6-[methyl(phenylsulphonyl)amino]hexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1)

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

other: Study conducted on formulated product containing the registered substance.

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study was conducted by a GLP accredited laboratory using ISO draft testing method 10253:1998. The study was conducted on a formulated product containing the registered substance.

Qualifier:

according to guideline

Guideline:

ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Details on sampling:

The sample was described as soluble therefore a 1 g/l stock solution was prepared in test media. The test media was Guillard's f/2 medium + Si. Aliquots of this stock were used to achieve the appropriate range of test concentrations. Upon receipt of the test material a rangefinder study was conducted using the concentrations 1, 10 and 100 mg/l. The rangefinder study allows a suitable definitive test range to be set. After 72 hours the cell numbers (per ml) were determined for the control group (10738 per ml), the 1 g/l group (58912 per ml), the 10 mg/l group (78943 per ml) and 100 mg/l (343144 per ml). From the results observed a definitive test range of 100 to 1000 mg/l was set.

Vehicle:

yes

Details on test solutions:

Nominal concentrations of the test material over a range of 100, 177.8, 316.2, 562.4 and 1000 mg/l were prepared from a 1 g/l stock solution.

Test organisms (species):

Skeletonema costatum

Details on test organisms:

Name: Skeletonema costatum CCAP1077/5
The test species were supplied by the Culture Collection of Algae and Protozoa, Dunstaffnage. Stock cultures were maintained in Guillard's f/2 medium + Si in accordance with the testing laboratory's Standard Operating Procedure (SOP).

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

Test material concentration (mg/l) Temperature (°C)

0 h 24 h 48 h 72 h
0 20 21 21 20
100 20 21 21 20
177.8 20 21 21 20
316.2 20 21 21 20
562.3 20 21 21 20
1000 20 21 21 20
DCP 20 21 21 20

pH:

Test material concentration (mg/l) pH

0 h 24 h 48 h 72 h
0 8.10 - - 7.81
100 8.27 - - 7.77
177.8 8.51 - - 7.80
316.2 8.58 - - 7.85
562.3 8.60 - - 7.92
1000 8.61 - - 8.04
DCP 8.10 - - 8.20

Nominal and measured concentrations:

Nominal concentrations of the test material over a range of 100, 177.8, 316.2, 562.4 and 1000 mg/l were prepared from a 1 g/l stock solution.

Details on test conditions:

Six replicate control flasks and three replicate flasks at each test concentration and reference material, were prepared with algae added from a culture concentrate to give an initial algal cell concentration of approximately 2530 cells per ml counted microscopically. This start cell density equated to a mean cell density of 3321 cells per ml when determined using the particle counter. The culture flasks were incubated in a rotary incubator at a target temperature of 20°C ± 2°C under continuous white light (6000-10000 lux) for 72 hours.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (DCP)

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

247 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

247 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

234.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

149.2 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

177.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 104.6 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Remarks on result:

other: Result is for the N-methyl salt component of the formulated product.

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

ca. 66.69 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Remarks on result:

other: Result is for the N-methyl salt component of the formulated product.

Details on results:

Microscopic examination indicate no unusual cell growth or deformity at any of the test concentrations. Algal cells were numerated using a Particle Count Analyser in this study. Negative inhibition was observed at test concentrations of 100 mg/l after 72 hours in this study. Negative inhibition was also observed at a concentration of 100 mg/l tested after 48 hours in this study. The lowest concentration of test material producing complete (100%) inhibition of the test culture was at a concentration of 316.2 mg/l after 72 hours in this study. There was clear evidence of a dose response in this study. The formulated product contains 53% of the registered substance. Assuming a linear dose-response relationship, 53% of 234.2 mg/l = 124.13 mg/l. Therefore the EC50 for the registered substance is proposed to be 124.13 mg/l.

Results with reference substance (positive control):

The mean cell number after 72 hours was 29763 per ml. After 72 hours 35.7% inhibition of growth rate was observed.

Mean cell numbers (per ml) determined for each control and test media

Exposure period (hours)	Test material concentration (mg/l)
	Control	100	177.8	316.2	562.3	1000	DCP
0	3321	3321	3321	3321	3321	3321	3321
24	3834	5235	4862	2829	1610	723	2286
48	14480	28483	12781	2484	1243	636	6850
72	100424	102282	59592	2811	1073	817	29763

 Percentage inhibition of growth rate (I_µi) values determiend for each test media and the positive control

Exposure period (hours)	Test material concentration (mg/l)
	Control	100	177.8	316.2	562.3	1000	DCP
24	-	Negative inhibition	Negative inhibition	>100	>100	>100	>100
48	-	Negative inhibition	8.5	>100	>100	>100	50.8
72	-	Negative inhibition	15.3	>100	>100	>100	35.7

Validity criteria fulfilled:

yes

Conclusions:

The 72 hour EC50 (growth rate) was 234.2 mg/l. There was clear evidence of a dose response in this study, however, the substance dose not require classification as toxic to algae/aquatic environment. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 234.2 mg/l = 104.6 mg/l. Therefore the EC50 for the registered substance is proposed to be 104.6 mg/l. The substance is not considered to be toxic to aquatic algae.

Executive summary:

The toxicity of the test material (a formulated product containing the registered substance) to aquatic algae was determined in accordance with the EN ISO Guideline for Testing of Chemicals 10253:1998. The study was conducted using the marine algae Skeletonema costatum. Algae was exposed to the test material over a range of 100, 177.8, 316.2, 562.3 and 1000 mg/l. The exposed algae was monitored over a period of 72 hours to determine the concentration of test material which inhibited algal growth rate by 50% i.e. the EC₅₀. The 72 hour EC₅₀ (growth rate) of the test material was 234.2 mg/l. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 234.2 mg/l = 104.6 mg/l. Therefore the EC₅₀ for the registered substance is proposed to be 104.6 mg/l. The registered substance is not considered to be toxic to aquatic algae.

Description of key information

The 72 hour EC50 of the a formulated product containing the registered substance was 234.2 mg/l. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 234.2 mg/l = 104.6 mg/l. Therefore the EC50 for the registered substance is proposed to be 104.6 mg/l. The substance is not considered toxic to aquatic algae.

Key value for chemical safety assessment

EC50 for marine water algae:

104.6 mg/L

EC10 or NOEC for marine water algae:

66.69 mg/L

Additional information

The toxicity of the test material (a formulated product containing the registered substance) to aquatic algae was determined in accordance with the EN ISO Guideline for Testing of Chemicals 10253:1998. The study was conducted using the marine algae Skeletonema costatum. Concentrations of the test substance were prepared over a concentration range of 100 mg/l to 1000 mg/l. The exposed algae was monitored over a period of 72 hours to determine the concentration of test substance which inhibited algal growth rate by 50% i.e. the EC₅₀. The 72 hour EC₅₀of a formulated product containing the registered substance was 234.2 mg/l. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 234.2 mg/l = 104.6 mg/l. Therefore the EC₅₀ for the registered substance is proposed to be 104.6 mg/l. The substance is not considered to be toxic to aquatic algae. An equivalent study was conducted on a formulated product containing a structurally similar substance (tosyl salt) to the registered substance. The EC₅₀ of the formulated product was found to be 23 mg/l. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 23 mg/l = 10.28 mg/l. Therefore the EC₅₀ for the registered substance is proposed to be 10.28 mg/l. The read-across substance is considered harmful to aquatic algae and is classified as Aquatic Chronic 3. Read-across between the registered substance and the test substance (tosyl salt) is considered justified owing to the structural similarity of the two substances. Both are salts of a carboxylic acid and triethanolamine. The acid components are structural isomers and differ only in the position of a single methyl group in the N-methyl salt. This is not expected to change the bioavailability of the substances, and both substances have shown similarity in the results of other physical endpoints such as water solubility. The EC₅₀ of triethanolamine was found to be >1000 mg/l. Triethanolamine was not considered to be toxic to aquatic algae.

An equivalent study was conducted on a formulated product containing a structurally similar substance (tosyl salt) to the registered substance. The EC₅₀ of the formulated product was found to be 23 mg/l. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 23 mg/l = 10.28 mg/l. Therefore the EC₅₀ for the registered substance is proposed to be 10.28 mg/l. The read-across substance is considered harmful to aquatic algae and is classified as Aquatic Chronic 3. Read-across between the registered substance and the test substance (tosyl salt) is considered justified owing to the structural similarity of the two substances. Both are salts of a carboxylic acid and triethanolamine. The acid components are structural isomers and differ only in the position of a single methyl group in the N-methyl salt. This is not expected to change the bioavailability of the substances, and both substances have shown similarity in the results of other physical endpoints such as water solubility. The EC₅₀ of triethanolamine was found to be >1000 mg/l. Triethanolamine was not considered to be toxic to aquatic algae.