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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Three  toxicity studies on marine algae have been assessed. 
The resulting EC50 and NOEC results for growth rate were:
- 72h EC50: 0.23 mg/l, NOEC: 0.02 mg/l
- 72h EC50: 0.080 mg/l, NOEC: 0.065 mg/l
- 72h EC50: 0.19 mg/l, NOEC: 0.108 mg/l
The results of these studies have been used in a 'geometric mean' approach (see discussion) to calculate the key EC50 value (based on growth rate).
Marine algae has been shown to be more sensitive to the test substance than marine fish or invertebrates.
Results from a toxicity study in freshwater fish have been read-across from a suitable structural analogue substance, Fatty acids, C18 unsaturated, reaction products with diethylenetriamine (also referred to a Tall oil diethylenetriamine imidazoline).
The following results were obtained: The EC50-values with 95 % confidence intervals for inhibition of specific growth rate (ErC50) and yield (EyC50) after 72 h were 0.505 (0.461 – 0.568) and 0.356 (0.347 – 0.367) mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.505 mg/L
EC50 for marine water algae:
0.15 mg/L
EC10 or NOEC for freshwater algae:
0.343
EC10 or NOEC for marine water algae:
0.052 mg/L

Additional information

Marine Data:

Three marine algal studies with Skeletonema costatum have been conducted on the substance (Fatty acids, C18 unsaturated, reaction products with diethylenetriamine, acetate salts), the results of which are discussed below:

Study reference: Beslagic A (2006)

A skeletonema costatum acute toxicity test (72 hours) has been performed on the test substance based on ISO 10253 "Water Quality Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum".

The tested concentrations were 0.02, 0.5, 1, 2.5 and 10 mg/l (nominal whole product).

The EC50 value found (nominal whole product) after 72 hours was 0.23 mg/l. The EC10 value was estimated to be 0.06 mg/l, the EC90 value was estimated to be 0.42 mg/l and the NOEC value estimated to be 0.02 mg/l.

No analytical measurement of test material concentrations in samples was performed.

All control parameters were within recommended ranges and the test considered valid.

Study reference: Anderson K (2006)

A study was performed to determine the 72-hour growth LOEC (lowest observed effect concentration) and NOEC (no observed effect concentration), and the 72-hour EC50 of the test item, PR-9026 Acetate Salt, to Skeletonema costatum growth under acute, non-renewal test conditions.

The study was conducted according to International Standard, ISO 10253, First Edition, 1995 -10 -01 Water Quality - Marine algal growth inhibition test with Skeletonema costatum and Phaeodactylum tricornutum.

Test concentrations were 0 (dilution water control), 0.065, 0.108, 0.180, 0.300 and 0.500 mg/L.

The 72-hour effect concentration (EC50) for PR-9026 Acetate Salt was determined to be 0.080 mg/L, and the 72-hour growth NOEC and LOEC value were determined to be 0.065 mg/L and 0.108 mg/L respectively.

No analytical measurement of test material concentrations in samples was performed.

Control exposures had acceptable growth and an interpretable dose-response curve was obtained.

All water chemistry values were within recommended thresholds.

Study reference: Steevens M W (2006)

A 72 hour acute algal assay was performed to assess the effect of BL5060 on the growth rate and biomass of Skeletonema costatum.

The test substance BL5060 was supplied as a 25.82% solution in water (i.e. active ingredient 25.82%).

The study was conducted to the following protocol: Water Quality - Marine algal growth inhibition test with Skeletonema

costatum and Phaeodactylum tricornutum. (Draft International Standard ISO/DIS 10253.2, ISO/TC 147/SC 5, 1994 -05-17)

Test concentrations were 0 (control), 0.04, 0.07, 0.13, 0.24, 0.42, 0.75, 1.3, 2.4, 4.3 mg/L (nominal whole product).

Upon addition of the product to the test media, it was observed that BL5060 was completely soluble in water.

Toxicity Values (in mg/l):

 

Biomass*

Growth rate*

24 hr EC50

0.49

0.49

48 hr EC50

0.56

0.69

72 hr EC50

0.58

0.74

72 hr EC90

0.75

0.87

72 hr NOEC

0.04

0.42

* Values given based on nominal whole product.

The 72 EC50 and NOEC values based on active ingredient are:

72 hr EC50 growth rate: 0.19 mg/l (active ingredient)

72 hr EC50 biomass: 0.15 mg/l (active ingredient)

72 hr NOEC growth rate: 0.108 mg/l (active ingredient)

72 hr NOEC biomass: 0.01 mg/l (active ingredient).

No analytical measurement of test material concentrations in samples was performed.

Key value for marine water algae:

As three studies in marine algae (Skeletonema costatum)

have been conducted (i.e. there are three validated short-term/acute toxicity studies available for the same species and end-point), it is considered appropriate to calculate a geometric mean result value, to harmonise the results of the separate studies.

This approach is in accordance with ECHA Guidance on information requirements and chemical safety assessment, Chapter R.10: Characterisation of dose [concentration]-response for environment. This guidance states that multiple values for the same endpoint with the same species should be investigated, looking for differences between results. For equivalent data on the same end-point and species, the geometric mean should be used as the input value.

An assessment of the three marine studies conducted concluded that the results were of a sufficiently similar magnitude to validate a 'geometric mean' approach. The studies were also run to sufficiently similar methods and under sufficiently similar test conditions. The differences in the three results obtained were assessed to be caused by normal biological variation between studies done on the same test substance (studies performed on different batches of test material with minor differences, differences between laboratories etc). It is therefore considered that the 'geometric mean' approach is justified in this case and no one study should be taken as the definitive result.

The key EC50 value (for growth rate) for marine algae is therefore given as the 'geometric mean' result of the three Skeletonema costatum studies.

The most sensitive marine species was determined to be algae. The 'geometric mean' algal result has therefore been used as the key result in the environmental assessment.

Freshwater data (Read-across data):

The results of a freshwater algal study on Fatty acids, C18 unsaturated, reaction products with diethylenetriamine (also referred to as Tall oil diethylenetriamine imidazoline) have been read-across to evaluate the toxicity to freshwater algae of Fatty acids, C18 unsaturated, reaction products with diethylenetriamine, acetate salts.

Study reference: Scheerbaum, D (2010):

Tall oil diethylenetriamine imidazoline (CAS No. 68442-97-7) was found to inhibit the growth of the freshwater green alga Pseudokirchneriella subcapitata after 72 h with the following effect values (nominal concentrations): The EC10-values with 95 % confidence intervals for inhibition of specific growth rate (ErC10) and yield (EyC10) after 72 h were 0.343 (0.325 – 0.371) and 0.265 (0.249 – 0.277) mg/L, respectively. The EC50-values with 95 % confidence intervals for inhibition of specific growth rate (ErC50) and yield (EyC50) after 72 h were 0.505 (0.461 – 0.568) and 0.356 (0.347 – 0.367) mg/L, respectively.

The concentrations of Tall oil diethylenetriamine imidazoline were analysed at the concentration levels 0.320 and 3.20 mg/L (prepared without algae) and the control at test start via LC-MS/MS analysis. The measured concentrations at test start were in the range of 79 – 89 % of the nominal values. At the end of the test Tall oil diethylenetriamine imidazoline was analysed at concentration levels 0.320 and 3.20 mg/L (prepared without algae) and gave recoveries of < LOQ - 22 % of the nominal values. Biodegradation as possible reason for this decrease is very unlikely considering the short time frame, also the river water was frozen before use to minimize the microbial activity. The decrease is attributed to additional sorption to suspended matter and DOC due to thermodynamically driven redistribution of the sorbed fraction. No test item could be recovered from the glassware (lower than 5 µg/L, which was the lowest analytical standard). This means that less than 1.6 % of the nominal concentration was observed sorbed to glassware. Therefore all effect values are given based on nominal concentrations of the test item.

The test item effect was observed to be reversible at 1.00 – 3.20 mg/L. Therefore, there is potential for recovery following exposure up to 3.20 mg/L (second highest test concentration).

Discussion on read-across results:

The read-across result for the freshwater algal study are in line (same order of magnitude) with the marine results obtained for the acetate salts. It should also be taken into account that the freshwater study included measurement of concentrations of test material in test samples, whereas the marine studies did not include analytical measurements of test material in samples, so the results are based on nominal concentrations.

In the freshwater study the concentrations of the test substance (Tall oil diethylenetriamine imidazoline) were not maintained throughout the exposure period, showing that test material was lost over the test period. It is considered likely that this would also be the case for theFatty acids, C18 unsaturated, reaction products with diethylenetriamine, acetate salts.

It is considered that the results obtained from studies on Fatty acids, C18 unsaturated, reaction products with diethylenetriamine (Tall oil diethylenetriamine imidazoline) are suitable to read-across to and for use in the evaluation of Fatty acids, C18 unsaturated, reaction products with pentaethylenehexamine acetate salts (cas 64754 -93 -4).

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