(tetrapropenyl)succinic acid

Endpoint summary

Description of key information

No experimental studies of the absorption, distribution, metabolism or elimination of 2-(C12-rich-branched olefins from propene oligomerization)-1,4-butanedioic acid

in mammals are available. However, the physical chemical properties and the existing toxicology studies on the compound have been used to infer as far as possible, the potential toxicokinetics of the substance.

 

The substance is an organic UVCB and is a viscous golden liquid. The molecular weight (MW) of the components ranges between 242.31 to 326.47 g/mol, with MW of the most prevalent component being 284.39 g/mol. The entire substance is poorly water-soluble (0.091 µg/L at 20ºC for the water soluble fraction and not for the entire substance).Given the chemical structure and nature of the substance, the partition coefficient (Log Kow/Log Pow) was estimated using Estimation Program Interface EPI ver. 4.1. to range from 3.2863 to 6.0859.The vapour pressure was determined to be 1.162×10^-4 Pa at 20°C and 1.933×10^-4 Pa at 25°C.

 

Absorption

The relatively low MW range would appear to favour oral absorption however, the low water-solubility and the diffuse octanol/water partition coefficient may limit the rate absorption from the gut. Acute oral studies, as well as repeat dose oral studies (dose range-finder for main studies) conducted at high doses showed that the substance is irritating to the stomach and gut. The substance is also irritating to the skin, and is more severely irritating to the mucous membranes of the eye. Irritation could theoretically increase absorption, and severe deterioration of general conditions requiring the sacrifice of the animals occurred following a couple of doses at 1000 mg/kg/day and, in the case of females, few more doses at 300 mg/kg/day. Following a single oral dose, mortalities were only observed at very high doses largely exceeding the limit dose of 2000 mg/kg bw. Considering the necropsy findings, these mortalities were all due to local irritation/loss of integrity of the gastric mucosa rather than systemic effects. Repeated oral doses of 100 mg/kg/day for 28 consecutive days (OECD 407) or more (OECD 421) were well tolerated, without any mortality and no evidence of any target organ of toxicity. Based on this information, it is clear that significant oral absorption is likely, but the exact extent cannot be determined, and so, in accordance with ECHA guidance, is assumed to be 50% for risk assessment purposes.

 

With respect to inhalation absorption, in the absence of any quantitative data, and as a worst-case assumption, for risk assessment purposes absorption by inhalation of the substance is assumed to be 100%.

 

Since the principal barrier of the skin is provided by the stratum corneum, superficial lesions of the skin may have a significant effect on dermal absorption. The substance is not a skin sensitiser but it is irritating to the skin (Cat. 2). Skin irritation can enhance dermal absorption/penetration that, in the case of mild irritation, is expected to be no more than 2-3 fold. In addition, a substance must be sufficiently soluble in water to partition from the stratum corneum into the epidermis, and the water solubility of even a water soluble fraction of the substance is very low. The range of estimated Log Pow values would also suggest that absorption would be favourable for some components, but limited to extremely-limited, for other components. In the absence of any quantitative data and in line with latest EC guidance on dermal absorption (EFSA Panel on Plant Protection Products and their Residues (PPR); Guidance on Dermal Absorption. EFSA Journal 2012;10(4):2665), 25% dermal absorption will be used for risk assessment purposes.

 

Distribution

Repeat-dose oral toxicity studies did not identified any target organ. The relatively low molecular weight of the components would suggest wider distribution although this might be countered by the low water solubility. The range of estimated Log Pow values suggest that the intracellular concentration of components may be higher than extracellular concentration, and preferential partition to fatty tissues. There was no evidence of bioaccumulation from the available repeat-dose toxicity studies, and no alteration of fat colour (the substance is a viscous golden liquid) was ever observed.

 

Metabolism and Excretion

Nothing could be inferred from the results of the Ames test or in vitro genotoxicity studies (chromosome aberration and gene mutations in mammalian cells), because the substance was not genotoxic, mutagenic or clastogenic in either the presence or absence of S9 metabolising system. Some of the components within the substance may be metabolised to facilitate the renal/biliary excretion of the metabolites through conjugation of the hydroxy groups to glucuronic acid and/or sulphate.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

25

Absorption rate - inhalation (%):

100