Linalyl acetate

Toxicity to microorganisms

Additional information

Two studies with the target substance linalyl acetate are available addressing the toxicity against microorganisms. Since linalyl acetate hydrolyses in aqueous media rapidly into linalool, alpha-terpineol and geraniol, the toxicity to microorganisms was evaluated by a read-across to these hydrolysation products as well.

In the first study performed with linalyl acetate, the respiration of the bacteria within 30 minutes in presence of the target substance was tested in compliance with ISO 8192 at nominal test item concentrations of 100 and 1000 mg/L. The initial biomass concentration in the test solutions and blank control was 1 g/L. Test solutions were prepared without solvents. Based on the nominal test concentration a 30-min EC20>1000 mg/L was determined (BASF AG, 1989).

In a non-GLP oxygen consumption test according to ROBRA (1979), Pseudomonas putida was exposed over the duration of 30 minutes to the target substance at nominal concentrations of 1250, 2500, 5000 and 10000 mg/L (BASF AG, 1988). A stock solution of nominal 10000 mg/L was prepared using Tween 80 (105 mg/L) as a solvent and by additional stirring. In addition, a solvent control containing 105 mg/L Tween 80 was conducted. No analytical monitoring of the test item concentrations in the test solutions was performed.  Based on inhibition of total respiration, the 30-min EC10 and EC50 were determined to be > 10000.0 mg/L (nominal). However, since a solvent (Tween 80) was used in this test and the documentation is insufficient, the study was disregarded and is not further used in risk assessment.

The toxicity of the source substance linalool towards microorganisms was assessed in a GLP-compliant test according to OECD 209 using activated sludge of a predominantly domestic sewage (DSM Nutritional Products, 1991). The nominal test item concentrations were: 100.7, 32.22, 10.07, 3.22 and 1.01 mg/L (1 bottle per concentration). A blank control without the test item and a positive control with the reference substance 3,5-Dichlorophenol (32, 10 and 3.2 mg/L) was performed in parallel (2 bottles per control). The sludge concentration in the test vessels was 1.6 g/L (dry weight). Due to the volatility of the substance the determination of the inhibitory concentration on the respiration of aerobic wastewater bacteria was done with bubbling duration of 30 minutes and 3 hours. Test item concentrations were analytically monitored by GC/FID analyses, but no information was reported on measured concentrations. In result, the EC50 (30 min) and 3-h EC50 of the reference substance was determined to be 24.0 and 19.9 mg/L, respectively, confirming the suitability of the test system. The 30-min EC50 and the 3-h EC50 as well as the 3-h EC10 of linalool were found to be >100 mg/L based on the nominal concentrations. The test is regarded to be valid because the respiration rates of the control samples were within 15% from each other and the 3-h EC50 of the reference substance was in accepted range.

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: The toxicity of alpha-Terpineol to microorganisms was determined as part of a toxicity control in a GLP-compliant OECD Guideline 310 study. Activated sludge (obtained from a wastewater treatment plant treating predominantly domestic wastewater) was exposed to 64.8 mg/L sodium acetate (positive control) with and without addition of 25.7 mg/L alpha-Terpineol. The oxygen depletion in both solutions was measured and compared. Inhibition of the degradation of sodium acetate by the addition of alpha-Terpineol did not occur. Moreover, inhibition of the endogenous respiration of the inoculum by the test substance was also not detected. The NOEC for microorganism toxicity is 25.7 mg/L.

Two guideline studies on the respiration and growth of microorganisms exposed to the source substance geraniol are available. A non-GLP study conducted in compliance with OECD 209 investigated the respiration inhibition induced by the substance in activated sludge. The activated sludge inoculum originated from laboratory wastewater treatment plants fed with municipal and synthetic sewage. The nominal test concentrations used were 12.8, 100 and 1000 mg/l. Based on the respiration rate an EC50 of 70 mg/l was determined after an inoculation time of 30 minutes based on nominal test substance concentration (BASF AG, 1994). In a second GLP study following DIN 38412, part 8 the effect of the substance on the growth of Pseudomonas putida was terminated after 16 hours inoculation time. For preparation of the stock solution, an aqueous extract was prepared by dissolving 10000 mg/l of the test substance in deionised water under constant stirring for ca. 17 hours. The resulting emulsion was permitted to separate for 3 hours. The phase containing undissolved product was removed and the remaining aqueous extract was used for preparation of the test dilutions with deionised water. Nominal test concentrations were 31.25, 62.5, 125, 250, 500, 1000, 2000, 4000 and 8000mg/l. The study reports an EC50 of 3832 mg/l (BASF AG, 1994).