Amides, C16-18, N-[3-(dimethylamino)propyl]

Toxicity to aquatic algae and cyanobacteria

Description of key information

72 h ErC50 = 140 µg/L (95% c.i.130 – 154 µg/L); 72 h ErC10 = 71 µg/L (95% c.i. 63-79 µg/L); 72 h NOEC=31.6 µg/L, nominal (OECD guideline 201, GLP, RL1); read across from Stearic acid 3-(dimethylaminopropyl)amide

Key value for chemical safety assessment

EC50 for freshwater algae:

140 µg/L

EC10 or NOEC for freshwater algae:

71 µg/L

Additional information

No experimental data are available for C16-18 DMAPA amidoamine. However, a toxicity test with aquatic algae with the read-across substance Stearic acid 3-(dimethylaminopropyl)amide is available. For justification for read-across see endpoint summary "Aquatic toxicity".

The toxicity of Stearic acid 3-(dimethylaminopropyl)amide to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201 (2006). The aim of the study was to assess the effects on growth rate and yield in natural river water over a period of 72 hours.The study was conducted under static conditions with an initial cell density of 4332 cells/mL. Based on a preliminary test, 5concentration levels were tested in a geometrical series with a dilution factor of (nominal): 10.0 - 31.6 - 100 - 316 - 1000 µg/L. Three replicates were tested for each test item concentration and six replicates for the control. Environmental conditions were determined to be within the acceptable limits.

Stearic acid 3-(dimethylaminopropyl)amide is a tertiary straight chain amine. The test item had low water solubility and sorbed to organic and inorganic materials by different mechanisms. The sorption processes are mostly non-linear, means are concentration dependent. Due to these properties the test item was difficult to test in artificial water (e.g. sorption to the test organism and walls of the test vessel). Natural river water contained particulate as well as dissolved organic carbon to which the test item could sorb partially preventing that the test item settled onto surfaces. The sorbed fraction of the test item was difficult to extract from the test system which normally led to low analytical recoveries. Nevertheless the test item was present in the test system and therefore available for exposure (dissolved in water and sorbed). Sorption of the test item to the glass ware of the test system was monitored as appropriate. Due to the properties of the test item nominal concentrations were used instead of measured ones.

All test concentrations of the test item and the control were analytically verified by LC-MS/MS analysis at the start of the exposure (0 h) and the end of the exposure (72 h).
In this study the test item was found to inhibit the growth of the freshwater green alga Desmodesmus subspicatus after 72 hours with the following effect values: The NOEC-values for both inhibition of growth rate and yield after 72 hours were 31.6 µg/L. The LOEC-values for both inhibition of growth rate and yield after 72 hours were 100 µg/L. The EC50-value for inhibition of growth rate (ErC50) after 72 hours was 140 (130 – 154) µg/L. The EC50-value for inhibition of yield (EyC50) with 95% confidence intervals after 72 hours was 74.3 (68.1 – 82.0) µg/L. All effect levels are given based on nominal concentrations.

 

The following study showing similar results with C20/22 ATQ is enclosed to justify the read-across approach for sediment and terrestrial toxicity studies.

 

The toxicity of C20/22 ATQ to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201.The aim of the study was to assess the effects on growth rate and yield over a period of 72 h. The test was carried out in natural river water with a DOC of 2.8 mg/L.

The study was conducted under static conditions with an initial cell density of approximately 2 – 5 E03 cells/mL. Seven concentration levels were tested in a geometrical series with a dilution factor of √10, nominal: 0.020 - 0.063 - 0.20 - 0.63 - 2.00 - 6.32 - 20.0 mg/L, corresponding to geometric mean measured concentrations of 0.0110 - 0.0405 - 0.128 - 0.443 - 1.39 - 4.39 - 15.4 mg/L. Three replicates were tested for each test item concentration and six replicates for the control.Environmental conditions were determined to be within the acceptable limits.

The concentrations of the test item were analysed at all concentration levels after 0 and   72 h via LC-MS/MS analysis. The test item has a low water solubility and sorbs to organic and inorganic materials by different mechanisms. The sorption processes are mostly non-linear, means are concentration dependent. Due to these properties the test item is difficult to test in synthetic water (e.g. sorption to the test organisms and glass walls of the test vessels) and results from such tests depend from the test settings applied. Using natural river water which contains particulate as well as dissolved organic carbon to which the test item can sorb partially reduces the difficulties encountered in tests with synthetic water (e.g. preventing that the test item settles onto surfaces). The sorbed fraction of the test item is difficult to extract from the test system which normally leads to low analytical recoveries. Due to the short exposure period these low recoveries cannot be associated to biodegradation. This means the test substance is present in the test system and therefore available for exposure (dissolved in water and sorbed also called bulk). This so called Bulk Approach is described by ECETOC (2003).

However, all effect values given are based on geometric mean measured concentrations of the test item.

In this study C20/22 ATQ was found to inhibit the growth of the freshwater green alga  Desmodesmus subspicatus after 72 h with the following effect values (nominal test item concentrations): The EC50-values with 95 % confidence intervals for inhibition of specific growth rate (ErC50) and yield (EyC50) after 72 h were 3.48 (3.28 – 3.70) and 1.17 (0.955 – 1.30) mg/L, respectively. The test effect was observed to be reversible at all tested concentrations following 72 h exposure and 3 – 7 days of growth under test conditions. All effect levels are given based on geometric mean measured concentrations.