Lithopone or sulphide of zinc white has been in general use for twenty years or more in many industries where a white pigment of considerable body or hiding power is required that is not subject to change like lead carbonate and has not the brittle character of zinc oxide, besides being sold at a lower figure than either of these. Nevertheless it is still comparatively new to the general painting trade. Because of our tariff protection its manufacture in this country has made great progress. Yet in spite of this and the duty imposed on it, the imports are still in excess of the quantity manufactured here. A short history of its origin will no doubt prove of interest to our readers.

• Genotoxicity and cytotoxicity 

• Australian researchers examined how titanium dioxide as a food additive affected gut microbiota in mice by orally administering it in drinking water. The study, published in the journal Frontiers in Nutrition in 2019, found the treatment could “alter the release of bacterial metabolites in vivo and affect the spatial distribution of commensal bacteria in vitro by promoting biofilm formation. We also found reduced expression of the colonic mucin 2 gene, a key component of the intestinal mucus layer, and increased expression of the beta defensin gene, indicating that titanium dioxide significantly impacts gut homeostasis.” The changes were then linked to colonic inflammation, along with a higher expression of inflammatory cytokines, which are signal proteins that help with regulation. The researchers concluded that titanium dioxide “impairs gut homeostasis which may in turn prime the host for disease development.”

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• Background and overview
  
  Globally, Iron Oxide is the second largest inorganic pigment after Titanium Dioxide and the first largest color inorganic pigment. Iron oxide pigments mainly include iron oxide red, yellow, black and brown with iron oxide as the basic material. Iron oxide yellow, also known as hydroxyl iron oxide (FeOOH), will be dehydrated and decomposed into red at about 177 ℃, so the application of ordinary iron yellow pigment in high-temperature occasions such as plastic processing and baking coatings is limited. Iron oxide yellow pigment can improve its temperature resistance through surface coating, so as to expand the application field of iron oxide yellow pigment.
  
  The chemical formula of iron oxide yellow (also known as hydroxyl iron) is α- Fe2O3 · H2O or α- FeOOH, with needle like structure and yellow powder, is a kind of particle size less than 0.1 μ m. Iron series pigment with good dispersibility in transparent medium has strong coloring power, high covering power, insoluble in alkali and slightly soluble in ACID. Synthetic iron oxide yellow has the characteristics of light resistance, good dispersion, non-toxic, tasteless and difficult to be absorbed by human body. It is widely used in coatings, plastics, ink and pharmaceutical industry.
  
  Physical and chemical properties and structure
  
  1. Iron oxide yellow pigment has acid and alkali resistance, resistance to general weak and dilute acids, and is very stable in alkaline solution of any concentration.
  
  2. Iron oxide yellow pigment has certain light resistance, heat resistance and weather resistance. Its coating color is durable and can keep the coating from being damaged in light. Iron oxide yellow pigment is stable in a certain temperature range, but beyond the limit temperature, its color begins to change, and the degree of change is more significant with the increase of temperature. Iron oxide yellow pigment is not affected by cold, heat, dry and wet weather conditions.
  
  3. Iron oxide yellow pigment is very stable in any ambient atmosphere (such as gases containing H 2S, Co, so 2, HCl, no, etc.). And resistant to pollution, water, oil and solvent penetration, insoluble in water, mineral oil or vegetable oil.
  
  4. Iron oxide yellow pigment has strong coloring power and high hiding power. With the decrease of pigment particle size, its coloring power is stronger.
  
  application
  
  Nano iron oxide yellow has the characteristics of acid resistance, alkali resistance, non toxicity and low price. It is widely used in coatings, plastics and rubber. The particle size of nano iron yellow is less than 100 nm, which makes it have some unique characteristics. When light shines on its surface, transmission and diffraction will occur, showing transparent yellow, and can strongly absorb ultraviolet rays, Therefore, it can be used as a functional pigment for the surface paint of high-grade cars, precision instruments, bicycles, motorcycles, cosmetics, food, drugs and other coloring additives.

• Spectrophotometric methods are also employed, where the absorbance of light by a sample is measured after a color-forming reaction specific to sulfate. By comparing the absorbance values to a calibration curve prepared with standards of known TiO2 content, the concentration of sulfate can be accurately determined.

• In its 2016 opinion, the ANS Panel recommended new studies be carried out to fill the gaps on possible effects on the reproductive system, which could enable them to set an Acceptable Daily Intake (ADI ). Uncertainty around the characterisation of the material used as the food additive (E 171) was also highlighted, in particular with respect to particle size and particle size distribution of titanium dioxide used as E 171.   

• TiO2 is typically produced by the sulfate process, which involves the oxidation of titanium ore with sulfuric acid to produce titanium sulfate. The titanium sulfate is then converted into titanium dioxide by a variety of methods, including the chloride process and the rutile process.
• Furthermore, environmental considerations also play a role in classification. Green calcium carbonate factories prioritize sustainable practices, such as recycling waste and utilizing energy-efficient processes, aligning with the growing global emphasis on eco-friendliness.
• In addition to risk assessment, NIOSH collaborates with industry partners, academia, and other government agencies to develop innovative technologies for real-time monitoring of TiO2 exposure. This collaborative effort aims to create safer work environments and foster a better understanding of the complex interactions between TiO2 and biological systems.