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Toxicity to soil microorganisms

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Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 217 (Soil Microorganisms: Carbon Transformation Test)
Deviations:
yes
Remarks:
Test temperature (25 °C) is slightly higher as recommended by OECD guideline (20 ° C +/- 2 °C). Test duration (40d) is longer than recommended by OECD guideline (28d). these deviations are not thought to compromise the test results.
GLP compliance:
not specified
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 100 and 1000 mg/kg
- Sampling method: On removal from the incubator, the replicates were mixed thorougly and half the quantity was freeze-dried. After freeze-drying three sampßles of each treatment were analysed.
Vehicle:
yes
Details on preparation and application of test substrate:
AMENDMENT OF SOIL
- Type of organic substrate: Reconstituted soil was used comprising a mixture of mature sewage sludge compost (1/3 d.m.) and sandstone (2/3 d.m.). The compost made from a mixture of digested sludge and sawdust was provided by the Sieg-Roche (Canton de Vaud, Switzerland) pilot plant after 9 months of maturation (Hubert 1985) and was mixed with a Permian sandstone without calcium carbonate from the Vosges massif (France).

APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: Test substance was dissolved in ethanol at 0.4 mL/g spiked compost. The dissolved substances were mixed with part of the compost (4g d.m.) nd the ethanol was left to evaporate. The spiked compost was then mixed thoroughly in an incubation cell with the rest of the 60g sample (16g d.m. compost + 40g d.m. sandstone).

VEHICLE:
- Chemical name of vehicle: Ethanol
- Evaporation of vehicle before use: Yes
Test organisms (inoculum):
other: aged mixture of sewage sludge compost and sandstone
Total exposure duration:
40 d
Test temperature:
25 °C
Moisture:
60% water-holding capacity
Details on test conditions:
TEST SYSTEM
- Test container (type, material, size): Incubation cell in a multipurpose assembly incubator ( with intermittent aeration)
- No. of replicates per concentration: 1 (triplicates were mixed on removal from test cells)
- No. of replicates per vehicle control: 1 (triplicates were mixed on removal from test cells)
- Other: Incubated in darkness.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Reconstituted soil was used comprising a mixture of mature sewage sludge compost (1/3 d.m.) and sandstone (2/3 d.m.). The compost made from a mixture of digested sludge and sawdust was provided by the Sieg-Roche (Canton de Vaud, Switzerland) pilot plant after 9 months of maturation and was mixed with a Permian sandstone without calcium carbonate from the Vosges massif (France).
- Soil texture of the sandstone
- % sand: 75%
- % silt: 12%
- % clay: 13%
- pH (in water): 6.80 (mixed soil)
- C:N ratio: 20 (mixed soil)
Total P: 1% (mixed soil)
- Maximum water holding capacity (in % dry weight): 51% WHC of mixed soil and adjusted to 60% WHC for the test
- Cation exchange capacity (mmol/kg): 22.1 meq/100g of the mixed soil

EFFECT PARAMETERS MEASURED: Respiration (CO2 evolution) was recorded daily throughout the test period of 40 days. The cells were flushed periodically with a stream of CO2-free air to remove accumulated CO2 and restore the O2 content, the effluent air being bubbled in 15 mL 0.1 N NaOH. The absorbed CO2 was determined by a conductivity method.

VEHICLE CONTROL PERFORMED: yes
Nominal and measured concentrations:
Nominal: 100 and 1000 ppm
Reference substance (positive control):
no
Key result
Duration:
40 d
Dose descriptor:
NOEC
Effect conc.:
100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Details on results:
Respiration started at the same rate (37 µg C/g organic C per h) in control and treatments. The rates then decreased progressively, indicating depletion of easily mineralizable C and N. CO2 evolution did not differ significantly between the 100 ppm samples and the controls. In contrast, in 1000 ppm samples, CO2 evolution was significantly depressed by the 4th day (F< 0.05). Respiration was depressed by an average o f 64% compared with controls between the 5th and the 40th days.
Validity criteria fulfilled:
yes
Conclusions:
In a long-term toxicity test performed similar to OECD guideline 217, a 40d-NOEC value of 100 mg/kg dw was measured for inhibition of microbial respiration of a mixture of sewage sludge compost and sandstone.
Executive summary:

In a long-term toxicity test performed similar to OECD guideline 217, soil microbes were incubated with 100 and 1000 ppm branched 4-nonylphenol (NP) over an exposure time of 40 days. An aged mixture of sewage sludge compost and sandstone was used as inoculum. Respiration (CO2 evolution) was recorded daily throughout the test period. Respiration started at the same rate (37 µg C/g organic C per h) in control and treatments. The rates then decreased progressively, indicating depletion of easily mineralizable C and N. CO2 evolution did not differ significantly between the 100 ppm samples and the controls. In contrast, in 1000 ppm samples, CO2 evolution was significantly depressed by the 4th day. Thus, the 40d-NOEC value is determined to be 100 mg/kg dw.

Endpoint:
toxicity to soil microorganisms
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
see Analogue justification document in chapter 13
Reason / purpose:
read-across source
Key result
Duration:
40 d
Dose descriptor:
NOEC
Effect conc.:
100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate

Description of key information

NOEC (40d) = 100 mg/kg (nominal) for respiration inhibition of mixture of sewage sludge compost and sandstone (read across)

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
100 mg/kg soil dw

Additional information

Since no study assessing the toxicity of Ethanone, 1-(2-hydroxy-5-nonylphenyl)-, oxime, branched (CAS 244235-47-0) to terrestrial microorganisms is available, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances, a read-across to Phenol, 4-nonyl-,branched was conducted, which is a secondary component and structurally similar to the main component of the substance. The only structural difference between the source substance and the target substance is the lack of a ketoxime group at the phenol ring of the molecule.

The read across is justified due to the following reasons:

1) The similarity of structure and functional groups and accordingly similar physico-chemical properties result in similar environmental behavior and fate.

2) Based on a profound ecotoxicological data set available for Phenol, 4-nonyl-,branched it can be concluded that Phenol, 4-nonyl-,branched exhibit a higher aquatic toxicity compared to Ethanone, 1-(2-hydroxy-5-nonylphenyl)-, oxime, branched (see table below). Therefore, using data from Phenol, 4-nonyl-,branched to assess the intrinsic hazard of Ethanone, 1-(2-hydroxy-5-nonylphenyl)-, oxime, branched is considered to be a very conservative approach (worst case scenario).

 

Substance

Ethanone, 1-(2-hydroxy-5-nonylphenyl)-, oxime, branched

Phenol, 4-nonyl, branched*

CAS number

244235-47-0

84852-15-3

Structure

see attachment (chapter 6.3)

 see attachment (chapter 6.3)

Molecular formula

C17H27NO2

C15H24O

Molecular weight

~ 277 g/mole

~ 220.35 g/mole

PC parameter

 

 

Water solubility

> 0.02 < 1 mg/L (EU method A.6)

5.7 mg/L (ASTM E 1148-02)

Partition coefficient

> 5.7(EU method A.8)

5.4 (OECD 117)

Vapour pressure

< 1.5 Pa at 20 °C (OECD 104)

~1 Pa at 20 °C (ASTM-D 2879)

Environmental fate

 

 

Biodegradability

1 % in 28 days (BODIS)

non-adapted inoculum:

0 % in 28 days (OECD 301B)

 

adapted inoculum:

48.2-62 % in 28 days (OECD 301B)

Adsorption [log KOC]

3.9 (OECD 121)

4.35 - 5.69 (EPA OTS 796.2750)

Hydrolysis

not relevant

Ecotoxicology

 

 

Short-term toxicity to fish

[96h-LC50]

0.46 mg/L (EU method C.1)

0.05 – 0.22 mg/L (different methods)

Long-term toxicity to aquatic invertebrates

[NOEC]

-

0.006 mg/L (ASTM E 1241-05)

Short-term toxicity to aquatic invertebrates

[48h-EC50]

9.55 mg/L (OECD 202)

0.08 – 0.14 mg/L (different methods)

Long-term toxicity to aquatic invertebrates

[21d-NOEC]

2.8 mg/L (OECD 211)

0.024 - 0.116 mg/L (different methods)

Short-term toxicity to algae

[72h-EC50]

760 mg/L(OECD 201)

0.33 - 1.3 mg/L (different methods)

Long-term toxicity to algae

[72h-NOEC/EC10]

472 mg/L (OECD 201)

0.5 mg/L (Algal growth inhibition test according to UBA 1984)

Toxicity to microorganisms

[EC50]

> 1000 mg/L (OECD 209)

950 mg/L (OECD 209)

* Data were taken from Phenol, 4-nonyl-,branched (CAS 84852-15-3) dossier published on the ECHA data base

 

In a long-term toxicity test performed similar to OECD guideline 217, soil microbes were incubated with 100 and 1000 ppm branched 4-nonylphenol (NP) over an exposure time of 40 days (Trocme et al. 1988). An aged mixture of sewage sludge compost and sandstone was used as inoculum. Respiration (CO2 evolution) was recorded daily throughout the test period. Respiration started at the same rate (37 µg C/g organic C per h) in control and treatments. The rates then decreased progressively, indicating depletion of easily mineralizable C and N. CO2 evolution did not differ significantly between the 100 ppm samples and the controls. In contrast, in 1000 ppm samples, CO2 evolution was significantly depressed by the 4th day. Thus, the 40d-NOEC value is determined to be 100 mg/kg dw.

Based on the reasons given above this value is considered to be sufficiently conservative to be used for the hazard assessment of Ethanone, 1-(2-hydroxy-5-nonylphenyl)-, oxime, branched (CAS 244235-47-0).