Amines, polyethylenepoly-, tetraethylenepentamine fraction

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:

2015-04-01 to 2015-04-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study according to OECD guidelines

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The effects of the test item on the metabolic activity of the nitrogen-N formation rate (nitrate) were measured on the day of treatment (day 0) and after 7, 14 and 28 days.

Vehicle:

no

Details on preparation and application of test substrate:

The respective test item amounts were weighed out for each test item concentration and dissolved in demineralised water. Afterwards the test item solutions were mixed carefully into the soil with a mixer to ensure a homogeneous distribution of the test item in the soil. Thereafter the soil was distributed to the replicates, there were three replicates per test concentration. Nominal test concentrations were 500, 250, 125, 62.5 and 31.3 mg/kg soil dry weight (nominal concentrations).

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

Nominal temperature range - 18 - 22°C, measured temperature range 20-22.5°C. The measured temperature as above 22°C for 48 hours, however this minor deviation is not considered to have affected the outcome of the study.

Moisture:

Start of exposure period (day 0) - 43.5 – 43.80 % of maximum water holding capacity, end of exposure period (day 28) - 43.6 - 44.1 % of maximum water holding capacity.

Details on test conditions:

Test chambers were plastic boxes (volume 1.0L, food grade) with perforated tops to enable gas exchange. Test chambers were kept in continuous darkness. Test concentrations were replicated in triplicate. 400 g soil dry weight was used per replicate. At experimental start the premoistened soil was adjusted to approximately 50% of its maximum water holding capacity. All replicates were checked once per week for water losses by evaporation (recommended maximum 5%, actual 0.2 - 1.3%). Compensation with demineralised water was done.

Nominal and measured concentrations:

Nominal test concentrations were 500, 250, 125, 62.5 and 31.3 mg/kg soil dry weight.

Reference substance (positive control):

yes

Remarks:

Cyanoguanidine

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 500 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

500 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

The rates of nitrate formation were consistently higher in all the TEPA treatments than in the untreated control at all timepoints throughout the study. Consequently, there was no evidence that exposure to TEPA inhibited the nitrogen transformation activity of soil microflora at the range of concentrations applied. The EC50 based on inhibition of nitrogen transformation processes could therefore not be determined reliably, but it exceeded 500 mg TEPA/kg soil dry weight, the highest concentration applied in the definitive test. The corresponding no-observed effect concentration (NOEC) was 500 mg TEPA/kg soil dry weight.
The cause of the dose-related increase in nitrate formation observed across the range of test item treatments is unknown. One explanation may be that TEPA stimulated the breakdown of the lucerne meal substrate and accelerated the mineralisation of plant-derived organic nitrogen relative to the control. Alternatively (or additionally), partial breakdown of the test item may have released nitrogen for mineralisation; the nitrate-nitrogen concentrations in the TEPA treatments at the end of the test exceeded the day 28 nitrate-nitrogen concentration in the control by amounts that are all within the range of the applied TEPA treatments expressed as N-equivalent concentrations. Discrimination between these two possibilities is not possible without making substantial alterations to the study design that are beyond the requirements and purpose of the test guideline.

Results with reference substance (positive control):

Inhibition compared to Control was calculated as; 68%, 87%, 86% at 7 d, 14d and 28d respectively for 50 mg/kg soil dry weight. 97%, 96%, 96% at 7 d, 14d and 28d respectively for 100 mg/kg soil dry weight.

Reported statistics and error estimates:

One Way Analysis of Variances (ANOVA) and DUNNETT'S test, if possible was carried out for the determination of statistically significant differences compared to control replicates. When running a One Way Analysis of Variances a Normality test and an Equal Variance test was done first. P-values for both Normality and Equal Variances test are 0.05. The ą -value for ANOVA and DUNNETT'S test (acceptable probability of incorrectly concluding that there is a difference) is ą = 0.05.

Table 1. Inhibition of Inorganic-N Formation Rates

Nitrate-N Formation Rate
Test concentration Inhibition [%] compared to control [mg/kg soil dry weight]	Inhibition [%] compared to Control
	7d	14d	28d
31.3	-43*	-29*	-10
62.5	-46*	-36*	-19*
125	-67*	-62*	-39*
250	-74*	-90*	-71*
500	-133*	-130*	-117*

*) Statistically significant difference compared to control (ANOVA, p≤0.05)

positive values = inhibition negative values = increase

Validity criteria fulfilled:

yes

Conclusions:

The effects of Tetraethylenepentamine, TEPA on the metabolic activity of soil micro-organisms was determined according to OECD Guideline 216 (2000) over a 28 day period. The effects of the test item on the metabolic activity of the nitrogen-N formation rate (nitrate) was measured on the day of treatment (day 0) and after 7, 14 and 28 days. The 28 day EC50 value was >500 mg/kg soil dry weight. The corresponding no-observed effect concentration (NOEC) was 500 mg TEPA/kg soil dry weight.

Executive summary:

The effects of Tetraethylenepentamine, TEPA on the metabolic activity of the nitrogen-N formation rate (nitrate) soil micro-organisms were determined according to OECD Guideline 216 (2000) over a 28 day period. Nominal test concentrations were 31.3, 62.5, 125, 250 and 500 mg/kg soil dry weight. Effects were recorded on the day of treatment (day 0) and after 7, 14 and 28 days. Untreated soil was tested as the control under the same test conditions as the test item replicates. The rates of nitrate formation were consistently higher in all the TEPA treatments than in the untreated control at all timepoints throughout the study. Consequently, there was no evidence that exposure to TEPA inhibited the nitrogen transformation activity of soil microflora at the range of concentrations applied. The 28 day EC50 value was >500 mg/kg soil dry weight. The corresponding no-observed effect concentration (NOEC) was 500 mg TEPA/kg soil dry weight. Test validity criteria were fulfilled.

Description of key information

NOEC (28 d): 500 mg/kg dw 

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

500 mg/kg soil dw

Additional information

The effects of the substance on the metabolic activity of the nitrogen-N formation rate (nitrate) of soil micro-organisms were determined according to OECD Guideline 216 (2000) over a 28 day period. Nominal test concentrations were 31.3, 62.5, 125, 250 and 500 mg/kg soil dry weight. Effects were recorded on the day of treatment (day 0) and after 7, 14 and 28 days. Untreated soil was tested as the control under the same test conditions as the test item replicates. The rates of nitrate formation were consistently higher in all treatment groups compared to the untreated control at all time points throughout the study. Consequently, there was no evidence that the nitrogen transformation activity of soil microflora was inhibited at the range of concentrations applied. The 28 day EC50 value was >500 mg/kg soil dry weight. The corresponding no-observed effect concentration (NOEC) was 500 mg/kg soil dry weight.