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Link to relevant study record(s)

Description of key information

Due to the high water solubility and the low logP value, dermal uptake will be very unlikely and a ratio of 0.1 for dermal to oral absorption is therefore used for DNEL derivation. For the oral and inhalatory route, the default absorption values from the REACH guidance (Chapter 8, R.8.4.2) are used for DNEL derivation, namely: 100% for inhalation, and 50% for oral absorption.

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
50
Absorption rate - dermal (%):
5
Absorption rate - inhalation (%):
100

Additional information

Since no toxicokinetic studies are available for the test substance the following assessment is based on the available physicochemical properties and results from other toxicological studies.

The test substance is a black powder with a molecular weight of 1253.41 g/mol. The calculated log Pow value is < -2.9 and the solubility in water is >178.3 g/L.

Gastrointestinal absorption: Water-soluble substances may readily dissolve into the gastrointestinal fluids. However, absorption of very hydrophilic substances by passive diffusion may be limited by the rate at which the substance partitions out of the gastrointestinal fluid. The high molecular weight of the test substance does also not favor absorption. The 28-days repeated dose study showed some non-adverse test substance related effects in the highest dose group. Furthermore, bluish or black discoloration of the mucosa of the ileum, caecum and colon as well as the mesenteric lymph nodes were recorded at necropsy in animals treated with 1000 mg/kg/day. It is thus expected that the test substance will be absorbed by the gastrointestinal tract in some degree.

Dermal absorption: The high water solubility (>10000 mg/L) and the log Pow lower than -1 suggests that the substance may be too hydrophilic to cross the lipid rich environment of the stratum corneum. Furthermore, in the available acute dermal study, no systemic effects were observed. Therefore, dermal uptake will be very unlikely and a ratio of 0.1 for dermal to oral absorption is therefore used for DNEL derivation.

Respiratory absorption: No experimental data is available concerning the respiratory hazard of the test substance. Water soluble dust would readily diffuse/dissolve into the mucus lining of the respiratory tract. However, very hydrophilic substances can be transported out of the respiratory tract, when molecular weights are larger than 200. Furthermore, the low log Pow does not favor absorption. However, signs of systemic effects present in the 28 -day repeated oral toxicity study indicates the potential for absorption following ingestion and it is therefore possible that the substance will also be absorbed if it is inhaled.