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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
Study period:
15 Dec 2011 - 26 Mar 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: 200 g soil dry weight (= one sub-sample) per test vessel was weighed. The soil was mixed with 0.5% (i.e. 1.0 g/200 g soil dw) lucerne meal by means of a hand-stirrer (the C/N ratio of the lucerne meal was 15.6/1). One additional soil sample (without lucerne meal) was used for determination of the initial NO3-N-content. The NO3-N content was 1.93 mg /100 g soil d.w. Since the water solubility was low, the test item was thoroughly mixed with quartz meal. Subsequently the obtained mixture was added and mixed with the soil by means of a hand stirrer. For an optimum distribution of the test item in the soil, the test item quartz meal mixture was applied at a ratio of about 10 g per kilogram soil dry weight.
Test organisms (inoculum):
soil
Total exposure duration:
100 d
Test temperature:
18.9 - 21.6 °C
Details on test conditions:
TEST SYSTEM
- Amount of soil: 200 g
- No. of replicates per concentration: 3
- No. of replicates per control: 3

SOIL INCUBATION
- Method: darkness

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): GPS position: 12.694435960 degrees East; 51.403774567 degrees North
- Soil texture: according to USDA
- % sand: (0.05 - 2.0 mm): 54.6
- % silt: (0.002 - 0.050 mm): 37.3
- % clay: (< 0.002 mm): 8.1
- Soil taxonomic classification:
- Soil classification system: sandy loam
- Soil texture: according to ISO 11277
- % sand: (0.05 - 2.0 mm): 53.0
- % silt: (0.002 - 0.050 mm): 38.9
- % clay: (< 0.002 mm): 8.1
- Soil classification system: loamy sand
- pH: 6.6
- Maximum water holding capacity (in % dry weigth): 34.16

- Initial microbial biomass as % of total organic C: 1.85 %

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The nitrogen transformation was determined on day O (after approximately 3 hours) and at intervals of 14, 28 and 100 days after application.

Nominal and measured concentrations:
Control, 1, 5, 10, 30, 60, 100, 300, 600 and 1000 mg test item/kg soil dry weight
Reference substance (positive control):
yes
Remarks:
Dinoterb
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
300 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Duration:
100 d
Dose descriptor:
NOEC
Effect conc.:
30 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
555.1 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Duration:
100 d
Dose descriptor:
EC50
Effect conc.:
395.1 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Details on results:
- Other: The test item caused a maximum inhibition of -60.7% and -72.2% at 1000 mg/kg soil dry weight 28 days and 100 days after application, respectively.
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: In a separate study the reference item Dinoterb caused a stimulation of nitrogen transformation of +42.0%, +68.1% and +92.3% at 6.80 mg, 16.00 mg and 27.00 mg Dinoterb per kg soil dry weight, respectively, 28 days after application
Reported statistics and error estimates:
Dunett t-test, one-sided smaller (a = 0.05) and Probit analysis using linear weight regression for day 28 and day 100 after application. Statistical program: ToxRat Professional 2.10 (2009).

Table 1: Effects on nitrogen transformation in soil after treatment with the test item

Treatment group

Days after application

0

14

28

100

Control

NO3-N [mg/100 g soil d.w.]

1.96

3.33

4.19

6.67

1

NO3-N [mg/100 g soil d.w.]

1.91

3.20

4.14

6.76

Deviation from control [%]1

- 2.9

- 3.7

- 1.4

+ 1.3

5

NO3-N [mg/100 g soil d.w.]

1.88

3.02

4.03

7.49

Deviation from control [%]1

- 4.2

- 9.3

- 3.9

+ 12.3

10

NO3-N [mg/100 g soil d.w.]

1.78

3.16

4.09

7.34

Deviation from control [%]1

- 9.5

- 5.0

- 2.5

+ 10.1

30

NO3-N [mg/100 g soil d.w.]

1.82

3.25

4.24

7.43

Deviation from control [%]1

- 7.1

- 2.3

+ 1.1

+ 11.3

60

NO3-N [mg/100 g soil d.w.]

1.79

3.62

4.74

7.76

Deviation from control [%]1

- 8.7

+ 8.9

+ 13.0

+ 16.3

100

NO3-N [mg/100 g soil d.w.]

1.79

3.73

4.78

8.07

Deviation from control [%]1

- 9.0

+ 12.1

+ 14.0

+ 21.0

300

NO3-N [mg/100 g soil d.w.]

1.78

1.76

3.91

8.57

Deviation from control [%]1

- 9.3

- 47.2

- 6.8

+ 28.5

600

NO3-N [mg/100 g soil d.w.]

1.80

1.81

1.85*

2.19*

Deviation from control [%]1

- 8.1

- 45.5

- 55.8

- 67.1

1000

NO3-N [mg/100 g soil d.w.]

1.79

1.60

1.65*

1.86*

Deviation from control [%]1

- 9.0

- 52.0

- 60.7

- 72.2

Table 2: Validity criteria

Criterion from the guideline

Outcome

Validity criterion fulfilled

The variation between replicate control samples should be less than ± 15%.

(OECD 216)

1.9%

Yes

Validity criteria fulfilled:
yes
Remarks:
For further details please refer to “Any other information on results incl. tables”.
Conclusions:
The NOEC of the test item was calculated to be 300 mg/kg soil dry weight 28 days and 30 mg/kg soil dry weight after 100 days of application.
The EC50 was calculated to be 555.1 mg/kg and 395.1 mg/kg soil dry weight 28 days and 100 days after application, respectively.
Executive summary:

The study investigated the effects of p-chloro-m-cresol on the activity of soil microflora. The test was performed in accordance with OECD guideline 216 (2000). Determination of the nitrogen transformation (N03-production) in soil enriched with lucerne meal (concentration in soil 0.5 %). Comparison of test item treated soil with a non-treated soil under consideration of formed NO3- delivered by the test item. Three replicates per treatment and concentration. NH/ , NO3- and NO2- were determined by using the Autoanalyzer. Sampling scheme: 0, 14, 28 and 100 days after treatment. The test item caused a maximum inhibition of -60.7 % and -72.2 % at 1000 mg/kg soil dry weight 28 days and 100 days after application, respectively. The NOEC of the test item was calculated to be 300 mg/kg soil dry weight after 28 days and 30 mg/kg soil dry weight after 100 days of application. The EC50 was calculated to be 555.1 mg/kg and 395.1 mg/kg soil dry weight 28 days and 100 days after application, respectively.

Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
14 Nov 2006 - 30 Jan 2007
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 217 (Soil Microorganisms: Carbon Transformation Test)
Deviations:
yes
Remarks:
For further details please refer to "Principles of method if other than guideline".
Qualifier:
according to
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
Principles of method if other than guideline:
Carbon transformation test: sampling was done on day 28 and 29 Reason: Sampling at day 28 was done but the data transfer from measuring heads was disturbed, the respiration curves could not be calculated. No presumed effects on the study, because the sampling was repeated immediately (day 29) and the results show clearly that the respiration rates on day 28 could not have been significantly different from day 29.
GLP compliance:
yes (incl. certificate)
Remarks:
Hess. Ministerium für Umwelt, ländlichen Raum und Verbraucherschutz, Wiesbaden, Germany
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: P-chloro-m-cresol was soluble in water; therefore an aqueous suspension in deionised water was prepared and mixed into the soil by means of a laboratory mixer. For the control, only deionised water was mixed into the soil. The carbon and nitrogen transformation tests were performed in two different experiments.
Test organisms (inoculum):
soil
Total exposure duration:
70 d
Remarks:
Duration of OECD 217 29 days.
Test temperature:
20 ± 2 °C
Moisture:
49 – 52% of its maximum water holding capacity
Details on test conditions:
TEST SYSTEM
- Test container (type, material, size): Carbon transformation: 1 L disposable plastic boxes; Nitrogen transformation: 0.5 L disposable plastic boxes
- Amount of soil: 2995.2 g (carbon transformation); 1497.6 g (nirogen transformation)
- No. of replicates per concentration: 3 units per treatment group

SOIL INCUBATION
- Method: bulk

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Longitude: 8° 45’ 28’’ E; Latitude: 49° 51’ 53’’ N
- History of site: Soil has not been subjected to any pesticide or fertilizer treatment for at least 2 years.
- Sample preparation: Soil samples were collected from fallow grassland, were air dried and sieved through a 2 mm sieve at room temperature. The samples were stored at 20 ± 2 °C for 1 week and then stored cooled in a refrigerator during 2 weeks.
- Depth of sampling: 5 - 20 cm
- Soil texture
- % sand: ≥ 63 – 2000 µm 59.3
- % silt: 63 µm to ≥ 2 µm 31.7
- % clay: < 2 µm 9.0
- Soil classification system: DIN 19683
- pH: 6.9
- Maximum water holding capacity (in % dry weigth): 49 – 52% of its maximum water holding capacity
- Cation exchange capacity (mmol/kg): 44 mmol Ba/kg dry weight
- Pretreatment of soil: Soil samples were collected from fallow grassland, were air dried and sieved through a 2 mm sieve at room temperature. The samples were stored at 20 ± 2 °C for 1 week and then stored cooled in a refrigerator during 2 week
- Initial microbial biomass as % of total organic C: 8.4% (910 mg C/kg soil dw)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Respiration was determined over a period of 6 h after test start, after 7, 14 and 29 days. Nitrification and ammonification were determined after 6 hours after test start, after 7, 14, 28, 43, 56 and 70 days.
Nominal and measured concentrations:
1.9 and 19 mg test item/kg dry weight soil
Reference substance (positive control):
yes
Remarks:
Sodium chloride
Duration:
70 d
Dose descriptor:
EC50
Effect conc.:
> 3.45 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other:
Remarks:
EC50 normalized and converted to a standard soil (see "Details on results" for details)
Duration:
29 d
Dose descriptor:
EC50
Effect conc.:
> 3.45 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Remarks on result:
other:
Remarks:
EC50 normalized and converted to a standard soil (see "Details on results" for details)
Duration:
70 d
Dose descriptor:
EC50
Effect conc.:
> 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other: Effect concentration without adaptation to organic carbon.
Duration:
29 d
Dose descriptor:
EC50
Effect conc.:
> 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Remarks on result:
other: Effect concentration without adaptation to organic carbon.
Duration:
70 d
Dose descriptor:
NOEC
Effect conc.:
>= 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Duration:
29 d
Dose descriptor:
NOEC
Effect conc.:
>= 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Details on results:
- Other: In order to have a better comparability, the result must be normalized and converted to a standard soil, which is defined as a soil with an organic matter of 3.4%. The equation is described below: EC50 standard = EC50 experiment x (Fomsoil standard / Fomsoil experiment) Fraction of organic carbon (Foc) was given in the study : 1.1% which corresponds to a Fom of 1.87%.
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: Sodium chloride had a significant impact on nitrogen turnover and respiration activities of soil microflora.
Reported statistics and error estimates:
Test for normality and homogeneity of variance using the R/S-Test (α = 0.05) and Cochran’s-Test (α = 0.05). Where the criterion of homogeneity was fulfilled, the Student-t-test (pair-wise comparison, two sided, α = 0.05) was used for comparison of treated and control values.

Table 1: Effects of test item on soil respiration (test a) in a loamy sand soil (sampling after 29 days)

Day

Control

test item
[mg a.i./kg dry wt soil]

1.9

19

Soil respiration1

SD

CV

Soil respiration1

SD

%2

Soil respiration1

SD

%2

0

12.721

0.340

2.67

12.073

0.329

-5.09 (n.s.)

12.322

0.418

-3.14
(n.s.)

7

10.810

1.203

11.13

11.683

0.177

8.08
(n.s.)

10.923

1.108

1.05
(n.s.)

14

11.892

0.332

2.79

11.516

1.009

-3.16
(n.s.)

11.756

0.127

-1.14
(n.s.)

29

11.397

0.348

3.05

11.459

0.085

0.54
(n.s.)

10.662

0.568

-6.45
(n.s.)

1 soil respiration [mg carbon dioxide / (hour * kg dry wt soil)], average from three samples

2 % deviation of corresponding control

SD: Standard deviation

CV: Coefficient of variation = SD / mean value * 100

n.s.: not statistically significant (according to Student-t-test, two sided α = 0.05)

Table 2: Effects of test item on soil nitrate content (test b) in a loamy sand soil (test duration 70 days)

Sampling

Control

Preventol CMK

[mg a.i./kg dry wt soil]

1.9

19

NO3– Nitrogen [mg / kg dry wt soil] mean values

 

Nitrate-N content

Replicate Variation CV1

Nitrate-N content

% Deviation2

Nitrate-N content

% Deviation2

Day 0

16.950

1.11

16.234 *

-4.22

16.797

-0.90

Day 7

8.055

13.78

4.936 *

-38.72

1.335 *

-83.43

Day 14

11.925

2.60

8.041 *

-32.57

4.445 *

-62.73

Day 28

25.757

0.73

22.558 *

-12.42

18.145 *

-29.55

Day 42

47.081

3.37

44.529 *

-5.42

38.026 *

-19.23

Day 56

59.574

3.31

55.868

-6.22

46.391 *

-22.13

Day 70

74.554

2.47

70.305

-5.70

64.118 *

-14.00

1 Replicate variation CV = % variation within control replicates (coefficient of variation, calculated as standard deviation / mean value * 100)

2 % deviation to control

+ stimulating effect

- inhibitory effect

* statistically significant different from control (Student-t-test, α = 0.05)

Table 3: Effects of test item on soil nitrate transformation (test b) in a loamy sand soil (test duration 70 days)

Interval3

Control

Preventol CMK

[mg a.i./kg dry wt soil]

1.9

19

NO3– Nitrogen Formation Rate [mg / kg dry wt soil per day]3

 

Nitrate-N formation

Replicate Variation CV1

Nitrate-N formation

% Deviation2

Nitrate-N formation

% Deviation2

Day 0 – 7

-1.27

-10.94

-1.61 *

26.8

-2.21 *

74.0

Day 0 – 14

-0.36

-10.00

-0.58 *

61.1

-0.88 *

144.4

Day 0 – 28

0.32

1.88

0.23 *

-28.1

0.05 *

-84.4

Day 0 – 42

0.72

4.44

0.67

-6.9

0.50 *

-30.6

Day 0 – 56

0.76

4.21

0.71

-6.6

0.53 *

-30.3

Day 0 - 70

0.83

2.77

0.77

-7.2

0.67 *

-19.3

1 Replicate variation CV = % variation within control replicates (coefficient of variation, calculated as standard deviation / mean value * 100)

2 % deviation to control

3 cumulative calculation

+ stimulating effect

- inhibitory effect

* statistically significant different from control (Student-t-test, α = 0.05)

Table 4: Effects of test item on soil mineral nitrogen content (test b) in a loamy sand soil (test duration 70 days)

Sampling

Control

Preventol CMK

[mg a.i./kg dry wt soil]

1.9

19

Mineral Nitrogen [mg / kg dry wt soil] mean values3

 

Mineral-N content

Replicate Variation CV1

Mineral-N content

% Deviation2

Mineral-N content

% Deviation2

Day 0

24.780

1.11

23.969 *

-3.27

23.673 *

-4.47

Day 7

9.616

12.19

6.481 *

-32.60

2.822 *

-70.65

Day 14

12.924

2.82

9.219 *

-28.67

5.585 *

-56.79

Day 28

26.516

0.71

23.321 *

-12.05

18.878 *

-28.81

Day 42

49.973

3.51

47.603

-4.74

40.928 *

-18.10

Day 56

60.330

3.13

56.668

-6.07

47.071 *

-21.98

Day 70

75.804

2.46

71.501

-5.68

65.197 *

-13.99

1 Replicate variation CV = % variation within control replicates (coefficient of variation, calculated as standard deviation / mean value * 100)

2 % deviation to control

3 sum of ammonium-N, nitrite-N and nitrate-N

+ stimulating effect

- inhibitory effect

* statistically significant different from control (Student-t-test, α = 0.05)

Tablee 5: Validity criteria

Criterion from the guideline

Outcome

Validity criterion fulfilled

The variation between replicate control samples should be less than ± 15%

(OECD 216).

The variation between the replicate control samples was

clearly below the validity criterion of 15%throughout the test.

Yes

The variation between replicate control samples should be less than ± 15%

(OECD 217).

The variation between the replicate control samples was

clearly below the validity criterion of 15% throughout the test.

Yes

Validity criteria fulfilled:
yes
Remarks:
For further details please refer to “Any other information on results incl. tables”.
Conclusions:
It can be concluded that Preventol CMK does not have long term influence on soil microorganisms up to concentrations of 1.9 mg a.i./kg dw soil.
Executive summary:

To study the effects of p-chloro-m-cresol on soil microorganisms, the carbon and nitrogen (ammonium-, nitrite- and nitrate-nitrogen levels) transformation in a loamy sand soil treated with p-chloro-m-cresol were determined (Reis, 2007). The study was conducted according to OECD-Guidelines 216 (Nitrogen transformation test) and 217 (Carbon transformation test). The effects of soil treated with 1.9 mg/kg dry weight soil and with 19 mg/kg soil were compared to a deionised water control.

The effects on CO2-production were measured using a BSB-Sensomat System over a period of up to 4 hours on day 0, 7, 14 and 29 after glucose has been added to the soil to induce maximum respiration rate (2 g glucose/kg natural soil). To determine the effects on nitrogen-transformation, Lucerne meal was added to the soil (concentration in soil 0.5%). The soil was sampled on day 0, 7, 14, 28, 43, 56 and 70.

Based on the results of this study, p-chloro-m-cresol had no impact on respiration activities of soil microflora when applied up to 1.9 mg/kg dry weight soil. Furthermore, p-chloro-m-cresol had no impact on soil nitrogen turnover (given as nitrate content and nitrate formation rate) in the test concentration of 1.9 mg/kg dry weight soil.

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:
Refer to analogue justification document provided in IUCLID section 13.
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
300 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other: source, CAS 59-50-7, key, rel 1, Schulz 2012
Duration:
100 d
Dose descriptor:
NOEC
Effect conc.:
30 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other: source, CAS 59-50-7, key, rel 1, Schulz 2012
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
555.1 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other: source, CAS 59-50-7, key, rel 1, Schulz 2012
Duration:
100 d
Dose descriptor:
EC50
Effect conc.:
395.1 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other: source, CAS 59-50-7, key, rel 1, Schulz 2012
Duration:
70 d
Dose descriptor:
EC50
Effect conc.:
> 3.45 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks:
EC50 normalized and converted to a standard soil (see "Details on results" for details)
Remarks on result:
other: source, CAS 59-50-7, rel 2, Reis 2007
Duration:
29 d
Dose descriptor:
EC50
Effect conc.:
> 3.45 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Remarks:
EC50 normalized and converted to a standard soil (see "Details on results" for details)
Remarks on result:
other: source, CAS 59-50-7, rel 2, Reis 2007
Duration:
70 d
Dose descriptor:
EC50
Effect conc.:
> 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks:
Effect concentration without adaptation to organic carbon.
Remarks on result:
other: source, CAS 59-50-7, rel 2, Reis 2007
Duration:
29 d
Dose descriptor:
EC50
Effect conc.:
> 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Remarks:
Effect concentration without adaptation to organic carbon.
Remarks on result:
other: source, CAS 59-50-7, rel 2, Reis 2007
Duration:
70 d
Dose descriptor:
NOEC
Effect conc.:
>= 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other: source, CAS 59-50-7, rel 2, Reis 2007
Duration:
29 d
Dose descriptor:
NOEC
Effect conc.:
>= 1.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Remarks on result:
other: source, CAS 59-50-7, rel 2, Reis 2007

Description of key information

EC50 (28 d): 555.1 mg/kg soil dw

NOEC (28 d): 300 mg/kg soil dw

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:
555.1 mg/kg soil dw
Long-term EC10 or NOEC for soil microorganisms:
300 mg/kg soil dw

Additional information

No study investigating the toxicity of sodium p-chloro-m-cresolate (CAS 15733-22-9) to soil microorganisms is available. Therefore, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to the source substance (p-chloro-m-cresol, CAS 59-50-7) which is the main transformation product of the target substance sodium p-chloro-m-cresolate (CAS 15733-22-9) is applied.

The source substance p-chloro-m-cresol is the common compound in this analogue approach and is solely responsible for the (absence of) effects. Thus, the source substance is considered a suitable representative for the evaluation of the toxicity of the target substance to terrestrial organisms. The read-across approach is justified in detail within the analogue justification in IUCLID section 13.

One key (Schulz 2007) and one supporting study (Reis 2012) are available investigating the toxicity of the source substance p-chloro-m-cresol (CAS 59-50-7) to soil microorganisms.  The key study investigated the effects of p-chloro-m-cresol on the activity of soil microflora. The test was performed in accordance with OECD guideline 216 (2000). Determination of the nitrogen transformation (NO3-production) in soil enriched with lucerne meal (concentration in soil 0.5 %). Comparison of test item treated soil with a non-treated soil under consideration of formed NO3- delivered by the test item. Three replicates per treatment and concentration. NH-, NO3- and NO2- were determined by using the autoanalyzer. Samples were taken 0, 14, 28 and 100 days after treatment. The test item caused a maximum inhibition of -60.7 % and -72.2 % at 1000 mg/kg soil dry weight 28 days and 100 days after application, respectively. The NOEC of the test item was calculated to be 300 mg/kg soil dry weight 28 days and 100 days after application. The EC50 was calculated to be 555.1 mg/kg and 395.1 mg/kg soil dry weight 28 days and 100 days after application, respectively. The supporting study was conducted according to OECD-Guidelines 216 (Nitrogen transformation test) and 217 (Carbon transformation test). The effects of soil treated with 1.9 mg/kg dry weight soil and with 19 mg/kg soil were compared to a deionised water control. The effects on CO2-production were measured using a BSB-Sensomat System over a period of up to 4 hours on day 0, 7, 14 and 29 after glucose has been added to the soil to induce maximum respiration rate (2 g glucose/kg natural soil). To determine the effects on nitrogen-transformation, Lucerne meal was added to the soil (concentration in soil 0.5%). The soil was sampled on day 0, 7, 14, 28, 43, 56 and 70. Based on the results of this study, the test item had no impact on respiration activities of soil microflora when applied up to 19 mg/kg dry weight soil. Furthermore, p-chloro-m-cresol had no impact on soil nitrogen turnover (given as nitrate content and nitrate formation rate) in the test concentration of 1.9 mg/kg dry weight soil and a tolerable impact in the test concentration of 19 mg/kg dry weight soil.

Based on the available results from a structurally similar source substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is the main transformation product of the target substance and is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that sodium p-chloro-m-cresolate has effects in the same range as the target substance.