p-menth-1-en-8-ol

Toxicity to aquatic algae and cyanobacteria

Description of key information

Effect of Terpineol multi was tested in a fresh water 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. The study met the acceptability criteria prescribed by the protocol and was considered valid. 
Terpineol reduced growth rate and inhibited the yield of this fresh water 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 EC50 for yield inhibition (72h-EyC50) was 17 mg/L with a 95% confidence interval ranging from 13 to 22 mg/L. The NOEC for both growth rate reduction and yield inhibition was 3.9 mg/L.

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

The ecotoxicological effects of alpha-Terpineol alpha and Terpineol multi are expected to be highly similar, because the main constituent is alpha-Terpineol in both substances and the other constituents in Terpineol multi are close structural isomers. In addition, all constituents are neutral organics. It is not expected that there is any significant difference in their aquatic toxicity.

The study of Ikawa et al. (1992) is disregarded because the methodology includes toxicity assessment via paper disks which cannot be compared with the standard guideline for algae toxicity testing.

Ikawa, M., Mosley, S., and Barbero B., 1992, Inhibitory effects of terpene alcohols and aldehydes on the growth of green alga Chlorella pyrenoidosa, J. Chemical Ecol., 18, 1755-1760.