Hexane, 1,6-diisocyanato-, homopolymer, 2-hydroxyethyl acrylate- and propylene glycol monoacrylate-blocked

Endpoint summary

Description of key information

No studies on the toxicokinetic properties of the test substance were available. However, according to the REACH guidance document R7.C (June 2017), information on absorption, distribution, metabolism and excretion may be deduced from the physicochemical properties. Based on the phys-chem properties and the available toxicological data, the substance is expected to be partially absorbed by the oral route but less likely by the dermal route, with an overall low bioaccumulation potential.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

There are no published data which could be identified on the toxicokinetics of the substance. However, as per REACH guidance document R7. C (June 2017), information on absorption, distribution, metabolism and excretion may be deduced from the physico-chemical properties including:

-       Water solubility

-       Partition coefficient

-       Vapour pressure

-       Molecular weight

The substance is a UVCB, with majority of the constituents having a molecular weight >500. It is a liquid with a tested water solubility of 183.5 mg/L. Volatility was determined to be very low (4.44 E-6 Pa at 20°C) and has a limited lipophilic character (log Kow of the major components between 1.323 and 3.617). Taking into account the upper limit of log Kow (3.6) and the water solubility (183.5 mg/L), accumulation of the substance is considered to be unlikely.

Oral and gastrointestinal (GI) absorption: Given the water solubility and partition coefficient range of the substance, it is likely to be partially soluble in GI fluid. However, based on the high molecular weight of majority of the constituents, it can then be expected to be partially absorbed through the GI system. Reversible, adaptive increase in liver weights was observed at the high dose animals in the repeated dose toxicity study. This confirms the oral absorption of the substance. However, in absence of actual data, the default value of 50% has been considered for the oral absorption.

 

Inhalation absorption: Given the log Kow range of the major constituents and the indication for oral absorption, possible systemic uptake of the substance after inhalation exposure could be expected, although this would occur only when aerosol or vapour is created under particular conditions (e.g. spraying, elevated temperature/pressure). Therefore, a worst-case value of 100% has been considered for the inhalation absorption.

 

Dermal absorption: Dermal absorption of the substance is expected to be slow due to binding to skin of the acrylate group. According to REACH guidance document R7.C (June 2017), dermal absorption is maximal for substances with molecular weights below 500 and log Kow values ranging between 1 and 2. The majority of the constituents of the substance have average molecular weights of >500 g/mol and log Kows between 1.3 and 3.6. This suggests that the substance may not penetrate very easily through skin. However, the substance is a skin irritant cat. 2 and a skin sensitizer cat. 1B which suggests dermal absorption to some extent. Predictions for dermal penetration from the DERMWIN software of EPISUITE 4.1 indicates that the low molecular weight constituents (which represents approx 30% of the total substance) have low dermal absorption. Therefore, owing to the observed local dermal effects a conservative estimate of 50% has been considered for human dermal absorption.

  

Bioaccumulation potential: Based on the physico-chemical information (log Kow, structure not containing ionisable elements and water solubility), it is concluded that the potential for bioaccumulation is low.

 

Metabolism: No specific information could be found on metabolism, but evidence from other types of acrylates suggests that hydrolysis of the ester bond is likely to occur, producing acrylic acid and the corresponding alcohol, which are subsequently metabolised through usual metabolic routes. This hydrolysis is mediated by the ubiquitous tissues and circulating carboxylesterases.