C8-18 alkylampho(di)propionates

Endpoint summary

Description of key information

Using a theoretical approach based on the available physico-chemical properties and toxicological data, the following absorption factors were derived for risk assessment purposes: oral absorption factor: 50%; dermal absorption factor: 50%; inhalation absorption factor: 100%

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

A substance can be absorbed via the gastro-intestinal tract, respiratory tract or the skin. An assessment of toxicokinetic parameters and specifically absorption is made here based on physicochemical parameters of the test substance (surfactant fraction only).

In general, a substance needs to be dissolved before it can be taken up from the gastro-intestinal tract. The critical micelle concentration (CMC) of C8 -18 alkylampho(di)propionate can be seen as an indication of the water solubility and hydrophilicity of the test substance. The moderate CMC of 131 mg solids/L indicates that this substance will dissolve in water, and to some extent in lipophilic environments. In addition, as the substance is manufactured as an aqueous solution at ca. 38.5% solid content, it is expected to dissolve in the gastro-intestinal fluid. The molecular weight of the main constituents (380 - 474 g/mol) of C8-18 alkylampho(di)propionate also favours absorption. The low partition coefficient octanol/water (−2.31) discourages passive diffusion. The presence of an ionisable group (or groups) may impair the absorption as ionised substances do not easily pass the gastro-intestinal wall. C8-18 alkylampho(di)propionate has weak surface-active properties, as shown by the surface tension of 36-39.5 mN/m. Based on this, local disruption of cell membranes is expected to be minimal, which is confirmed by the absence of local effects in the studies performed.

Based on the available physical/chemical properties of C8-18 alkylampho(di)propionate, for risk assessment purposes the oral absorption of C8-18 alkylampho(di)propionate is set at 50%. The results of the toxicity studies do not provide reasons to deviate from this proposed oral absorption factor.

Once absorbed in the gastro-intestinal tract, C8-18 alkylampho(di)propionate might be metabolized. Excretion of C8-18 alkylampho(di)propionate and its metabolites will occur via the bile (high molecular weight) or the urine (low molecular weight). Based on the log partition coefficient of −2.31, C8-18 alkylampho(di)propionate is not expected to accumulate in adipose tissue.

The low vapour pressure (< 5.8 x 10^-3 Pa) indicates that it is not likely that C8-18 alkylampho(di)propionate will reach the nasopharyncheal region or subsequently the tracheo/bronchial/pulmonary region by inhalation of vapour. However, if C8-18 alkylampho(di)propionate reaches the tracheobronchial region, C8-18 alkylampho(di)propionate dissolves within the mucus as indicated by its favourable water solubility. The low log Pow (−2.31) is less favourable for absorption directly across the respiratory tract epithelium by passive diffusion. Therefore, for risk assessment purposes the inhalation absorption of C8-18 alkylampho(di)propionate is set at 100%.

The molecular weight of 380-474 g/mol and the moderate to high water solubility are in favour of dermal absorption. The low log Pow disfavours dermal absorption. The substance has weak surface active properties, but is not expected to damage the skin (only slight erythema observed - reversible within 48 hours - in skin irritation studies). According to the criteria given in the REACH Guidance, 10% dermal absorption will be considered in case MW >500 and log Pow <-1 or >4, otherwise 100% dermal absorption should be used. As the physical/chemical properties of C8-18 alkylampho(di)propionate do not meet the criteria for limited dermal absorption, for risk assessment purposes dermal absorption should be set at 100%. However, as it is generally accepted that dermal absorption does not exceed oral absorption, 50% dermal absorption is considered to be a more realistic dermal absorption factor. The results of the toxicity studies do not provide reasons to deviate from this proposed dermal absorption factor.