What are UV filters?
Ultraviolet (UV) filters are the protective elements that stop solar radiation from burning your skin by reflecting, dispersing or absorbing UV rays. They are separated into two categories, chemical and mineral. Confusingly, chemical filters can also be called organic filters (no this has nothing to do with being natural) and mineral filters go by the names of inorganic and/or physical UV filters. UV filters can also be defined by their particle size (nano/non nano).
Chemical (organic) UV filters are the most popular kind of sun protection due to their aesthetically pleasing application to the skin. However, their use raises some serious health concerns. Some chemical filters are able to penetrate the skin and reach the circulatory system.When these chemicals make it into your blood they can disrupt the endocrine system, which in turn can cause developmental or reproductive issues.Not the kind of thing you want for you, or your family. Unfortunately, the bad news does not end there. Chemical UV filters have also been implicated in ecological damage, due to their effect on the marine environment.
To find out more about the effects of organic UV filters on your health check out our research page, in which we have collected scientific papers relating to the most commonly used UV filters.
Mineral (inorganic) filters sit on top of your skin creating a protective barrier that does not penetrate your skin. This first simple fact is the reason why mineral sunscreens are the safer option for UV protection. The two mineral UV filters available are Zinc oxide and Titanium dioxide. Zinc oxide is an essential mineral that has been used by humans for hundreds of years. When topically applied it has antimicrobial properties, helping to protect and heal the skin. Zinc oxide naturally protects against both UVA & UVB rays, meaning it has broad spectrum protection. Titanium dioxide has been used in many applications for decades, and is generally considered an inert and safe material. It effectively blocks UVB rays (the ones that burn you) however it does not fully protect against UVA (the ones that cause photoaging). Therefore, used on its own it cannot be considered broad spectrum protection.
However, the safety of both Zinc oxide and Titanium dioxide changes when these minerals are ground into a nano-form.
Nanoparticles in sunscreen
Nano-particles refer to particles that are less than 100 nanometers (nm) in diameter.
This means nano-particles are so small that they are invisible, even when using a conventional microscope. Nanotechnology is exploding at the moment, and can be found across diverse fields including electronics, clothing, pharmaceuticals and cosmetics.It is also what is driving the mineral sunscreen revolution that has taken place over the last few years. Consumers unhappy with spreading a cocktail of chemicals onto their skin have looked to this new technology applied to traditional inorganic UV filters in search of a safer solution. However, scientific studies on the safety of nano-particles have had mixed results.
Nanoparticles of Zinc oxide or Titanium dioxide, are made through a process of gamma radiation or microwave irradiation (among other things) until they become so tiny that they are completely invisible (unless you have a transmission electron microscope handy). This allows the smooth and transparent application of mineral sunscreen, and freedom from the dreaded white cast without the use of dangerous chemicals.
However, this explosion in nanotechnology has been accompanied by an explosion in research on the toxicity of these new materials. This is because when substances are changed into nano-form they interact differently with biological systems than their non-nano counterparts. For example, there has been some research to demonstrate that nano-particles can penetrate the skin, turning these inert minerals into cytotoxic chemicals and other research demonstrating the opposite.
This is a controversial area of research that is constantly being updated. It is always best to do your own research, and decide what is best for you and your family. Click this link for our collection of research papers on UV filters, including nano-zinc oxide and nano-titanium dioxide.
Geoffrey, K., Mwangi, A. N., & Maru, S. M. (2019). Sunscreen products: Rationale for use, formulation development and regulatory considerations. Saudi pharmaceutical journal : SPJ : the official publication of the Saudi Pharmaceutical Society, 27(7), 1009–1018. https://doi.org/10.1016/j.jsps.2019.08.003
Wang J, Pan L, Wu S, Lu L, Xu Y, Zhu Y, Guo M, Zhuang S. Recent Advances on Endocrine Disrupting Effects of UV Filters. International Journal of Environmental Research and Public Health. 2016; 13(8):782. https://doi.org/10.3390/ijerph13080782
Kyu-Bong Kim, Young Woo Kim, Seong Kwang Lim, Tae Hyun Roh, Du Yeon Bang, Seul Min Choi, Duck Soo Lim, Yeon Joo Kim, Seol-Hwa Baek, Min-Kook Kim, Hyo-Seon Seo, Min-Hwa Kim, Hyung Sik Kim, Joo Young Lee, Sam Kacew & Byung-Mu Lee (2017) Risk assessment of zinc oxide, a cosmetic ingredient used as a UV filter of sunscreens, Journal of Toxicology and Environmental Health, Part B, 20:3, 155-182, DOI: 10.1080/10937404.2017.1290516
Rainieri S, Barranco A, Primec M, Langerholc T, Occurrence and toxicity of musks and UV filters in the marine environment, Food and Chemical Toxicology, Volume 104, 2017, Pages 57-68, ISSN 0278-6915, https://doi.org/10.1016/j.fct.2016.11.012.
Schneider, SL, Lim, HW. A review of inorganic UV filters zinc oxide and titanium dioxide. Photodermatol Photoimmunol Photomed. 2019; 35: 442– 446. https://doi.org/10.1111/phpp.12439
Amir Moezzi, Andrew M. McDonagh, Michael B. Cortie, Zinc oxide particles: Synthesis, properties and applications, Chemical Engineering Journal, Volumes 185–186, 2012, Pages 1-22, ISSN 1385-8947 https://doi.org/10.1016/j.cej.2012.01.076.
Dardenne, M. Zinc and immune function. Eur J Clin Nutr 56, S20–S23 (2002). https://doi.org/10.1038/sj.ejcn.1601479
Lansdown, A.B.G., Mirastschijski, U., Stubbs, N., Scanlon, E. and Ågren, M.S. (2007), Zinc in wound healing: Theoretical, experimental, and clinical aspects. Wound Repair and Regeneration, 15: 2-16. https://doi.org/10.1111/j.1524-475X.2006.00179.x
Skocaj, Matej, Filipic, Metka, Petkovic, Jana and Novak, Sasa. "Titanium dioxide in our everyday life; is it safe?" Radiology and Oncology, vol.45, no.4, 2011, pp.227-247. https://doi.org/10.2478/v10019-011-0037-0
Smijs, Threes G, and Stanislav Pavel. “Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness.” Nanotechnology, science and applications vol. 4 95-112. 13 Oct. 2011, doi:10.2147/NSA.S19419