Linalyl acetate

Toxicity to aquatic algae and cyanobacteria

Key value for chemical safety assessment

EC50 for freshwater algae:

68 mg/L

EC10 or NOEC for freshwater algae:

3.9 mg/L

Additional information

Two studies on toxicity to aquatic algae were available for the target substance. However, due to major methodological deficiencies both studies with the target substance were disregarded. Since linalyl acetate hydrolyses in aqueous media rapidly into linalool, alpha-terpineol and geraniol, the toxicity to algae was evaluated by a read-across to these hydrolysation products (see Read-across justification).

Desmodesmus subspicatus was exposed to linalyl acetate in a study conducted in compliance with OECD guideline 201 (F. Hoffmann-La Roche AG, 1994). Based on growth rate, the 72-h EC50 and NOEC were 62 and 9.6 mg/L (nominal), respectively. However, since no test substance could be detected in all concentrations at the end of the exposure, the study was disregarded and was not further used in risk assessment.

In a study according to the German standard method DIN 38412, part L9 with linalyl acetate (BASF AG, 1989), Desmodesmus subspicatus was exposed to nominal test item concentrations of 5, 10, 25, 50, 100 and 250 mg/L (4 replicates per concentration) over a total duration of 72 hours.  A stock solution of linalyl acetate was prepared using Cremophor as a solvent and ultrasonication. The stock solution was serially diluted with culture medium to obtain the desired test concentration. The maximum solvent concentration in the test was 25 mg/L. A blank control, a vehicle control and a positive control with the reference substance potassium dichromate was performed in parallel. In result, the 72-h EC10 and EC50 for the growth rate were determined to be 12.36 and 63.71 mg/L (nominal). As the linalyl acetate is not stable in aqueous media, but no analysis of the test item concentration was conducted, the study is not regarded to be valid and it was thus disregarded.

In a valid non-GLP study according to the German standard method DIN 38412 L9 with the source substance linalool (BASF AG, 1988), Desmodesmus subspicatus was exposed for 96 hours to nominal test item concentrations of 10, 32, 100, 320 and 1000 mg/L. The test solutions were prepared with 10% of Tween 80. Analyses of the test item concentrations were not performed. Therefore, biological results are based on nominal concentrations. The 96-h EC10 and EC50 (growth rate) was determined to be 54.3 and 156.7 mg/L (nominal), respectively. Based on biomass, the 96-h EC10 and EC50 were determined to be 38.4 and 88.3 mg/L (nominal). Even though there was no analytical verification of the test concentration, the study is considered as valid since it could be already demonstrated, that linalool is stable under aquatic test conditions (cf. section 6.2.3 Short-term toxicity to aquatic invertebrates). The results based on growth rate are used for the hazard evaluation. This toxicity study is classified as acceptable and satisfies the guideline requirements for the acute algae study.

Key study:

No study reports were available for source substance alpha-terpineol. However, an information summary could be collected from the ECHA disseminated dossier for CAS 98-55-5 on the ECHA website. The following description of key information regarding short-term toxicity to aquatic invertebrates was provided:

Effect of Terpineol multi was tested in a freshwater growth inhibition test on algae (Pseudokirchneriella subcapitata), following OECD guideline 201, 2006. In addition, the procedures were designed to meet the test methods of the Commission Regulation (EC) No 440/2008, Part C.3, 2008; Amended by EC No. 761/2009 and the ISO International Standard 8692, 2004. Three replicates of exponentially growing algal cultures were exposed to nominal Terpineol concentrations of 4.6, 10, 22, 46 and 100 mg/L. The initial cell density was 1E+04 cells/mL and the total test period was 72 hours. Samples for analytical confirmation of actual exposure concentrations were taken at the start, after 24 hours of exposure and at the end of the test. At the start of the test, the actual test concentrations were in agreement with nominal (96-101%). These concentrations remained stable during the first 24 hours of exposure (89-97% of initial) and slightly decreased towards the end of the test (77-92% of initial). Given these results, effect parameters were based on Time Weight Average exposure concentrations that were calculated to be 3.9, 8.8, 21, 44 and 91 mg/L. Terpineol reduced growth rate and inhibited the yield of this freshwater algae species significantly at 8.8 mg/L and higher. The EC50 or growth rate reduction (72h-ErC50) was 68 mg/L with a 95% confidence interval ranging from 55 to 82 mg/L. The NOEC for both growth rate reduction a was 3.9 mg/L.

Data on the acute toxicity of source substance geraniol itself to algae are not available. The evaluation is based on a study with reaction mass of geraniol and nerol. The toxicity of the substance to algae was tested in a GLP guideline study following OECD 201. Algal cells of the species Desmodesmus subspicatus were exposed to nominal substance concentrations of 0 (control), 1.0, 3.2, 10, 32, and 100 mg/l for 72 hours. For preparation of the stock solution, the test substance was dissolved in acetone. However, the solvent was completely evaporated and subsequently test medium was added. The solution was stirred for ca. 24 hours at 60 °C. The test solutions were prepared by dilution of the stock solution. The test substance concentration in the test medium was verified by HPLC. The growth rate of the algae was determined by measuring the vivo chlorophyll-a fluorescence. Based on the algal growth rate an EC50 of 13.1 mg/l (NOEC: 1.0 mg/l) based on measured concentration was detected (BASF SE, 2010).

Conculsion:

In conclusion, both study reports using the target substance have to be disregarded based on technical deficiencies. Therefore, the assessment of toxicity to aquatic algae is based on the hydrolysation products of linalyl acetate. Among these, green algae turned out to be most sensitive to geraniol revealing an EC50 of 13.9 mg/L. However, as mentioned above, geraniol is of only minor relevance for the assessment based on the estimated quantities after hydrolysis in an OECD 111 guideline study. After 64 hours of incubation the initially added 10.23 mg/L of linalyl acetate was reduced by hydrolysis to 0.44 mg/L geraniol, which is 4.3% of the used linalyl acetate. In contrast, alpha-terpineol and linalool are the most relevant source substances with respect to the level of their formation during hydrolysis (3.03 mg/L linalool = 29.6% and 2.03 mg/L alpha-terpineol = 19.8%). Amongst those two products, alpha-terpineol shows the most conservative EC50 and NOEC. Accordingly, the assessment of toxicity to aquatic algae is based on the information on alpha-terpineol as derived from ECHA website.