5-methylhexan-2-one

Endpoint summary

Description of key information

Short-term toxicity to fish:

Three reliable studies using two species of fish are available.

- EPA OPP 72-1 (Fish Acute Toxicity Test) - Pimephales promelas, flow-through, freshwater, LC50 (96h) = 159 mg/L, EC50 (96h) = 159 mg/L; NOEC (96h) >= 135 mg/L 

- EU Method C.1 (Acute Toxicity for Fish) - Oncorhynchus mykiss (previous name: Salmo gaidneri), flow-through, freshwater, LC50 (96h) > 74 mg/L, NOEC (96h) >= 74 mg/L

- OECD Guideline 203 (Fish, Acute Toxicity Test)  - Pimephales promelas, static, freshwater, LC50 (96h) > 100 a.i./L, NOEC (96h) >= 100 a.i./L

 

Short-term toxicity to aquatic invertebrates:

Two reliable studies conducted on Daphnia magna are available.

- OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) - Daphnia magna, semi-static, freshwater, EC50 (48h) > 100 mg/L; NOEC (48h) >= 91 mg/L 

- EU Method C.2 (Acute Toxicity for Daphnia) - Daphnia magna, static, freshwater, NOEC (48h) >= 100 µL/L; NOEC (96h) >= 100 µL/L;EC50 (48h) > 100 µL/L, EC50 (96h) > 100 µL/L

 

Toxicity to aquatic algae and cyanobacteria:

One study using raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum) is available.

- OECD Guideline 201 (Alga, Growth Inhibition Test) - Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum), static, freshwater, EyC10 (72h) = 19 mg/L, EyC20 (72h) = 44 mg/L, EyC50 (72h) > 100 mg/L, NOEC (72h) for biomass = 24 mg/L, ErC10 (72h) = 76 mg/L, ErC20 (72h) > 100 mg/L, ErC50  (72h) > 100 mg/L, NOEC (72h) for growth rate = 24 mg/L

 

Toxicity to microorganisms:

One study using activated sludge of a predominantly domestic sewage plant is available:

- OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test, activated sludge of a predominantly domestic sewage, 3 h, EC50 > 1000 mg/L, NOEC > 1000 mg/L

Additional information

Short-term toxicity to fish:

Three short-term 96 -hour acute fish studies have been conducted with methyl isoamyl ketone (5 -methly-2 -hexanone). One study with fathead minnows (Pimephales promelas) was conducted as a limit test at a nominal concentration of 100 µL/L and no mortalities were observed. Two additional studies were conducted as flow-through studies with measured exposure concentrations. Rainbow trout were exposed to 5 nominal concentrations up to 100 mg/L in a flow-through system. In that study no mortality was observed up through the highest test concentration which had a mean measured concentration of 74 mg/L. The key study for this endpoint was a second flow-through study with fathead minnows that resulted in a LC50 of 159 mg/L and an NOEC for mortality of 135 mg/L (both endpoints based upon mean measured concentrations).

 

Short-term toxicity to aquatic invertebrates:

The acute toxicity to Daphnia magna was evaluated under semi-static renewal conditions following OECD Guideline #202. The test was conducted using a closed system with minimal headspace to avoid losses due to volatility. The test was conducted using mean measured concentrations of 5.0, 12, 23, 45 and 91 mg/L. Based on mean measured concentrations, the 48-hour EC50 value for Daphnia magna and methyl isoamyl ketone was empirically estimated to be > 91 mg/L, the highest nominal concentration tested. The 48-hour EC50 value for Daphnia magna and methyl isoamyl ketone was extrapolated to be > 100 mg a.i./L (mean measured concentration) using linear regression. The No-Observed-Effect Concentration (NOEC) was determined to be ≥ 91 mg/L.

 

Toxicity to aquatic algae and cyanobacteria:

The 72 hour acute toxicity of methyl isoamyl ketone to the freshwater green alga Pseudokirchneriella subcapitata was conducted in a closed system following OECD Guideline 201. The test was conducted at nominal concentrations of 6.3, 13, 25, 50 and 100 mg/L in the definitive exposure. Analytical determinations of the test solutions were made at test initiation, 24 hours and test termination (72 hours) and a time-weighted mean was calculated for each treatment level. The mean measured concentrations (as time weighted average) ranged from 92 to 110 % of nominal concentrations and defined the treatment levels tested as 5.8, 12, 24, 53 and 99 mg/L. The 72-hour EyC10 value was determined to be 19 mg/L with 95 % confidence intervals of 9.0 to 40 mg/L. The 72-hour EyC20 value was determined to be 44 mg/L with 95 % confidence intervals of 30 to 67 mg/L. Since no treatment level tested resulted in ≥ 50 % reduction in yield, the EyC50 value was empirically estimated to be > 100 mg/L, the highest time weighted average concentration tested. The 72-hour NOEC for growth rate was determined to be 24 mg/L. The 72-hour ErC10 value was 76 mg a.i./L with 95 % confidence intervals of 46 to 96 mg/L. Since no treatment level tested resulted in ≥ 20 % reduction in growth rate, the 72-hour ErC20 and ErC50 values were empirically estimated to be > 100 mg/L, the highest time weighted average concentration tested.

 

Toxicity to microorganisms:

An activated sludge respiration inhibition test following OECD Guideline 209 was conducted on methyl isoamyl ketone (CAS No.110-12-3). The test was conducted using nominal concentrations of 0.1, 1.0, 10, 100 and 1000 mg a.i./L. Following three hours of aeration the oxygen depletion rate was determined during a 10 minute period. The percent inhibition was calculated at each concentration of test substance and reference substance. Based on these results, the EC50 value for methyl isoamyl ketone was determined to be greater than 1000 mg a.i./L. The EC15 (NOEC) value was calculated by linear regression in Excel and determined to be greater than 1000 mg a.i./L. The EC50 value for the reference substance, 3,5-dichlorophenol, was calculated to be 5.1 mg a.i./L, which was within the acceptable limits (5 to 30 mg a.i./L) as specified in the OECD 209 Guideline.