Excessive exposure to the harmful ultraviolet rays of the sun leads to premature aging of the skin, photoallergies and ultimately, malignant melanomas and skin cancer. The increased use of ultraviolet filters for protection has become of paramount importance in our daily lives. Scientists have been busy during the last two decades researching novel ingredients and techniques to reduce the spiraling statistics in the proliferation of skin cancer, estimated to top 1.5 million new cases annually in the United States alone. This alarming statistic, along with the emerging evidence of the damaging effects of UVA rays, the depletion of the ozone layer, as well as demographic changes, and the modern popularity of outdoorsy lifestyles, are but a few of the imperatives for the need for photoprotection. Primary to this research effort has been the development of new ultraviolet filters. Organic and inorganic ultraviolet filters have been developed and incorporated into a variety of cosmetic formulations containing a plethora of ingredients for enhanced protection.
The sunscreen industry has benefited from the introduction of many new ultraviolet filters, novel biologically active ingredients (antioxidants, repair ingredients, SPF boosters, etc.) as well as technologically advanced analytical techniques. These topics and the regulatory status of all 55 ultraviolet filters that are currently approved worldwide will be reviewed.
Mechanism of UV Absorption
Ultraviolet filters are generally aromatic molecules that are conjugated with a carbonyl group. In many examples, an electron releasing group (an amine or a methoxyl) is substituted in the ortho- or para- position of the aromatic ring.
Molecules with this configuration absorb the harmful short-wave (high-energy) UV rays (280 to 400 nm) and convert the remaining energy into innocuous longer wave (lower energy) radiation (usually above 400 nm). Quantum mechanical calculations show that the energy of the radiation quanta present in the UVB and UVA region lies in the same order of magnitude as that of the resonance energy of electron delocalization in aromatic compounds.
The energy absorbed from the UV radiation corresponds to the energy required to cause a “photochemical excitation” in the ultraviolet filter. The molecule is excited to a higher energy state from its ground state by absorbing this radiation.
As the excited molecule returns to the ground state, energy is emitted that is lower in magnitude than the energy initially absorbed to cause the excitation. Thus, the energy is emitted in the form of longer wavelengths since the energy is lower than the shorter wavelengths originally absorbed. If the loss in the energy is quite large, that is, the wavelength of the emitted radiation is of sufficient length that is in the infrared region, it may be perceived as a mild heat radiation on the skin. This minuscule heat effect is undetected because the skin receives a much larger heat effect from the direct exposure to the sun’s heat. If the emitted energy lies in the visible region, then it may be perceived as either a fluorescent or a phosphorescent effect. In the extreme case, the emitted radiation is sufficiently energetic (lower wavelength) that it may cause a fraction of the sunscreen molecule to react photochemically. Cis-Trans, Keto-Enol photochemical isomerization has been observed in some organic molecules.
Data on Ultraviolet Filters in Commerce Worldwide
Two compilations for all ultraviolet filters in commerce worldwide are included in this book. The first is comprised of Tables 17 – 19. Table 17 lists the regulatory data for the ultraviolet filters used worldwide. Table 18 contains the chemical and optical properties. Table 19 lists the manufacturers and distributors of ultraviolet filters worldwide. The second compilation is the “Compendium of Global Ultraviolet Filters,” which basically is a two-page summary of the data accumulated on each of the 55 ultraviolet filters used worldwide.
They are both designed for quick reference as follows:
1. The ultraviolet filters are alphabetically listed by their (INCI) name.
2. Another icon lists ten major organizations that regulate ultraviolet filters in their own countries, namely: ASEAN (AN), Australia/New Zealand (AU), Canada (CA), People’s Republic of China (CN), European Union (EU), South Korea (KS), Japan ( JP), MERCOSUR (MR), the United States (US) and South Africa (ZA).
3. Each UV filter has a product identification listing its molecular formula, molecular weight, chemical abstracts service (CAS) number, the EINECS number, its USAN name (United States Adopted Name), other common names as well as trade names and suppliers. A major obstacle for practitioners in sunscreens is the confusion generated by the use of trade names, USAN, INCI, IUPAC or common names for the same ultraviolet filter. The inclusion of all of these names in the ”Compendium“ will assist in the demystifying of names of ultraviolet filters in use.
4. The Toxicity data and Regulatory status of each ultraviolet filter approved worldwide are listed where available. For Europe, the EEC designation along with the COLIPA (S-number) is listed. The maximum allowable concentration (MC) for each UV filter is also included. The reader should double-check all of these regulations with their supplier and the government agency involved prior to committing any resources solely based on the compilation of the data in this book.
5. Stability and storage conditions are outlined for each UV filter.
6. The molecular weight and formula of each ultraviolet filter are listed along with a drawing of the molecular structure.
7. The physical and chemical properties for each UV filter are listed.
About the Author
Dr. Nadim Shaath received his BSc degree (Honors) in Chemistry from the University of Alexandria, Egypt, and his PhD in Organic Chemistry from the University of Minnesota. After three years as a Postdoctoral Fellow in the School of Pharmacy, Medicinal Chemistry Department at the University of Minnesota, he joined the chemistry faculty at the State University of New York (SUNY) at Purchase where he also served as the Chairman of the Chemistry Department, and later joined Felton Worldwide, a flavor, fragrance and sunscreen company, as Director of Research.
Until 1990, he served as the Executive Vice President and Technical Director of Felton Worldwide where he also assumed full responsibility for the promotion of their sunscreen products. In his first year he managed to triple the sales of this Division turning the Sunarome brand into a multi-million dollar business venture that was sold later to Haarman and Reimer.
In 1990, Dr. Shaath became the President and Chief Executive Officer of KATO Worldwide, Ltd., a flavor, fragrance, sunscreen and essential oil company. In 2000 he founded Alpha Research & Development, Ltd., and is currently its President. Alpha R&D, Ltd. is a research, sourcing and product development company in the fields of cosmetics, sunscreens, analytical testing, fragrances, essential oils and aromatherapy.
Dr. Shaath is a frequent speaker and moderator at many scientific meetings, and is the author of numerous articles in chemical, flavor, pharmaceutical, cosmetic, food and sunscreen journals and publications. He has represented the Cosmetic, Toiletry & Fragrance Association (CTFA) on sunscreens to the FDA, and is an expert witness on several litigations in the Cosmetic and Sunscreen Industries. He is the editor of several books on Sunscreens, including Sunscreens published in 2005 by Marcel Dekker (Taylor & Francis).