Dimethylcyclohex-3-ene-1-carbaldehyde

Endpoint summary

Description of key information

Abiotic degradation:

Air: No experimental data on the phototransformation of the substance in air are available. Based on estimation with the QSAR model AopWin (v1.92), in air the substance undergoes rapid degradation after reaction with hydroxyl radicals. The DT50-value after reaction with hydroxyl radicals is 1.03 hours. Degradation after reaction with ozone radicals is also rapid with a DT50-value of 38.38 min. This indicates that the substance is not a long-range transported chemical in air according to EU CLP (1272/2008 and its amendments). (http://www.unece.org/fileadmin/DAM/env/documents/2000/ece/eb/ece%20eb%20air.60.e.pdf). 

Water: The hydrolysis test is not needed because it is an aldehyde and does not contain hydrolysable groups such as ester, carbamates, epoxides, halomethanes, acylhalides (see Hydrowin, EpiSuite for all hydrolysable groups). 

Biodegradability

Ready biodegradability: The biodegradation of the substance was tested in a modified MITI test according to OECD 301C under GLP conditions. The test item was not biodegraded (0%) during the 28 -days and is therefore not readily biodegradable. The test item was fully primary degraded; the aldehyde functional group was converted to an acid and/or an alcohol. 

Biodegradation in a water-simulation test: Based on DRAFT REPORT

In accordance with OECD TG 309 the time course of biodegradation of a test substance in aerobic natural water at 12C is determined at 10 and 100 µg/l. The parent substance Vertoliff disappeared within minutes (<1 day) and turned into Vertoliff-acid/alcohol(s) (ROI 7), which remained stable for 14 days in the low and high concentration groups. Thereafter primarily further oxidation products were found (ROI 6 to ROI 1) and one reduction reaction towards Vertoliff-alcohol (ROI 8).

The low mineralisation of Vertoliff required identification by means of log Kow (HPLC, OECD TG 117) for all metabolites (ROIs) when exceeding the 10% level (OECD TG 309, paragraph 40). In both low and high treatment groups ROI 8, 7, 6 and 5 all decreased to <10%, mostly show a decreasing trend and therefore do not need to be considered further. In the high treatment group only ROI 4 is above 10% but shows a decreasing trend in the low treatment group. This ROI has a log Kow of 1.95, which log Kow is <2. In the low treatment group ROI 3 is just above 10% and shows a decreasing trend in both low and high treatment groups. ROI 3 has a log Kow of 1.8, which is <2. In both low and high treatment groups ROI 2 and 1 are well above 10% and increase from day 28 onwards. The log Kow values of these ROIs are 1.77 and 1.5, respectively.

Bioaccumulation

Bioaccumulation in aquatic species is based on the available information (log Kow 3.1 and calculated BCF values) and is deemed sufficient to take into account as a worst case value for the chemical safety assessment. The BCFs for aquatic and terrestrial organisms were calculated using QSARs of Veith et al. (1979) and Jager (1998), both incorporated in the EUSES model, and yielded values of 86.1 and 15.9 L/kg ww, respectively.

Bioaccumulation for air-breathing organisms based on DRAFT report of OECD TG 309: Vertoliff fulfils the screening criteria for concern for bioaccumulation in air breathing organisms: log Kow (3.1: >2) and log Koa (5.1: >5). Such bioaccumulation in air-breathing organisms may occur for non-metabolising substances because the lungs may present a less effective route for elimination compared to e.g. gills. Based on meeting the screening criteria for bioaccumulation in air-breathing organisms a water-simulation test (OECD TG 309) was performed to address the persistency of the substance and the bioaccumulation of the transformation products. In the OECD TG 309 study, Vertoliff degraded within minutes. Several transformation products were found and their log Kow were determined (HPLC using OECD TG 117). In total 8 regions of interest (ROI) were found. All ROIs were further characterised using log Kow. These log Kow decreased from ROI 8 (closest to Vertoliff) towards ROI 1, more polar products. The bioaccumulation assessment focussed on those ROIs which were exceeding the 10% at day 63 and were not transient. ROI 8, 7, 6 and 5 were all <10% after 63 days. ROIs 4 exceeded the 10% level at the high treatment group (100 µg/l) and ROI 3 at the low treatment group (10 µg/l). ROI 2 and 1 were increasing and >10% after day 63. ROI 4 to 1 all had log Kow values <2. This means that for all transformation products there is no concern for bioaccumulation in air-breathing organism either because of presence <10% or log Kow <2. In addition, there is information that Vertoliff metabolises in air-breathing organisms (see toxico-kinetic section) and the excretion pathway is via the kidneys further assuring absence of such bioaccumulation.

Environmental distribution

Adsorption/Desorption: The log Koc for Vertoliff has been determined as 2.2 (Koc = 160) using HPLC method (OECD TG 121).

The Henry’s law constant: This constant is calculated using the equation from EUSES. Using a molecular weight of 138.21 g/mol, and the experimentally determined vapour pressure of 66.1 Pa (at 24 °C) and water solubility of 381.8 mg/L (at 24 °C) the Henry’s law constant at environmental temperature (12 °C) is calculated to be 12.1 Pa·m³/mol. According to ECHA guidance R7a on Henry C: “Table R.7.1–17 Conditions that have influence on HLC values: Important for aldehydes, which hydrate nearly completely in water, resulting in HLC apparent being several orders of magnitude lower than the intrinsic constant”. 

Mackay Level III distribution: Based on Level III environmental distribution modelling using EPISUITE (using the Smiles code O=CC1CC=C(C)CC1C (and not the CAS no. because the Cas no. in EpiSuite shows an alpha-beta conjugated aldehyde while the double bond is actually not conjugated) assuming equal and continuous releases to air, water and soil) and the measured physico-chemical parameters (water solubility and log Kow) as input, it is estimated that the majority of the substance released to the environment will partition mainly into soil (66%) and water (33.8%) with small amounts to air (0.084%) and sediment (0.103%).

Distribution in the STP: The SimpleTreat model, which is incorporated in EUSES, simulates the distribution of the substance in a Sewage Treatment Plant. Model calculations show that 0% of the substance will be degraded and that 81.7%, 1.89% and 16.4% will partition to water, sewage sludge and air, respectively.