Decyldimethylamine

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For details on endpoint-specific justification, please see read-across justification document (analogue approach) in section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

assessment report

Analytical monitoring:

no

Details on sampling:

No analytical monitoring

Vehicle:

no

Test organisms (inoculum):

soil

Total exposure duration:

28 d

Test temperature:

19 - 20 °C

Nominal and measured concentrations:

1000 - 400 - 160 - 64 - 25.6 mg/kg soil dry weight

Reference substance (positive control):

yes

Remarks:

Cyanoguanidin

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

605.6 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

other: RA from HYEQS; value converted based on MW

Basis for effect:

nitrate formation rate

Remarks on result:

other: Orig. value source: 1000 mg/kg dw

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: No

Results with reference substance (positive control):

Mean Nitrate-N Content of the Reference Item [mg N/kg Soil Dry Weight]
Test concentrations
[mg/kg soil dry weight] Mean Nitrate-N Content [mg N/kg soil dry weight]
0 d 7d 14 d 28 d
Control 8.70 14.7 17.7 27.6
50 8.21 10.6 10.9 13.7
100 8.00 9.26 10.2 10.1

Changes of the Nitrate-N Formation Rates of Reference Item Soils Compared to the
Control Soils [%]

Formation Rates
Day 7 14 28
Cyanoguanidine 50 mg/kg soil dry weight 60 70 72
Cyanoguanidine 100 mg/kg soil dry weight 79 75 90

Reported statistics and error estimates:

One Way Analysis of Variance (ANOVA) with following DUNNETT’s test were carried out for the determination of statistically significant differences compared to control replicates. When running a One Way Analysis of Variance 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.
EC25 and EC50 values were calculated by sigmoidal dose-response regression. Calculations of the confidence intervals for EC25 and EC50 were carried out using standard procedures.

Nitrate-N Contents in Comparison to the Untreated Soil [%]

Test concentration	Nitrate-N Contents [%]
[mg/kg soil dry weight]	0 d	7 d	14 d	28 d
25.6	-2	-2	-5	4
64	6	4	-2	2
160	1	6	-5	2
400	4	1	10	6
1000	5	16	24	8

Nitrate-N Formation Rates of Test Item Soils Compared to the Untreated Soil [%]

Test concentration [mg/kg soil dry weight]	Nitrate-N Formation Rates [%]
	7 d	14 d	28 d
25.6	-4	-10	9
64	2	-15	-2
160	16	-14	5
400	-5	-18	9
1000	36*	51*	11

Nitrate-N Formation Rate: NOEC, LOEC and EC- Values with Confidence Intervals

	Day 7	Day 14	Day 28
	[mg/kg soil dry weight]
EC50	> 1000	908	> 1000
95 % confidence interval	–	738 - > 1000	–
EC25	782	562	> 1000
95 % confidence interval	657 - 955	465 - 688	–
LOEC	1000	1000	> 1000
NOEC	400	400	1000

Nitrate-N Contents - Day 0

Test concentration [mg/kg soil dry weight]	Nitrate-N
	Repl.	MV ± Std. Dev.	CV [%]
	[mg N/kg soil dry weight]
Control	14.2	14.6 ± 0.67	5
	15.4
	14.3
25.6	13.2	14.9 ± 1.51	10
	16.1
	15.4
64	13.7	13.7 ± 0.06	0
	13.7
	13.6
160	13.6	14.5 ± 0.85	6
	14.6
	15.3
400	14.1	14.0 ± 0.40	3
	13.6
	14.4
1000	13.6	13.9 ± 0.55	4
	13.5
	14.5

Nitrate-N Contents and Nitrate-N Formation Rates - Day 7

Test concentration [mg/kg soil dry weight]	Nitrate-N			Nitrate-N Formation Rate
	Repl.	MV ± Std. Dev.	CV [%]	Repl.	MV ± Std. Dev.	CV [%]
	[mg N/kg soil dry weight]			[mg NO3-N × (kg soil dry weight × d)^-1]
Control	22.7	22.6 ± 1.11	5	1.16	1.14 ± 0.16	14
	21.4			0.97
	23.6			1.29
25.6	22.5	23.1 ± 0.85	4	1.09	1.18 ± 0.12	10
	24.1			1.31
	22.8			1.13
64	22.0	21.6 ± 0.40	2	1.19	1.12 ± 0.06	5
	21.2			1.07
	21.5			1.11
160	21.3	21.2 ± 1.30	6	0.97	0.96 ± 0.19	20
	22.5			1.14
	19.9			0.77
400	22.8	22.4 ± 0.32	1	1.26	1.20 ± 0.05	4
	22.3			1.19
	22.2			1.17
1000	19.1	19.0 ± 0.56	3	0.74	0.73 ± 0.08	11
	18.4			0.64
	19.5			0.80

Nitrate-N Contents and Nitrate-N Formation Rates - Day 14

Test concentration [mg/kg soil dry weight]	Nitrate-N			Nitrate-N Formation Rate
	Repl.	MV ± Std. Dev.	CV [%]	Repl.	MV ± Std. Dev.	CV [%]
	[mg N/kg soil dry weight]			[mg NO3-N × (kg soil dry weight × d)^-1]
Control	23.7	24.7 ± 1.00	4	0.65	0.72 ± 0.07	10
	24.6			0.71
	25.7			0.79
25.6	25.5	25.9 ± 0.67	3	0.76	0.79 ± 0.05	6
	26.7			0.84
	25.6			0.76
64	26.9	25.3 ± 1.42	6	0.94	0.83 ± 0.10	12
	24.4			0.76
	24.5			0.77
160	25.7	26.0 ± 0.74	3	0.80	0.82 ± 0.05	6
	25.4			0.78
	26.8			0.88
400	22.7	22.3 ± 0.93	4	0.62	0.59 ± 0.07	12
	22.9			0.64
	21.2			0.51
1000	18.6	18.8 ± 0.32	2	0.34	0.35 ± 0.02	6
	18.7			0.34
	19.2			0.38

Nitrate-N Contents and Nitrate-N Formation Rates - Day 28

Test concentration [mg/kg soil dry weight]	Nitrate-N			Nitrate-N Formation Rate
	Repl.	MV ± Std. Dev.	CV [%]	Repl.	MV ± Std. Dev.	CV [%]
	[mg N/kg soil dry weight]			[mg NO3-N × (kg soil dry weight × d)^-1]
Control	34.2	33.0 ± 1.07	3	0.70	0.66 ± 0.04	6
	32.4			0.64
	32.3			0.63
25.6	30.6	31.8 ± 1.53	5	0.56	0.60 ± 0.05	8
	31.2			0.58
	33.5			0.66
64	32.8	32.5 ± 1.04	3	0.68	0.67 ± 0.04	6
	33.3			0.70
	31.3			0.63
160	34.7	32.2 ± 2.37	7	0.72	0.63 ± 0.08	13
	31.8			0.62
	30.0			0.55
400	32.6	30.9 ± 1.60	5	0.66	0.60 ± 0.06	10
	29.4			0.55
	30.8			0.60
1000	33.5	30.4 ± 2.84	9	0.70	0.59 ± 0.10	17
	27.9			0.50
	29.9			0.57

Validity criteria fulfilled:

yes

Executive summary:

The study used as source investigated the toxicity of HYEQS in a Soil Microorganisms: Nitrogen Transformation Test (OECD 216). The study results of the source substance were considered applicable to the target substance. Justification and applicability of the read-across approach (structural analogue) is outlined in the read-across report in section 13.

Description of key information

In a reliable study (reliability category 1) assessing long-term effects of the supporting substance HYEQS on nitrogen transformation rate of terrestrial microorganisms, after 28 days no inhibitory effects were determined (NOEC ≥ 3.27 mmol/kg soil dry weight).

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:

605.6 mg/kg soil dw

Additional information

Long-term effects on nitrogen transformation rate of terrestrial microorganisms after single exposure to the supporting substance HYEQS was assessed in a reliable (category 1) study performed according to OECD 216 and compliant to GLP over a period of 28 days. The validity criterion of the guideline was met.

HYEQS is of high similarity to C12-14 DMA in that it has essentially the same alkyl chain distribution and – like DMA category members - two methyl substituents at the amino group. The only difference is an additional hydroxyethyl substituent at the amino group rendering it a quaternary amine, being permanently positively charged. This is however a minor difference as due to protonation at environmentally relevant pH values also DMA category members are predominantly positively charged at the amino group.

HYEQS was tested at five different application rates between 25.6 and 1000 mg/kg soil dry weight. The NOEC, EC50 and EC25 for nitrogen transformation rate in soil measured as nitrate on day 7 was 400, > 1000 and 782 mg/kg soil dry weight, respectively.

The NOEC, EC50 and EC25 for nitrogen transformation rate in soil measured as nitrate on day 14 was 400, 908 and 562 mg HYEQS/kg soil dry weight, respectively.

The NOEC for nitrogen transformation rate in soil measured as nitrate on day 28 was ≥1000 mg HYEQS/kg soil dry weight: NOEC (28 d; nitrate formation rate) >= 3.27 mmol/kg soil dry weight).

In conclusion, no long-term inhibitory effects of DMA category members on the nitrogen transformation rate of terrestrial microorganisms are expected, even at high exposure concentrations. Because molar concentrations cannot be used for environmental hazard and risk assessment, in a conservative way the molecular weight of C10-DMA is used to transform the molar into mass-based concentration:
Key value for terrestrial microorganism toxicity of DMA category members: NOEC (28 d; nitrate formation rate) >= 605.6 mg/kg soil dry weight.