Polyethylene polyamine, pentaethylenehexamine 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:

2015-05-05 to 2015-06-02

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)

Deviations:

yes

Remarks:

The soil was stored at 6 ±2 °C instead of 4 ± 2 °C due to organisational reasons. This deviation is considered to have no impact on outcome or the quality and integrity of the study.

Principles of method if other than guideline:

The soil was stored at 6 ±2 °C instead of 4 ± 2 °C due to organisational reasons. This deviation is considered to have no impact on outcome or the quality and integrity of the study.

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:

yes

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 into 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. There were three replicates per test concentration. Nominal test concentrations were 250, 125, 62.5, 31.3 and 15.6 mg/kg soil dry weight. Untreated field soil, adjusted to a moisture content corresponding to nominally 47% of its maximum water holding capacity and mixed with a source of organic nitrogen (lucerne meal), was tested as the control under the same test conditions as the test item replicates.

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

Nominal test temperature range 20 ± 2 °C, measured range 19 - 22 °C.

Moisture:

Start of exposure period (day 0) 45.9 - 46.8 % of dry weight, end of exposure period (day 28) 45.2 - 46.4 % 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 47% of its maximum water holding capacity. All replicates were checked once per week for water losses by evaporation (recommended maximum 5%, actual 0.5 - 1.3%). Compensation with demineralised water was done.

Nominal and measured concentrations:

Nominal test concentrations were 250, 125, 62.5, 31.3 and 15.6 mg/kg soil dry weight.

Reference substance (positive control):

yes

Remarks:

Cyanoguanidine

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 250 mg/kg soil ww

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 250 mg/kg soil ww

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

There was no evidence of significant inhibition of the nitrate formation rate throughout the 28 day definitive test at all concentrations up to and including 250 mg PEHA/kg soil dry weight, the highest concentration applied. Instead, concentrations of nitrate were higher in all the PEHA treatments than the control throughout the study, with the amount of NO3-N production above that of the control replicates generally increasing in response to the applied concentration of PEHA.
The EC50 based on inhibition of nitrogen transformation processes could therefore not be determined reliably, but it exceeded 250 mg PEHA/kg soil dry weight, the highest concentration applied in the definitive test. The corresponding no-observed effect concentration (NOEC) was 250 mg PEHA/kg soil dry weight.

Results with reference substance (positive control):

Cyanoguanidine is tested once per year as toxic reference with 50 and 100 mg/kg soil dry weight. Inhibition [%] compared to the control on Day 7 14 28 respectively was;
Cyanoguanidine 50 mg/kg soil dry weight 68* 87* 86*
Cyanoguanidine 100 mg/kg soil dry weight 97* 96* 96*
* Difference to control ≥25 %

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 compared to control replicates. When running the tests 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: Reduction of Nitrate-N Content in soil containing PEHA, 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
15.6	-1	-4	-5	-4
31.3	-1	-4	-9	-8
62.5	-3	-13	-11	-7
125	-4	-22	-25	-30
250	-3	-34	-41	-37

negative values = increase              

 

Table 2:Inhibition of Nitrate-N Formation Rates in soil containing PEHA, 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
15.6	-8	-8	-6
31.3	-11	-20*	-12
62.5	-37*	-20*	-9
125	-65*	-52*	-42*
250	-107*	-88*	-54*

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

                negative values = increase

 

 

Validity criteria fulfilled:

yes

Conclusions:

The effects of Pentaethylenehexamine, PEHA 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 >250 mg/kg soil dry weight. The 28 day NOEC value was 250 mg/kg soil dry weight.

Executive summary:

The effects of Pentaethylenehexamine, PEHA on the metabolic activity of soil micro-organisms was determined according to OECD Guideline 216 (2000) over a 28 day period. Nominal test concentrations were 250, 125, 62.5, 31.3 and 15.6 mg/kg soil dry weight. The effects of Pentaethylenehexamine, PEHA was measured 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 PEHA treatments than in the untreated control at all time points throughout the study therefore the EC50 based on inhibition of nitrogen transformation processes could not be determined reliably, but it exceeded 250 mg PEHA/kg soil dry weight, the highest concentration applied in the definitive test. The corresponding no-observed effect concentration (NOEC) was 250 mg PEHA/kg soil dry weight. Test validity criteria were fulfilled.

Description of key information

NOEC (28 d): ≥ 250 mg/kg soil dw 

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

250 mg/kg soil dw

Additional information

The effects of the substance on the metabolic activity of soil micro-organisms were determined according to OECD Guideline 216 over a 28 day period. Nominal test concentrations were 250, 125, 62.5, 31.3 and 15.6 mg/kg soil dry weight. The effects of the substance were measured 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 therefore the EC50 based on inhibition of nitrogen transformation processes could not be determined reliably, but it exceeded 250 mg /kg soil dry weight, the highest concentration applied in the definitive test. The corresponding no-observed effect concentration (NOEC) was ≥ 250 mg/kg soil dry weight. Test validity criteria were fulfilled.