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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity of C16-22-(even numbered)-alkylamines o the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201 under GLP conditions. The EC50 was established to 0.444 mg/L and the EC10 to 0.282 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.444 mg/L
EC10 or NOEC for freshwater algae:
0.282 mg/L

Additional information

The toxicity of C16-22-(even numbered)-alkylamines o the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201 with the definitive exposure phase from 2011 -11 -21 to 2011 -11 -24.The aim of the study was to assess the effects on growth rate and yield over a period of 72 hours. Five concentration levels were tested in a geometrical series with a dilution factor of√10, nominal: 0.0500 - 0.159 - 0.501 - 0.1.58 - 5.00 mg/L. Three replicates were tested for each test item concentration and six replicates for the control.Environmental conditionswere determined to be within the acceptable limits.

The concentrations of C16-22-(even numbered)-alkylamineswereanalysed at all concentration levels after 0 and 72 hours via LC-MS/MS analysis.The measured initial concentrations of C16-22-(even numbered)-alkylamines were in good accordance with the nominal concentrations.The per cent of nominal in the fresh media (0 hours) of the fractions C18 and C22 of C16-22-(even numbered)-alkylamines were determined to be in the range of 91 to 116 % and 93 to 137 % of the nominal values, respectively. In 72 h old media, the C18 and C22 fractions had decreased, but were still detectable. The recoveries in the old media (72 hours) of the fractions C18 and C22 of C16-22-(even numbered)-alkylamines decreased to values in the range between 19 to 53 % and 27 to 107 % of the nominal values, respectively.

Adsorption to the test vessels after 72 hours of exposure were determined at the three highest dosage levels 0.501 to 5.00 mg/L. The absorbed amount of the C16- and the C22-fraction was in the range of 2.64 to 5.63 % of the applied amount.

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. Nevertheless the test item is present in the test system and therefore available for exposure (dissolved in water and sorbed). 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).

Due to the properties of the test item, all effect values given are based on nominalconcentrations of C16-22-(even numbered)-alkylamines instead of measured ones (seeTable1).

EC - Values and 95 % Confidence Intervals of C16-22-(even numbered)-alkylamines

                      (0-72 hours)

                      (based on the nominal concentrations of C16-22-(even numbered)-alkylamines [mg/L]

Rate-related Inhibition

NOEC

0.159

LOEC

0.501

ErC10

0.282 (0.247 – 0.326)

ErC20

0.333 (0.298 – 0.366)

ErC50

0.444 (0.424 – 0.455)

Inhibition of Yield

NOEC

0.159

LOEC

0.501

EyC10

0.191 (0.171 – 0.235)

EyC20

0.218 (0.194 – 0.260)

EyC50

0.274 (0.240 – 0.318)