1,6-Octadien-3-ol, 3,7-dimethyl-, acid-isomerized

Endpoint summary

Additional information

Lime oxide is a multi-constituent substance with poorly soluble components of different solubility. For such a mixture, the acute effect loading level (typically expressed as the EL50 or LL50) from aquatic tests using water-accommodated fractions (WAFs) may be used directly for classification. Studies performed on Lime oxide gave an acute daphnia 48h EL50 of 5.3mg/L and a green algae 72h ErL50 of 15mg/L. Based on a valid fish study for the read-across substance Sinpine P, which has a similar composition to Lime Oxide, the 96h LL50 is estimated to be 6.8mg/L. Since all EL50 values are > 1mg/L, the substance is not classified for short-term hazards to the aquatic environment according to the CLP Regulation 1272/2008/EC.

 

Chronic aquatic toxicity data is only available for one trophic level (algae). Therefore, the long-term hazard has been assessed based on both:

a)   The chronic aquatic toxicity data for algae (ErL10 = 11 mg/L) which results in no classification and

b)   The acute aquatic toxicity data (daphnia EL50 = 2.8mg/L, fish LL50 = 6.8mg) and environmental fate data for the constituents of Lime oxide (log Kow range of 3.3 to 4.9) which results in a chronic 2 classification for the substance because the majority of constituents have a log Kow > 4,

and classifying according to the most stringent outcome.

 

Thus it is concluded that the substance is classified Aquatic Chronic 2 (H411) according to the CLP Regulation 1272/2008/EC & adaptation 286/2011/EC. Under the old DSD regulation the substance would be classified as R51/53 (harmful to aquatic organisms and may cause long-term adverse effects in the aquatic environment).

 

The components present in Lime Oxide can be divided into unsaturated monoterpene hydrocarbons (C10H16, MW 136) and monoterpene ethers (C10H18O, MW 154). These two types of components have different environmental fate and aquatic toxicity properties. Therefore, two assessment entities have been used to assess the environmental exposure and environmental risk of Lime Oxide. One assessment entity is the group of unsaturated monoterpene hydrocarbons and the other assessment entity is the group of monoterpene ethers. In order to derive appropriate PNECS for the risk assessment, the aquatic toxicity of the individual constituents and impurities have been considered and, applying a conservative approach, the worst-case EC50 or LC50 value chosen for each assessment entity.

 

 Assessment Entity: Unsaturated Monoterpene Hydrocarbons

 

The unsaturated monoterpene hydrocarbons present in Lime oxide are listed in the table below. In the absence of any experimental data owned by the lead registrant, the acute EC50 or LC50 values for three trophic levels were estimated using ECOSAR v1.11. All substances are assigned to the neutral organic ECOSAR class confirming that they are expected to act via the same mode of action, baseline narcosis.

 

Component (reference substance name)	CAS	Concentration range, %	Fish 96h LC50 mg/L	Daphnia 48h LC50 mg/L	Green Algae 96h EC50 mg/L
p-mentha-1,3-diene	99-86-5	20-30	0.380	0.278	0.592
p-mentha-1,4-diene	99-85-4	10-20	0.380	0.278	0.592
p-mentha-1,4(8)-diene	586-62-9	10-15	0.291	0.215	0.482
3-methyl-6-(1-methylethylidene)cyclohexene	586-63-0	3-9	0.380	0.278	0.592
1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene	138-86-3	2-7	0.323	0.238	0.522
(E)-3,7-dimethylocta-1,3,6-triene	3779-61-1	1-5	0.292	0.216	0.483
(Z)-3,7-dimethylocta-1,3,6-triene	3338-55-4	0.5-3	0.343	0.252	0.547
7-methyl-3-methyleneocta-1,6-diene	123-35-3	0.5-3	0.292	0.216	0.483

 

The EC50 or LC50 QSAR estimates across all species and all components are within a narrow range with the lowest value being 0.215mg/L and the highest value 0.592mg/L. The estimates are considered reliable given that the QSAR models are valid and the components fall within their applicability domain. Experimental data available for (R)-p-mentha-1,8-diene supports the reliability of the predictions: 96h fish LC50 = 0.720 mg/L, 48h daphnia EC50 = 0.307 mg/L, 72h algae ErC50 = 0.320 mg/L (key studies in REACH registration, EC 227-813-5). Given that the estimated and experimental data shows that daphnia is the most sensitive species for this group of chemicals, only the daphnia LC50 predictions for the unsaturated monoterpene hydrocarbon components are included in the dossier as a robust study summary. The lowest estimated value of 0.215 mg/L has been chosen for derivation of PNEC aquatic for the assessment entity “Unsaturated Monoterpene Hydrocarbons”.

Assessment Entity: Monoterpene Ethers

 

The monoterpene ethers present in Lime oxide are: 

 

(E)-tetrahydro-2,2-dimethyl-5-(1-methyl-1-propenyl)furan, CAS 56058-69-6, concentration range 15-25%

(Z)-tetrahydro-2,2-dimethyl-5-(1-methyl-1-propenyl)furan, CAS 56058-70-9, concentration range 0.5-3%

Cineole, CAS 470-82-6, concentration range 2-7%

1-methyl-4-(1-methylethyl)-7-oxabicyclo[2.2.1]heptane, CAS 470-67-7, concentration range 0.5-3%

 

Experimental data is available for cineol (CAS 470-82-6). All studies are valid and rated “reliable without restrictions”. They were conducted according to OECD guidelines, under GLP and with analytical determination of the test substance. The daphnia 48h EC50 was > 100mg/L, the algae 72h ErC50 > 74mg/L and the fish 96h LC50 was 57 mg/L. All studies are available in the respective REACH registration. The close structurally related saturated ether (CAS 470-67-7) would be expected to have similar aquatic toxicity.

 

In the absence of experimental data for the unsaturated components (CAS 56058-69-6 and 56058-70-9), read-across to a closely related structurally analogue has been used. The source substance (Limetol, CAS 7392-19-0, EC 230-983-3) is an Annex VII REACH registered substance, with reliable experimental data for acute daphnia and algae. The respective 48h and 72h EC50 values are 32mg/L and 72mg/L.

Based on the above experimental data for the monoterpene ether constituents, the lowest EC50 of 32mg/L has been used to derive PNEC aquatic for the assessment entity “monoterpene ethers”. The daphnia source study and read-across justification are included in this dossier.

Toxicity to Microorganisms

Information on toxicity to STP microorganisms is required as part of the environmental risk assessment. An activated sludge respiration test (e.g. OECD 309) has not been performed on the registered substance because any effect results obtained would be unsuitable for derivation of PNEC STP. Different partitioning in the environment of the components present in Lime oxide would make comparison with PEC meaningless. In order to derive appropriate PNECs, relevant information for the two assessment entities employed in the environmental exposure and risk assessment has been used.

Absence of microbial toxicity can often be inferred from biodegradation studies. If a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value.

- For the "monoterpene ether" group, the representative component Cineole was found to be readily biodegradable in tests performed at 100 and 10 mg/L. In the former an inhibition control was also included. It showed that Cineol has no inhibitory effect on the micro-organisms at the test concentration of 100mg/L. Thus this concentration has been used to represent the NOEC for this group.

- For the "unsaturated monoterpene hydrocarbon" group, the representative substance Limonene was shown to readily biodegradable in a test performed at 10mg/L. Thus this concentration has been used to represent the NOEC for this group.