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EC number: 252-772-5 | CAS number: 35869-64-8
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data

Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
The substance is considered to be too large to be taken up after ingestion or after dermal uptake. This consideration is based on the physico-chemical properties and the findings of the subacute oral toxicity studies. It is insoluble in both hydrophilic and lipophilic solvents and cannot accumulate in tissues.
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
Additional information
COLOUR INDEX NAME CAS NUMBER
Pigment Brown 23 35869-64-8
Pigment Brown 41 68516-75-6
Pigment Red 144 5280-78-4
Pigment Red 166 3905-19-9
Pigment Red 214 40618-31-3
Pigment Red 220 68259-05-2
Pigment Red 221 71566-54-6
Pigment Red 242 52238-92-3
Pigment Red 262 79665-24-0
The high molecular weights ranging from 781.7 g/mol (Pigment Red 262) to 930.5 g/mol (Pigment Red 242) are just below the general threshold of 1000 g/mol for cellular uptake. Both water and octanol solubility is less than 0.1 mg/L which impedes transport in both aqueous and non-aqueous compartments. None of the groups are ionisable at physiological pH; specifically no increased solubility or degradation in stomach acid is possible.
Modelling of the molecular dimensions shows that the substances are large and bulky; all dimensions are larger than 10 Angström for Pigment Red 262, which has the lowest molecular weight (BASF 2012). As the pigments completely consist of conjugated systems, the molecule is not flexible which again hinders uptake.
All the disazocondensation red pigments included in this category contain azo and amide bonds which according to textbook knowledge on xenobiotic metabolism are susceptible to enzymatic cleavage. This would in all cases result in the formation of aromatic mono- and p-di-amines. Available toxicity data on these amines is summarized in table C below. Their hazard potential depends on the electron-donating or withdrawing character of the substituent as well as its position on the ring. For example, if Pigment Red 166 would be metabolized, p-phenylene diamine would be released and for this substance, a NOAEL of 16 mg/kg bw for subchronic oral exposure was obtained (ECHA dissiminated dossier on CAS 106-50-3).
Therefore, absence of systemic toxicity upon subacute oral exposure to Pigment Red 220 and 166 is a strong argument against systemic uptake and consequential metabolism of disazocondensation red pigments.
Also, azo-pigments which are smaller in size and soluble in stomach acid such as Pigment Red 57:1 (CAS 5281-04-9) cause signs of systemic effects upon subacute gavage exposure. For details it is referred to the dissiminated REACH dossiers.
Release of aromatic amines would also have been detected via genotoxicity in the in-vivo study for unscheduled DNA synthesis with Pigment Brown 23 and in the in-vivo micronucleus assays with Pigment Brown 23, Pigment Red 166 and Pigment Red 221. However, all of these tests were negative, as were the in-vitro tests both with and without Prival modification for azo compounds. Pigment Red 144 and 166 were tested with the Prival modification. Absence of uptake into cells and the body is consistent with the physico-chemical properties. Indeed, the red chromophore of the pigment remains intact during the passage through the gastrointestinal tract, as indicated by the red color of the feces of orally treated rats.
For Pigment Brown 23, no systemic toxicity was observed in the combined repeated dose toxicity and reproductive toxciity screening study (OECD 422, 2022).
Dermal route of exposure
The molecular weight of each category member is well above the threshold of 500 g/mol which is given in the EU guidance document on dermal absorption (Sanco/222/2000 rev. 7, March 19, 2004). This threshold allows the assumption of 10% dermal permeation if the n-octanol/water partition coefficient is either very low (-1) or high (> 4). The threshold for log Pow is not reached for every member, but this is due to the overall very poor solubility of the pigments. Solubility is in the lowmg/L range which is hindering any transport process.
None of the available data indicates that the pigments cause skin irritation which would damage the dermal barrier. Absence of systemic uptake after ingestion postulated.
Inhalation route of exposure
No systemic toxicity was observed in the short-term - inhalation study in rats. Pigment particlces were found in the lung, together with local effects.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
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