Tosylchloramide sodium

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Extractions were made at two time point (14 and 28 days) in stead of T= 0, 7, 14 and 28. The temperature during incubation is not reported. Although it was stated that it was above guideline values for some time. Data on monitoring moisture content is not shown.

Qualifier:

according to guideline

Guideline:

other: CTB guideline section H.4.1(1993)

Deviations:

yes

Remarks:

The value the carbon in the biomass of the total soil organic carbon of the low humic content sand soil is below the 1% limit, it is characteristic for this soil. Only one dose was tested while the guideline specifies that two doses should be tested.

Qualifier:

according to guideline

Guideline:

other: Draft OECD 216

Deviations:

yes

Remarks:

The value the carbon in the biomass of the total soil organic carbon of the low humic content sand soil is below the 1% limit, it is characteristic for this soil. Only one dose was tested while the guideline specifies that two doses should be tested.

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on preparation and application of test substrate:

Before the start of the experiment the soiI samples were partly air-dried until sievabIe. They were then sieved to obtain soil granules 12 mm. The sieved soil samples were analysed for silt, day, sand, CaC03, totaI nitrogen and organic matter content, and for pH and cation exchange capacity.
The dry weight of the soil samples was determined by drying subsamples at about 105 °C in triplicate. The moisture content of the soil was adjusted to 0.32 bar moisture pressure (i.e. 12.7% for the sandy loam soil and 4.3% for the low humic content sand soil). Subsequently, the soils were stored at 20 ± 2 °C for 11 days to restore microbial activity. During the last day of the pre-incubation the soils were allowed to evaporate about 0.5 g of water per 50 g weight. Before the start of the experiment, the active microbial biomass was determined according to the fumigation-extraction method. Through fumigation, intact microbial cells are lysed and the microbial matter released. Non-microbial soiI organic matter is not seriously affected by such fumigation. Soil samples are fumigated with chloroform for 24 hours. The organic carbon extracted by 0.5 M potassium sulfate is determined in fumigated and unfumigated samples, and the increase in extracted carbon used to determine microbial biomass carbon.

A stock solution of Halamid was prepared as follows: 30.3 mg Halamid was dissolved in 100 ml ultrapure water (pH adjusted to 8.1 with NaOH) and 0.5 m1 of this stock solution was applied per 50 g (dry weight) pre-incubated soil type. The control soiIs received 0.5 ml ultrapure water (pH adjusted to 8.1 with NaOH) per 50 g dry weight.
The test substance or control solution was mixed thoroughly with the soils, and the conical flasks were closed with sponge caps and incubated at 20 ± 2 °C in the dark.

Test organisms (inoculum):

other: other bacteria: soil micro-organisms

Total exposure duration:

28 d

Test temperature:

20 ± 2 °C

Moisture:

0.5 ml/50 g dw (1%)

Details on test conditions:

- soils: sandy loam soil (Heerewaard, The Netherlands) and low humic content sand soil (Lisse, The Netherlands). Type 2 and 3 (CTB, The Netherlands). The soils were amended with powdered lucerne meal (7.5 g /1500 g soil)
- Exposure vessel type: conical flasks glass with sponge capps
- Test performed in closed vessels: Flasks were closed with sponge caps
- Measuring equipment: Nitrate analyses were carried out using a Dr Lange test-kit (LCK 339, batch 6557, range 0.23 - 13.5 rng/L NO3-N) and a CADAS 30 spectrophotometer
- Number of replicates: fourfold
- Concentrations: 3 mg/kg DW soil
- pH: 8.1

After 14 and 28 days of incubation, nitrates were extracted from the soils by shaking the 50 g dry weight samples with 250 ml of a 0.1 M potassium chloride solution (KCI) for about one hour. The mixtures were then filtrated and stored at freezer temperature prior to analysis.
Nitrate analyses were carried out using a Dr Lange test-kit (LCK 339, batch 6557, range 0.23 - 13.5 mg/l N03-N) and a CADAS 30 spectrophotometer. A validation procedure was carried out in order to determine whether the Dr Lange test-kit was suitable for the nitrate analysis. For this purpose a 10 g soil sample of each soil type was extracted with 50 mI 0.1 M KCI- solution. After filtration 0.1 ml of a standard solution of 25 ± 2 mg/I N03-N was added to 0.9 mI of each extract.
The nitrate content was determined and the results showed a recovery of less than 90%, indicating that the concentration of K+ and CI- ions was too high and disturbed the measurements. It was therefore decided to dilute the extracts I0 times with ultrapure water, which then gave appropriate results. All extracts were therefore diluted 10 times with ultrapure water prior to analysis.

Nominal and measured concentrations:

nominal: 3 mg/kg dw

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

3 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

- The values for microbial biomass show that soils were microbially active at the beginning of the test, containing 20 and 96 μg C/g in the biomass of low humic content sand soil and the sandy loam soil, respectively. This was calculated by subtracting DOC in the non-fumigated from that found in the fumigated soil.
- Effect data/Element values: NOEC was 3 mg/kg DW soil for both soil types. In the low humic content soil a maximum stimulation of 15% was found after 28 days of incubation.

STATISTICAL RESULTS: sandy loam soil : 0% inhibition; low humic content soil: 13-15% stimulation.

Reported statistics and error estimates:

Two-tailed Dunnet's test was used.

The variation in replicate concentration was 15%. The results indicate that Chloramine-T trihydrate at the tested concentration either stimulated the nitrogen transformations or had no effect. Chloramine-T trihydrate itself contains mineralisable nitrogen, however, at the concentration tested, the contribution to the formation of

nitrate was negligible. The nitrogen mineralisation rate of the sandy loam soil was higher than that of the low humic content sand soil. This is in agreement with the lower amount of microbial biomass of the latter soil. The mean values of the nitrate formation rates and their standard deviations were evaluated using a two-tailed Dunnett test. The results of the statistical evaluation demonstrated that there was no significant difference in the nitrate formation rates of control and treated soil samples in the sandy loam soil. In the low humic content sand soil, however, a significant difference (at 99% significance level) was found, meaning that Chloramine-T trihydrate at 3 mg/kg dry weight stimulated the formation of nitrate in this soil.

Validity criteria fulfilled:

yes

Conclusions:

The percentage deviation from the control was 15% or less and this leads to the conclusion that Chloramine-T trihydrate will have no long term negative influence on nitrogen mineralization in the tested soil.

Executive summary:

The effects of Halamid (3 mg/kg dry soil) on the nitrogen mineralisation activity of soil micro-organisms was investigated in a 28 day study in a sandy loam soil and a low humic content sand soil. Nitrogen was added as powdered lucerne meal to the soils (5 g/kg dry soil) and the conversion to nitrate was measured by extracting the soils with 0.1 M potassium chloride after 14 and 28 days and

analysing the nitrate content.

The study was carried out essentially according to the draft document of the OECD Guidelines for the Testing of dhemicals and the guideline section H.4. I issued by the Dutch Board for the Authorization of Pesticides (CTB), and in compliance with the QECD Principles of Good Laboratory Practice (GLP).

Halamid contains mineralisable nitrogen, however, at the concentration tested, its contribution to the formation of nitrate was negligible.

The nitrogen mineralisation rate of the sandy loam soil was higher than that of the low humic content sand soil. This was in agreement with the lower amount of microbial biomass of the latter soil.

The mean values of the nitrate formation rates and their standard deviations were evaluated using a two-tailed Dunnett test. The results of the statistical evaluation demonstrated that there was no significant difference in the nitrate formation rates of control and treated sandy loam soil samples.

In the low humic content sand soil, however, a significant difference (at 99% significance level) was found, meaning that Halamid at 3 mg/kg dry soil stimulated the formation rate of nitrate in this soil. The percentage deviation from the control , however, was positive (15% or less), thus it may be concluded that Halamid at 3 mg/kg dry soil will not have a negative long-term influence on nitrogen mineralisation in the soils tested.

Description of key information

The effects of Halamid (3 mg/kg dry soil) on the nitrogen mineralisation activity of soil micro-organisms was investigated in a 28 day study in a sandy loam soil and a low humic content sand soil. The study was based on GLP, OECD and CTB (H.4.1 section) guidelines. The Nitrogen was added as powdered lucerne meal to the soils (5 g/kg dry soil) and the conversion to nitrate was measured by extracting the soils with 0.1 M potassium chloride after 14 and 28 days and analysing the nitrate content. Halamid contains mineralisable nitrogen, however, at the concentration tested, its contribution to the formation of nitrate was negligible. The nitrogen mineralisation rate of the sandy loam soil was higher than that of the low humic content sand soil. This was in agreement with the lower amount of microbial biomass of the latter soil.The mean values of the nitrate formation rates and their standard deviations were evaluated using a two-tailed Dunnett test. The results of the statistical evaluation demonstrated that there was no significant difference in the nitrate formation rates of control and treated sandy loam soil samples. In the low humic content sand soil, however, a significant difference (at 99% significance level) was found, meaning that Halamid at 3 mg/kg dry soil stimulated the formation rate of nitrate in this soil. The percentage deviation from the control, however, was positive (15% or less), thus it may be concluded that Halamid at 3 mg/kg dry soil will not have a negative long-term influence on nitrogen mineralisation in the soils tested.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

3 mg/kg soil dw

Additional information

The NOEC value is 3 because no negative effect was noted.