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Description of key information

Short description of key information on absorption rate: 
The dermal absorption of quaternary ammonium compound, di-C16-18-alkyldimethyl, chloride was assessed using:
- An in vivo dermal absorption study performed in rabbits. The study predated GLP but followed accepted scientific standards at the time of performance (Drotman, 1977)
- The physico-chemical data available for the substance ( water solubility,structure, ionogenic state, molecular weight)
- The results of the acute dermal toxicity and skin sensitization studies
The available in vivo dermal absorption study supported by the physico-chemical properties of the substance and the toxicological data using dermal route provide evidence that the dermal absorption is very low.
Therefore and in accordance with ECHA guidance R7-12, the default value of 10% skin absorption is used for the risk characterization.

Key value for chemical safety assessment

Absorption rate - dermal (%):
10

Additional information

After dermal administration of 10 mg (≈ 30μCi) 14C-labelled dialkyl (octadecyl) dimethylammonium chloride to the back of each of four rabbits over a 5 . 8 cm area most of the radioactivity remained at the site of application (88 ± 2.3%). Only traces of administered radioactivity were detected over a 72 h-period in urine (0.15 %), faeces (0.16 %), exhaled carbon dioxide (0.27 %), other skin (0.2%) and cage wash (0.3%). From the data it was concluded that dioctadecyldimethylammonium chloride does not effectively penetrate the skin (Drotman, 1977). The quality of the study was evaluated by an expert panel of the American Chemistry Council who concluded that the endpoint has been adequately characterized (Klimisch 2D, reliable with restrictions). The study of Drotman (1977) predated GLP but followed accepted scientific standards at the time of performance.

In in vitro studies on human abdominal skin, no absorption of Dioctadecyldimethylammonium chloride was detected (no further information was given) (Drotman, 1977). These experimental findings are supported by the physicochemical properties of quaternary ammonium compound, di-C16-18-alkyldimethyl, chloride being insoluble in water and in an ionic state which limits absorption across the skin. Furthermore, quaternary ammonium compound, di-C16 -18 -alkyldimethyl, chloride has a molecular weight of about 580 g/mol, whereas usually only substances with lower molecular weight are absorbed. No signs of systemic toxicity were observed after acute dermal exposure onto the rat skin indicating that dermal absorption if any, is likely to be very low. Moreover, the substance is not a skin sensitizer. Based on the experimental data, the physicochemical properties of the substance , the results of the acute dermal toxicity and the skin sensitization studies, the dermal absorption and the concentration of quaternary ammonium compound, di-C16 -18 -alkyldimethyl, chloride in the skin can be assumed to be very low. No valid data are available on toxicokinetics and metabolism of quaternary ammonium compound, di-C16 -18 -alkyldimethyl, chloride using the oral or inhalation routes of exposure.

Discussion on absorption rate:

Experimental study on the dermal absorption with dioctadecyldimethylammonium chloride has revealed, that the absorption rate of this quaternary compound is very low. An increase of the concentration in the skin following dermal application was also not observed. For risk characterisation, the default factor of 10% skin absorption is used. This default factor has been selected taking into account the physico-chemical properties of the substance and the other toxicological data using dermal route.