Reaction Mass of (4R)-4-isopropenyl-1-methylcyclohexene and (4R)-4-(2-methoxypropan-2-yl)-1-methylcyclohexene

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

07- 10 November 2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Guideline:

other: REACH guidance on QSARs R.6, OECD Guideline 201 (Freshwater Alga and Cyanobacteria Growth Inhibition Test), with modifications from OECD Series on Testing and Assessment no. 23 on ecotoxicity testing of difficult substances.

Principles of method if other than guideline:

The QSAR method was validated using data from tests preformed using the OECD document 23 recommnedations for poorly water soluble complex mixtures. The QSAR is thus validated ot be compliant inline with such methods/recommendations.

Specific details on test material used for the study:

The QSAR method was validated using data from tests preformed using the OECD document 23 recommnedations for poorly water soluble complex mixtures. The QSAR is thus validated not be compliant inline with such methods/recommendations.

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

9.3 mg/L

Remarks on result:

other: QSAR predicted value

Details on results:

Result is based on growth rate inhibition of algae.

The approach uses a thermodynamically based module to calculate the water concentrations and the individual toxicity of each of the constituent is first derived from a QSAR model validated to be compliant with the OECD recommandations for QSAR modeling (OECD, 2004). Then the effective loading rate of the mixture to the test organisms (i.e. algae) is determined as a Water Accommodated Fraction (WAF) test (OECD, 2000).

The overall validity of the approach depends on the validity of the input endpoints. All endpoints estimated for each constituent were within the applicability domain of the QSAR used. Therefore, the overall EL50 predicted for algae is conisdered relaible.

Conclusions:

The 72 hour ErL50 to algae of the reaction mass of (4R)-4-isopropenyl-1-methylcyclohexene and (4R)-4-(2-methoxypropan-2-yl)-1-methylcyclohexene, estimated from the iSafeRat v.2.2 QSAR inputs from each constituent, calculations based on thermodynamics of each constituent and there eventual contribution to the toxicity was 9.3 mg/L. The endpoint value is considered valid for use in risk assessment (including PBT assessment) and classification and labelling. The prediction is adequate as contributing data for the Classification and Labelling or risk assessment of the substance as indicated in REACH Regulation (EC) 1907/2006: Annex XI Section 1.3.

Executive summary:

The approach uses a thermodynamically based module to calculate the water concentrations and the individual toxicity of each of the constituent is first derived from a QSAR model validated to be compliant with the OECD recommandations for QSAR modeling (OECD, 2004). Then the effective loading rate of the mixture to the test organisms (i.e. algae) is determined as a Water Accommodated Fraction (WAF) test (OECD, 2000).

The inputs into the model all came from reliable QSAR estimations. The endpoint value is considered valid for use in risk assessment (including PBT assessment) and classification and labelling. The prediction is adequate as contributing data for the Classification and Labelling or risk assessment of the substance as indicated in REACH Regulation (EC) 1907/2006: Annex XI Section 1.3.

The 72 hour ErL₅₀ for the test substance was estimated to be 9.3 mg/L.

Description of key information

Constituent 1: (4R)-4-isopropenyl-1-methylcyclohexene: 72 h ErC₅₀ = 0.50 mg/L; REACH guidance on QSARs R.6, OECD Guideline 201 (Freshwater Alga and Cyanobacteria Growth Inhibition Test), with modifications from OECD Series on Testing and Assessment no. 23 on ecotoxicity testing of difficult substances (Anon., 2017).

Key value for chemical safety assessment

EC50 for freshwater algae:

0.5 mg/L

Additional information

Algal growth inhibition endpoints and expected concentrations of each constituent in the mixture

Constituent Name	72h-ErC50^a (mg/L)	Concentration in the WAF (mg/L)
(4R)-4-isopropenyl-1-methylcyclohexene (limonene)	0.50	1.7
(4R)-4-(2-methoxy-2-propanyl)-1-methylcyclohexene (ether MT)	9.6	4.3
1-methyl-4-(2-propanylidene)cyclohexene (terpinolene)	0.60	0.72
cis-1-methoxy-1-methyl-4-(1-propen-2-yl)cyclohexane (cis-1-methoxy-8-pmenthene)	9.1	0.37
2-[(1S)-4-methyl-3-cyclohexen-1-yl]-2-propanol (α-terpineol)	62	0.25
trans-1-methoxy-1-methyl-4-(1-propen-2yl)cyclohexane (trans-1-methoxy-8-p-menthene)	9.1	0.12
1-methoxy-1-methyl-4-(2-propanylidene)cyclohexane (1-methoxy-4-p-menthene)	11	0.22
cis-1-methoxy-4-(2-methoxypropan-2-yl)-1-methylcyclohexane (cis-1,8-dimethoxy-p-menthane)	174	0.69
trans-1-methoxy-4-(2-methoxypropan-2-yl)-1-methylcyclohexane (trans-1,8-dimethoxyp-menthane)	174	0.10
7-methyl-3-methylene-1,6-octadiene (myrcene)	1.1	0.02
1-methyl-4-(2-propanyl)-1,3-cyclohexadiene (α-terpinene)	1.4	0.03
1-methyl-4-(2-propanyl)-1,4-cyclohexadiene (γ-terpinene)	0.60	0.05

^aindividual reports for each constituent presented in Section 6.1.5

Constituent 1 ( (4R)-4-isopropenyl-1-methylcyclohexene) 72h ErC50 = 0.50 mg/L used for chemical safety assessment.