Dimethyldioctylammonium chloride

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Source study Klimisch 2. Remains as Klimisch 2.

Justification for type of information:

Justification for read-across approach - see read across justification in Section 13.

Reason / purpose for cross-reference:

read-across source

GLP compliance:

yes

Specific details on test material used for the study:

Bardac 22C50
Batch number 5628-137
purity 49.85% DDACarbonate

Analytical monitoring:

yes

Details on sampling:

Measured test concentrations were determined on samples collected on Days 0 and 7.

Vehicle:

no

Details on test solutions:

Three replicates of five fronds of duckweed, Lemna gibba, were exposed to Bardac 22C50 at nominal concentrations of 2.1, 4.7, 10, 23, 51, 113 and 250 µg a. i./L

Test organisms (species):

Lemna gibba

Details on test organisms:

Originally supplied by United States Department of Agriculture and maintained in-house

Test type:

static

Limit test:

no

Total exposure duration:

7 d

Test temperature:

25 ± 2°C

pH:

Test initiation: 8.1-8.2
Exposure termination: 8.6-9.0

Nominal and measured concentrations:

Nominal test substance concentrations: 2.1, 4.7, 10, 23, 51, 113 and 250 µg a.i./L

Details on test conditions:

Test chambers were sterile, 250 mL glass beakers with 100 mL Bardac 22C50 test solution at the respective treatment levels or control medium, covered with disposable petri dishes. Effects upon the duckweed were assessed through direct counts of duckweed frond numbers conducted on Days 3, 5 and 7 of the test. Observations for chlorosis, necrosis, break-up of duckweed colonies, root destruction, death and any other abnormalities in plant or frond appearance were also performed on those days.

Duration:

7 d

Dose descriptor:

EC50

Remarks:

Frond Growth

Effect conc.:

ca. 57 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

frond number

Duration:

7 d

Dose descriptor:

EC50

Remarks:

Growth Rate

Effect conc.:

ca. 69 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

7 d

Dose descriptor:

NOEC

Remarks:

Growth rate and frond growth

Effect conc.:

ca. 12.34 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Details on results:

Percent inhibition of frond growth in the 3.8, 4.8, 9.1, 23, 53, 117 and 249 µg a. i. /L treatment groups at exposure termination were 2.0, -1.5, 0.43, 6.3, 13, 60 and 74% respectively. Percent inhibition of growth rate in the 3.8, 4.8, 9.1, 23, 53, 117 and 249 µg a. i. /L treatment groups at exposure termination were 0.83, -0.65, 0.19, 2.8, 6.0, 39 and 58% respectively. Statistically significant treatment related effects for frond growth and growth rates were apparent in the three highest concentrations

Frond growth:
EC50 104 µg a. i./L
NOAEC 23 µg a. i. /L.
Growth rate:
EC50 194 µg a.i./L
NOAEC 23 µg a. i. /L
Frond growth was the most sensitive endpoint, as defined by the lower EC50 value.

RMS evaluation:
Results are based on Day 0 measured concentrations (due to the decline in test substance concentrations during the test). The endpoints have been recalculated from the mean measured concentrations and are as follows:
7-Day frond number EC50 = 57 µg l-1
7-Day growth rate number EC50 = 69 µg l-1
NOEC = 12.34 µg l-1

Nominal test substance concentration: 2.1, 4.7, 10, 23, 51, 113 and 250 µg/L

Actual substance concentration: Day 0: 3.8, 4.8, 9.1, 23, 53, 117 and 249 µg a. i. /L.Day 7: 0.12, 0.44, 0.82, 1.67, 1.9, 6.2 and 90 µg a. i /L.

Percent inhibition of frond growth in the 3.8, 4.8, 9.1, 23, 53, 117 and 249 µg a. i /L treatment groups at exposure termination were 2.0, -1.5, 0.43, 6.3, 13, 60 and 74% respectively. 

Percent inhibition of growth rate in the 3.8, 4.8, 9.1, 23, 53, 117 and 249 µg a. i /L treatment groups at exposure termination were 0.83, -0.65, 0.19, 2.8, 6.0, 39 and 58% respectively. 

Statistically significant treatment related effects for frond growth and growth rates were apparent in the three highest concentrations.

Frond growth:
EC50 104 µg a. i./L
NOAEC 23 µg a. i./L.

Growth rate:
EC50 194 µg a. i. /L
NOAEC 23 µg a. i. /L

Comments from RMS evaluation: Results are based on Day 0 measured concentrations (due to the decline in test substance concentrations during the tet). The endpoints have been recalulcated from the mean measured concentrations and are as follows:

7-Day frond number EC50 = 57 µg a. i. l^-1

7-Day growth rate number EC50 = 69 µg a. i. l^-1

NOEC = 12.34 µg a. i. l^-1

Herbicial symptoms and mortality shown in table:

Mean percentage of fronds observed dead, chlorotic or necrotic per treatment
Day 0 measured concentration (µg a. i. /L)		Day 3 Percentage^1					Day 5 Percentage^1					Day 7 Percentage^1
		N^2	Dead	Chlorotic	Necrotic		N^2	Dead	Chlorotic	Necrotic		N^2	Dead	Chlorotic	Necrotic
Negative control		34	0.0	0.0	0.0		69	0.0	0.0	0.0		153	0.0	0.88	0.0
3.8		34	0.0	0.0	0.0		68	0.0	0.0	0.0		150	0.0	0.89	0.0
4.8		37	0.0	0.0	0.0		74	0.0	0.0	0.0		156	0.0	0.64	0.0
9.1		35	0.0	0.0	0.0		71	0.0	0.46	0.0		153	0.0	1.1	0.0
23		35	0.0	0.93	0.0		65	0.0	0.51	0.0		144	0.0	0.95	0.0
53		35	0.0	1.9	0.0		61	0.0	1.6	0.0		133	0.0	1.7	0.0
117		29	0.0	7.9	13		45	0.0	15	18		62	2.2	11	7.8
249		25	0.0	23	16		30	5.6	34	23		40	15	15	26

¹Values represent the average percentage of dead, chlorotic or necrotic fronds for the three replicates per treatment. Calculations were performed on Excel 2000. Manual calculations may differ

²N = mean number of fronds per treatment or control group on each observation daily. Number of fronds per treatment and control group on Day 0 = 15

Validity criteria fulfilled:

no

Conclusions:

Following RMS evaluation: The endpoints using mean measured concentrations are as follows:
7-Day frond number EC50 = 57 µg a. i l-1
7-Day growth rate number EC50 = 69 µg a. i. l-1
NOEC = 12.34 µg a. i l-1

Executive summary:

A study was conducted according to EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II)) and to GLP on the substance N,N-Didecyl-N,N-dimethylammonium carbonate (DACCcarbonate) (Desjardins, 2004). Three replicates of five fronds of duckweed, Lemna gibba, were exposed to Bardac 22C50 (purity 49.58%) at nominal concentrations of 2.1, 4.7, 10, 23, 51, 113 and 250 µg A.I /L. Lemna were exposed for 7 days. The concentration of active ingredient (A.I) was measured at Day 0 and at Day 7. At day 0, the measured concentrations we 3.8, 4.8, 9.1, 23, 53, 117 and 249 µg A.I /L. At 7 days the measured concentrations had dropped to 0.12, 0.44, 0.82, 1.67, 1.9, 6.2 and 90 µg A.I /L, ranging from 4.8 to 36% of the nominal concentrations. Based on the Day 0 concentrations, EC50's for frond growth and growth rate and NOAEC's for frond growth and growth rate were determined at 104 and 194 µg A.I /L and 23 µg A.I /L and 23 µg A.I /L, respectively.

Due to the significant drop in exposure concentration during the 7 day period, an average exposure concentration for each exposure concentration has been determined and used to calculate alternative EC50's and NOAEC's. Mean EC50's for frond growth and growth rate, and mean NOAEC's for frond growth and growth rate are calculated at 57 and 69 µg A.I /L, and 12.34 and 12.34 µg A.I /L.

Description of key information

One study is available for toxicity to aquatic plants other than algae, based on the read across substance N,N-Didecyl-N,N-dimethylammonium carbonate (DDACarbonate) (Desjardins, 2004). The study was conducted according to EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II)) and to GLP. Three replicates of five fronds of duckweed, Lemna gibba, were exposed to Bardac 22C50 at nominal concentrations of 2.1, 4.7, 10, 23, 51, 113 and 250 µg a. i./L. The purity of the substance wa 49.58%.

The concentration of active ingredient (A.I) was measured at Day 0 and at Day 7. At day 0, the measured concentrations we 3.8, 4.8, 9.1, 23, 53, 117 and 249 µg A.I /L. At 7 days the measured concentrations had dropped to 0.12, 0.44, 0.82, 1.67, 1.9, 6.2 and 90 µg A.I /L, ranging from 4.8 to 36% of the nominal concentrations. Based on the Day 0 concentrations, EC50's for frond growth and growth rate and NOAEC's for frond growth and growth rate were determined at 104 and 194 µg A.I /L and 23 µg A.I /L and 23 µg A.I /L, respectively.

Due to the significant drop in exposure concentration during the 7- day period, average exposure concentrations were determined and used to calculate alternative EC50's and NOAEC's. Mean EC50's for frond growth and growth rate, and mean NOAEC's for frond growth and growth rate are calculated at 57 and 69 µg A.I /L, and 12.34 and 12.34 µg A.I /L (accounting for purity of 49.58%).

The EC50’s and NOAECs based on the average concentrations are considered the most relevant here, as they represent the worst case scenario. 

Key value for chemical safety assessment

EC50 for freshwater plants:

57 µg/L

EC10 or NOEC for freshwater plants:

12.34 µg/L