Fenamiphos

Toxicity to terrestrial arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to terrestrial arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Test period of 28 days

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

ISO 11267 (Inhibition of Reproduction of Collembola by Soil Pollutants)

Version / remarks:

Version 1999

Deviations:

no

Principles of method if other than guideline:

not applicable

GLP compliance:

yes (incl. QA statement)

Application method:

mixed into soil

Specific details on test material used for the study:

The test item is Fenamiphos CS 240 (Nemacur CS 240)

Analytical monitoring:

no

Details on sampling:

not applicable

Vehicle:

yes

Remarks:

deionized water

Details on preparation and application of test substrate:

Deionized water was added to the dry artificial soil to give a moisture content of about 25 % of the dry weight. The test item was introduced by dispersing the quantity of the test item (to obtain the desired test concentration) in a portion of deionised water necessary to wet the soil substrate to the required water content of 35 % of the dry weight.
The control substrate contained the corresponding amount of deionised water only.

Test organisms (species):

Folsomia candida

Animal group:

Collembola (soil-dwelling springtail)

Details on test organisms:

Origin of the test organisms: originally purchased from "Biologische Bundesanstalt" (BBA), Berlin-Dahlem in May 2000
Origin of the organisms used in the test: reared in the laboratory of the test facility under ambient laboratory conditions

Study type:

laboratory study

Limit test:

no

Total exposure duration:

28 d

Post exposure observation period:

No post exposure observation period. Observations were done at the end of the exposure period after 28 days.

Test temperature:

17 to 20°C

pH (if soil or dung study):

pH at test start: 5.9 to 6.0
pH at test end: 5.8 to 5.9

Humidity:

Water content at test start: 34.9 to 35.6% (i.e. 54 to 55% of maximum water holding capacity)
Water content at test end: 34.4 to 35.1%

Photoperiod and lighting:

source: artificial light
intensitiy: 600 lux
duration: light : dark cycle = 16 : 8 hours

Details on test conditions:

The aim of the test was to evaluate possible toxic effects of the test item on the reproduction of springtails during a test period of 28 days. After 4 weeks, the number of offspring and the mortality of adults were determined. About 24 hours before starting the test, the artificial soil was prepared minus the amount of water, which was intended to introduce the test item (for details please see point "Details on preparation and application of test substrate"). Each test item concentration and the control treatment were replicated five times.
The test was started with a synchronised breeding batch of juveniles at the age of 10 - 12 days. Ten juvenile springtails of the species Folsomia candida were transferred to each test vessel containing artificial soil to which the test item had been applied at the selected concentrations (the control did not contain the test item). The artifical soil composited of 10% sphagnum peat, 20% kaolin clay, 69.5% industrial quartz sand and 0.5% calcium carbonat.
The test organisms were fed twice during the experiment (at the beginning of the experiment and after 14 days) with 2 mg of granulated dry yeast per test vessel. Twice a week, the water content was checked and water losses were compensated if they exceeded 2 % of the initial water content. Four weeks after introducing the test organisms, the parental springtails and offspring were counted. For this purpose the test and control substrate of each replicate was poured into separate 500 - 600 ml containers and floated with water. The number of parental springtails and offspring which floated to the surface after gently stirring was determined.

Nominal and measured concentrations:

nominal concentrations of 0.313, 0.625, 1.25, 2.5, 5 and 10 mg a.s./kg soil dry weight

Reference substance (positive control):

yes

Remarks:

The reference item Betosip® (a.i. = phenmedipham 157 g/L, Batch No 02007320) is regularly tested at concentrations of 50 - 100 - 200 - 400 mg/kg d.w. of artificial soil. The most recent test for for this study was dated 23.05.01.

Duration:

28 d

Dose descriptor:

LC50

Effect conc.:

4.07 mg/kg soil dw

95% CI:

> 2.71 - < 6.84

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1.25 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

1.14 mg/kg soil dw

95% CI:

> 0.55 - < 2.04

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

reproduction

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

0.313 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

reproduction

Details on results:

- Mortality at end of exposure period: 2 %, 2 %, 8 %, 24 %, 56 % and 90 % parental mortality at test concentrations of 0.313, 0.625, 1.25, 2.5, 5 and 10 mg a.i./kg soil dw, respectively. 0 % parental mortality was observed in the control

- No. of offspring produced: average number of juveniles of 213.2, 215.2, 115.2, 84.4, 63, 24 and 8.2 for the control and test concentrations of 0.313, 0.625, 1.25, 2.5, 5 and 10 mg a.i./kg d.w of artificial soil, respectively

Results with reference substance (positive control):

In the most recent toxic reference test, the determined EC50 (reproduction) was 84 mg Betosip/kg d.w. of artificial soil. The adult collembolans died with 2 %, 2 %, 23 %, 100 % at the end of the test in the treated vessels. The number of juveniles was reduced to -1 % (negative value indicates an increase), 60 %, 74 %, 96 % in comparison to the control by the toxic standard.
The EC 50 value for the reduction of reproduction was slightly below the range of 100-150 mg product/kg d.w. of artificial soil determined in the ring test and thus showed that the test system was sensitive.

Reported statistics and error estimates:

The parental mortality results were analysed using the Bonferroni-Holm-U-test. The accepted significance level was p ≤ 0.05 (one-sided). The Dunnett test was used for statistical analysis of reproduction values (p ≤ 0.05, one-sided).
The EC50 with respect to the number of juveniles (reproduction rate) was calculated by Probit analysis according to the maximum likelihood method (Finney 1971). The goodness-of-fit of the model was evaluated by Pearson's chi-square test). The calculation of statistical significance and the EC50 were performed using the computer program EASY ASSAY (Multiple Testing and Critical Values) by Ratte (1998).

Validity criteria fulfilled:

yes

Remarks:

The validity criteria for the control group were accomplished: • adult mortality: ≤ 20 % (observed: 0 %) • minimum number of instars/vessel: 100 (observed: average of 213.2/vessel) • coefficient of variation of juvenile number: ≤ 30 % (observed: 17 %)

Conclusions:

After 28 days of exposure of Folsomia candida to the test item in artificical soil, the NOEC for the parameter adult mortality was 1.25 mg a.i./kg soil dw. The LC50 (adult mortality) was 4.07 mg a.i./kg soil dw (95% CI: 2.71 to 6.84 mg test item/kg soil dw).
The NOEC for reproduction was 0.313 mg a.i./kg soil dw and the EC50 for the number of juveniles was 1.14 mg a.i./kg soil dw (95% CI: 0.55 to 2.04 mg a.i./kg soil dw).
The reference item showed results in the expected range and thus the sensitivity of the test system. All validity criteria were met. The study is considered acceptable.

Executive summary:

The aim of the test was to evaluate possible toxic effects of the test item on the reproduction of springtails during a test period of 28 days at nominal concentrations of 0.313, 0.625, 1.25, 2.5, 5 and 10 mg a.i./kg soil dw by mixing the test item into the artificial soil. Five replicates per treatment group each includes 10 parental springtails were used.

After 28 days of exposure of Folsomia candida to the test item in artificical soil, the NOEC for the parameter adult mortality was 1.25 mg a.i./kg soil dw. The LC50 (adult mortality) was 4.07 mg a.i./kg soil dw (95% CI: 2.71 to 6.84 mg a.i./kg soil dw).
The NOEC for reproduction was 0.313 mg a.i./kg soil dw and the EC50 for the number of juveniles was 1.14 mg a.i./kg soil dw (95% CI: 0.55 to 2.04 mg a.i./kg soil dw).
The reference item showed results in the expected range and thus the sensitivity of the test system. All validity criteria were met. The study is considered acceptable.

Description of key information

After 28 days of exposure of Folsomia candida to the test item in artificical soil, the NOEC for the parameter adult mortality was 1.25 mg a.i./kg soil dw. The NOEC for reproduction was 0.313 mg a.i./kg soil dw.
The reference item showed results in the expected range and thus the sensitivity of the test system. All validity criteria were met. The study is considered acceptable.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil dwelling arthropods:

0.313 mg/kg soil dw

Additional information

The aim of the test was to evaluate possible toxic effects of the test item on the reproduction of springtails during a test period of 28 days at nominal concentrations of 0.313, 0.625, 1.25, 2.5, 5 and 10 mg a.i./kg soil dw by mixing the test item into the artificial soil. Five replicates per treatment group each includes 10 parental springtails were used.

After 28 days of exposure of Folsomia candida to the test item in artificical soil, the NOEC for the parameter adult mortality was 1.25 mg a.i./kg soil dw. The LC50 (adult mortality) was 4.07 mg a.i./kg soil dw (95% CI: 2.71 to 6.84 mg a.i./kg soil dw.
The NOEC for reproduction was 0.313 mg a.i./kg soil dw and the EC50 for the number of juveniles was 1.14 mg a.i./kg soil dw (95% CI: 0.55 to 2.04 mg a.i./kg soil dw).
The reference item showed results in the expected range and thus the sensitivity of the test system. All validity criteria were met:

• adult mortality: ≤ 20 % (observed: 0 %)
• minimum number of instars/vessel: 100 (observed: average of 213.2/vessel)
• coefficient of variation of juvenile number: ≤ 30 % (observed: 17 %)

The study is considered acceptable.