We are here! School is out for many and that means the start of summer. Summertime brings about more sunshine and forces parents to make a decision on what baby sunblock to use and why. The safety concern of titanium dioxide has been circulating over the past few years through more news stories, more blogs, and more social media posts on the matter. Dr. Amy and the Baby Pibu team strive to bring forth a summary of recent research and conclusion into practical day-to-day decision-making and help answer the question – is titanium dioxide safe in sunscreens and other consumer products.
What is titanium dioxide?
Titanium dioxide is a pigment that can be found in a multitude of consumer products including candy, chewing gum, toothpaste, foods like powdered donuts, cosmetics, and sunscreens. In the food-based products, titanium dioxide is commonly used to provide a more white background. It has also been used in toothpastes at its larger sizes for its “scrubbing” effects.
The concern of titanium dioxide safety centers on its size. Most food-graded titanium dioxide is not considered a nanomaterial (less than 100 nanometers in size). It is difficult for the larger, non-nanoparticles to be absorbed into cells. Following ingestion, most titanium dioxide passes through the body unchanged in feces, but a small amount (less than 0.1%) could be absorbed by the gut and distributed to various organs. This absorption concern warrants more testing and research be done to determine whether certain systems like the reproductive system can be affected.
Although the main focus of this blog is centered on answering the question of whether titanium dioxide is safe in sunscreen, it is important to be aware of the other questions and concerns that are out there regarding how titanium dioxide is being used in food. Remember, that both the gut and skin are part of our whole body, but the features of the gut and skin differ in how they work, what cells they have, and what inherent protective properties they have. Don’t assume that conclusions made about the gut and titanium dioxide are the same for the skin and titanium dioxide.
Let’s move on to the discussion of titanium dioxide safety in sunscreens and the effect on the skin and the whole body.
What are titanium dioxide and zinc oxide nanoparticles? And, are they safe ingredients in sunscreens? To answer the latter question, two additional questions will be answered: Can these nanoparticles penetrate the skin to reach viable cells? Are these nanoparticles toxic to the viable cells that they encounter?
Both zinc oxide and titanium dioxide have been used as the active ingredients in sunscreens for over 30 years. They work to protect our skin from both UVA and UVB rays by physically blocking the UV rays from hitting our skin. Think about them as acting like an umbrella to the skin cells. The con to these physical blockers is their unattractive whiteness in their larger particle sizes. If you can see the white from the zinc oxide and titanium dioxide of your sunscreen, then it is likely micronized zinc oxide and titanium dioxide and not nanoparticle-sized. Baby Pibu Sunscreen is contains micronized zinc oxide and titanium dioxide and not nanoparticles.
Both zinc oxide and titanium dioxide nanoparticles came about to both lessen the whitishness and also provide more UV protective coverage by having the ability to more evenly protect the skin. Both zinc and titanium dioxide nanoparticles are defined as having a range of 1 to 100 nanometers (nm).
A helpful summary to the research on the safety of titanium dioxide nanoparticles is found via the Australian Therapeutic Goods Administration (TGA). TGA’s most recent reviews include data and literature review up to 2016. The majority of both in vitro (in petri dish) and in vivo (in animals or humans) studies have shown that both zinc oxide and titanium dioxide nanoparticles do not penetrate or minimally penetrate the stratum corneum (outermost skin layer) and underlying layers of skin. Since both zinc oxide and titanium dioxide nanoparticles cannot reach viable cells of the innermost layers of the skin, toxicity and systemic absorption of these nanoparticles is highly unlikely.
You may be wondering what toxicity zinc oxide and titanium dioxide nanoparticles can cause. There has been in vitro (petri dish experiments) evidence that both zinc oxide and titanium dioxide nanoparticles can induce reactive oxygen species (ROS) in the presence of light and as a result, cause cytotoxic and genotoxic effects on various cell types. Before jumping to conclusions, take a pause and remember that the majority of studies do not demonstrate that nanoparticles penetrate skin and reach viable skin cells. It has been shown that that both zinc oxide and titanium dioxide nanoparticles remain on the skin surface and on the stratum corneum, the outermost layer of the skin that has non-viable, keratinized cells. As a result of the zinc oxide and titanium dioxide nanoparticles staying on non-viable cells of the stratum corneum, it is highly unlikely that the nanoparticles will cause toxic effects and outcomes on our whole body. Be cautious to assume that research studies based off of animal experiments means the same for humans. Animal and human skins are fundamentally and biologically different. Do not assume that results from animal studies mean the same results will happen in human skin. This is mentioned because some studies from animals showed nanoparticles reaching viable animal cells, but in human studies, nanoparticles stayed in the stratum corneum and did not penetrate deeper to the viable cells and layers of our skin.
Finally, zinc oxide and titanium dioxide nanoparticles in sunscreens are modified to reduce their potential to generate ROS. The nanoparticles are typically coated to reduce ROS formation. Furthermore, our cells are not defenseless- they harbor a natural defense mechanism to ward off ROS.
In conclusion, in answering the question of whether titanium dioxide is safe in sunscreens, the most current review of both in vitro and in vivo research has shown that the use of titanium dioxide is safe and the minor risks potentially associated with titanium dioxide nanoparticles is outweighed by the benefit of titanium dioxide in sunscreens helping to minimize UV damage to the skin and ultimately reduce the risk of skin cancer, which is the most common cancer in both men and women.