Compendium of the most significant studies with reference to properties, intake, effects.

Voss L, Hsiao IL, Ebisch M, Vidmar J, Dreiack N, Böhmert L, Stock V, Braeuning A, Loeschner K, Laux P, Thünemann AF, Lampen A, Sieg H. The presence of iron oxide nanoparticles in the food pigment E172. Food Chem. 2020 Oct 15;327:127000. doi: 10.1016/j.foodchem.2020.127000.

Montes-Hernandez G, Pironon J, Villieras F. Synthesis of a red iron oxide/montmorillonite pigment in a CO2-rich brine solution. J Colloid Interface Sci. 2006 Nov 15;303(2):472-6. doi: 10.1016/j.jcis.2006.07.064.

Felton LA, Wiley CJ. Blinding controlled-release tablets for clinical trials. Drug Dev Ind Pharm. 2003 Jan;29(1):9-18. doi: 10.1081/ddc-120016679.

Vahur S, Knuutinen U, Leito I. ATR-FT-IR spectroscopy in the region of 500-230 cm(-1) for identification of inorganic red pigments. Spectrochim Acta A Mol Biomol Spectrosc. 2009 Aug 15;73(4):764-71. doi: 10.1016/j.saa.2009.03.027.

Rowe RC. The effect of the particle size of synthetic red iron oxide on the appearance of tablet film coatings. Pharm Acta Helv. 1985;60(5-6):157-61.

Ishikawa Y, Orito S, Oya M. Statistical analysis of washing efficiency for solid particle soil. J Oleo Sci. 2007;56(4):163-8. doi: 10.5650/jos.56.163.

Photos-Jones E, Knapp CW, Venieri D, Christidis GE, Elgy C, Valsami-Jones E, Gounaki I, Andriopoulou NC. Greco-Roman mineral (litho)therapeutics and their relationship to their microbiome: The case of the red pigment miltos. J Archaeol Sci Rep. 2018 Dec;22:179-192. doi: 10.1016/j.jasrep.2018.07.017.

Castro K, Vandenabeele P, Rodríguez-Laso MD, Moens L, Madariaga JM. Improvements in the wallpaper industry during the second half of the 19th century: micro-Raman spectroscopy analysis of pigmented wallpapers. Spectrochim Acta A Mol Biomol Spectrosc. 2005 Aug;61(10):2357-63. doi: 10.1016/j.saa.2005.02.035.

Luna-Bastante L, Gatica-Ortega ME, Pastor-Nieto MA, Vergara-de-la-Campa L, Gómez-Dorado BA, Alonso-Naranjo L, Pérez-Hortet C. Allergic contact dermatitis to Tinosorb S, Scutellaria baicalensis, and other emerging allergens in cosmetics. Contact Dermatitis. 2020 May;82(5):307-309. doi: 10.1111/cod.13460.

 Motolese A, Truzzi M, Giannini A, Seidenari S. Contact dermatitis and contact sensitization among enamellers and decorators in the ceramics industry. Contact Dermatitis. 1993 Feb;28(2):59-62. doi: 10.1111/j.1600-0536.1993.tb03342.x.

Iron oxide and hydroxide are chemicals of various colors used as food additives in the food industry and are labeled with the number E172 as food additives and as CI 77491 as colorants.

The complete table includes:

• E172 (i) black iron oxide, CI 77499
• E172 (ii) red iron oxide, CI 77491
• E172 (iii) yellow iron oxide, CI 77492

Typical characteristics of commercial dyes:

Industrial surface treatments:

• With Triethoxycapilisilane, are easily dispersible in oil, has optimal hydrophobicity.
• With Lauroyl Lysine has optimal skin affinity, is hydrophobic and will look smooth and soft.
• With Perfluorooctyl Triethoxysilane is suitable for long lasting makeup products, excellent hydrophobicity and oleophobicity.
• With Titanium dioxide you can create different shades of color, but it is a chemical compound that is harmful to human health.

Applications:

Cosmetics, construction, paints, detergents, waterproof flooring, ceramics, PVC, plastics, glues, pharmaceuticals, medicine.

Red Iron Oxide is an insoluble powder but miscible in oils and water. It has high covering power and high tinting strength. It is easily dispersible, shows excellent light fastness and resistance to external weathering. Non-toxic, non-irritating.

Ultraviolet rays from the sun cause skin aging and smartphones emit high-energy visible light from which you should protect yourself. Iron oxides (yellow, red and black) in sunscreens have the property of effectively blocking high-energy visible light especially when combined with zinc oxide (1).

Safety

The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion re‐evaluating the safety of iron oxides and hydroxides used as food additives (E 172): yellow iron oxide (FeO(OH)·H2O), red iron oxide (Fe2O3) and black iron oxide (FeO·Fe2O3). Brown Iron Oxide has been included in this assessment for completeness, due to its importance as a commercial blend. The Panel considered that the particle size and particle size distribution should be included in the specifications. In 1980, an ADI of 0‐0.5 mg/kg bw/day was established by JECFA. Absorption of iron from iron oxides is low. The acute oral toxicity of iron oxides is greater than 10 g iron oxide/kg bw. From a subacute and a subchronic toxicity study, the Panel identified a NOAEL for red iron oxide of 1 000 mg/kg bw/day, the highest dose tested. Red (Fe2O3) and black (FeO·Fe2O3) iron oxide, both in nano‐ and micro‐form, were positive in in vitro genotoxicity assays in mammalian cells. Due to the limitations of the database, and considering the impossibility to read‐across between iron oxides with different redox state, the Panel considered that the genotoxicity of iron oxides cannot be evaluated based on the available data. Concerning carcinogenicity and reproductive and developmental toxicity, no signs of toxicity were observed in unpublished studies which were not available and could not be evaluated by the Panel. The Panel concluded that an adequate assessment of the safety of E 172 could not be carried out because a sufficient biological and toxicological database was not available. Refined exposure estimates show that exposure to E 172 ranged from 0.03 mg/kg bw/day for infants to 3.7 mg/kg bw/day for toddlers at the mean and from 0.1 mg/kg bw/day for infants to 9.5 mg/kg bw/day for toddlers at the 95th percentile for the non‐brand‐loyal scenario (2).

Red iron oxide CI 77491 studies

• Molecular Formula : Fe₂O₃    Fe₂H₆O₃
• Molecular Weight : 159,69 g/mol
• CAS : 1309-37-1    1332-37-2
• UNII 
• EC Number: 215-168-2
• DSSTox Substance ID: 
• MDL number  
• MFCD00011008
• PubChem Substance ID 329753614
• InChI=1S/2Fe.3H2O/h;;3*1H2
• InChl Key      YOBAEOGBNPPUQV-UHFFFAOYSA-N
• SMILES    O.O.O.[Fe].[Fe]
• IUPAC iron;trihydrate
• ChEBI    

Synonyms:

• CI77491
• E172 (ii)
• Ferric oxide

References________________

(1) Bernstein EF, Sarkas HW, Boland P. Iron oxides in novel skin care formulations attenuate blue light for enhanced protection against skin damage. J Cosmet Dermatol. 2021 Feb;20(2):532-537. doi: 10.1111/jocd.13803. 

(2) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS)
First published: 08 December 2015 https://doi.org/10.2903/j.efsa.2015.4317