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 77499 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.

Applications.

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

Black 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).  (2).

Cosmetic safety

Restricted cosmetic ingredient as IV/137 a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported:     Iron Oxide Black.  Purity criteria as set out in Commission Directive 95/45/EC (E172)

Iron oxide CI 77499 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:

• CI77499
• E172 (i)
• 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

Abstract. 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

Safety

CI 77499 is a black colored pigment, for which all the warnings concerning iron oxide in general are valid. In this regard, there is a large documentation of EFSA (1).

Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles as drug transporters can add further functionalities, such as guidance or heating by external magnetic fields (Magnetic Drug Targeting or Magnetic Hyperthermia), and imaging-controlled therapy (Magnetic Resonance Imaging) (2).

The objective of this work is to address this problem from the theoretical side by performing detailed simulations to investigate the effect of incorporation of magnetic nanoparticles in clusters on the amount of heat generated as a function of the particle size, cluster size and particles magnetic properties (3).

Polyethyleneimine-coated Iron Oxide Nanoparticles as a Vehicle for the Delivery of Small Interfering RNA to Macrophages In Vitro and In Vivo (4).

Iron Oxide as a Contrast Agent

This study focuses on the function of iron oxide as a contrast agent for cell tracking by magnetic resonance (5).

Iron Oxide as Dietry Supplement

Comparison of the Effects of Iron Oxide, as a New Form of Iron Supplement, and Ferrous Sulfate on the Blood Levels of Iron and Total Iron-Binding Globulin (6).

References_____________________________________________________________

(1) EFSA JOURNAL Safety and efficacy of iron oxide black, red and yellow for all animal species
Volume 14, Issue 6, June 2016, EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP)
Version of Record online : 6 JUN 2016, DOI: 10.2903/j.efsa.2016.4482

(2) Janko C, Ratschker T, Nguyen K, Zschiesche L, Tietze R, Lyer S, Alexiou C. Functionalized Superparamagnetic Iron Oxide Nanoparticles (SPIONs) as Platform for the Targeted Multimodal Tumor Therapy.  Front Oncol. 2019 Feb 13;9:59. doi: 10.3389/fonc.2019.00059. eCollection 2019

(3) Lattuada M. Effect of Clustering on the Heat Generated by Superparamagnetic Iron Oxide Nanoparticles. Chimia (Aarau). 2019 Feb 27;73(1):39-42. doi: 10.2533/chimia.2019.39.

(4) Jia N, Wu H, Duan J, Wei C, Wang K, Zhang Y, Mao X. Polyethyleneimine-coated Iron Oxide Nanoparticles as a Vehicle for the Delivery of Small Interfering RNA to Macrophages In Vitro and In Vivo. J Vis Exp. 2019 Feb 5;(144). doi: 10.3791/58660.

(5) Korchinski DJ, Taha M, Yang R, Nathoo N, Dunn JF. Iron Oxide as an MRI Contrast Agent for Cell Tracking.  Magn Reson Insights. 2015 Oct 6;8(Suppl 1):15-29. doi: 10.4137/MRI.S23557. eCollection 2015. Review.

(6) Kheiri R, Koohi MK, Sadeghi-Hashjin G, Nouri H, Khezli N, Hassan MA, Hoomani F, Shams G, Rasouli A, Motaghinejad M. Comparison of the Effects of Iron Oxide, as a New Form of Iron Supplement, and Ferrous Sulfate on the Blood Levels of Iron and Total Iron-Binding Globulin in the Rabbit.  Iran J Med Sci. 2017 Jan;42(1):79-84.