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Key value for chemical safety assessment

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The toxicokinetic profile of a substance comprises its absorption into the body, its distribution in the body, its metabolism in the body and its excretion from the body. Taking into account the physicochemical properties and the toxicological test results, qualitative estimates for these aspects may be deduced for Pigment Red 112.


Absorption: a prerequisite for a relevant absorption is that the substance can be dissolved in either aqueous (e.g., gastrointestinal fluid, blood plasma, sweat) or lipophilic (e.g., lipoproteins, lipid membranes, triglycerides) media or in both. Pigment Red 112 can be considered insoluble because it has an extremely low solubility in water and n-octanol. Therefore, it is unlikely that Pigment Red 112 becomes systemically bioavailable after oral, dermal or inhalation exposure.

The results of acute oral toxicity, acute dermal toxicity and repeated oral toxicity studies also give valuable indications with regard to absorption of the test substance.

Based on the acute oral toxicity and the 28-day oral toxicity studies, which did not reveal any systemic effects that would indicate that the pigment had entered the body, no indications of significant absorption via the gastrointestinal tract has to be assumed.

Pigment Red 112 does not have particular skin or eye irritating or skin sensitizing properties that would imply a dermal absorptive potential.

In the unlikely event of exposure to aerosolized pigment in respirable form, the substance is considered likely to behave like an inert dust. Therefore, the deposited pigment particles will mostly be cleared from the lung via the mucocilliary transport. As the pigment will not dissolve in the lung surfactant, the only way the pigment can enter the body is via phagocytosis of pigment particles by lung macrophages followed by migration of the macrophages into the interstitium and into the draining lymph nodes. However, the internal dose delivered via this mechanism can be considered negligible.


Distribution: the 28-day oral repeated dose toxicity study did not indicate any relevant histopathological changes in any of the investigated organs. This may indicate that either the pigment does not affect special organs as targets, i.e., is non-toxic, or is not distributed within the body in significant amounts. As indicted above, the physico-chemical parameters of the pigment support the conclusion that the pigment is not absorbed into the body and thus does not become systemically available. There were also no other signs of deposition of the pigment in any organ including excretory organs, like the kidney, indicating that even exposure to high doses of the pigment does not lead to bioaccumulation in special compartments of the body. 


Metabolism: Since the dissolution of the substance in cellular fluid or cellular membranes is a prerequisite for its metabolism, it is unlikely that the insoluble pigment becomes accessible for metabolizing systems in relevant amounts. The results of the mutagenicity tests provide useful indications for qualitative consideration of the metabolic fate of Pigment Red 112. In the mutagenicity tests, the pigment proved to be non-toxic and non-mutagenic in the absence as well as in the presence of an exogenous metabolizing system, indicating that the pigment is not converted into toxic or genotoxic metabolites. This conclusion is also supported by the lack of any morphological and histopathological changes of organs involved in xenobiotic metabolism, such as the liver, in the repeated dose toxicity study.


Excretion: the available data indicate that Pigment Red 112 is not absorbed into the body. In line with this conclusion, the 28-day oral repeated dose toxicity study did not indicate morphological or histopathological effects of the pigment on organs involved in excretion of chemicals from the body, such as the kidney. There was no indication that the substance was present in the urine. Moreover, from the repeated oral toxicity studies, it can be concluded that, after oral exposure, the pigment is excreted unchanged via the faeces.