In the U. S., there are 16 UV filters which are approved for use in sunscreen products and are listed in Table 2. Of these 16, there are nine which appear in most currently marketed sunscreen products in the U. S. (41). There is much overlap in the use of such ingredients between U. S. and other regions throughout the world such as Europe (42), the latter having a larger number of UV filters available for use. The human safety of UV filters has been reviewed (39,43-45). In general, the human safety profile of UV filters used in U. S. sunscreen products is favorable based on extensive toxicological data and marketing history. This view is reflected in the appearance of these ingredients on either positive lists in various regions of the world such as Europe and Australia or as Category I ingredients,
i. e., safe, and effective, according to the U. S. FDA. Detailed information regarding the human safety of individual UV filters can be found in the review by Nash (39).
The UV filters in sunscreen products are primarily, if not solely, responsible for the absorption/reflection/scattering of solar UV. To achieve the SPF and breadth of UV protection, a combination of UV filters is selected based on their individual absorption profiles and other physiochemical characteristics. For example, to create a sunscreen product with an SPF 15, nearly any combination of UV filters listed in Table 2 can be used. The selection of filters must absorb wavelengths from 290-340 nm to achieve the desired SPF 15. If protection against long wavelength UV is to be achieved, then in the U. S. the options are much more limited. Specifically, one must select either avobenzone or zinc oxide, both of which absorb long wavelength UVA-I (340-400 nm). As the SPF of the product increases so too does the concentration and number of UV filters. This is represented in Figure 1. The percent concentration of UV filters in a hypothetical SPF 15 product ranges from 10-15% and for an SPF 45, up to 30% and beyond. Net, the higher the SPF, the higher the concentration of UV filters.