picoxystrobin (ISO); methyl (2E)-3-methoxy-2-[2-({[6-(trifluoromethyl)pyridin-2-yl]oxy}methyl)phenyl]acrylate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-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:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline Number 202, Part II - Reproduction Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EPA 540/9-86-141, Daphnia magna Life Cycle Toxicity Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

Aqueous samples of the test substance were extracted into hexane. The samples were quantified against standards of the test substance in hexane, prepared from an acetone stock.

Vehicle:

yes

Remarks:

Dimethylformamide (DMF)

Details on test solutions:

Primary stock of 100 and 400 mg/L were prepared on Day 0 by dissolving 0.01 and 0.04 g of test substance, respectively in 100 ml volumes of an organic solvent, DMF. Both stock solutions were observed to be clear and colorless. These stock solutions were used for the remainder of study.

On each test solution renewal day, the nominal 1.0, 2.0 and 4.0 µg/L test solutions were prepared by the addition of appropriate aliquots of the 100 mg/L stock solution to dilution water. The 8.0, 16 and 32 µg/L test solutions were similarly prepared by the addition of appropriate aliquots of the 400 mg/L stock solution to dilution water. All additions were carried out using a microlitre syringe, Whilst stirring with a magnetic follower.

Equalizing additions of DMF were made in the same way such that all test substance concentrations and the solvent control contained 0.1 ml of DMF per litre. The dilution water control consisted of dilution water only. The test solutions were observed to be clear and colorless.

Old and new solutions: The test solutions were prepared on the day of use and were renewed every Monday, Wednesday and Friday. On each renewal day, new test solutions were dispensed to a second set of test vessels. The surviving P0 generation were transferred to the new solutions, using a wide bore pipette, minimising transfer of medium. The old solutions were sampled, as appropriate, for physical and chemical analyses and the F1 generation removed from each vessel and counted.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Waterflea
- Source: Brixham Environmental Laboratory
- Age of parental stock: 19 ± 1 days
- Food type: Cultured algae (Chlorella vulgaris) and commercially available microencapsulated diet, Frippak Booster
- Amount: 3.0 x 10e7 algal cells and 57 µg of Frippak Booster as a suspension per day
- Frequency: Daily

ACCLIMATION
- Type of food: Algae (Chlorella vulgaris) and commercially available microencapsulated diet, Frippak Booster
- Acclimation conditions: Temperature of 20 ± 2°C, photoperiod of 16 hours light: 8 hours dark

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

New solutions: 240.8 ± 0.40 mg/L as CaCO3
Old solutions: 243.8 ± 1.66 mg/L as CaCO3

Test temperature:

20 ± 1°C

pH:

New solutions: 7.81 to 8.16
Old solutions: 7.53 to 8.30

Dissolved oxygen:

Dilution water (new): 9.0 to 9.2 mg/L
Test solutions (old): 6.0 to 9.1 mg/L

Conductivity:

New solutions: 605 ± 11.5 µS/cm at 25°C
Old solutions: 622 ± 9.54 µS/cm at 25°C

Nominal and measured concentrations:

Nominal: 1.0, 2.0, 4.0, 8.0, 16, and 32 µg/L
Measured: 1.0, 2.0, 4.0, 8.2, 16, and 32 µg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Borosilicate glass beakers
- Type: Closed
- Aeration: Not aerated
- Renewal rate of test solution: Thrice weekly
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10
- No. of vessels per vehicle control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Preparation of dilution water: The reconstituted water medium, Elendt M4 medium (two batches of dilution water were used in this study)
- Dissolved non-purgeable organic carbon: 7.4 and 7.5 mg/L
- Metals: Cd: <1 µg/L, Cu: 1 and 2 µg/L, Co: <1 µg/L, Fe: 7 and 9 µg/L, Mn: 17 and 48 µg/L, Ni: <1 µg/L, Zn: 1 and 3 µg/L
- Alkalinity as CaCO3: 44.0 and 48.4 mg/L
- Conductivity at 25°C: 632 and 651 µS/cm
- pH: 7.96 and 8.05
- Total hardness as CaCO3: 237 and 241 mg/L

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light: 8 hours dark with 20 minute dawn and dusk transition period
- Light intensity: 608 lux

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

LC50

Effect conc.:

26 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 95% CI: 20-44 µg/L

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

8 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

16 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

other: MATC

Effect conc.:

11 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

16 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: length

Key result

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

32 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: length

Duration:

21 d

Dose descriptor:

other: MATC

Effect conc.:

23 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: length

Details on results:

There were no mortalities in the dilution water control or the nominal 2.0 and 8.0 µg/L concentrations after 21 days. The single mortality observed in the solvent control after 18 days was considered to be a random death.

A single mortality was also observed in both the 1.0 and 4.0 µg/L nominal test concentrations after 4 and 17 days, respectively. Both deaths were considered to be random mortalities as no other deaths were observed in these or the nominal 2.0 and 8.0 µg/L concentrations. The daphnid in the 1.0 µg/L concentration was observed to be unhealthy (small, pale or immobile) before dying. At the nominal concentration of 16 µg/L, there was 10% mortality after 4 days and remained so until the end of the study. At the nominal concentration of 32 µg/L there was 70% mortality after 21 days.

Validity criteria fulfilled:

yes

Conclusions:

21 day LC50: 26 µg/L (mortality)
21 day NOEC: 8.0 µg/L (reproduction)
21 day LOEC: 16 µg/L (reproduction)

Executive summary:

A study on the chronic toxicity of the test substance to Daphnia magna was conducted according to OECD guideline 202. The daphnids were exposed to dilution water control, solvent control and nominal concentrations of 1.0, 2.0, 4.0, 8.0, 16, and 32 µg/L. The daphnids were observed for mortalities and symptoms of toxicity.

There were no mortalities in the dilution water control or at 2.0 and 8.0 µg/L concentrations after 21 days. The single mortality observed in the solvent control after 18 days was considered to be a random death. A single mortality was also observed at 1.0 and 4.0 µg/L after 4 and 17 days, respectively. Both deaths were considered to be random mortalities as no other deaths were observed in these at 2.0 and 8.0 µg/L. The daphnid at 1.0 µg/L was observed to be unhealthy (small, pale or immobile) before dying. At 16 µg/L, there was 10% mortality after 4 days and remained so until the end of the study. At 32 µg/L there was 70% mortality after 21 days. Based on these observations, the 21 d LC50 value was 26 µg/L with 95% confidence intervals of 20-44 µg/L.

Reproduction at 32 µg/L was considered to be significantly reduced. There was a significant decrease (p = 0.05) in the numbers of offspring (F1) produced at 16 µg/L compared to the pooled control. At concentrations up to and including 8 µg/L, reproduction was not significantly reduced. Based on these observations, the 21 d NOEC value for reproduction was 8.0 µg/L and LOEC was 16 µg/L. Maximum allowable toxicant concentration for reproduction was 11 µg/L.

There was a significant decrease (p = 0.05) in the length of the P0 Daphnia at 32 µg/L compared to the pooled control. At concentrations up to and including 16 µg/L daphnid length was not significantly reduced. Based on these observations, the 21 d NOEC value for length was 16 µg/L and LOEC was 32 µg/L. Maximum allowable toxicant concentration for length was 23 µg/L.

Description of key information

21-day NOEC (Daphnia magna): 0.008 mg/L; OECD 202; Reliability = 1

28-day NOEC (Americamysis bahia): 0.004 mg/L; EPA OPPTS 850.1350; Reliability = 1

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.008 mg/L

Additional information

The NOEC from the 21-d chronic aquatic invertebrate toxicity test in Daphnia magna is 0.008 mg a.s./L, based on reproduction and development parameters. Americamysis bahia and Chironomus riparius were also tested, with NOEC values based on mean measured concentrations of 0.0036 and 0.0084 mg a.s./L, respectivley. Marine and freshwater species showed similar toxicity. The chronic NOEC for aquatic invertebrates are less than 0.1 mg a.s./L.