Bis(2-butoxyethyl) adipate

Endpoint summary

Description of key information

A basic toxicokinetics assessment was prepared based on physicochemical and toxicological properties according to REACH R.7C Guidance. Absorption was considered to be most likely by oral route. Distribution is considered to be possible, but  limited due to low water solubility. Intracellular concentration is expected to be higher than extracellular concentration, based on its rather lipophilic character.   Although urinary excretion is not expected, most probably biotransformation to more polar and water soluble substances will lead to elimination via the kidney. As the substance is rather lipid soluble, other excretion routes such as via the bile are possible.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

80

Absorption rate - dermal (%):

20

Absorption rate - inhalation (%):

100

Additional information

Absorption of Bis(2-butoxyethyl) adipate was assessed based on physicochemical/toxicological data:

-   Oral absorption is assumed to be possible, but moderate. Based on the low water solubility (101 mg/L), a high systemic exposure seems unlikely as in general a compound needs to be dissolved before it can be taken up from the gastro-intestinal tract. However, its rather highly lipophilic character (log P 3.78) may promote uptake by micellular solubilisation and the molecular weight (346.46) also allows absorption. The oral route is considered to be the default route for toxicity testing. An oral absorption of 80% is proposed from a conservative viewpoint for risk assessment purposes.

- Bis(2-butoxyethyl)adipate aerosol particles may theoretically be absorbed by the lungs, however based on the very low vapour pressure (0.00559 Pa), the probability that it enters the airways is low, certainly at the lower respiratory tract (alveoli).If reaching the alveoli, an inhalation absorption of 100% is considered from a conservative viewpoint for risk assessment purposes (or for DNEL calculation).

-   Dermal absorption is considered to be very low, which is confirmed by the calculation in Dermwin, demonstrating a very low dermal permeability coefficient (0.006 cm/hour) and very low dermally absorbed daily dose (0.015 mg/kg bw/day).A dermal absorption of 20% is proposed for risk assessment purposes (or for DNEL calculation).  

Once absorbed, further assessment of distribution, metabolism and accumulation and excretion of Bis(2-butoxyethyl) adipate were assessed as follows:

-   Distribution is considered to be possible, however limited due to low water solubility. However, as distribution mostly takes place by protein binding, it is possible, as demonstrated by toxicity in the repeated dose toxicity study. Intracellular concentration is expected to be higher than extracellular concentration, based on its rather lipophilic character.

-   Based on the lipid solubility it may concentrate in adipose tissue depending on the conditions of exposure, however accumulation is not expected. Once exposure stops, the concentration in the body will most probably decline at a rate determined by the half-life of the substance.

-   Although urinary excretion is not expected, most probably biotransformation to more polar and water soluble substances will lead to elimination via the kidney. As the substance is rather lipid soluble, other excretion routes such as via the bile and milk (if applicable) are possible. Accumulation is not expected.