C16-18-(even numbered, C18-unsaturated)-alkylamines acetates

Sediment toxicity

Description of key information

For long-term toxicity on sediment organisms, the most relevant chronic test (key study) was performed on Chironomus riparius larvae according to OECD 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment). The test item was C16-18(even numbered)-alkylamine acetate. Any adverse effects on the development of the common non-biting midge Chironomus riparius in a water-sediment system were determined.

A dose response test was conducted by spiking the sediment layer. Five test item concentrations with the nominal concentrations in the sediment layer of 12.8 – 32 – 80 – 200 – 500 mg/kg sediment dry weight (factor of 2.5), corresponding to initial measured test item concentrations of 9.22 – 27.5 – 73.6 – 188 – 455 mg/kg sediment dry weight, were tested. A number of 80 first instar larvae were exposed to each test concentration and to untreated sediment serving as control (4 replicates with 20 larvae each). Water quality parameters such as temperature, pH-value and O₂-content were determined regularly throughout the study. Also, ammonium and total hardness were analysed at the day of application (day 0) and at test end (day 28) from the control sediment and the highest test item group.

The total amounts of the test item measured at day 0 were in the range of 75 to 101 % for C16-alkylamine and 70 to 94 % for C18-alkylamine of the nominal values. At day 7 the total amounts of the test item were in the range of 71 to 90 % for C16-alkylamine and 73 to 90 % for C18-alkylamine of the nominal values and at day 28 the total amount of the test item were in the range of 66 to 77 % for C16-alkylamine and 69 to 80 % for C18-alkylamine of the nominal values.

In the aqueous layer and the pore water samples the concentrations were constantly at 1 % to < LOQM during the test. The concentrations of the sediment samples during the test were 70 to 101 % at day 0, 71 to 90 % at day 7 and 66 to 80 % at day 28.

The recovery of the total amount was 72 to 94 % on day 0, 72 to 104 % of the initial measured amount on day 7 and on day 28, respectively.

In the control, emergence of the midges started 17 days after larvae insertion and was finished at day 27 after larvae insertion with an emergence of 78 %. The initial measured EC₅₀ for mortality is determined to be 412 mg/kg sediment dry weight.

Statistically significant differences of the midge emergence rate and the development rate of the midges were observed at the initial measured test item concentration of 455 mg/kg sediment dry weight when compared to the control. The results indicate a NOEC for the emergence rate and the development rate at the initial measured test item concentration of 188 mg/kg sediment dry weight. All effect values are given based on the initial measured test item concentrations. All validity criteria were met throughout the study. 

A further long-term sediment toxicity test is available for primary fatty amines:

Höß (2000) examined the toxicity of tallow alkyl amine on the nematode Caenorhabditis elegans using artificial sediment according to the method of Traunspurger et al. 1997. C. elegans is a widespread, free living nematode which is primarily found in terrestrial soils but also occurs in aquatic sediments. The nematode feeds primarily on bacteria but also on small particles such as sediment.

During the study artificial sediment (particle size distribution: 44% sand, 48% silt, 8% clay, organic content: 2%) was spiked with the test substance in various concentrations (nominal concentration range between 811 and 2030 mg/kg sed dw). Two test series were carried out, a range finding test and the main test. For spiking of sediments tallow alkyl amine was dissolved in pure ethanol and 10 µl of the ethanol stock solution was added to 0.5 g sediment that was already mixed with 0.5 ml of M9-medium (phosphate buffer). Thus, the maximum ethanol concentration did not exceed 1% which is tolerated by the nematodes. In order to allow the chemicals to equally distribute between aqueous and solid phase, the spiked sediment was incubated for 24 h before the start of the test.

Test parameters were growth (body length in µm), egg production (number of eggs inside the body) and fertility (percentage of gravid worms). Before the start of the assay, 0.25 ml of bacterial suspension (E. coli in M9 medium) were added to each vessel as food for the nematodes. After that 10 juvenile worms of the first stage (J1) were added to each vessel, containing now 0.5 g sediment (ww), 0.5 ml test solution and 0.25 ml bacterial suspension. The vessels were then incubated for 72 h on the shaker at 20°C. Five (three) replicates were set up for the main test (range finding test). In order to stop the assay, the nematodes were heat killed and stained with Rose Bengal. After extracting the nematodes from the sediment, body length and number of eggs inside the body were determined under a microscope. For tallow alkyl amine no effect up to the highest tested concentration of 2030 mg/kg sed (dw) was found. Therefore a nominal NOEC of 2030 mg/kg sed (dw) was derived from this study.

Due to their physico-chemical properties primary fatty amines and acetates are expected to sorb on sediments to a significant extent resulting in a very low concentration in the porewater. Thus, in the environment, sediment organisms will mainly be exposed to the bound substance in the solid phase by sediment ingestion and direct contact. In the available study these exposure pathways are not adequately covered as the nematodes are not representative organisms for the exposure via sediment ingestion. In addition, the nematodes were supplementary fed with a bacteria suspension, thus further reducing possible uptake of contaminated sediment by the test organisms. Summarising, this study on nematodes alone would not appropriately cover potential effects of primary alkyl amines to the benthic community. However, as nematodes are an important organism group for water and sediments, this study complements the results from the long-term sediment toxicity study on Chironomus riparius by an important further taxon.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:

188 mg/kg sediment dw

Additional information

Category Approach for Primary alkyl amines and their salts e.g. Acetates

Primary alkyl amines were already assessed for their environmental and human health hazards and risks under the EU Existing Chemicals Regulation 793/93/EEC. Industry has provided a justification for the category approach to the German rapporteur BAuA on 2001-04-07. This justification was accepted as basis for the EU Risk assessment and is used for the REACH registration as well.

Speciation of Primary alkyl amines

In aqueous medium the unprotonated and the protonated amine are in equilibrium. The percentage of the unprotonated and the protonated amine is determined by the acid constant pKa and the given pH. In the table the percentages are given as function of pH and the pKa of 10.5 for Primary alkyl amines.

pH	Percentage Protonated amine (N+)	Percentage Unprotonated amine (N)
9	97.5%	2.5%
7	99.975%	0.025%
4	99.99997%	0.000003%

CONCLUSION:

Under environmental conditions it is not relevant if the unprotonated or the protonated amine will be introduced in an aquatic medium. The composition of the protonated and unprotonated amine is solely determined by the pKa and the ambient pH (see table above). Therefore aquatic test results from the unprotonated and protonated amine are equivalent.