Ammonium sodium 2-[4-[[1-[[(2-methoxy-5-methyl-4-sulphonatophenyl)amino]carbonyl]-2-oxopropyl]azo]phenyl]-6-methylbenzothiazole-7-sulphonate

Endpoint summary

Description of key information

Based on physico-chemical characteristics, particularly molecular weight (size), water solubility and octanol-water partition coefficient, absorption via oral, dermal and inhalative route is unlikely. This assumption is supported by the results of acute oral and dermal toxicity studies as well as the repeated dose oral toxicity study, revealing no toxic effects. The substance will pass the gastrointestinal tract and be excreted via feces in its unchanged form. Bioaccumulation does not take place.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

The test substance is a yellow solid (powder) with a molecular weight of 671.6975 g/mol. Its partition coefficient between octanol and water (log Kow) is -3.3 (at 20 °C and pH 4.1). The substance has no melting point up to its decomposition temperature of about 270 °C. The water solubility is 160 g/L. Hydrolyis of the moclecule is not expected based on its structure.

  

Absorption

Generally, oral absorption is favoured for molecular weights below 500 g/mol. Therefore, the oral absorption is limited by the size of the molecule. Due to its very high water solubility, the substance will readily dissolve in the gastrointestinal fluid and absorption may additionally be limited by the rate at which the substance partitions out of the fluid. The low log Pow value does also not favour absorption by passive diffusion.

The available studies on acute oral toxicity as well as toxicity after repeated dosing did not reveal any signs of systemic toxicity. A yellow discoloration of the contents in the glandular stomach of males and females and in the jejunum, colon and cecum of males was observed in the OECD 422 study (combined repeated dose toxicity study with the reproduction/ developmental toxicity screening test), indicating that the substance will most probably pass the GI tract without being broken down or absorbed.

Dermal absorption will be very low due to the size of the molecule and the low log Pow value, as the molecular weight is above the cut-off point of 500 g/mol (according to "Guidance on information requirements and chemical safety assessment, Chapter R.7c: Endpoint specific guidance", ECHA-17-G-11-EN) and the log Pow value is below -1. The low log Pow value suggests that the substance is not likely to be sufficiently lipophilic to cross the stratum corneum. This assumption is confirmed by the results of the available acute dermal toxicity study in rabbits, where no signs of systemic toxicity were noted. The test item does also not show skin irritant or corrosive properties which might facilitate dermal uptake.

Inhalative exposure of the substance in its solid form (powder) is unlikely as it is marketed and used in a non-solid form. The substance decomposes before boiling and will not be available as a vapour. If the substance should nevertheless enter the lungs as a vapour or mist, it would be retained within the mucus due to its high water solubility and not taken up due to the low log Pow value.

Taken together, physico-chemical properties and experimental data indicate poor bioavailability of the test substance via oral, dermal and inhalation route.

 

Metabolism, Distribution and Excretion

As mentioned above, the physico-chemical properties, especially the size of the molecule, inhibit systemic absorption. After oral uptake the substance will pass the gastrointestinal tract and be excreted via feces without being metabolised. Bioaccumulation does not occure.