Preventing Long-term Damage with Balanced UV Protection

Interview with Dr. Myriam Sohn,
Principal Scientist – Scientific Liaisons – IP Manager Sun Care at BASF

Myriam, you are principal scientist at BASF’s Global Technical Center for Sun Care. What is the main focus of your work?

I have been working in the domain of UV protection for skin for many years now. In my current role, I am involved in various research and application-oriented technical sun care topics and serve as IP manager for sun care.  

From time to time, there have been discussions about the effectiveness of sunscreen products. We occasionally hear from skeptical stakeholders who doubt the ability of sunscreen products to decrease the skin cancer rate, especially given that it has not decreased in the last decade(s) despite the increase in the use of sunscreen products. Are sunscreen products not as effective as we might think?     

When we look at the figures, we see indeed that skin cancer rates have not significantly decreased in recent years, even with an increased use of sunscreen products. However, these figures are predicted to stabilize and even decrease in the coming years [1]. A randomized trial conducted in Australia in the 1990s showed that regular application of sunscreen products over a period of five years decreased the occurrence of new primary melanomas for up to 10 years after the end of the trial [2]. The UV filter system of the sunscreen product used in this study was far less efficient than today’s state-of-art formulations. Nonetheless, the outcome of this study showed that sun protection is a fundamental aspect of maintaining skin health and an important means to mitigate the long-term harmful effects of UV radiation, ranging from premature skin aging to the development of skin cancer. Sunscreen products are a complementary means to sun avoidance measures which include seeking shade, avoiding the sun during the midday hours and wearing clothes such as hats or long sleeves (especially for children). 

How do you explain the fact that the skin cancer rate has not fallen significantly?

There are several aspects that explain why the statistics do not yet reflect the effectiveness of today’s sunscreen products or the improved usage behavior from consumers. The most critical to take in consideration is the time shift between UV exposure and the development of skin cancer. It is known that intense and intermittent UV exposure in early life as well as the occurrence of sunburn before the age of 20 are significant risk factors for developing melanoma and non-melanoma skin cancers later in life [3-4]. This means that skin cancer when diagnosed today is often the result of negligent behavior from decades ago. Additionally, Sun Protection Factors (SPFs) in the past were significantly lower than those of today’s sunscreen products. In the 1980s, the average SPF value was around 10 to 15 compared to 30 and above today. Over the years, the development and launch of more effective and photostable UV filters has paved the way for more sophisticated sun care products. However, improved sunscreen products with higher SPF have only been on the market for 15 to 20 years. The expectation is that their benefits with regard to long-term damage are still to come. Additionally, the EU commission recommendation for UVA protection in 2006 was a huge milestone when it came to creating better sun protection products. 

What does the 2006 EU recommendation say? 

The European Commission recommended that sunscreen products should have UVA protection of at least one third of their SPF value [5]. This led to a major improvement in the performance of sunscreens in the UVA range and ensures a minimum UVA protection level is provided with a more balanced UV spectrum when compared to sunscreen products produced before 2006. The improvement of UVA protection since 2006 is a significant advancement. UVA rays, together with UVB rays, were shown to contribute to skin cancer. Therefore, it is expected that the positive effects of high UVB and UVA protection with regard to long-term damage like skin cancer will be seen in two to three decades. In the last ten years, a lot of attention was paid to the development of sunscreen products with a higher SPF but not with improved UVA protection. Our recommendation is for future sunscreen products to strive for a UVA-PF/SPF ratio that is higher than the minimum of one third to achieve a more uniform level of UV protection. This is essential to prevent chronic harm caused by UVA and becomes especially important when it comes to daily products offering photoprotection. Numerous day care products focus solely on SPF and do not offer sufficient UVA protection, since the one-third ratio recommendation does not directly apply to skin care products. Therefore, consumers should pay particular attention to good UVA protection and buy market products with the UVA logo whenever possible.

Are there other factors that could explain why skin cancer rates have not decreased in recent years? 

Globalization is certainly playing its part here. It is much more common these days to travel to distant countries with UV indexes that are higher than at home. In the cold season, people long for sunshine and travel to the other side of the world to escape the winter. However, their skin is completely unprepared for this initial exposure to the sun and is much more susceptible to UV damage because there was no gradual acclimatization. Additionally, it is important to know that the advertised SPF only can be achieved if the sunscreen product is applied evenly in the same quantity as in the tests carried out to determine the SPF (2mg/cm²), and people tend to apply much less.

You mentioned earlier that you would recommend increasing the UVA protection in sun protection products even further. What should a modern sunscreen product look like from your perspective?

Yes, we definitely encourage the development of both sunscreen and day care products offering UV protection that allows for more uniform absorption throughout the UV spectrum. With the current recommended UVA-PF being one third of the SPF value, a significant amount of UVA – in particular UVAI rays – are still not being blocked by the sunscreen product. In fact, UVAI has less energy and fewer immediate effects compared to UVB, but it has higher skin penetration through to the dermis. UVAI has been shown to induce a decrease in the immune response, diminish the ability of the DNA’s repair system, and cause inflammation, skin cancers, photoaging and pigmentation disorders [6]. We therefore believe that modern sunscreen products should strive to have an UVA PF of half or even two thirds of the SPF.

Is this technically already feasible with the UV filters available today? 

Yes, the available filter palette allows for the development of sunscreen products that offer more uniform protection. We have developed a formulation with a high SPF and a UVA-PF of two thirds of the SPF. To achieve this level of UV performance, we combined different UV filter types – Uvinul^® T 150 and Uvinul^® A Plus for effective photostable UVB and UVA protection, respectively – as well as two broad-spectrum UV filters (Tinosorb^® M dispersed in water and Tinosorb^® S added in oil for more synergy). The formulation was rated five Boots Stars, a rating system used in the UK [7], and is also suitable for eco-conscious-oriented sunscreen products, since it meets the BASF EcoSun Pass criterion. This example shows that sunscreen products of the future are already possible today.

References:

[1] Garbe C. et al. Epidemiology of cutaneous melanoma and keratinocyte cancer in white populations 1943-2036. European Journal of Cancer. 2021;152_18-25

[2] Green AC, Williams GM, Logan V, Struttonet GM: Reduced melanoma after regular sunscreen use: randomized trial follow-up. Journal of Clinical Oncology. 2011; 20;29 (3): 257-63.

[3] Green AC, Wallingford SC, McBride P. Childhood exposure to ultraviolet radiation and harmful skin effects: epidemiological evidence. Prog Biophys Mol Biol. 2011;107(3):349-55.

[4] Whiteman DC, Whiteman CA, Green AC. Childhood sun exposure as a risk factor for melanoma: a systematic review of epidemiologic studies. Cancer Causes & Control. 2001;12(1):69-82.

[5] Commission recommendation of 22 September 2006 on the efficacy of sunscreen products and the claims made relating thereto 2006/647/EC, (2006).

[6] Marionnet et al, PLoS One. 2014 Aug 20;9(8):e105263

[7] Measurement of the UVA:UVB ratios according to the Boots Star rating system, (2011): https://cdnmedia.eurofins.com/apac/media/601375/boots-star.pdf

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