3-methylbutanone

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.044 mg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.442 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.004 mg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

100 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.877 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.088 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.15 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Short-term aquatic toxicity was assessed in pre-GLP studies using a nominal concentration of 100 mg/L with six species of invertebrates (Daphnia magna,Dugesiadorotocephala, Lumbriculus variegates, Gammarus fasciatus, Caecidotea intermediaandPlanorbella trivolvis) and one vertebrate fish species (Pimephales promelas). No adverse effects were observed in this study. Due to concerns over the volatility of this substance a subsequent GLP, 96-hour acute study (OECD 203) withOncorhynchus mykisswas conducted using a flow through system and nominal concentrations up to 100 mg/L. Some losses of the test substance were recorded but no mortality was observed in the study at mean measured concentrations up to 68 mg/L. A subsequent GLP, 48-hour acute study (OECD 203) withDaphnia magnawas also conducted using a static renewal exposure and measured test concentrations.  Some losses of the test substance occurred during this study and the mean measured concentration for the highest exposure was 81 mg/L. 5% immobilization was observed in the highest concentration but this was not considered an adverse response from exposure to the test substance. Therefore, the NOEC was reported as 81 mg/L, the highest concentration tested. While the GLP studies did not achieve a mean measured concentration of 100 mg/L due to losses attributed to volatility of the substance, the lack of adverse effects at the highest concentrations tested, along with the lack of effects in the tests using nominal concentrations of 100 mg/L, support a weight of evidence that the LC/EC50 for fish and invertebrates are ≥ 100 mg/L. A 72-hour algal growth inhibition study was also conducted usingSelenastrum capricornutumusing five nominal concentrations up to 125 mg/L. Significant losses (67 -78%) of the test material were observed over the 72 -hour exposure period and the results were expressed as the geometric mean of the measured test concentrations. The 72 hour EC50 for biomass was estimated to be 34.0 mg/L. The 72 hour EC50 for growth rate was estimated to be 44.2 mg/L. The 72-hour NOEC value for both biomass and growth rate was estimated to be 14.8 mg/L. The results for the growth rate endpoints are being used as the key values for the chemical safety assessment for algal toxicity.  No test for inhibition of sewage sludge microorganisms is available for MIPK.  However, for purposes of defining the key value for the chemical safety assessment, read across to the activated sludge respiration inhibition test results for the structural analog substance, Methyl Isoamyl Ketone (MIAK), is being performed. In addition to both substances being structurally similar, both substances underwent ready biodegradation studies using the same methodology, OECD 301D Closed Bottle Test, and both substances were found to be readily biodegradable. MIAK exhibited 67% degradation in the 28 day study and MIPK exhibited 85.1%. As MIAK exhibited less degradation it is believed that this the result from the MIAK activated sludge respiration inhibition test is conservative for read across to MIPK. The activated sludge respiration inhibition test of MIAK exhibited no inhibition to the microorganisms under the conditions of the test (NOEC =1000 mg/L) which has been used to define the PNEC using an assessment factor of 10.

Toxicity data for terrestrial organisms are not available. As the substance is readily biodegradable and has a low adsorptive (log Koc < 3) as well as a bioaccumulative (log Kow < 3) potential, direct and indirect exposure of the soil compartment is unlikely. The equilibrium partitioning method is utilized to assess the hazard to terrestrial organisms.

Conclusion on classification

Adequate acute data for aquatic invertebrates, fish, and aquatic algae are available along with ready biodegradation and log Kow data for assessing classification according to CLP and GHS criteria. In addition the chronic NOEC from the algal toxicity study allows further assessment of classification according to GHS and the March 2011 revision of the CLP for substances with adequate chronic data available. MIPK is rapidly degradable based upon a demonstration of ready biodegradability. MIPK also has a log Kow of < 4. Based upon the most sensitive acute endpoint of an algal EC50 for growth rate of 44.2 mg/L, and the most sensitive chronic endpoint from the algal study NOEC of 14.8 mg/L, in conjunction with the persistence and bioaccumulation data, MIPK does not meet the criteria for classification for environmental effects under the European CLP regulation.  However, under the GHS regulations MIPK would be classified as Acute Category 3 based upon the algal EC50 being >10 but < 100 mg/L. MIPK would not be classified for chronic effects under the GHS regulations.