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Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
50
Absorption rate - dermal (%):
25
Absorption rate - inhalation (%):
100

Additional information

In accordance with point 8.8.1 of column 1 (Standard Information Required), Annex VIII of REACH (Regulation EC No. 1907/2006), assessment of the toxicokinetic behaviour of the substance is performed to the extent that can be derived from the relevant available information. A toxicokinetic assessment was performed based on the available physical-chemical data and toxicological information available. Further testing for the assessment of toxicokinetic behaviour is omitted on this basis.

Introduction

The substance is a brown liquid and is a UVCB organic substance. No experimental studies of the absorption, metabolism, distribution, or elimination of Alkenes, C15-18 α-, sulfurized in mammals are available. However toxicology studies on the substance are available and these data are used to infer, where possible, the potential toxicokinetic profile of the substance.

 

Physicochemical properties

Systemic availability of the substance depends on its ability to be absorbed across body surfaces. Factors that affect this process include water solubility, lipophilicity (measured by the partition coefficient, Kow), degree of ionization (the dissociation constant, pKa), and molecular size. The components of the substance have molecular weights ranging in the region of 176-602 g/mol, with a mean molecular weight of 520 g/mol. The substance is virtually insoluble in water (≤5.6 mg/L in 20 ºC). The dissociation constant was not technically feasible. The log Kow was >9.4. With respect to the boiling point, the test material lost a volatile fraction from approximately 229 °C with decomposition as heating continued. The vapour pressure at 25 ºC was 0.052 Pa.

Absorption

Oral absorption

The acute oral LD50was greater than 2000 mg/kg bw in an acute oral gavage toxicity study (OECD 423), with no treatment related clinical signs and no effect on body weight were observed. In addition, no treatment related gross abnormalities were observed at necropsy. In an OECD 422 repeat-dose/reproductive toxicity study with there was a complete absence of any indication of toxicity up to the limit dose of 1000 mg/kg. 

Nothing can be inferred about the nature of oral absorption from these studies, although given the very high log Pow, one interpretation might reasonably be that this is a consequence of no absorption across the GIT. 

In the absence of useful qualitative or quantitative information, 50% bioavailability following oral administration is assumed for the purposes of human risk assessment.

Dermal absorption

No adverse effects were observed in an acute dermal toxicity study (OECD 402, limit dose test). Eye irritation, skin irritation and skin sensitisation studies gave no signs that the test material reacted chemically with living layers of the skin or eye. Nothing can be inferred about the dermal penetration properties of the substance from these studies. From guidance, components with MW less than 400 are expected to cross this skin barrier fairly easily but this may be mitigated to a large extent by the extremely high Kow value. As with absorption across the GIT, dermal absorption might also reasonably be considered zero.

For the purposes of risk assessment however, estimation of mammalian dermal absorption is made in accordance with principles adopted by the EFSA guidance on estimating dermal absorption of pesticide active substances (EFSA, 2012). On this basis, dermal absorption is estimated at 25% for undiluted substance.

Inhalation absorption

In the absence of any qualitative or quantitative data, absorption of the substance is considered to be 100%.

 

Distribution, Metabolism and Elimination

In an OECD 301B ready biodegradability study, a biodegradation value of 51% was obtained for the test material after 28 days. No further information is available to describe the distribution, metabolism or elimination of any substance that might be absorbed, although degradation would likely occur in the peroxisomes.

 

Conclusion

For the purposes of human risk assessment oral absorption of the substance is estimated at 50%, inhalation absorption is estimated at 100% and dermal absorption is estimated at 25%.