2-Naphthalenesulfonic acid, 7-amino-4-hydroxy-8-[2-[2-sulfo-4-[[2-(sulfooxy)ethyl]sufonyl]phenyl]diazenyl]-, potassium sodium salt, coupled with diazotized 2-[(4-amino-5-methoxy-2-methylphenyl)sulfonyl]ethyl hydrogen sulfate

Endpoint summary

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 oral to dermal 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 dark red brownish powder with a high molecular weight. The log Pow value is <-5.5 and the solubility in water is ≥419 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. However, in the 28-days repeated dose study, slightly lower mean body weights in males treated with 200 mg/kg bw/day and 1000 mg/kg bw/day during the treatment period, passive fecal and urine discoloration, as well as minor macroscopical discoloration of some tissues of the excretory pathway was observed. Thus the test substance will be absorbed by the gastrointestinal tract.

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 effects were observed. Therefore, dermal uptake will be very unlikely and aratio of 0.1 for oral to dermal absorption is therefore used for DNEL derivation.

Respiratory absorption: No experimental data is available concerning the respiratory hazard of the test substance. However, generally, water soluble dust would readily diffuse/dissolve into the mucus lining of the respiratory tract. Furthermore, signs of systemic toxicity present in the oral toxicity study indicates the potential for absorption following ingestion and it is therefore likely that the substance will also be absorbed if it is inhaled.