Methyl hexanoate

Short-term toxicity to fish

Description of key information

LC50 (48 h)= 170 mg/L (nominal)
LC50 (48 h)> 100 mg/L < 300 mg/L (nominal)
LC50 (48 h) = 1700 mg/L (nominal)
LC50 (96 h) > 0.52 mg/L (measured)

Additional information

A study evaluating the acute toxicity of methyl hexanoate (CAS No. 106-70-7) to fish is available, lasting for 48 hours. According to the Guidance on information requirements and chemical safety assessment, chapter R.7b, results obtained at shorter test durations that the standard 96 hours (OECD 203) should be treated with caution and always in combination with other data (read-across, non-testing, etc.). Therefore, according to Regulation (EC) No. 1907/2006, Annex XI, 1.2, a Weight of Evidence (WoE) approach is applied to cover adequately this endpoint, using the available data from methyl hexanoate in conjunction with the acute fish tests from structurally related category members in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5.

A test conducted according to DIN Guideline 38412/15 (German national standard method) is available for methyl hexanoate (CAS No. 106-70-7) (Richterich and Mühlberg, 2001). Fish (Leuciscus idus) were exposed to the test substance within a static water regime for 48 hours, at nominal concentrations ranging from 10 to 10,000 mg/L. After the exposure period, mortality was reported at nominal concentrations of 300 mg/L and above (100%), leading to a LC50 (48 h) of 170 mg/L (nominal).

There are two additional reports available by the same authors (Richterich and Mühlberg, 2001) for methyl octanoate (CAS No. 111-11-5) and methyl decanoate (CAS No. 110-42-9). Both were conducted according to the German national DIN Guideline 38412/15 as well, using Leuciscus idus as test organism and the same static procedure as for methyl hexanoate for 48 hours, with concentrations ranging from 10 to 10000 mg/L (nominal). After exposure to methyl octanoate (CAS No. 111-11-5) 100% mortality was observed at concentrations of 300 mg/L and above, with effects observed as well at a concentration of 100 mg/L (40% mortality). The LC50 (48 h) for this substance was determined to be > 100 mg/L and <300 mg/L. In the case of methyl decanoate, mortality was observed only at the two highest concentrations tested (3000 and 10000 mg/L) whereas no effects were observed at any other concentration. This values lead to a LC50 (48 h) of 1700 mg/L (nominal).

Additionally, a study conducted with methyl laurate (CAS No. 111-82-0) according to OECD Guideline 203 (Fish, Acute toxicity) and the Japanese Circular on Test Methods of New Chemical Substances under GLP conditions, is available (Japanese Ministry of Environment, 2006).Oryzias latipeswas exposed to the test substance within a flow-through water regime for 120 hours, at a concentration of 1 mg/L (nominal). No mortality or other adverse effects were observed at the concentration tested, leading to a LC50 (96 h) > 0.52 mg/L (measured).

 

Even considering the limitations of the 48-hour studies, effect concentrations lower than those observed in aquatic invertebrates and algae for methyl hexanoate are unlikely after a 96-hour exposure. Since results from 96 hour-studies in the category show that fish species are not the most sensitive aquatic organisms when exposed to this type of substance, the combined results from the acute fish studies for methyl hexanoate (CAS No. 106-70-7), methyl octanoate (CAS No. 111-11-5), methyl decanoate (CAS No. 110-42-9) and methyl laurate (CAS No. 111-82-0) are considered adequate to cover this endpoint.