I, personally, are cautious with every ingredient on a INCI list that isn’t pure plant extract or oil or butter. I am not paranoid, I just tend to investigate on what exactly it is I put on my body. I know that there are certain ingredients that, seen from a manufacturers perspective, need to be in a product for preservation reasons or for the texture or the scent. I do understand that preservation/conservation is essential but I am okay with a really natural, unrefined scent if the INCI list only contains 4 ingredients in return.
Well, here I want to begin a series about special ingredients no one is really sure about or has certain doubts. I want to show you what I could find on scientific databases like NCBI and Pubmed and maybe warn you or make you appreciate some ingredients more or less, at least educate you about the facts so that you yourself can make a decision without any alteration from advertising/marketing instruments/agencies.
Todays series deals with what I was able to find on titanium dioxide, an ingredient that is quite wide-spread in the green beauty market in products like sunscreen, lipstick and eyeshadow.
Titanium dioxide, when used as a pigment, is present in many powder products, eyeshadows and similar. You can check that if you look for CI 77891 on the ingredient list. It is one of the brightest pigments and therefore used if a white colour is needed.
The ICSC data sheet says, that “the substance can be absorbed into the body by inhalation of its aerosol”. So I personally always try to hold my breath when I apply easily dispersed products. Yes, I know… I am crazy.
Here’s an excerpt of a summary about titanium dioxide from the International Agency for Research on Cancer (IARC):
5.2 Experimental carcinogenicity data
Titanium dioxide was tested for carcinogenicity by oral administration in one strain of mice and in one strain of rats, by inhalation in two strains of rats, by intratracheal administration in one strain of hamsters, by subcutaneous injection in one strain of rats and by intraperitoneal administration in one strain of male mice and two strains of female rats. Increased incidences of lung adenomas in rats of both sexes and of cystic keratinizing lesions diagnosed as squamous-cell carcinomas in female rats were observed in animals that had inhaled the high but not the low doses of titanium dioxide. Oral, subcutaneous, intratracheal and intraperitoneal administration did not produce a significant increase in the frequency of any type of tumour in any species. Intratracheal administration of titanium dioxide in combination with benzo[a]pyrene to hamsters resulted in an increase in the incidence of benign and malignant tumours of the larynx, trachea and lungs over that in benzo[a]pyrene-treated controls.
[this sadly is how some of the data about chemicals are obtained]
[benzpyrene is present in cigarette smoke and causes cancer]
5.3 Human carcinogenicity data
The only available epidemiological study provided inconclusive results.
5.4 Other relevant data
Titanium dioxide did not induce morphological transformation in mammalian cells or mutation in bacteria.
There is inadequate evidence for the carcinogenicity of titanium dioxide in humans.
There is limited evidence for the carcinogenicity of titanium dioxide in experimental animals.
Titanium dioxide is not classifiable as to its carcinogenicity to humans (Group 3).
Now we specify on titanium dioxide in sunscreens:
“Physical UV absorbers such as titanium dioxide or zinc oxide have been found to be highly protective against ultraviolet radiation. Sun protection factor depends on the accumulation of the minerals on the skin. UV-absorbing agents must accumulate within the upper skin layers in order to provide a dense light-absorbing layer and guarantee water resistance”
- All sunscreens that claim to be water-resistant have to use very small particles of zinc oxide and titanium dioxide in order for them to penetrate the outer skin layer
As they then developed sunscreen containing nano scale ingredients:
“Traditional sunblocks incorporate chemicals that require constant reapplication and may cause skin irritation. Zinc oxide (ZnO) lotions provide a longer lasting nonirritating broad spectrum physical sunblock. However, large ZnO particles result in a white barrier that is not cosmetically appealing. Currently, nanoscale titanium dioxide (TiO2) and micronized ZnO nanoparticles (NP) less than 100 nm have been incorporated in sunscreens to provide effective broad spectrum physical sunblock.”
Note: the SOIL association for example only allows particles above 100 nm in products certified by them.
So there was the need of a study on these nanoparticles that were originally designed to improve the protective effect of a natural sunscreen. They evaluated the properties of nanoparticle-sized titanium dioxide and zinc oxide:
“In summary, UVB-sunburned skin slightly enhanced the in vitro [in a living cell but outside of the organism] or in vivo [in the original organism setting] SC [stratum corneum, the horny layer of the epidermis] penetration of the TiO2 or ZnO NP present in the sunscreen formulations. Although TiO2 and ZnO NP were found to penetrate into the SC by TEM [transmission electron microscopy] and into the epidermis and dermis by TOF-SIMS [time-of-flight mass spectrometry], we found no definitive evidence that the NP penetrated the skin in vitro into the perfusate. In most cases, TiO2 penetration into the SC was greater than ZnO. These results viewed together suggest minimal penetration of TiO2 and ZnO NP into the upper epidermal layers when applied topically in sunscreen formulations to normal and UVB-sunburned skin, with no evidence of systemic absorption.”
As they said, there is no direct evidence about these nanoparticles entering the bloodstream and only minimal penetration of the upper skin layers. I, anyways, always stay cautious as long as there wasn’t heaps of studies on this ingredient showing all the same results. Because I am a biologist and I know how great the variation between experiments can be. Having said this, there was another study comparing silver (Ag) nanoparticles (NP) with titanium dioxide (TiO²) and zinc oxide (ZnO) nanoparticles stating that silver could provide protection from UVB-induced oxidative DNA damage whereas TiO² and ZnO nanoparticles weren’t able to do so but rather increased oxidative DNA damage via an increased production of reactive oxygen species. The outcome of this study suggests careful evaluation and raised concern about the safety of these nanoparticles and promotes silver nanoparticles as superior.
[there will be an article on silver, too, soon]
Therefor my conclusion from all these studies is:
- when sitting in the sun for a long time, I do not care about a white residue on my skin from natural, non-nano sunscreen as the protection without adsorption into my body is my main interest
- more helps more, at least in the natural sunscreen case
- skin that is already burnt or otherwise injured is more likely to absorb nanoparticle-sized sunscreen ingredients (and other chemicals used in conventional, not natural formulations) –> it may be better to cover injured skin with clothes than with sunscreen
- ask the brand owner if they use nanoparticle-sized titanium dioxide in their products
- COSMOS bio and the SOIL association have strict (maybe the strictest) guidelines for the usage of nanoparticles in beauty products. Nevertheless they can only prohibit nanoparticles with an average size of less than 100 nm so not actually ALL nanoparticles are prohibited and can therefore be found in a product.
To not leave anything about titanium dioxide out I also have to take into consideration that the substance is present in lipsticks and in toothpaste so that we are ingesting it daily to a certain extend.
https://www.ncbi.nlm.nih.gov/pubmed/26330118 –> this study shows that a fraction of pharmaceutical/food grade titanium dioxide is absorbed systemically [and that means entered the bloodstream] by humans following ingestion. Further work should quantify human exposure and uptake of such persistent particles. Powell and colleagues have estimated that adult humans may absorb 1012 TiO2 particles/person/day (that’s a lot!).
source: Fine and ultrafine particles of the diet: influence on the mucosal immune response and association with Crohn’s disease. Lomer MC, Thompson RP, Powell JJ
“Nanoparticles can be divided into two groups: i) soluble and/or biodegradable nanoparticles which disintegrate upon application on the skin into their molecular components (e.g. liposomes, microemulsions, nanoemulsions), and ii) insoluble particles (e.g. TiO2, fullerenes, quantum dots).
It is crucial when assessing possible risks associated with nanoparticles to consider their uptake. It is primarily for the insoluble particles that health concerns related to possible uptake may arise. Should they become systemically available, translocation/ transportation and eventual accumulation in secondary target organs may occur.”
- as TiO² is an insoluble particle it may accumulate in the human body upon ingestion for example via wearing a lipstick –> that only accounts for nano-sized titanium dioxide
Disclaimer: I am not able to read all published papers and therefore I can only give you the information I’ve found in some of them. I do not guarantee that there are no other scientific findings and I do not guarantee to show you the most recent studies, I just read some studies to give you an insight into the results of several studies.
This is not my final conclusion, I will try to read on and update this article as soon as possible.
To be honest, this article was really difficult to write and took me like a hundred corrections and re-reading. So please give me input on how I can improve this series regarding ease of reading, understandability and informational value for you. Also let me know how you feel about titanium dioxide as a consumer, as a manufacturer or as a scientist. Thanks! 🙂