zinc oxide content, %
Although barium sulfate is almost completely inert, zinc sulfide degrades upon exposure to UV light, leading to darkening of the pigment. The severity of this UV reaction is dependent on a combination of two factors; how much zinc sulfide makes up the pigments formulation, and its total accumulated UV exposure. Depending on these factors Lithopone B301, Lithopone B311 powder itself may vary in shade over time, ranging from pure white all the way to grey or even black. To suppress this effect, a dopant might be used, like small amount of cobalt salts, which would be added to the formulation. This process creates cobalt-doped zinc sulfide. The cobalt salts help to stabilize zinc sulfide so it will not have as severe a reaction to UV exposure.
When choosing lithopone, you must choose a good brand and pay attention to its production date. Some people just don’t pay attention to this aspect and often pursue cheap prices. As a result, they buy products that are close to their expiration date and have not been stored for long. It is no longer usable. This is very important.
The lack of clear regulations and controls explains that P25TiO2NPs are still found in many of the commercialized sunscreens in the market. Some of them are coated to reduce the photoactivity of the anatase form, which is known to be responsible for tissue damage, but not enough studies were made on these coated forms. The anatase photoactivity could trigger the production of reactive oxygen species (ROS) generation, as it was stated before. The ROS are chemically reactive species containing oxygen, such as peroxides, superoxide, hydroxyl radical, and singlet oxygen. They are regularly produced in the biological milieu and counterbalanced by physiological antioxidant defense mechanisms. However, an abrupt increase of ROS may result in non-reversible damage to the skin cells. The effects of coated and uncoated P25TiO2NPs need therefore to be studied, and articles on this topic present different conclusions. [11], [12], [13] Recent literature on this topic found that TiO2NPs inhalation provokes serious genotoxicity and DNA damage [14], [15], [16], [17]. On the other hand, some studies in rats have reported no significant harm to genetic material [18], [19], [20], [21], [22].
Separately, concerns have been raised about titanium dioxide impacting one's genetic code. This can be traced to a 2009 study which found that titanium dioxide nanoparticles caused DNA damage and genetic instability in mice. A 2022 study published in Food and Chemical Toxicology also raised concerns about the DNA-damaging effects of titanium dioxide as a food additive. The study noted that results evidenced a DNA-damaging effect, and added that there may also be impacts to chromosomal integrity, an indicator of cancer risk.