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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.