mancozeb (ISO); manganese ethylenebis(dithiocarbamate) (polymeric) complex with zinc salt  

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-02-23 to 2016-04-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Version / remarks:

adopted January 21, 2000

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not required

Details on sampling:

not applicable

Vehicle:

no

Details on preparation and application of test substrate:

To prepare a stock solution (SL) a quantity of 243 mg of the test item were weighed into a 200 mL volumetric flask and made up with deionised water. The resulting nominal test item concentration in the stock solution was 1.0 mg a.s./mL. For treatment T5, a volume of 50 mL of the stock solution was made up to 90.4 mL with deionised water and mixed quantitatively into 1000 g dry weight of test soil.

For treatment T1, a volume of 10 mL of the stock solution was made up to 90.4 mL with deionised water and mixed quantitatively into 1000 g dry weight of test soil. For treatment C (control) a volume of 90.4 mL of deionised water was mixed quantitatively into 1000 g dry weight of test soil. By adding a volume of 90.4 mL of either test solution (T1 and T5) or water (control) the soil moisture was adjusted to 45% of the maximum water holding capacity (WHCmax).
The soil for all three treatments had been amended with finely ground lucerne meal at 5.0 g/kg dw soil immediately before test item application. The soil was distributed equally to four test vessels per treatment (= four replicates).

Test organisms (inoculum):

soil

Total exposure duration:

56 d

Test temperature:

20 ± 2 °C

Moisture:

35.4 % ± 1.5 % (WHCmax)

Organic carbon content (% dry weight):

0.67

Nitrogen content (% dry weight):

0.08

Details on test conditions:

TEST SYSTEM
- Testing facility: ECT Oekotoxikologie GmbH
- Test container: Glass jars with lids (volume 370 mL, diameter 100 mm, Weck, Germany)
- Amount of soil: 285 ± 5 g soil fresh weight equivalent
- No. of replicates per concentration: 4
- No. of replicates per control: 4

SOIL INCUBATION
- Method: series of individual sub-samples

SOURCE AND PROPERTIES OF SUBSTRATE
- Supplier: Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer,
Obere Langgasse 40, D-67346 Speyer, Germany
- Sampling location: Germany, Rhineland-Palatinate, Offenbach, field name „rechts der Landauer Str." field number 826/7.
- History of site: During the last four years the sampling location of the soil was uncultivated and was not treated with pesticides. In 2014 it was fertilised three times (June, September and December) with 3500 kg/ha CaO, each, and once (December) with 1463 kg/ha MgO.
- Treatments with pesticides: none
- Depth of sampling: ca. 20 cm
- Soil texture
- % sand: 59.7 ± 1.6
- % silt: 33.8 ± 0.1
- % clay: 6.5 ± 1.6
- Soil taxonomic classification: Sandy loam
- Soil classification system: USDA
- pH (in water): 5.7 ± 0.6
- Cation exchange capacity: 7.5 ± 0.9 meq/100g
- Pre-treatment of soil: Air drying (only until sievable) from February 02 to February 08, 2016; final sieving to 2 mm on February 09, 2016
- Initial microbial biomass: 120 µg Cmic/g soil

EFFECT PARAMETERS MEASURED: Determination of nitrate on day 0, 7, 14, 28, 42 and 56; endpoint: nitrate formation rates

RANGE-FINDING STUDY: not performed

Nominal and measured concentrations:

Nominal: 10 mg a.s./kg soil dry weight (T1) and 50 mg a.s./kg soil dry
weight (T5)

Reference substance (positive control):

no

Key result

Duration:

56 d

Dose descriptor:

NOEC

Effect conc.:

10 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

On day 0, nitrate concentration of test-item treated soil T1 did not differ significantly from the control, while in soil treated at the fivefold concentration (T5) nitrate concentration was significantly reduced. From day 0 to day 7 nitrate concentrations declined in the two treatments and the control. On day 28 nitrate concentration in treatment T5 was significantly reduced compared to the control while it was significantly increased in T1.
Thereafter up to day 56, the nitrate concentration in the test soil increased in both test item treatments and in the control. Deviation from the control was smaller than 25% in treatment T1 except for day 14, and larger than 25% except for day 0 in treatment T5. The average nitrate formation rate from day 0 to day 56 differed from the control by less than 25% in T1and by more than 25% in T5.

VALIDITY
The validity criterion given by the guideline was fulfilled (variability of less than 15% within the control). The maximum coefficient of variation (CV) for nitrate of control samples was 4.6 %.

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

Normal distribution and homogeneity of variances was tested by the Kolmogorov Smirnov test on normal distribution and the F- test on variance homogeneity, respectively. The NOEC was determined by applying the Student’s t-test (alpha = 0.05, twosided).

Table: Daily nitrate transformation rate [mg NO3 kg-1 soil dw] d-1] and nitrate transformation rate in test item treated soil relative to the control soil; mean ± standard deviation (n = 4)

Time interval	C	T1	T5	T1 (% C)	T5 (% C)
d0 - d7	n.a.	-9.5^a	n.a.	n.a.	n.a.
d7 - d14	n.a.	9.3	n.a.	n.a.	n.a.
d14 - d28	4.6	4.8	n.a.	104	n.a.
d28 - d42	3.1	2.8	11.4	90.3	368^b
d42 - d56	3.1	2.8	2.6	90.3	83.9
d0 - d28	1.4	2.4	0.1	171b	7.1
d0 - d42	2.0	2.5	3.8	125	190^b
d0 - d56	2.2	2.6	3.5	118	159^b

a = negative values represent nitrate consumption (e.g. caused by growing microbial biomass); b = deviation from the control >25%; n.a. = nitrate concentration during the time interval was below the limit of detection (5
mg/kg soil dry weight); hence no rate could be calculated.

Validity criteria fulfilled:

yes

Conclusions:

According to the OECD Test Guideline No. 216 the test item can be considered to have no long term effect on soil microbial nitrogen transformation in soil if the deviation from the control is equal to or less than 25% after a maximum of 100 days.

The daily nitrate formation rates in soil treated with the test item at 10 mg/kg soil dry weight differed from the control by less than 25% at test end (day 56). Therefore it can be concluded that the test item has no long term effect on soil microbial nitrogen transformation in soil at concentrations up to and including 10 mg/kg soil dry weight.

Executive summary:

To determine possible effects of the test item on soil microorganisms a GLP-compliant Soil Microorganisms: Nitrogen Transformation Test according to OECD TG 216 was carried out. The test item was dissolved in deionised water and mixed into sieved field soil (Lufa standard soil type 2.3) that was amended with powdered lucerne meal at a concentration of 5.0 g/kg soil dry weight, and incubated for a test period of 56 d at 20±2 °C in the dark. Two test item concentrations were tested: 10 mg a.s./kg soil dry weight (T1) and 50 mg a.s./kg soil dry weight (T5). A stock solution (SL) was prepared by dissolving 243 g of the test item in 200 mL deionised water. Volumes of 10 mL of SL (treatment T1) and 50 mL of SL (treatment T5) were mixed into 1000 g dry weight of soil, each. Soil of the control (treatment C) did not receive any SL. Soil moisture of the test soils was adjusted to 45% of the maximum water holding capacity (WHCmax) and was kept within a range of ± 5% of 45% of WHCm a x throughout the study. Nitrate concentration in soil was determined in soil extracts on day 0, 7, 14, 28, 42 and 56. The validity criterion given by the guideline was fulfilled (variability of less than 15% within the control). The maximum coefficient of variation (CV) for nitrate of control samples was 4.6. On day 0, nitrate concentration of test-item treated soil T1 did not differ significantly from the control, while in soil treated at the fivefold concentration (T5) nitrate concentration was significantly reduced. From day 0 to day 7 nitrate concentrations declined in the test item treated soil as well as in the control soil. On day 28 nitrate concentration in treatment T5 was significantly reduced compared to the control while it was significantly increased in T1. Thereafter up to day 56, the nitrate concentration in the test soil increased in both test item treatments and in the control. Deviation from the control was smaller than 25% in treatment T1 except for day 14, and larger than 25% except for day 0 in treatment T5. The average nitrate formation rate from day 0 to day 56 differed from the control by less than 25% in T1 and by more than 25% in T5. In conclusion, in compliance with the OECD Test Guideline No. 216 the test item can be considered to have no long term effect on soil microbial nitrogen transformation in soil if, in the lower of the two tested concentrations, the deviation from the control is equal to or smaller than 25%. The daily nitrate formation rates in soil treated with the test item at 10 mg/kg soil dry weight differed from the control by less than 25% at test end. Therefore it can be concluded that the test item has no long term effect on soil microbial nitrogen transformation in soil at concentrations up to and including 10 mg/kg soil dry weight. Accordingly, the 56-day NOEC of the test item was determined to be 10 mg/kg soil dry weight.

Description of key information

In a study according to the OECD Test Guideline No. 216 with Mancozeb the 56-day NOEC on nitrogen transformation in soil was determined to be 10 mg/kg soil dw.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

10 mg/kg soil dw

Additional information

Key study

Mancozeb: Effects on Soil Microorganisms - Nitrogen Transformation Test (Foerster 2016 (Doc. No. 841-006, cross reference to Risk Assessment Report according to Regulation (EU) No 1107/2009: 10.4)

To determine possible effects of the test item on soil microorganisms a GLP-compliant Soil Microorganisms: Nitrogen Transformation Test according to OECD TG 216 was carried out (Foerster, 2016). The test item was dissolved in deionised water and mixed into sieved field soil (Lufa standard soil type 2.3) that was amended with powdered lucerne meal at a concentration of 5.0 g/kg soil dry weight, and incubated for a test period of 56 d at 20±2 °C in the dark. Two test item concentrations were used: 10 mg a.s./kg soil dry weight (T1) and 50 mg a.s./kg soil dry weight (T5). A stock solution (SL) was prepared by dissolving 243 g of the test item in 200 mL deionised water. Volumes of 10 mL of SL (treatment T1) and 50 mL of SL (treatment T5) were mixed into 1000 g dry weight of soil, each. Soil of the control (treatment C) did not receive any SL. Soil moisture of the test soils was adjusted to 45% of the maximum water holding capacity (WHCmax) and was kept within a range of ± 5 % of 45 % of WHCm a x throughout the study. Nitrate concentration in soil was determined in soil extracts on day 0, 7, 14, 28, 42 and 56. The validity criterion given by the guideline was fulfilled (variability of less than 15 % within the control). The maximum coefficient of variation (CV) for nitrate of control samples was 4.6. On day 0, nitrate concentration of test-item treated soil T1 did not differ significantly from the control, while in soil treated at the fivefold concentration (T5) nitrate concentration was significantly reduced. From day 0 to day 7 nitrate concentrations declined in the test item treated soil as well as in the control soil. On day 28 nitrate concentration in treatment T5 was significantly reduced compared to the control while it was significantly increased in T1. Thereafter up to day 56, the nitrate concentration in the test soil increased in both test item treatments and in the control. Deviation from the control was smaller than 25 % in treatment T1 except for day 14, and larger than 25% except for day 0 in treatment T5. The average nitrate formation rate from day 0 to day 56 differed from the control by less than 25 % in T1 and by more than 25 % in T5. In conclusion, in compliance with the OECD Test Guideline No. 216 the test item can be considered to have no long term effect on soil microbial nitrogen transformation in soil if, in the lower of the two tested concentrations, the deviation from the control is equal to or smaller than 25 %. The daily nitrate formation rates in soil treated with the test item at 10 mg/kg soil dry weight differed from the control by less than 25 % at test end. Therefore it can be concluded that the test item has no long term effect on soil microbial nitrogen transformation in soil at concentrations up to and including 10 mg/kg soil dry weight. Accordingly, the 56-day NOEC of the test item was determined to be 10 mg/kg soil dry weight.