5-(diisopropylamino)-2-[[4-(dimethylamino)phenyl]azo]-3-methyl-1,3,4-thiadiazolium trichlorozincate(1-)

Endpoint summary

Description of key information

No bioaccumulation potential.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

According to the Annex VIII of the REACH Regulation (EC 1907/2006), the assessment of the toxicokinetics behaviour of the substance should be done to the extent that can be derived from the relevant available information.

Based on the physicochemical properties of the substance (mainly physical state and particle size, chemical structure and functional groups, molecular weight, water solubility, octanol/water partition coefficient), absorption is expected to occur mainly by oral route, while low absorption is expected by dermal route and by inhalation.

In particular, absorption, distribution and excretion of the substance are controlled by:

1. nature of the substance, i.e. a salt

2. molecular weight of the 2 ions well below 500 a.u.,

3. higher affinity to aqueous phase than to organic phase with log P_ow of -0.3993 at 20 °C,

4. particle size distribution with less than 2 % volume of particles below 4 µm size, less than 8 % volume of particles below 10 µm and ca. 100 % volume of particles below 100 µm

5. high water solubility, i.e. ca. 25.22 mg/l at 20 °C.

As for the potential of bioaccumulation, it is expected to be low, based on log P_ow far below the threshold value of 4 for bioaccumulation.

Once entered the body, molecules may undergo cleavage of the diazo bond as well as dealkylation of the amines. Such process are expected to enhance water solubility and, consequently, rate of excretion of the substance.

Excretion of both substance and metabolites mainly occur in faeces and urine.

In available toxicological studies by oral route, treatment related mortality was recorded in an acute toxicity study, leading to a LD50 between 50 and 300 mg/kg; severe toxic effects at the dose of 80 mg/kg were seen in a preliminary teratogenicity assay in dams, but no teratogenic evidences were seen. In a repeated dose toxicity study, reversible effects on liver and kidney were recorded at the dose of 40 mg/kg; in a reproductive/developmental toxicity study at doses up to 15 mg/kg, no toxic effect was recorded.

Overall, such findings proved absorption of the substance by oral route and effects of the substance itself and/or of its metabolites.

Low absorption rate by dermal route was expected based on the hydrophilicity along with the presence of a heterocyclic ammonium ion in the chemical structure. Furthermore, low absorption was confirmed by the lack of toxic effects upon acute exposure by dermal route at dose of 2000 mg/kg, compared to the remarkable toxicity upon acute oral exposure.

No studies via inhalation were conducted. However, absorption by this exposure route was expected to be negligible based on the particle size distribution of test substance along with its hydrophilic character, that limit exposure of alveolar region as well as absorption across the epithelium. As for particles in the upper respiratory tract, mainly dissolved in mucus, either clearance from the body or swallowing was expected.