3-trimethoxysilylpropyl methacrylate

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:

definitive exposure from 2015-08-17 to 2015-09-14

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study in compliance with GLP, but no analysis of test concentrations.

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate: The soil amounts were amended with powdered lucerne-green-grass-meal (0.5 % of soil dry weight). The C/N ratio was between 12/1 and 16/1. A ratio of 5 g Lucerne per kg of soil (dry weight was used.
- Other:

APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: The soil was divided into six portions of equal weight. The respective test item volume for each test item concentration was given on quartz sand (1 % of the entire soil amount per concentration) and blended thoroughly. Afterwards the test item - quartz sand mixture was mixed carefully into the corresponding portion of the soil with a mixer to ensure a homogeneous distribution of the test item in the soil. Subsequently the soil was distributed to the replicates (three replicates each per concentration and control).

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

18-21 °C

Moisture:

Moisture content as [%] of Maximum Water Holding Capacity:
Day 0: 42.5 - 43.9 %
Day 28: 43.4 - 44.7 %

Details on test conditions:

TEST SYSTEM
- Testing facility: DR.U.NOACK-LABORATORIEN
Käthe-Paulus-Str. 1
31157 Sarstedt
Germany

- Test container (type, material, size): Plastic boxes (volume 1.0 L, food grade) with perforated tops to enable gas exchange. Incubation was performed in bulk and sub-samples were taken for the experimental phase.
- Amount of soil: 400 g (dry weight)
- No. of replicates per concentration: 3
- No. of replicates per control: 3
- No. of replicates per vehicle control: N/A

SOIL INCUBATION
- Method: bulk - Incubation was performed in bulk and sub-samples were taken for the experimental phase.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Offenbach, “rechts der Landauer Str.“ Nr. 826/7, Rheinland-Pfalz, Germany, R-439683; H-5449554.
- History of site: 2011 - 2014: uncultivated.
- Vegetation cover: Not reported
- Treatments with pesticides or fertilizers: Fertilisation:
2015: none
2014: 3500 kg/ha CaO (05.06.2014 and 24.09.2014)
3500 kg/ha CaO; 1463 kg/ha MgO (15.12.2014)
2013: none
2012: none
2011: none

Pesticides No crop protection products applied during the year of sampling and 4 preceding years.

- Accidental contamination: None reported.
- Other:
- Depth of sampling: approximately 20 cm
- Soil texture (dry weight):
- % sand: 2.0 - 0.63 mm = 2.7 ± 0.8
0.63 - 0.2 mm = 30.3 ± 0.6
0.2 - 0.063 mm = 24.6 ± 1.5
- % silt: 0.063 - 0.02 mm = 19.0 ± 1.8
0.02 - 0.006 mm = 11.5 ± 0.6
0.006 - 0.002 mm = 5.4 ± 0.8
- % clay: < 0.002 mm = 6.6 ± 1.7
- Soil taxonomic classification: silty sand (uS) (LUFA-soil 2.3, Batch-No. F2.31615)
- Soil classification system: German DIN classification
- pH (in water): 5.7 ± 0.6
- Initial nitrate concentration for nitrogen transformation test (mg nitrate/kg dry weight): 11.8 mg NO3-N/kg DW
- Maximum water holding capacity (in % dry weight): 35.4 ± 1.5 g/100 g DW
- Cation exchange capacity (mmol/kg): 7.5 ± 0.9 meq / 100 g
- Pretreatment of soil:
- Storage (condition, duration): The soil was stored for 91 days (2015-04-22 to 2015-07-22) in the dark at 6 ± 2 °C in a climatic room (TE1200, VIESSMANN).
- Initial microbial biomass as % of total organic C: 4.44

DETAILS OF PREINCUBATION OF SOIL (if any): The soil was pre-incubated at room temperature (ca. 20°C) for 26 days (2015-07-22 to 2015-08-17) to adapt the micro-organisms to test conditions before the start of the study.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Measurements of nitrate concentrations were carried out after 0, 7, 14 and 28 days. The pH values and water contents were determined on day 0 and 28. The room temperature was measured and recorded continuously with a thermohygrograph.

VEHICLE CONTROL PERFORMED: yes/no - N/A

RANGE-FINDING STUDY
- Test concentrations: 1, 10, 100 and 1000 mg/kg soil DW
- Results used to determine the conditions for the definitive study: 28-d % inhibition at 1 mg/kg soil DW = -6%.
28-d inhibition at 1000 mg/kg soil DW = 66%.

Nominal and measured concentrations:

Nominal: 10, 31.6, 100, 316 and 1000 mg/kg soil dry weight.

Reference substance (positive control):

yes

Remarks:

Cyanoguanidine

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

353 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

462 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Key result

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

620 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Remarks on result:

other: 95% CL 535-701

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

100 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Results with reference substance (positive control):

Nitrate-N Formation Rate % compared to Untreated Control at 28-d:
50 mg/kg soil dry weight = 44 %
100 mg/kg soil dry weight = 98 %

Reported statistics and error estimates:

One Way Analysis of Variances (ANOVA) and DUNNETT’S test, were carried out for the determination of statistically significant differences of the nitrate formation rate at day 7, 14 and 28 compared to control replicates. When running a One Way Analysis of Variances a Normality test and an Equal Variance test were done first. P-values for both Normality and Equal Variance test are 0.05. The a-value for ANOVA and DUNNETT’S test (acceptable probability of incorrectly concluding that there is a difference) is a = 0.05.

Table 1 Reduction of Nitrate-N Content in soil containing 3-trimethoxysilylpropyl methacrylate, relative to the untreated control

Nitrate-N Content
Test concentration	Inhibition [%] compared to control
[mg/kg soil dry weight]	0 d	7 d	14 d	28 d
10	0	2	-3	0
31.6	2	4	4	0
100	-2	0	6	1
316	2	14	13	13
1000	0	48	40	44

negative values = increase

Table 2 Inhibition of Nitrate-N Formation Rates in soil containing 3-trimethoxysilylpropyl methacrylate, relative to the untreated control

Nitrate-N Formation Rate
Test concentration	Inhibition [%] compared to control
[mg/kg soil dry weight]	7 d	14 d	28 d
10	5	-8	0
31.6	9	7	-1
100	5	18	3
316	38*	29*	20*
1000	n.d.*	95*	72*

*) Statistically significant difference compared to control (ANOVA, p = 0.05) negative values = increase

n.d. not determinable, due to negative Nitrate-N Formations rates

Validity criteria fulfilled:

yes

Conclusions:

A 28 day EC50 value of 620 mg/kg soil dw has been determined for the effects of 3-trimethoxysilylpropyl methacrylate on nitrogen transformation rate by soil micro-organisms.

Description of key information

28-day EC₅₀ 620 mg/kg dry weight and NOEC 100 mg/kg dry weight (nominal) (OECD 216), terrestrial microorganisms. The EC₅₀ and NOEC values are equivalent to 515 mg/kg dry weight and 83 mg/kg dry weight, when expressed in terms of the silanol hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate.

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:

515 mg/kg soil dw

Long-term EC10 or NOEC for soil microorganisms:

83 mg/kg soil dw

Additional information

28-day EC₅₀, EC₂₅ and NOEC values of 620 mg/kg dry weight, 359 mg/kg dry weight and 100 mg/kg dry weight, respectively (nominal), have been determined for the effects of the registration substance, 3-trimethoxysilylpropyl methacrylate (CAS 2530-85-0, EC 219-785-8), on the nitrogen transformation of a native population of soil microbes (Noack, 2016). The test was conducted according to OECD test guideline 216 and in compliance with GLP. In view of the test media preparation method and exposure regime, it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance, 3-(trihydroxysilyl)propyl methacrylate and methanol.

The results may be expressed in terms of concentration of the silanol hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate, by applying a molecular weight correction: (MW of silanol = 206.27 / MW of parent = 248.35) * 620, 359 and 100 = 515, 298 and 83 mg/kg dry weight, respectively.

Additional 7-day and 14-day EC₅₀ values of 353 mg/kg dry weight and 462 mg/kg dry weight were also reported in the same study for the effects of the test substance on nitrate transformation rate. This increase of EC₅₀ values with time may reflect increasing tolerance in the test system, progressive degradation of the test substance by hydrolysis in the moist soil substrate, or a combination of the two. The 28-day values are used as the key values for chemical safety assessment, as they represent the standard exposure duration for a toxicity to soil microorganisms study.