Spectral Homeostasis - The Fundamental Requirement for an Ideal Sunscreen.

Sunscreen application to UV-exposed skin is promoted to prevent skin cancer and sun damage, within a comprehensive photoprotection strategy that also includes sun avoidance and wearing UV protective clothing. The benefits of sunscreen are verified in preventing sunburn but appear to be largely presumptive in skin cancer prevention. Contemporary science establishes UVA as a primary driver of melanoma and photoaging. Consequentially, the traditional UVB-skewed protection of sunscreens provides an intellectual and logical explanation for rising skin cancer rates and, in particular, their failure to protect against melanoma. Better protection could be achieved with more balanced UVB/UVA sunscreens, toward spectral homeostasis protection. Greater balanced protection has another advantage of attenuating fewer UVB rays, which aid synthesis of vitamin D and nitric oxide. Percutaneous absorption of Soluble Organic UV Filters leads to systemic exposure, which becomes the relevant safety consideration. It is minimized by selecting Insoluble UV Filters with low absorption potential from a molecular weight above 500 Da. The filters must also be very hydrophilic, very lipophilic, or consist of particles. The risk-benefit ratio is a medical imperative, more so for cosmetics or sunscreens, since in principle there should be no risk from their use. The production of ideal sunscreens that mimic the effective, balanced UVB/UVA attenuation of textiles and shade is now possible, while maintaining an acceptable therapeutic margin of safety in humans and a favorable ecologic profile. Sunscreens with a favorable risk-benefit ratio and good esthetic properties or other consumer-friendly attributes will improve compliance and may achieve substantial clinical benefits.

Interpreting Risk from Sunscreens in the Marine Environment.

Recent and pending bans in specific jurisdictions of some organic ultraviolet (UV) filters have resulted in significant concern and controversy over the potential impacts of these contaminants in the marine environment. Organic UV filters have been quantified in the aquatic environment as contaminants in water, sediments, and the tissues of aquatic organisms. The limited available laboratory studies on the toxicity of UV filters to keystone marine species such as reef-building corals describe a wide variety of impacts, from significant acute effects to no observed effects. However, interpretation of results is complicated by differences in methodology, and exposures to single agents in vitro may not reflect the effects of longer exposure to finished sunscreens containing UV filters in combination with numerous other chemicals. Relatively short-term observations of laboratory effects thus may not translate to real-life field conditions, where organisms may be subject to the effects of long-term chronic exposure to UV filters as well as other environmental contaminants and stressors. The lack of current understanding of the full impacts of UV filters, both in the laboratory and in the environment, represents a significant challenge in interpreting the environmental risk associated with the widespread use of sunscreens.