Sodium mentholate

Endpoint summary

Description of key information

Key_Short-term toxicity to aquatic invertebrates: EC₅₀(48h) = 44.2 mg/L (arithmetic mean measured), NOEC (48h) = 29.4 mg/L (arithmetic mean measured) for Daphnia magna (static, freshwater, OECD 202, GLP)

Key_Toxicity to aquatic algae and cyanobacteria: E_rC₅₀(72h) = 1.86 mg/L, E_rC₁₀(72h) = 1.17 mg/L and NOE_rC (72h) = 0.556 mg/L based on arithmetic mean measured concentrations for Pseudokirchneriella subcapitata (static, freshwater, OECD 201, GLP)

Additional information

Short-term toxicity to aquatic invertebrates

The toxic effect of the test item Sodium mentholate to the aquatic invertebrate Daphnia magna was assessed in a static concentration-response test according to OECD TG 202 taking into account the guidance document no. 23. Young daphnids, less than 24 hours old, from in-house laboratory culture were exposed to 5 test concentrations and a control in groups of 5 individuals per test vessel. Four replicates were prepared for each concentration and the control. To avoid loss of test item due to volatilisation, the test vessels were kept closed during the exposure period of 48 hours. The test conditions (water temperature, dissolved oxygen content, pH and light) were within the ranges requested by OECD TG 202 and the validity criteria stated in the guideline were met.

The biological results were based on the endpoint immobility which was assessed every 24 hours. Besides the highest concentration with 100% immobility, immobility was detected only in the test concentration of 13.4 mg/L (10% immobility). At the lower test concentrations and the control no immobility or other sign of intoxication were observed.

The initial concentrations and the maintenance of the exposure concentrations during the test were analytically verified by GC-MS. The quantification of the test item Sodium mentholate was performed indirectly by analysing the hydrolysis product menthol in the test samples using liquid/liquid extraction followed by measurement via gas chromatography with MS detection. Direct analysis of Sodium mentholate was not feasible due to its hydrolysis instability (DT50< 5min). Since the test item concentrations were not within ± 20% of the nominal concentrations during the test, the biological results refer to arithmetic mean measured concentrations.

Based on the arithmetic mean measured concentrations of the test item the 48-hour NOEC was determined to be 29.4 mg test item/L. The 48-hour LOEC was determined to be 66.3 mg test item/L and the 48-hour EC50 value was determined to be 44.2 mg test item/L, both values also based on arithmetic mean measured test concentrations.

 

Toxicity to aquatic algae and cyanobacteria

The study was conducted under GLP according to OECD 201 and taking into account the OECD guidance document no. 23. The purpose of this test was to determine the inhibitory effect of the registered substance on the growth of the freshwater green algae Pseudokirchneriella subcapitata.

For this purpose, exponentially growing cultures of this unicellular green algal species were exposed to concentrations nominal 7.5, 2.4, 0.75, 0.24 and 0.075mg test item/L and a control under defined conditions. The inhibition of growth in relation to control cultures was determined over a test period of 72 hours, and thus over several algal generations. To avoid loss of test item due to volatilisation, the test vessels were kept closed with a reduced headspace during the exposure period of 72 hours. The test conditions (water temperature, dissolved oxygen content, pH and light) were within the ranges requested by OECD TG 201 and the validity criteria stated in the guideline were met.

The initial concentrations and the maintenance of the exposure concentrations during the test were analytically verified by GC-MS. The quantification of the test item was performed indirectly by analysing the hydrolysis product menthol in the test samples using liquid/liquid extraction followed by measurement via gas chromatography with MS detection. Direct analysis of the test material was not feasible due to its hydrolysis instability (DT50 < 5min). Since the test item concentrations were not within ± 20% of the nominal concentrations during the test, the biological results refer to arithmetic mean measured concentrations.

Based on the arithmetic mean measured concentrations of the test item the 72-hour E_yC₅₀was calculated to be 1.08 mg test item/L and the 72-hour E_rC₅₀value was calculated to be 1.86 mg test item/L. The 72-hour NOE_yC was determined to be 0.556 mg test item/L and the associated 72-hour LOE_yC was 1.71 mg test item/L based on arithmetic mean measured test concentrations. The 72-hour NOE_rC was determined to be 0.556 mg test item/L and the associated 72-hour LOE_rC was 1.71 mg test item/L,both values also based on arithmetic mean measured test concentrations.

 

Due to the fast hydrolysis of the registered substance (DT₅₀ < 5min), the ready biodegradability could not be determined experimentally. However, it could be successfully demonstrated that the main hydrolysis product menthol is inherently biodegradable, with a degradation of 95.1 % within 5 days with a rate of 17.7 mg COD g^-1h^-1. Accordingly, the registered substance can be considered to be readily and rapidly degradable.

Taking into account the rapid degradability and considering all available data on short- and long-term toxicity to aquatic organisms, the registered substance does not show any acute or chronic hazard for the aquatic environment and does not need to be classified according to Regulation (EC) No 1272/2008.