1-(5,5-dimethyl-1-cyclohexen-1-yl)pent-4-en-1-one

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

1.7 µg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

17 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.17 µg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

PNEC marine water (intermittent releases):

1.7 µg/L

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

4.6 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.242 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.024 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:

0.047 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

5.67 mg/kg food

Assessment factor:

90

Additional information

Aquatic toxicity:

Two experimental studies of reliability 1 (based on international guidelines and GLP compliance) and three QSAR results(ECOSAR v1.11 QSAR model) are available to assess the aquatic toxicity of the registered substance to the three aquatic trophic levels: aquatic invertebrates, algae and fish.

Experimental acute studies, assessed as key studies and performed on the registered substance, are available on the aquatic invertebratesDaphnia magnaand on the freshwater green algaePseudokirchneriella subcapitata.The 48h-EC50 value on aquatic invertebrates was determined at 1.7 mg/L and the 72h-ErC50 value on algae was determined at 3.4 mg/L. Also, the72h-ErC10 value on algae was determined at 1.7 mg/L.

No experimental study is available on fish but a valid QSAR prediction was provided to fulfil the endpoint. This QSAR (ECOSAR v1.11 available from the U.S. EPA), assessed as a key data for the acute fish endpoint, was performed on the registered substance. The estimated 96h-LC50 value was determined at 1.90 mg/L.

This QSAR model was also used, as supporting information, to predict the acute toxicity of the substance to daphnid and green algae. Similar results or results slightly more conservative were predicted with the QSAR model, validating the model for use with this substance, for the acute fish endpoint.

In conclusion, the most sensitive species in acute conditions is the aquatic invertebrates, Daphnia magna, with a 48h-EC50 value at 1.7 mg/L.

As the registered substance is biodegraded totally in the environment to form two degradation products: succinic acid (degraded also and mineralized completely) and 3,3 -dimethyl cyclohexanone (DMCH). The aquatic toxicity of the relevant degradation product of the registered substance, DMCH, to the three trophic levels were estimated using the same QSAR model presented above, ECOSAR v1.11.The estimated endpoint values (E(L)C50) were all greater than 40 mg/L. Therefore,the relevant degradation product of the registered substance, DMCH, is presumably not Toxic (T) in the PBT assessment context.

In addition, no experimental study was performed on the registered substance to assess the toxicity to microorganisms. However, a study was performed on a read-across substance, to assess the effect of the test substance on the respiration rate of activated sludge after a contact time of 3 hours, according to OECD Guideline 209 with GLP statement. This source substance is a mixture of two isomers:1-(5,5-Dimethyl-1-cyclohexen-1-yl)-4-penten-1-one, present as the major constituent at ca. 66% in the mixture, and corresponding to the registered/target (mono-constituent) substance, and 1-(3,3-Dimethyl-1-cyclohexen-1-yl)-4-penten-1-one, present at ca. 30% as second constituent.

According to this study, no statistically significant inhibition of the respiration rate of the sludge was recorded at a loading rate of 46 mg/L. At higher loading rates the inhibitory effect of test substance on aerobic waste water (activated sludge) bacteria increased with increased loading rate, ranging from 22% inhibition at 100 mg/L to 47% at 1000 mg/L. In conclusion, the test substance is considered not toxic to waste water bacteria (activated sludge) at a loading rate of 46 mg/L (NOEL). Based on structural/composition similarity, comparing physicochemical and environmental properties and ecotoxicological profile, both substances (the source and the target substances) no significant differences between the two is expected on the activated sludge respiration inhibition. Therefore, the same conclusion applies on the registered/target substance.

Sediment/Terrestrial toxicity and secondary poisoning:

In the absence of any ecotoxicological data for sediment-dwelling/soil organisms, the PNEC sediment/soil were calculated using the equilibrium partitioning method (EPM). Furthermore, no toxicity studies reporting the secondary poisoning effects on bird were available, therefore the combined toxicity study performed on a read-across substance with the reproductiuon/developmental toxicity screening test in rats by dietary administration was used to derive the PNECoral.

Environmental fate and pathways:

The registered substance is considered hydrolytically stable at environmentally relevant pH and not readily biodegradable. However, the registered substance disappears totally in the biodegradation study to form two degradation products: succinic acid (degraded and mineralized completely) and 3,3-dimethyl cyclohexanone (called DMCH, which is present at 100% after 28 days). Therefore, the registered substance is not considered persistent. DMCH also is not considered persistent in the environment according to QSAR prediction: 62% biodegradation after 60 days and predicted ultimate half life at 19 days (well below the threshold value of 40 or 60 days for P or vP criteria).

The registered substance is low mobile in soils (according to P.J. McCall et al., 1980) with a Koc value at 1386 L/kg (log Koc = 3.142) and with a log Kow value at 4.1, is considered to be bioaccumulative according to CLP criteria (> 4.0) but is not considered to be bioaccumulative according to PBT criteria (< 4.5).

Conclusion on classification

No harmonised classification is available on the registered substance.

1 < lowest E(L)C50 value < 10 mg/L; EC10 algae > 1 mg/L; not readily biodegradable; log Kow > 4.0.

Classification according to the Annex VI of the Regulation (EC) No 1272/2008 (CLP): The registered substance is classified as Chronic Category 2 (H411) for the environment.