Decyldimethylamine

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Justification for type of information:

For details on endpoint-specific justification, please see read-across justification document (category approach) in the linked category of dimethylalkylamines.

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

Daphnia magna

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

Not observed

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

64.4 µg/L

Nominal / measured:

nominal

Conc. based on:

other: RA from C16-18-DMA; value converted based on MW

Basis for effect:

reproduction

Remarks:

and adult mortality

Remarks on result:

other: Orig. value source: 100 µg/L; river water test

Details on results:

- Mortality of parent animals:
The test item induced significant adult mortality of 100 % at the concentration level of 200 µg/L after 21 days. All parental daphnids survived until the end of the study in the concentration levels of 12.5 to 100 µg/L and in the control. The EC50 for the adult mortality after 21 days was estimated using the geometric mean of the highest concentration with 0 % adult mortality and the lowest concentration causing 100 % adult mortality to be 141 µg/L, because only 0 and 100 % mortality was observed within the tested concentration range.
- No. of offspring produced per day per female:
Four broods were observed during the test period at all surviving parental daphnids of the control and the concentration levels 12.5 to 100 µg/L. At the concentration level of 200 µg/L, no daphnid survived until the end of the test.
The average number of juveniles per parent in the control group was 104 after 21 days. The reproductive output was not statistically significant reduced in comparison to the control at the concentration levels 12.5 to 100 µg/L (One Way Analysis of Variance, p = 0.05).
An EC10- or EC50-value for the reduction of the reproductive output could not be estimated, because no reduction of the reproductive output > 10 % was observed within the tested concentration levels with surviving daphnids of 12.5 to 100 µg/L.
The tested concentration levels and the control showed low variances between the test replicates. For the mean number of living offspring produced per parent in the control and the concentration levels 12.5 to 100 µg/L, the coefficients of variation were in the range of 6 to 10 %
- Body length and weight of parent animals:
The mean body lengths of the surviving parental daphnids at the nominal test item concentrations 12.5 to 100 µg/L were determined to be in the range of 5.25 to 5.45 mm per daphnid and 5.40 mm per daphnid at the control group, respectively.
The mean dry body weight was determined to be in the range of 1.22 to 1.52 mg per daphnid in the test groups and 1.49 mg per daphnid in the control, respectively.
For details please refer to the respective table
- Type and number of morphological / behavioural abnormalities:
Related to the total number of produced juveniles (dead + alive) the percentage of dead juveniles and aborted eggs was < 2 % in the tested concentration levels of 25.0 to 100 µg/L. In the control and in the concentration level of 12.5 µg/L, no dead juveniles or aborted eggs were observed.
- Time to first brood release or time to hatch: The first day of appearance of juveniles in all replicates of the tested concentration levels of 12.5 to 100 µg/L and the control was between day 8 and day 9.
Four broods were observed during the test period at all surviving parental daphnids of the control and the concentration levels 12.5 to 100 µg/L.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50 (24 h) = 1.74 (CI 1.49 - 2.00) mg/L

Reported statistics and error estimates:

The NOEC and the LOEC for the reproductive output and for the adult mortality were determined directly from the observation data. Significant deviations were determined in comparison to the control using statistical standard procedures as Normality Test, Equal Variance Test and Analysis of Variance.
For the determination of significant deviations of the reproductive output and the intrinsic rates of natural increase, One Way Analysis of Variance (p = 0.05) was used. The coefficients of variation around the mean number of living offspring produced per parent in the control and the test groups were evaluated.

Number of Juveniles in the Control and the Test Groups after 21 Days

Nominal Test Item Conc. [µg/L]												No. of Parents prod. Juv.	Mean No. of Juveniles per Parent producing Juveniles			Comparison versus Control
	Number of Juveniles in Replicate No.										Total No.				CV
																Red.	Stat.
	1	2	3	4	5	6	7	8	9	10	Sum	N	MV ± SD		[%]	[%]
200	--	--	--	--	--	--	--	--	--	--	--	0	--		--	--	--
100	83	112	101	105	104	110	104	105	107	110	1041	10	104 ±	8	8	-0.580	no
50.0	118	87	110	100	114	97	102	88	109	101	1026	10	103 ±	10	10	0.870	no
25.0	115	108	103	99	130	106	99	106	106	110	1082	10	108 ±	9	8	-4.54	no
12.5	97	103	88	89	94	94	103	105	101	93	967	10	97 ±	6	6	6.57	no
Control	107	113	111	105	88	104	106	102	95	104	1035	10	104 ±	7	7	—	—

Relative Number of Dead (Stillborn + Aborted Eggs) to Total Number of Juveniles

Nominal Test Item Concentration	Number of Juveniles			Percentage of Dead Juveniles * [%]
[µg/L]	Dead	Alive	Total
200	--	--	--	--
100	14	1041	1055	2
50.0	7	1026	1033	1
25.0	7	1082	1089	1
12.5	0	967	967	0
Control	0	1035	1035	0

First Appearance of Living Juveniles and Mean Number of Broods in the Individual Groups

Nominal Test Item Concentration	Day of First Appearance of Living Juveniles										First	Mean Number
	in Replicate No.										Appearance	of
[µg/L]	1	2	3	4	5	6	7	8	9	10	Mean Day	Broods
200	--	--	--	--	--	--	--	--	--	--	--	--
100	9	8	9	9	9	8	9	9	8	9	8.7	4
50.0	8	9	9	9	9	8	9	9	9	9	8.8	4
25.0	9	9	9	9	8	9	8	9	9	9	8.8	4
12.5	9	8	9	8	9	9	9	8	8	9	8.6	4
Control	8	8	9	9	9	9	9	9	9	9	8.8	4

Mortality [%] of the Adult Daphnids after 7, 14 and 21 Days of Exposure

                 (n = 10)

Nominal Test Item Concentration	Adult Mortality [%]
[µg/L]	7 days	14 days	21 days
200	0	0	100*
100	0	0	0
50.0	0	0	0
25.0	0	0	0
12.5	0	0	0
Control	0	0	0

Total Body Length and Dry Weight of the Parental Daphnids

Nominal Test Item Concentration [µg/L]	Total Length of the Parent Animals [mm]										MV	N	Dry Weight [mg]
	Replicate No.
	1	2	3	4	5	6	7	8	9	10	[mm]		Sum	MV
200	--	--	--	--	--	--	--	--	--	--	--	0	--	--
100	5.25	5.00	5.25	5.00	5.00	5.50	5.00	5.50	5.75	5.25	5.25	10	12.2	1.22
50.0	5.50	5.25	5.25	5.50	5.25	5.25	5.25	5.25	5.50	5.50	5.35	10	13.5	1.35
25.0	5.25	5.00	5.50	5.25	5.75	5.25	5.50	5.50	5.50	5.75	5.43	10	14.4	1.44
12.5	5.50	5.25	5.75	5.25	5.00	5.50	6.00	5.50	5.25	5.50	5.45	10	15.2	1.52
Control	5.25	5.50	5.50	5.25	5.25	5.50	5.75	5.50	5.50	5.00	5.40	10	14.9	1.49

Validity criteria fulfilled:

yes

Executive summary:

The study used as source investigated the toxicity of C16-18-DMA in the Daphnia magna reproduction test according to OECD 211. The study results of the source substance were considered applicable to the target substance. Justification and applicability of the read-across approach (category approach) is outlined in the read-across report in the linked category of dimethylalkylamines.

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Justification for type of information:

For details on endpoint-specific justification, please see read-across justification document (category approach) in the linked category of dimethylalkylamines.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Analysis of the new media was performed on the days: 0, 5, 12 and 19. Analysis of the old media was performed on days 2, 7, 14 and 21.

Vehicle:

no

Test organisms (species):

Daphnia magna

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

> 90 mg CaCO3/L, <=111 mg/L

Test temperature:

20 +/- 2 deg C

pH:

7.3 - 7.96

Dissolved oxygen:

7.65 - 8.29 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

30.3 µg/L

Nominal / measured:

nominal

Conc. based on:

other: RA from C12-14-DMA; value converted based on MW

Basis for effect:

reproduction

Remarks on result:

other: Orig. value source: 36 µg/L; river water test

Details on results:

The number of juveniles produced in the 10 replicates of the test and control groups between the 8th and 21 th day were added to the total turnover and plotted versus concentration of the test item. The mean number of offspring alive produced per parent animal surviving at the end of the test was 79.4 juveniles in the control group indicating Böhme water to be a suitable medium for testing the reproductive output of daphnids.
The coefficient of variation around the mean number of living offspring produced per parent in the control group was 5.1 % (see table in section "Any other information on resutls incl. tables"). The quality criteria that the coefficient of variation in the control should be < 25 % was fulfilled.
The mean number of juveniles of the surviving daphnids of the treatment groups were compared by the multiple comparisons Method of Dunnett's for significance of differences (a = 0.05) from controls. The differences in the mean values among the treatment groups were greater than would be expected by chance. There was a statistically significant difference (p < 0.05) in the concentration 0.32 mg/L compared to control.
No statistically significant difference was seen in the tested concentration levels ranging from 0.0013 to 0.108 mg/L compared to control.
The concentration that caused a 50 % reduction in reproduction ( EC50 reproduction ) was calculated to be 0.31 mg/L with confidence interval (CI) ranging from 0.21 to 0.44 mg/L.
The number of stillborn juveniles in the treatment groups 0.0013 to 0.32 mg/L are shown in Table 2 section "Any other information on resutls incl. tables". A significant number of stillborn juveniles occurred in the concentration 0.108 mg/L. No stillborns were found in the lower dosage levels and untreated control. Regarding these observations as well as the well running development of the parental animals which had been introduced as juveniles at test initiation, the significant number of stillborns at the 0.108 mg/L has to be seen as a test item related effect.
Number of aborted eggs producing no juveniles: No unhatched eggs were observed at all.
The immobilisation rates of parental animals in % after 7, 14 and 21 days of exposure are given in Table 3 section "Any other information on resutls incl. tables". After 21 days of exposure a biologically significant mortality of 70 % was seen at the concentration 0.32 mg/L.

Results with reference substance (positive control):

Potassium dichromate p.a. (MERCK)
Test concentrations 0.58 - 1.0 - 1.8 - 3.2 - 5.8 mg/L
Range of validity 1.0 mg/L < EC50 (24 hours) < 2.5 mg/L
Test duration: 2000-12-20 to 2000-12-21

24 h EC10 : 1.4 mg/L
24 h EC50 :2.1 mg/L (1.9 - 2.4)
24 h EC100 : 5.8 mg/L

The 24 hours EC50 value is in the range 1.0 to 2.5 mg/L.

Reported statistics and error estimates:

The NOEC and LOEC for the reproduction were determined directly from the results obtained.
The EC50 for reproduction and immobilisation was calculated by probit analysis.
Significant deviations concerning reproduction rate and body length were determined in comparison with the control group using the One Way Analysis of Variance (Normality Test, Equal Variance Test and Multiple Comparisons Method of Dunnett's).
The coefficient of variation around the mean number of living offspring produced per parent in the control group was evaluated.

The calculations were carried out using the software SIGMA STAT of Jandel Scientific Version No. 2.0 (Windows). The EC50-values for reproduction, immobilisation and the reference item were calculated with probit analysis using software SigmaPlot rel. 2000 (2000), SPSS CORPORATION.
Probit values were taken from Weber (1986). Confidence intervals were calculated according to a standard procedure (Breitig & Ttimpling 1982).

Number of juveniles in the control and test groups after 21 days
Conc. (mg/L)	Number of juveniles in replicates no.										Total number	Number of parentals alive	Juveniles per parent mean. +/-SD	CV (%)	Comparision vs. Control
	1	2	3	4	5	6	7	8	9	10					Red. (%)	Stat.*
0.32	-	-	41	-	-	-	-	36	-	35	112	3	37.3 ± 3.2	8.6	53	yes
0.108	70	96	64	69	76	65	61	100	82	77	760	10	76.0 ± 13.3	17.5	4	no
0.036	64	76	74	64	86	110	76	69	65	78	762	10	76.2 ± 13.8	18.2	4	no
0.012	86	68	73	84	100	87	76	74	71	75	794	10	79.4 ± 9.7	12.2	0	no
0.004	69	63	68	77	70	86	81	68	65	58	705	10	70.5 ± 8.5	12.1	11	no
0.0013	82	85	70	80	68	97	108	78	78	-	746	9	82.9 ± 12.6	15.3	0	no
control	79	83	76	81	77	82	76	84	72	84	794	10	79.4 ± 4.1	5.1	-	-

Stat.*= Statistical significance (Dunnett's Method)

yes= Statistically significant

no= statistically significant

Red.= Reduction of reproduction

- = Animal died before end of test

Conc. = Concentration

CV= Coefficient of variation

Number of stillborn juveniles:

Nominal concentration [mg/L]	Number of stillborn juveniles
0.32	0
0.108	13
0.036	1
0.012	1
0.004	0
0.0013	0
control	0

Immobilisation [%] of daphnids after 7, 14 and 21 days of exposure (n = 10):

Conc. [mg/L]	Immobilisation [%]
	7 days	14 days	21 days
0.32	70	70	70
0.108	0	0	0
0.036	0	0	0
0.012	0	0	0
0.004	0	0	0
0.0013	0^1)	0^1)	0^1)
control	0	0	0

1) one animal died by manual mistreatment, death was not considered to significance immobilisation and not

test item induced.

Summary of all Test Item Related Effects in the Test Concentrations:

Effects	Nominal concentrations (mg/L)
	0,0013	0,004	0,012	0,036	0,108	0,32
Number of juveniles (Reproduction rate)	---	---	---	---	---	++
Stilborn juveniles	---	---	---	---	++	---
Aborted eggs	---	---	---	---	---	---
Immobilisation of the parental	---	---	---	---	---	++
Dry weight of the parental	---	---	---	---	---	++
Lenght of the parental	---	---	---	---	---	---
Occurrence of males, winter eggs	---	---	---	---	---	---
Summary of all item related effects	---	---	---	---	++	++

---: no significant effect

++: statistically significant effect

Validity criteria fulfilled:

yes

Executive summary:

The study used as source investigated the toxicity of C12-14-DMA in the Daphnia magna reproduction test according to OECD 211. The study results of the source substance were considered applicable to the target substance. Justification and applicability of the read-across approach (category approach) is outlined in the read-across report in the linked category of dimethylalkylamines.

Description of key information

For two category members reliable studies (reliability category 1) are available resulting in NOEC values (21 d, reproduction) between 0.163 µM (C12-14 DMA) and 0.347 µM (C16-18 DMA).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

36 µg/L

Additional information

Dimethyl Alkyl Amines (DMA), which are cationic surfactants at pH relevant in the environment, exhibit strong sorption to test organisms and walls of test vessels due to a combination of ionic and hydrophobic interaction. The sorption coefficient was found to be concentration dependent. Due to these properties, the test items are difficult to test in synthetic water and results from such tests depend on the test settings applied. In river water, which contains particulate as well as dissolved organic carbon, Dimethyl Alkyl Amines (DMA) are either dissolved in water or adsorbed to dissolved and particulate matter. This reduces the difficulties encountered in tests with synthetic water caused by the high adsorption potential (adsorption losses due to settling on surfaces). In general, the adsorbed fraction of DMA is difficult to extract from the test system, which normally leads to low analytical recoveries especially in the old media, while initially measured concentrations (fresh media) are generally within +/- 20% as recommended by the guidelines. Due to the short exposure periods applied in these tests (semi-static design) these low recoveries cannot be explained by biodegradation. No, or negligible sorption to glassware occurs under these conditions, which was confirmed by measurements. This ensures reliable as well as reproducible results and means that the test substance is present in the test system and therefore available for exposure (dissolved in water and adsorbed, also called bulk). This so-called Bulk Approach is described by ECETOC (2003). Consequently, nominal concentrations were used for these tests instead of measured ones.

Therefore, reliable (without restrictions, reliability category 1) tests with river water as dilution water were performed for two category members with different chain length (C12-14 DMA and C16-18 DMA). These tests were of semi-static test design (daily renewal for C16-18 DMA and 3 times/week for C12-14 DMA) and involved analytical determination of test item in the stock solution, adsorbed to glass walls (C16-18 DMA only) as well as initial and final test item concentration in test water and are regarded to be of higher reliability and relevance than tests performed with synthetic dilution water would be. Natural river water from river “Innerste” (Lower Saxony; C16-18 DMA) and “Boehme” (Lower Saxony; C12-14 DMA) was used as dilution water in these tests. These rivers had been chosen due to their properties representing typical conditions of German medium sized rivers. The concentrations of suspended matter measured in the river waters was 14.0 and 19 mg/L, respectively and the organic carbon concentration was 3.2 mg/L (NPOC, Innerste) and 6.6 mg/L (DOC, Boehme). Both tests were performed according to OECD 211, compliant to GLP and fulfilling validity criteria of the guideline.

For C16-18 DMA, the NOEC (21 d) for reproduction and adult mortality was 0.347 µM (100 µg/L test material). EC10- or EC50 values for the reduction of the reproductive output could not be estimated, because no reduction of the reproductive output > 10 % was observed within the tested concentration levels with surviving daphnids of 12.5 to 100 µg/L C16-18-DMA. At the next higher concentration (200 µg/L C16-18-DMA) there were no surviving adults, i.e. the endpoint reproduction wasn't any more sensitive than the endpoint adult mortality. Comparing the calculated chronic EC50 (21 d) for adult mortality of 141 µg/L C16-18-DMA with the determined acute toxicity of C16-18 DMA (48-h EC50: 190 µg/L; river water test) shows no significant higher sensitivity upon chronic exposure. This may point to toxicity due to adsorption of the test item to the surface of daphnids, i.e. physicochemical mechanism of toxicity.

Due to 13 stillborn juveniles found at 108 µg/L C12-14-DMA but n≤1 for all other tested concentrations of the test item, this effect was determined to be statistically significant in spite of a reproductive output of 760 living juveniles (n= 10 parental daphnids) at this concentration, corresponding to a statistically not significant reduction of the reproductive output by 4% compared to the control. At the next higher concentration (320 µg/L C12-14-DMA) only 3 parental daphnids survived (21-d EC50 immobilization: 280 µg/L C12-14-DMA) and the EC50 (21 d) for reproductive output was determined as 310 µg/L C12-14-DMA. In comparison, the 48-hour EC50 for immobilisation is lower than the chronic one. This uncommon finding is probably due to the higher concentrations of DOC (6.6 mg/L) and suspended matter (19 mg/L) of “Boehme” water compared to water from “Innerste” used in the acute daphnia test. Thus, in principle the same may hold true for C12-14 like what was stated above for C16-18 DMA, i.e. reproduction being not any more sensitive than survival and toxicity being probably due to physicochemical interaction (adsorption). However, due to the statistically significant number of stillborn juveniles found at 108 µg/L C12-14-DMA the NOEC (21 d, reproduction) was set at 0.163 µM (36 µg/L C12-14-DMA).

In conclusion, members of the DMA category are to be regarded as chronically toxic to aquatic invertebrates. However, chronic toxicity seems not to be pronouncedly higher than acute toxicity exerted by DMA and compared to immobilization the reproductive endpoint is of similar sensitivity.

 

Based on the highest toxicity observed for C12-14-DMA in the reliable river water test, this NOEC (21 d; reproduction) of 0.163 µM is used as the key value for the category. However, the original value obtained with C12-14-DMA of 36 µg/L C12-14-DMA is used as key value. This is justified because a) molar concentration cannot be used for environmental hazard and risk assessment and b) correction for MW would theoretically result in somewhat lower values for shorter chain DMAs, but the available reliable river water studies for acute Daphnia toxicity demonstrate a much lower toxicity for C10-DMA (EC50 4.99 µM) compared to C12-14-DMA (0.253 µM).

 

References
ECETOC, European Centre for Ecotoxicology and Toxicology of Chemicals (2003)
Technical Report No. 88. Environmental Risk Assessment of Difficult Substances
Brussels, Belgium