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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity to algae was tested according to OECD guideline 201 under GLP. The ErC50 was observed to be 65.2 µg/L and the ErC10 was observed to be 40.6 µg/L (Reliability 1).

Key value for chemical safety assessment

EC50 for freshwater algae:
65.2 µg/L
EC10 or NOEC for freshwater algae:
40.6 µg/L

Additional information

The toxicity of N-C12-14-alkyltrimethylenediamines(CAS No. 90640-43-0) to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the principles of OECD-Guideline 201 (2006) (Noack, 2009). The aim of the study was the determination of EC10- , EC20- and EC50- values of growth rate and yield over a period of 72 h.

An individual test design was applied. Natural river water was used as dilution medium. The study was conducted under static conditions with an initial cell density of approximately 1 x 104cells/mL. Five concentrations were tested in a geometrical series with a dilution factor of 2, nominal:6.25 - 12.5 - 25.0 - 50.0 - 100 µg/L. Three replicates were tested for each concentration level and 6 replicates for control. Environmental conditions were determined to be within the acceptable limits.

The concentrations of N-C12-14-alkyltrimethylenediamines (CAS No. 90640-43-0) were analysed at all concentration levels at test start and test end via LC-MS/MS analysis. The measured concentrations at test start were in the range of 100 - 132 % of the nominal values. At the end of the test N-C12-14-alkyltrimethylenediamines gave recoveries of below the limit of quantification (LOQ) to 8 % 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 was attributed to additional sorption to suspended matter and DOC due to thermodynamically driven redistribution of the sorbed fraction. Therefore all effect values are given based on nominal concentrations of the test item.

N-C12-14-alkyltrimethylenediamines (CAS No. 90640-43-0) 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 40.6 (31.3 – 45.8) and 29.2 (24.3 – 34.9) µg/L, respectively. The EC50-values with 95 % confidence intervals for inhibition of yield (EyC50) and specific growth rate (ErC50) after 72 h were 65.2 (57.5 – 81.6) and 43.1 (37.2 – 49.5) µg/L, respectively.

After 72 h algae were transferred from the nominal concentration of 50 and 100 µg/L and control to fresh untreated medium and allowed to grow for further 5 d under test conditions. The test item effect was observed to be reversible at this concentration. Therefore, there is potential for recovery following exposure up to 100 µg/L (highest test concentration). The effects are expressed as nominal values because the tests were performed with river water as they are intended to be used in an evaluation of the environmental risks based on the Bulk approach.