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Toxicity to terrestrial arthropods

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Reference
Endpoint:
toxicity to terrestrial arthropods: long-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30 September 1996 - 20 August 1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted according to GLP requirements. Study carried out according to ISO/CD 11267.
Qualifier:
according to
Guideline:
ISO 11267 (Inhibition of Reproduction of Collembola by Soil Pollutants)
GLP compliance:
yes
Application method:
soil
Analytical monitoring:
no
Vehicle:
yes
Details on preparation and application of test substrate:
AHTN was dissolved in acetone. The AHTN solution was mixed with quarz sand. The acetone was evaporated and the quarz sand (containing AHTN) was mixed with the artificial soil.
Test organisms (species):
Folsomia candida
Animal group:
Collembola (soil-dwelling springtail)
Details on test organisms:
The study was performed with 10 to 12 day old juvenile springtails of the species Folsomia candida (Willem) bred under standardized conditions by IBACON. The springtails were placed in a defined artificial soil containing AHTN at six different concentrations. The number of offspring and the number of surviving adults after 28 days of exposure were determined.
At the beginning of the test about 2 mg of granulated dry yeast was spread over the soil surface of each test container. Food consumption was checked during the test period and yeast was added when necessary.
Study type:
laboratory study
Limit test:
no
Total exposure duration:
4 wk
Test temperature:
Temperature was recorded. The test containers were exposed at 17 - 25 °C instead of 20 ± 2 °C. Deviations are slight and of no significant effect on the development or fertility of the springtails. This is within the validity criteria of the study guidelines and hence is not considered to be significant.
pH (if soil or dung study):
At the beginning of the study, the pH of the artificial soil was between 6.1 and 6.4. At the end, the pH of the artificial soil was in a range between 5.7 and 6.0.
Humidity:
The water content of artificial soil was adjusted to 40 - 60 % of total water holding capacity. The water content was between 33.3 % and 34.9 % (dry weight) at the start and in a range of 25.8% to 31.1% at the end of the study.
Photoperiod and lighting:
Light intensity was recorded and a dark/light cycle of 8h/16h at 400 – 540 Lux was used.
Reference substance (positive control):
yes
Remarks:
Name: Betanal (CQ 532) Active ingredient/Purity: 160 g/L Phenmedipham Manufacturer: Hoechst Schering AgrEvo GmbH, D-38288 Wolfenbüttel Batch: 441067
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
45 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
28 d
Dose descriptor:
LOEC
Effect conc.:
105 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
45 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
28 d
Dose descriptor:
LOEC
Effect conc.:
105 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Details on results:
Mortality of the Springtails (table 1).
The results revealed significant acute toxic effects of AHTN to Folsomia candida at a dosage of 105 mg AHTN / kg artificial soil. 18.0 %± 10.9% of the springtails exposed to 105 mg/kg died (mean ± standard deviation) during the entire study time of 4 weeks compared with 0.0 % in the control.

Reproduction of the Springtails (table 2)
Mean reproduction in the control after 4 weeks was 395 ± 88 juvenile springtails (mean ± standard deviation). Treatments with AHTN did not reveal any sub-lethal effects up to concentrations of 45 mg AHTN/kg artificial soil. Reproduction rates were increased but were not significantly different to the control (STUDENT t-test, p = 0.05).
At the highest concentration tested, 105 mg/kg, the reproduction rate was significantly reduced by 45.3 % (179 juveniles ± 54, mean ± standard deviation) compared to the control
Results with reference substance (positive control):
In the treatment with the reference compound, 47.8 % less juveniles were produced as compared to the control.
Reported statistics and error estimates:
No significant difference between the water treated control and the solvent control was observed. Appropriate statistical analysis was performed to determine whether differences between the control and the test concentrations are significant (p = 0.05).

Table 1 Mortality of adult springtails

surviving adult springtails Mortality
mg/kg artificial soil dry weight Replicates
1 2 3 4 5 mean % mean % SD
control 10 10 10 10 10 10 0 0
solvent control 10 9 10 10 10 9.8 2 4.3
1 10 10 9 9 9 9.4 6 4.4
3 10 10 10 10 10 10 0 0
8 10 10 10 8 9 9.4 6 8.3
19 10 10 9 10 10 9.8 2 4.3
45 10 8 9 10 9 9.2 8 7.1
105 8 10 8 8 7 8.2 18 10.9
reference compound 10 10 10 10 10 10 0 0

Table 2 Number of juvenile springtails. Each test unit started with 10 adult springtails

mg/kg artificial soil dry weight Replicates reproduction rate
1 2 3 4 5 mean SD % of control
control 311 385 331 518 432 395 83
solvent control 212 353 404 321 403 339 79 85.6
1 328 394 307 378 453 372 58 94.1
3 284 476 705 438 479 476 151 120.5
8 533 393 531 231 293 396 137 100.2
19 673 524 577 348 394 503 133 127.3
45 374 655 340 204 281 371 171 93.8
105 202 103 213 234 143 179 54 45.3
reference compound 202 290 221 177 143 207 55 52.3

In the treatment with the reference compound, 47.8 % less juveniles were produced as compared to the control.

Validity criteria fulfilled:
yes
Remarks:
Mortality of adult Folsomia candida in the control did not exceed 20 % at the end of the test. Reproduction rate reached a mean minimum of 100 offspring per control vessel. Coefficient of variation for reproduction in the control did not exceed 30 %.
Conclusions:
In a study according to ISO 11267 carried out under GLP (Rel. 1), survival and reproduction of the springtail Folsomia candida were affected by exposure to concentrations of 105 mg AHTN/kg artificial soil (dry weight). AHTN also caused sub-lethal effects on Folsomia candida at concentrations of 105 mg/kg. The NOEC was 45 mg/kg.
Executive summary:

The effect of AHTN on the survival and reproduction of springtails of the species Folsomia candida, 10 to 12 days of age were investigated in a 4-week study according to ISO 11267 carried out under GLP (Rel. 1). The springtails were exposed in artificial soil containing 10% of dry organic matter. Nominal test concentrations were 1, 3, 8, 19, 45 and 105 mg/kg soil. The animals were fed with granulated dry yeast. No significant mortality (-7%) or effects on reproduction (0%) were observed in concentrations up to and including 45 mg/kg. Mortality was significant (18%) in the highest concentration of 105 mg/kg. The reproduction, expressed as the number of juveniles per container, was also significantly reduced (51%) in 105 mg/kg. The NOEC for springtails was 45 mg/kg.

Description of key information

The NOEC was determined by exposing springtails to AHTN in artificial soil. A total of 50 springtails per dose were exposed to test material in artificial soil for 4 weeks. Reproduction, mortality and behavioural abnormalities were recorded. The lowest NOEC was found for mortality and reproduction.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil dwelling arthropods:
15.3 mg/kg soil dw

Additional information

The NOEC of 45 mg/kg soil dw was determined by exposing springtails to AHTN in artificial soil. The lowest NOEC was found for mortality and reproduction. This NOEC is normalised to the standard soil. The soil in the test contains 10% sphagnum and standard soil 3.4% organic material. Consequently, the adjusted NOEC is 45 / 10% x 3.4% = 15.3 mg/kg.