3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene

Endpoint summary

Additional information

There are no studies available in which the toxicokinetic behaviour of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) has been investigated.

Therefore, in accordance with Annex VIII, Column 1, Section 8.8.1, of Regulation (EC) No 1907/2006 and with Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2017), assessment of the toxicokinetic behaviour of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) is conducted to the extent that can be derived from the relevant available information. This comprises a qualitative assessment of the available substance specific data on physico-chemical and toxicological properties according to the Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2017).

3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooct-1-ene (CAS 25291-17-2) is a liquid at room temperature with a molecular weight of 346.09 g/mol and a water solubility of 1.21 mg/L at 25 °C. The determined log Pow value is 4.9 at 25° C and the vapour pressure is estimated to be 4640 Pa at 25 °C.

Absorption

Absorption is a function of the potential for a substance to diffuse across biological membranes. The most useful parameters providing information on this potential are the molecular weight, the octanol/water partition coefficient (log Pow) value and the water solubility. The log Pow value provides information on the relative solubility of the substance in water and lipids (ECHA, 2017).

Oral

In general, molecular weights below 500 and log Pow values between -1 and 4 are favourable for absorption via the gastrointestinal (GI) tract, provided that the substance is sufficiently water soluble (> 1 mg/L). Moderate log P values (between -1 and 4) are favourable for absorption by passive diffusion. Any lipophilic compound may be taken up by micellular solubilisation but this mechanism may be of particular importance for highly lipophilic compounds (log P >4), particularly those that are poorly soluble in water (1 mg/l or less) that would otherwise be poorly absorbed (ECHA, 2017).

The water solubility of 1.21 mg/L and the log Pow value of 4.9 of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) indicate that absorption is likely to occur by micellular solubilisation.

The available data on acute oral toxicity with 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) revealed no signs of systemic toxicity resulting in a LD50 value greater than 2000 mg/kg bw (Key, 2017). Available data on repeated dose toxicity following oral administration of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) resulted in a treatment-related increase of absolute and relative liver weights that were supported histopathologically by centrilobular lipid droplets in hepatocytes and microgranuloma, and macroscopically by an enlargement of the liver (Key, 2007). Based on the results of the conducted study, the NOAEL was determined to be 5 mg/kg bw/day and the LOAEL was determined to be 25 mg/kg bw/day for male rats.

In conclusion, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS25291-17-2) has a potential for oral absorption.

Dermal

There are no data available on dermal absorption or on acute dermal toxicity of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2). On the basis of the following considerations, the dermal absorption of the substance is considered to be low.

A molecular weight less than 100 favours dermal uptake. Above 500 the molecule may be too large. Log P values between 1 and 4 favour dermal absorption (values between 2 and 3 are optimal) particularly if water solubility is high. Above 4, the rate of penetration may be limited by the rate of transfer between the stratum corneum and the epidermis, but uptake into the stratum corneum will be high. To partition from the stratum corneum into the epidermis, a substance must be sufficiently soluble in water (ECHA, 2017). With a water solubility of 1.21 mg/L, dermal uptake of the test substance is therefore considered to be low to moderate.

The dermal absorption potential can be calculated from log Pow and molecular weight (MW) applying the following equationdescribed in US EPA (2014):

log(Kp) = -2.80 + 0.66 log Pow – 0.0056 MW

The Kp was calculated for 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2). A dermal flux rate of 3.67E-05 mg/cm2 per h was calculated indicating low dermal absorption potential for the test substance (please refer to Table 1, Dermwin v2.02, EpiSuite 4.1).

Table 1: Dermal absorption value for 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) (calculated with Dermwin v 2.02, Epiweb 4.1)

Component	Structural formula	Flux (mg/cm2/h)
3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene	C8 H3 F13	3.67E-05

 

If the substance is a skin irritant or corrosive, damage to the skin surface may enhance penetration (ECHA, 2017). However, no increased uptake of the test substance is expected, as the irritation studies with 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) showed no irritating effects (Key, 2017).

Overall, taking into account the physico-chemical properties of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2), the QSAR calculations and available toxicological data on the registered substance, the dermal absorption potential of the substance is anticipated to be low.

Inhalation

The vapour pressure of a substance indicates whether the substance may be available for inhalation as a vapour or not. Highly volatile substances are those with a vapour pressure greater than 25 kPa. Substances with low volatility have a vapour pressure of less than 0.5 kPa. Moderate log P values (between -1 and 4) are favourable for absorption directly across the respiratory tract epithelium by passive diffusion. Any lipophilic compound may be taken up by micellular solubilisation but this mechanism may be of particular importance for highly lipophilic compounds (log P >4), particularly those that are poorly soluble in water (1 mg/L or less) (ECHA, 2017).

3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) is a liquid with an estimated moderate vapour pressure (4640 Pa at 25 °C) by QSAR analysis. As the registered substance is imported in the EU solely as bound monomer in polymer,it is expected, that the vapour pressure is reduced by polymerization.

Overall, inhalation potential of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) is considered to be low.

Distribution and accumulation

Distribution of a compound within the body depends on the rates of the absorption and the physico-chemical properties of the substance; especially the molecular weight, the lipophilic character and the water solubility. In general, the smaller the molecule, the wider is the distribution. Lipophilic molecules (log P >0) are favourable for distribution into cells and the intracellular concentration may be higher than extracellular concentration particularly in fatty acids (ECHA, 2017).

Thus, due to the molecular weight (346.09 g/mol) and a lipophilic character (log P of 4.9) of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) a wider distribution is assumed and a distribution into cells and the intracellular concentration may be higher than the extracellular concentration particular in fatty tissue. Lipophilic substances will tend to concentrate in adipose tissue and depending on the conditions of exposure may accumulate. If the interval between exposures is less than 4 times the whole body half-life of the substance then there is the potential for the substance to accumulate. It is generally the case that substances with high log Pow values have long biological half-lives. On this basis, daily exposure to a substance with a log Pow value of around 4 or higher could result in a build-up of that substance within the body. Substances with log Pow values of 3 or less would be unlikely to accumulate with the repeated intermittent exposure patterns normally encountered in the workplace but may accumulate if exposures are continuous. Once exposure to the substance stops, the substance will be gradually eliminated at a rate dependent on the half-life of the substance. If fat reserves are mobilized more rapidly than normal, e.g. if an individual or animal is under stress or during lactation there is the potential for large quantities of the parent compound to be released into the blood (ECHA, 2017). Since no experimental data are available a bioaccumulation potential is assumed.

 

Metabolism

No data are available regarding metabolism. Prediction of compound metabolism based on physicochemical data is very difficult. Structure information gives some but no certain clue on reactions occurring in vivo. The potential metabolites following enzymatic metabolism were predicted using the QSAR OECD toolbox (v4.0, OECD, 2017). This QSAR tool predicts which metabolites may result from enzymatic activity in the liver and in the skin, and by intestinal bacteria in the gastrointestinal tract. Up to 7 metabolites were predicted to result from all kinds of microbiological metabolism for the test substance. Most of the metabolites were found to be a consequence of the oxidation of the molecule to increase the water solubility of the metabolites.Genetic toxicity tests in vitro showed no observable difference in effects with and without metabolic activation for 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2).

 

Excretion

The major routes of excretion for substances from the systemic circulation are the urine and/or the faeces (via bile and directly from the GI mucosa) (ECHA, 2017).

Based on the metabolism described above, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooct-1-ene (CAS 25291-17-2) is expected to be metabolised in the body to a high extent. The estimated metabolites are probably not excreted to a significant degree via the exhaled air or faeces but excreted via urine.

References

ECHA (2017). Guidance on information requirements and chemical safety assessment, Chapter R.7c: Endpoint specific guidance. Version 3.0, June, 2017.