Safe and efficient sunscreens

COSSMA: What are the latest developments in the field of sun care?

Stanislaw Krus: We can observe some dramatic changes in the sun care field. These are mainly driven by the avoidance of two widely used UVB filters in new sunscreen developments: Octocrylene (OCR) and Ethylhexyl Methoxycinnamate (EHMC).

There are increasing concerns regarding their safety profile for humans and for the environment. So far, the discussed UV filters have not lost their approval in 
Europe but are the subject of investigation initiated either at the level of REACH (registration, evaluation, authorisation and restriction of chemicals) or the EU Commission and SCCS (scientific committee on consumer safety).

We can already see the effects of this uncertainty: according to Mintel GNPD (global new products database), the number of products without OCR and without EHMC rose from 15% in 2015 to more than 50% in 2021 in Europe. This creates new challenges for formulators since it is not easy to achieve good performance in a sunscreen product without using EHMC or OCR. Ethylhexyl Triazone (EHT) and Bis-ethylhexyloxyphenol Methoxyphenyl Triazine (BEMT) are often used as replacements, but to achieve a higher SPF, additional UVB filters are required.

We investigated several options, and our solution for an additional UV filter is the broad-spectrum filter Tris-Biphenyl Triazine (TBPT) as it offers many benefits compared to other UV filters.

What are the properties of Tris-Biphenyl Triazine? 

TBPT offers many opportunities in modern sunscreens. We evaluated its benefits in comparison to Phenylbenzimidazole Sulfonic Acid (PBSA) and Titanium Dioxide (TiO2). TBPT combines the best of both worlds, being organic like PBSA and particulate like TiO2.

The tests and measurements showed that TBPT offers unique absorbance coverage; it greatly contributes to an increase in SPF without unbalancing the UVA protection thanks to its UVAII shield. Compared to PBSA, it does not decrease water resistance thanks to its particulate nature and allows an extension of protection up to the blue waveband.

In addition, TBPT is photostable with both commonly used UVA filters BMDBM and DHHB, which is crucial to not generate free radicals under UV exposure. In a test setup around the sensitive eye area, TBPT has not led to any undesirable skin reactions. Finally, TBPT allows the development of eco-friendly sunscreens up to SPF 50+.

When it comes to sun protection, the topic of sustainability has so far been less of a focus. What role does it play today?

Over the past years, the topic of sustainability has become more and more important and is now a key driver for new developments in the sun care industry. Sunscreen products contain UV filters, which after use, in most cases, end up in the environment. An assessment of the environmental impact of such UV filters is desirable because it could provide the possibility to design sunscreens with minimal environmental impact.

We have therefore developed a methodology¹ that supports the transparent and holistic assessment of UV filters based on internationally recognised criteria. It considers eight different parameters, e.g., acute, and chronic aquatic toxicity or biodegradation. It is the first scientifically sound and transparent system of its kind and offers a way to develop sunscreens with improved environmental compatibility. 

There is a discussion about the adverse effects of sunscreens on coral reefs. What are the latest findings and how can coral reefs be better protected?

Coral reefs are extremely sensitive and highly endangered ecosystems. To be able to better protect them, it is essential to identify the potential stress factors. Sunscreen products and their possible impact on coral reefs have been discussed widely in the media in recent years. However, only very limited data exists on their potential effects and impact on corals, so further investigation is needed. Even though all UV filters are functionally similar, their structural features are very diverse. Their impact on limnic organisms² is highly variable ranging from no or low to high toxicity. We can therefore expect that their effect on corals also differs significantly.

Research and studies on this topic have been done, but there is still a lack of standardised methods. They differ in many aspects, including the species and life stage used, field and laboratory approaches, and exposure times ranging from hours to weeks.

It is therefore impossible to gain reliable data from these studies. We work closely with our partners from the University of Oldenburg, Germany, to describe what a scientifically sound testing proposal should include to obtain reliable and reproducible data, which ultimately should result in an internationally organised, standardised ring test trial. For the future, we plan to include such data on coral reefs in our methodology for transparent and holistic assessment of UV filters, but this will only be possible once standardised tests are available.

You also help customers in finding the best individual sun protection formulation. What are the latest conclusions in your research? 

We are constantly doing research on how to improve sunscreen formulations. Of course, UV filters are the key ingredients of sunscreens. Another prerequisite for good performance of these products is the vehicle, which is needed to distribute the UV filters as uniform as possible on the human skin. Vehicles are cosmetic formulations such as creams, lotions, sprays, and gels. Some of the most efficient UV-absorbers for sunscreens are solid at ambient temperature and must be dissolved in the oil phase of the formulation.

The solubility of such oil-soluble UV-absorbers can be a limiting factor when aiming for high protection against UV-radiation. The oil phase is often heated to high temperatures, which may lead to oversaturated UV-absorber concentrations after cooling. We therefore experimentally investigated the crystallisation behaviour of four different oil-soluble UV-absorbers and found striking differences in the crystallisation velocities.

These can be explained by quantum-chemical calculations. We then backed upour theoretical calculations with experimentally determined solubilities. This indicates that these kinds of calculations may serve in the future to better understand and predict the solubility behaviour of UV-absorbers in sunscreens.

How are safety and quality tandards for sun care products guaranteed?

Quality and product safety are of very high importance throughout the entire production chain. Global ISO standards ensure that sun care products meet the highest requirements worldwide. Customers and the end consumers want to be sure that they are always getting the same quality of a product and that the claims on the packaging are not empty promises. Therefore, all processes in the plant are subject to ISO 9001 certification, the global standard for process and quality improvements and the creation of transparency.

Standards to describe protection factors also play an important role in the quality of sun protection products, e.g., ISO 24444. It defines and regulates the in vivo determination of the sun protection or sunlight protection factor. If you buy a sun cream with a sun protection factor of 50, this standard assures that SPF 50 is actually provided.

As it is in our own interests, as well as those of the customers, to have standardised methods for checking the sun protection factor, BASF is heavily involved in the development and continuous improvement of these standards. During the last revision of standard 24444, our team succeeded in establishing new standard formulations and introducing further reference formulations with high protection factors. 

For many years, you have been supporting “Beyond Suncare”, which aims to ensure that no person with albinism dies unnecessarily from skin cancer. Can you tell more about this project?

This project is very close to our heart. Mafalda Soto, the co-founder of “Beyond Suncare”, and her team are doing impressive work, and we are proud that we can contribute.

The organisation works to educate and raise awareness among persons with albinism living in remote and neglected places and distributes tailor-made sunscreen to them. They  also train and empower local healthcare personnel. Initially, we supplied ingredients free of charge and technical expertise, but in 2014 we began to work more intensely with the founders to develop a highly efficient sunscreen formulation that was even better adapted to the needs and sensory preferences of people with albinism in Africa. And we continued to supply local manufacturers with the respective sun care ingredients free of charge. we have now renewed our collaboration for the next three years to ensure that the most vulnerable people are safe in the sun.

References:

1 EcoSun Pass

2 Organisms (and the sediments that may form from them) that occur in the freshwater environment.