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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), low absorption is expected to some extent, depending on tested species, exposure route, exposure duration...

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

1. molecular weight above 500 a.u,

2. higher affinity to aqueous phase than to organic phase with log Pow of -2.2671 at 20 °C,

3. particle size distribution with only 14 % in volume of particles below 4 µm size,

4. high water solubility, i.e. ca. 305 mg/l at 20 °C.

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

Once entered the body, molecules may undergo oxidative and reductive processes as well as functionalisation and bond cleavage. The last two process are expected to enhance water solubility and, consequently, rate of excretion of test substance. In particular, main metabolites derive from reduction and cleavage of diazo bond.

In available toxicological studies by oral route, no treatment related mortality was recorded. In an acute toxicity study, signs and symptoms included slight colouration of animals, faeces and urine; in a repeated dose toxicity at doses of ca. 50, 500 and 1000 mg/kg bw/d, treatment related effects were noted in haematology and clinical biochemistry starting at the highest dose; in a reproductive/developmental toxicity study at doses of 50, 500 and 1250 mg/kg bw/d, all dose groups showed pink colouration of the fur and soft faeces starting at 500 mg/kg bw/d.

Overall, such findings proved absorption of test substance and effects of test substance itself and/or of its metabolites.

Low absorption rate by dermal route was expected based on the high hydrophilicity along with the molecular weight above 500 a.u.. Furthermore, low absorption was confirmed by an in vitro experiment using human epidermis and by the lack of systemic effects in available skin irritation and skin sensitisation studies.

No studies via inhalation route 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 high hydrophilic character, that limit exposure of alveolar region as well as absoprtion across the epithelium.

As for particles in the upper respiratory tract, mainly dissolved in mucus, either clearance from the body or swallowing may occur.