Allyl (cyclohexyloxy)acetate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The PBT Assessment for the substance is based on the criteria set out in the “Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT Assessment”.

 

Persistence

The substance is not readily biodegradable based on screening criteria. This was shown in a study according to EU Method C.4-E (24% biodegradation after 28 d) and a BOD test (24.1% biodegradation after 28 d). Thus, the substance meets the screening criterion for persistency and is considered to be potentially persistent (P) or very persistent (vP) in the environment.

 

Bioaccumulation

In accordance with ECHA Guidance R.11 (ECHA, 2017) the substance is not considered to meet the screening criterion for bioaccumulation in aquatic species since the log Kow of 2.8 is below the trigger value of 4.5.

However, according to ECHA Guidance R.11 (ECHA, 2017) there is indication that accumulation in air breathing organisms might occur based on the calculated log Koa of 5.4 (calculated with KOAWIN v.1.1 using the Henry’s law constant of 6.23 Pa m³/mol and the Log Pow of 2.8 as input parameters) in combination with the log Kow > 2. These screening values (Kow and Koa) referred to in the ECHA Guidance R.11 are a function of the modelled organisms, food webs and environments used to obtain these values. To develop this partition coefficient combination it was clearly indicated in the guidance that biomagnification potential is only assumed for substances with high chemical absorption efficiency from the diet, no biotransformation after absorption and negligible active transport (in or out).

The evaluation of the toxicokinetic behavior indicates a high absorption potential of the substance from the lung, skin and gastrointestinal tract. The relatively low molecular weight of 198.26 g/mol, moderate log Pow of 2.8 and relatively high water solubility of the substance (1.655 g/L) favour oral and skin absorption. However, there is evidence for biotransformation and active transport of the substance after uptake. The molecular weight (< 300 g/mol) and the water solubility of the molecule (1.655 g/L) are properties favouring excretion via urine. The potential metabolites following enzymatic metabolism were predicted using the QSAR OECD toolbox (v4.1, OECD, 2017). 16 hepatic and 2 dermal metabolites were predicted for the test substance, respectively. Primarily, hydroxylation of the substance occurs in the liver, while only hydrolysis occurs in the skin. In general, the hydroxyl groups make the substances more water-soluble and susceptible to metabolism by phase II-enzymes. Up to 78 metabolites were predicted to result from all kinds of microbiological metabolism for the substance. Most of the metabolites were found to be a consequence of the degradation of the molecule. For further details on the toxicokinetic behavior please refer to the toxicokinetic statement in IUCLID section 7.1.

A repeated dose 28-day oral toxicity study according to OECD 407 is available and did not show mortalities or adverse systemic effects on mammals. According to the ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11 (2017) absence of effects in the long-term study is an indication that the compound is not bioaccumulative and chronically non-toxic to mammals.

Reliable QSAR models (BCFBAF Program v3.01) incorporated in the EPI Suite v4.1 interphase, were additional used to calculate the bioconcentration factors (BCF) of the substance. A BCF value of 32.69 L/Kg was predicted by the regression based model (Meylan, 1997) while a BCF of 20.36 L/Kg was estimated by the Arnot & Gobas model (2003) taking biotransformation into account (biotransformation rate kM = 9.349/d). These results show a low bioaccumulation potential of the substance and support the toxicocinetics outcome concerning the biotransformation of the substance after uptake. 

In conclusion, the trigger values for biomagnification in air-breathing (terrestrial) organisms as stipulated in the ECHA Guidance R.11 are likely to overestimate the potential for biomagnification in the food chain. Even though absorption via oral exposure has been evident the described metabolic and excretion pathways are likely to minimize biomagnification in the food chain.

Thus, the substance does not meet the screening criterion for bioaccumulation and it is not considered to be bioaccumulative (B) or very bioaccumulative (vB) in the environment.

Toxicity

Long-term aquatic toxicity results are available for aquatic invertebrates and algae. The lowest long term effect value was identified for aquatic invertebrates with a NOEC (21 d) of 3.2 mg/L which is above the trigger value of 0.01 mg/L. The substance is furthermore not classified for carcinogenicity, mutagenicity, reproduction toxicity or specific target organ toxicity according to Regulation (EC) No 1272/2008 (CLP) and all further amendments (ATPs). Thus, the criteria set out in Annex XIII of Regulation (EC) No 1907/2006 are not met and the substance is not considered to meet the T criterion.

In conclusion, the substance is not considered to be PBT or vPvB.