mL of control and test solution per vessel per cycle. The diluter delivered the control and test solutions to the exposure aquaria (39 L/aquarium/day) at a rate sufficient to provide approximately seven aquarium volumes per 24 hour period, with a 90% replacement time of approximately seven hours.
- No. of fertilized embryos per vessel: 30 embryos (approximately 24 hours old) were allocated to each replicate aquaria, 20 were impartially selected for the 28-d post-hatch larval exposure.
- No. of vessels per concentration: 4
- No. of vessels per control: 4
- Biomass loading rate: Not reported

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dilute, filtered, natural seawater
- Culture medium different from test medium: Same
- Intervals of water quality measurement: At exposure initiation, dissolved oxygen concentration, pH, temperature and salinity were measured in each replicate aquarium. For the remainder of the exposure, one alternating replicate of each concentration and control was measured for these parameters.

OTHER TEST CONDITIONS
- Adjustment of pH: Not reported
- Photoperiod: 16 hours fluorescent light and 8 hours dark; 30-minute transition period
- Light intensity: 540 to 810 lux

EFFECT PARAMETERS MEASURED: larval survival, behaviour and appearance.
Daily observations were made for hatching, larval survival, behaviour and appearance. At 28 days post-hatch, the exposure was terminated. The surviving larvae in each exposure aquarium were euthanized, counted to determine larval survival and then measured individually to determine total length and wet weight. Larvae were then dried in an oven at a temperature of approximately 100 ºC for approximately 24 hours, cooled and individually weighed to determine dry weight.

VEHICLE CONTROL PERFORMED: no

RANGE-FINDING STUDY
- Test concentrations:
- Results used to determine the conditions for the definitive study:

POST-HATCH DETAILS
- Begin of post-hatch period: Day 5
- No. of hatched eggs (alevins)/treatment released to the test chamber: 20
- Release of alevins from incubation cups to test chamber on day no.: 5

FERTILIZATION SUCCESS STUDY
- Number of eggs used:
- Removal of eggs to check the embryonic development on day no.:

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1.7 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

length

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

4.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

length

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

9.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

> 9.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

- Mortality/survival at embryo and larval stages: Throughout the 28-day post-hatch period, mean larval survival was not significantly affected in all treatments relative to the control group.
- Days to hatch and numbers hatched: Completion of hatch was on day 5.
- Hatching succes: Mean embryo hatching success was similar in all treatments (87 - 93 %).
- Data for length and weight of surviving fish: Mean total length was not altered up to 1.7 mg/L. In the two highest treatments (4.1 mg/L and 9.9 mg/L), a decrease in length was observed. No significant effects on mean wet and dry weight were recorded.
- Type of and number with morphological abnormalities: Aside from the decrease in total length, no abnormalities were reported.
An overview of the results is presented in 'Any other information on materials and methods incl. tables'.

Reported statistics and error estimates:

Percent survival, percent hatch success and percent live, normal larvae at hatch were analysed using Fisher’s Exact with Bonferroni-Holm Adjustment Test to establish exposure level effects. Total length and wet weight data were evaluated using Dunnett Multiple Comparison Test, a parametric procedure, to establish exposure level effects. Dry weight also exhibited a non-monotonic response but did not meet the assumptions for normal distribution and equality of variance; therefore, dry weight was analyzed using Dunn/Bonferroni-Holm’s Test, a non-parametric procedure.

Table:Effects of the test substance onCyprinodon variegatus

Mean Measured Concentration (mg/L)	Mean Embryo Hatching Success (%)*	Mean Live, Normal Larvae at Hatch (%)	Larvae (28 days post-hatch)
			Mean Larval Survival (%)	Mean Total Length (mm)**	MeanWetWeight(g)**	Mean Dry Weight (g)**
Control	87	98	99	20.1 (0.61)	0.1161 (0.0187)	0.0249 (0.0018)
0.090	93	99	99	19.6 (0.61)	0.1075 (0.0074)	0.0237 (0.0014)
0.23	89	99	98	19.5 (0.37)	0.1087 (0.0051)	0.0251 (0.0014)
0.74	91	100	96	19.6 (0.20)	0.1098 (0.0065)	0.0253 (0.0014)
1.7	92	100	96	19.7 (0.20)	0.1136 (0.0020)	0.0264 (0.0008)
4.1	92	99	99	19.0 (0.53)***	0.1048 (0.0025)	0.0280 (0.0068)
9.9	88	100	99	18.4 (0.53)***	0.1120 (0.0074)	0.0252 (0.0016)
Endpoint Summary (µg/L)
LC50/EC50****	>9.9	>9.9	>9.9	>9.9	>9.9	>9.9
NOEC	9.9	9.9	9.9	1.7	9.9	9.9
LOEC	>9.9	>9.9	>9.9	4.1	>9.9	>9.9

* Values presented represent hatching success at the completion of hatch (test day 5).

** Standard deviation for each replicate is presented in parentheses.

*** Significantly reduced compared to the control, based on Dunnett’s Multiple Comparison Test.

**** The conditions in the protocol for determining an ECx were not satisfied (i.e., the test concentrations will bracket the ECx and the ECx comes from linear interpolation rather than extrapolation) therefore, the NOEC approach was used.

Validity criteria fulfilled:

yes

Remarks:

See 'Any other information on materials and methods'.

Conclusions:

The 28-day NOEC was determined to be 1.7 mg/L and 28-d LOEC value was determined to be 4.1 mg/L for sheepshead minnow exposed to the substance (mean measured values).

Executive summary:

The chronic toxicity of the substance to marine water fish was determined in a GLP-compliant study according to OECD 210 (fish early-life stage toxicity test). In this study, groups of sheepshead minnow (Cyprinodon variegatus) embryos and larvae (80 larvae per treatment) were exposed to nominal concentrations of 0 (control), 0.10, 0.26, 0.64, 1.6, 4.0 and 10 mg/L for 33 days (5 days pre-hatch; 28-days post hatch) under flow-through conditions. Analytical confirmation of nominal test concentrations showed that all test concentrations remained well within ±20% of nominal concentrations throughout the test (<LOQ, 0.090, 0.23, 0.74, 1.7, 4.1 and 9.9 mg/L mean measured). Following 28 days post-hatch exposure, data for embryo hatching success, the percent of live, normal larvae at hatch, larval survival, total length, wet weight and dry weight were evaluated. Based on mean measured concentrations and mean total length (determined to be the most sensitive endpoint), the 28-day NOEC was determined to be 1.7 mg/L and 28-d LOEC value was determined to be 4.1 mg/L for sheepshead minnow exposed to the substance.

Reference 2

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-4 (Fish Early Life-Stage and Aquatic Invertebrate Life-Cycle Studies)

Version / remarks:

1982

Qualifier:

according to guideline

Guideline:

other: ASTM Standard E1241-88 Standard Guide for Conducting Early Life-Stage Toxicity Tests with fish

Version / remarks:

1988

Qualifier:

according to guideline

Guideline:

other: U.S. Environmental Protection Agency Standard Evaluation Procedure, Fish Early Life-Stage Test

Version / remarks:

1986

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Prior to test initiation, samples were collected from one replicate test chamber from the control and each treatment level to evaluate diluter performance. During the definitive test, water samples were collected from alternate replicates of the control and each treatment group at test initiation and termination and weekly during the test to measure concentrations of the test substance. Additional samples were collected when a power failure occurred on Day 16. Water samples were also collected on Day 17 to document that nominal concentrations were restored. All samples were collected in glass scintillation vials and acidified with 10% phosphoric acid. The samples were analysed immediately or stored for one day prior to analysis.

Vehicle:

no

Details on test solutions:

One stock solution was prepared for each of the five concentrations tested. A primary stock was prepared by dissolving the test substance in well water at a concentration of 2.00 mg a.i./mL. The primary stock was stirred with an overhead electric mixer for approximately 2 hours to aid in solubilization of the test substance. Aliquots of the primary stock solution were proportionally diluted with well water to prepare four additional stock solutions at concentrations of 1.00; 0.500, 0.250 and 0.125 mg a.i./mL. Stock solutions were prepared nine times during the test period. The five stocks were injected into the diluter mixing chambers (at a rate of 125 mL/minute) where they were mixed with well water (at a rate of 125 mL/minute) to achieve the desired test concentrations. The resultant test concentrations were adjusted for the purity of the active ingredient in the test substance (99.2%).

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Source: Unfertilized eggs and sperm were obtained from Mt. Lassen Trout Farm, Red Bluff, California. Gametes from three females and four males were used in the test. The eggs were fertilized at Wildlife International Ltd. and the test initiated within 4 hours of fertilization.
- Feeding: Larval fish were fed salmon-starter mash supplied by Zeigler Brothers, Inc. Gardners, Pennsylvania, beginning on Day 45 (the end of the swim-up stage). Food was provided three times daily during the first 7 days. Thereafter they were fed three times per day on weekdays and at least two times daily on weekends and holidays. The fish were not fed approximately 48 hours prior to the termination of the test to allow for clearance of the digestive tracts before weights were measured. To ensure that the feeding rate per fish remained constant, rations were adjusted each week to account for losses due to mortality. Excess feed was siphoned from the bottoms of the test chambers, as needed.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

88 d

Remarks on exposure duration:

Includes a 28-day hatching period and a 60-day post-hatch period.

Hardness:

124 - 136 mg/L as CaCO3

Test temperature:

11.6 - 12.3 °C

pH:

8.3 - 8.5

Dissolved oxygen:

- Test start: 10.0 - 10.1 mg O2/L
- Test end: 7.6 - 7.8 mg O2/L

Conductivity:

270 - 280 µmhos/cm

Nominal and measured concentrations:

- Nominal concentrations: 0 (control), 1.3, 2.5, 5.0, 10 and 20 mg a.i./L
- Mean measured concentrations:

Details on test conditions:

TEST SYSTEM
- Embryo cups: The embryo incubation cups were suspended in the water column of each test chamber and attached to a rocker arm. The reciprocating motion of the rocker arm (approximately 2 rpm) facilitated circulation of test water around the embryos during incubation. The incubation cups were constructed from glass cylinders approximately 50 mm in diameter with 425 μm nylon screen mesh attached to the bottom with silicone sealant.
- Test vessel: 9-L glass aquaria; the depth of the test water in a representative chamber was approximately 17 cm.
- Fill volume: 7 L
- Type of flow-through: A continuous-flow diluter was used to deliver each concentration of the test substance and a negative (dilution water) control. Peristaltic pumps (Cole-Parmer Instrument Company) were used to deliver the five test substance stock solutions into mixing chambers assigned to each treatment group. The stock solutions were mixed with dilution water in the mixing chambers in order to obtain the desired test concentrations. The flow of dilution water to the mixing chambers was controlled by rotameters. The flow oftest water from each mixing chamber was split and allowed to flow into four replicate test chambers. The proportion of test water that was split into each replicate was checked prior to the test and at approximately weekly intervals thereafter to ensure that flow rates varied by no more than ±10% of the mean for the four replicates. The diluter was adjusted so that each test chamber received approximately 6 volume additions of test water every 24 hours. The stock solution delivery pumps and the dilution water rotameters were calibrated before the test and at weekly intervals during the test. The general operation of the diluter was checked visually at least two times per day during the test and once at the end of the test.
- No. of fertilized embryos per embryo cup: 15. Thirty embryos were held in each of our extra incubation cups in dilution water and were sacrificed on Day 10 to evaluate the fertilization success.
- No. cups per test vessel: 2
- No. of vessels per concentration: 4
- No. of vessels per control: 4
- Biomass loading rate: Biomass loading (the total wet weight of the fish in the negative control per liter of test water) at the end of the test was measured in one negative control replicate and was calculated to be 0.42 g fish/L/day of test water that passed through the test chamber during a 24-hour period. Instantaneous loading was 2.7 g fish/L of test water in the test chamber at any given time.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The water used for holding and testing was freshwater obtained from a well approximately 40 meters deep located on the Wildlife International Ltd. site. The well water is characterized as moderately-hard water. The well water was passed through a sand filter to remove particles greater than approximately 25 μm, and pumped into a 37,800-L storage tank and aerated with spray nozzles. The dilution water again was filtered (0.45 μm) to remove microorganisms and particles. Prior to use, a UV sterilizer was provided as an additional method of water treatment.
- Alkalinity: 174 – 182 mg/L as CaCO3
- Culture medium different from test medium: Same

OTHER TEST CONDITIONS
- Photoperiod: A photoperiod of 16 hours of light and 8 hours of darkness were controlled with an automatic timer. A 30-minute transition period of low light intensity was provided when lights went on and off to avoid sudden changes in lightning.
- Light intensity: Light intensity was approximately 113 lux at the surface of the water. Lightning was provided by fluorescent tubes that emitted wavelengths similar to sunlight (Colortone® 50).

WATER QUALITY MEASUREMENTS
- Temperature was measured in each test camber at the beginning and the end of the test and at weekly intervals during the test using a hand-held thermometer. Temperature also was measured continuously in one negative control replicate using a Fulscope ER/C Recorder. The target test temperature during the study was 12 ± 1°C.
- pH: Measurements of pH were made on water samples collected from alternate replicates of each treatment and the control group at the beginning and end of the test and at weekly intervals during the test. Measurements of pH were made using a Fisher Accumet Model 915 pH meter.
- Dissolved oxygen concentrations were measured daily in alternate replicates of each treatment and the control group during the first 7 days of the test at weekly intervals during the test, and at test termination. Dissolved oxygen was measured using a Yellow Springs Instrument Model 51B dissolved oxygen meter.
- Hardness alkalinity and specific conductance: Hardness alkalinity and specific conductance: were measured in alternate replicates in the negative control and one treatment level (5.0 mg a.i./L, nominal concentration) at the beginning of the test, once a week during the test, and at test termination. Specific conductance was measured using a Yellow Springs Instrument Model 33 Salinity-Conductivity Temperature meter. Hardness and alkalinity measurements were made by titration.

EFFECT PARAMETERS MEASURED: clinical signs, hatching success, time to hatch, time to swim-up of the larvae, post-hatch survival, post-hatch growth, total length, wet and dry weight of the juvenile fish.
Daily observations were made during the embryo incubation and post-hatch exposure periods to evaluate the numbers if individuals exhibiting clinical signs of toxicity or abnormal behaviour. Hatching success, time to hatch, time to swim-up of the larvae and post-hatch survival were evaluated from these observations. Hatching success was calculated as the percentage of viable eggs that hatched successfully. Post-hatch percent survival was calculated for two intervals, prior to and after thinning. Post-hatch survival prior to thinning was the number of larvae alive at thinning on Day 17 post-hatch divided by the number of larvae successfully hatched. Survival at the end of the test was the number of juvenile fish alive on Day 60 post-hatch divided by the number of larvae after thinning. Post-hatch growth of the rainbow trout were measured on Day 31 post-hatch and at the conclusion of the test. Fish total lengths were measured at 31 days post-hatch by the photometric method of Martin using the SIGMA SCAN™ scientific measurement system. At test termination system and wet and dry weights were measured using an analytical balance.

Reference substance (positive control):

no

Key result

Duration:

88 d

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: There were no apparent treatment-related effects on all measured endpoints

Remarks:

See 'Any other information on results incl. tables'

Details on results:

- Percent fertilization: Mean percent fertilization was 90% in the fertilization control cups 1 and 2 in both replicate A and B.
- Hatching success: Rainbow trout embryos began hatching on Day 27, and all surviving embryos in the control and treatment groups hatched by Day 28. There was no apparent difference among the experimental groups in the time required for hatching. Hatching success in the negative control group averaged 77%. Hatching percentage in the 1.3, 2.5, 5.1, 10 and 20 mg a.i./L treatment groups were 73, 74, 75, 76 and 73%, respectively. When compared to the negative control group, differences were slight and neither dose-responsive or statistically different (P>0.05).
- Time to swim-up: Swim-up was first noted on Day 14 post-hatch, and by Day 17, greater than 90% of the negative control group had attained swim-up. There was no statistically significant difference in the proportion of swim-up period (Day 14 through Day 17) in comparison to the negative control.
- Larvae and Fry survival: Survival in the negative control group before thinning (the period between Day 1 post-hatch to thinning) was 98%. Survival in the 1.3, 2.5, 5.1, 10 and 20 mg a.i./L treatment groups prior to thinning was 99, 99, 100, 100 and 100%, respectively. There were no statistically significant differences among those survival percentages when compared to the negative control group.
Survival in the negative control group from thinning to the end of the test was 100%. Survival in the 1.3, 2.5, 5.1, 10 and 20 mg a.i./L treatment groups during this period was 100, 100, 98, 100 and 100%, respectively. There were no statistically significant differences among those survival percentages when compared to the negative control group.
- Biological observations: All organisms were observed daily to evaluate the numbers of mortalities and the numbers of individuals showing sublethal signs of toxicity. All surviving fish in the negative control group appeared normal and healthy throughout the test. All surviving organisms appeared normal and healthy in the 1.3, 2.5, 5.1, 10 and 20 mg a.i./L treatment levels and there were no apparent treatment-related sublethal signs of toxicity at these concentrations.
- Growth: When compared to the negative control, no statistically significant effects on growth at Day 31 post-hatch or at test termination existed in the test substance treatment groups. Any differences in mean total lengths, mean wet weights or mean dry weights were slight and were neither dose-responsive nor considered treatment-related.

Reported statistics and error estimates:

Test endpoints that were analyzed statistically included: hatching success, time to swim-up, percent survival, total length on Day 31, and total length, wet and dry weight of the juvenile fish at test termination. Hatching success, time to swim-up and percent survival were analyses using 2 x 2 contingency tables and the chi-squared test to identify treatment groups that showed a statistically significant difference (P≤0.05) from the negative control group. Length and weight data were evaluated for normality using the chi-square test and for homogeneity of variance using Bartlett’s test. When data failed the tests for normality or homogeneity, data transformations were performed to correct the condition. For data which passed both homogeneity of variance test and normality tests, Dunnett’s Multiple comparison test was used to evaluate differences between treatment and control means. When the conditions of normality and homogeneity of variance were not met and data transformation did not correct the conditions, the Kruskal-Wallis test was used. The results of statistical analyses were used to aid in the determination of the NOEC and LOEC. All statistical tests were performed on a personal computer using TOXSTAT®3.2 or SPSS/PC Version 2.0 statistical software.

Validity criteria fulfilled:

not specified

Conclusions:

There were no apparent treatment-related effects on time to hatch, hatching success, time to reach the swim-up stage of development, larvae survival, fry survival and growth of rainbow trout (Oncorhynchus mykiss) exposed to the test substance. For this study, the 88-d NOEC was 20 mg a.i./L, the highest concentration tested, while the 88-d LOEC and MATC were estimated to be greater than 20 mg a.i./L.

Executive summary:

The long-term toxicity of the test substance to fish was examined in an early life-stage toxicity study according to the FIFRA 72-4 guideline and in compliance with GLP criteria. In this study groups of Rainbow Trout (Oncorhynchus mykiss) were exposed to nominal test concentrations of 0 (control), 1.3, 2.5, 5.0, 10 and 20 mg a.i./L for 88 days (which included a 28-day hatching period and a 60-day post-hatch

period) under flow-through conditions. Nominal test concentrations were analytically verified and determined to remain well within ± 20% of nominal. Embryo survival (hatching success), time to hatch, time to swim-up of the larvae, and the post-hatch growth and survivalwere measured for the rainbow trout in each treatment and the control group. Observations were made during the embryo incubation and post-hatch periods to assess the effects of the test substance on these parameters. Fish lengths were measured at 31 days post-hatch and at test termination. The wet weight and dry weight of each surviving fish were measured at test termination. There were no apparent differences among the experimental groups in the time required for hatching. Hatching success in the negative control group averaged 77%. Hatching percentages in the 1.3, 2.5, 5.1, 10 and 20 mg a.i./L treatment groups were 73, 74, 75, 76 and 73%, respectively. Furthermore, there were no apparent treatment-related effects on time to hatch, time to reach the swim-up stage of development, larvae survival, fiy survival and growth of the organisms in the control group or any of the test substance treatment groups throughout the study. Based on these findings, the 88-d NOEC was determined to be 20 mg a.i./L.

Description of key information

All available data were assessed and the studies representing the worst-case effects were included as key or weight-of-evidence studies. Other studies are included as supporting information. The key studies are considered to be worst-case and were selected for the CSA.

The 28-day NOEC was determined to be 1.7 mg/L and 28-d LOEC value was determined to be 4.1 mg/L for the marine species sheepshead minnow exposed to the substance. The 88-day NOEC was determined to be 20 mg/L for the freshwater species rainbow trout exposed to the substance.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

NOEC

Effect concentration:

20 mg/L

Marine water fish

Marine water fish

Dose descriptor:

NOEC

Effect concentration:

1.7 mg/L

Additional information

Information on the long-term toxicity of the substance to freshwater and saltwater fish is available from a number of GLP studies performed to the relevant guidelines (OECD TG 210, FIFRA 72-4). Rainbow trout (Oncorhynchus mykiss) were exposed under flow-through conditions to a series of test substance concentrations over a period of 88 days in an early life-stage toxicity test. No adverse effects on hatching percentages, time to hatch, larvae survival and development, fish survival and growth were observed up to the highest test concentration. The 88-day NOEC in this study was 20 mg/L. The long-term toxicity of the substance to the marine fish species sheepshead minnow (Cyprinodon variegatus) was studied under flow-through conditions. Embryos and larvae were exposed to a range of test concentrations for a period of 33 days. No adverse effects on hatching success, larval survival and mean larval weight were observed. However, the mean total length of larvae was reduced at the two highest test concentration. The 28-day NOEC was thus 1.7 mg/L, and the 28-day LOEC was 4.1 mg/L.