[4-[p,p'-bis(dimethylamino)benzhydrylidene]cyclohexa-2,5-dien-1-ylidene]dimethylammonium m-[[p-anilinophenyl]azo]benzenesulphonate

Endpoint summary

Description of key information

No experimental study available.

Based on molecular structure, molecular weight, water solubility, octanol-water partition coefficient, it can be expected that both oral and inhalation absorption rate are moderate to low and that dermal absorption is low.

The oral acute toxicity study confirms that the substance has at least a moderate oral absorption, and that is not widely distributed.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

10

Absorption rate - inhalation (%):

50

Additional information

Oral absorption rate

Given the extremely low water solubility (< 0.01 mg/l) and high partition coefficient (> 5.7) characteristics, together with the high molecular weight (> 700), Solvent Black 46 is expected to not be readily absorbed after ingestion. However, a conservative oral rate of 50% is selected because of the lack of consistent data.

The acute and repeated dose toxicity studies shows that the Solvent Black 46 is neither readily distributed as no organs distant from the gastrointestinal tract were coloured. Furthermore, coloration of faeces was observed, but not of the kidney, the urinary organs and/or of urine, so Solvent Black 46 undergoes most exclusively under biliary excretion with a slight or non-existent renal excretion.

Inhalation absorption rate

The substance Solvent Black 46 is a powder exhibiting a fine granulometry. In the key study, the particles size distribution has been determined by laser diffraction. 90% of the particles size stands below 227 µm; 50% below 71.71 µm and 10% below 11.8 µm. In the supporting study, the size of 83.6 % of the total sample is less than 125 µm. Thus the MMAD is most probably below 100 µm.

It is then expected that this powder will be present all along the respiratory tract, however, only a small fraction (~10%) will penetrate deeply in the lungs.

Furthermore, as stated in the guidance document chapter R.7.c, given the extremely low water (< 0.01 mg/l) solubility and high partition coefficient (> 5.7), powder depositing in the nasopharyngeal region can be coughed or sneezed out of the body or swallowed. In case of deeper deposit in the tracheo-bronchial region, clearance from the lungs by the mucocilliary mechanism followed by swallowing will allow the elimination of the particules from the respiratory tract. For the small fraction of ~10% that could penetrate deeply in the lungs, would mainly be engulfed by alveolar macrophages and be either translocated to the ciliated airways or carried into the pulmonary interstitium and lymphoid tissues. Therefore, an absorption rate of 50% is selected.

Dermal absorption rate

According to the guidance document chapter R.7.c, a value of 10% skin absorption is chosen because of its extremely low water solubility (<0.01 mg/L) and high partition coefficient characteristics (> 4), together with the high molecular weight (> 500), Solvent Black 46 is likely to have a limited extent to cross the skin.

The dermal toxicity study did not show any systemic nor local effect when diluted in paraffin oil. The application site was colored in black.

This lack of systemic toxicity could be due to a lack of toxicological potential and/or a lack of absorption.

However, the sensitization skin study gives a positive answer, so some uptake must have occurred but the application site was colored in blue (color of the cationic starting material, i.e. the BV3). In this study, the solvent use was the DMF. Therefore, dissociation may have occurred. The BV3 contains quaternary ammonium cation, which rate of penetration across the epidermis should be slow. On the contrary, the physicochemical properties of the AY 36 (molecular weight ~300, soluble and log Kow in the range of 0 to 4) are in favor of dermal absorption which may explained that uptake occurs.

It seems that when diluted in DMF, a dissociation of SBl 46 occurs and that the AY 36 is dermally absorbed, while the BV3 remains at the surface of the skin coloring the application site in blue.

In real condition of uses, if some powder of SBl 46 or if some final product is applied onto the skin, it remains black, i.e. under the non-dissociated form which is expected to have a limited extent to cross the skin