Photoprotection at a Glance
- Photoprotection measures include seeking shade during the peak ultraviolet (UV) B hours of 10:00 am to 2:00 pm and the use of high sun protection factor broad-spectrum sunscreen, clothing, wide-brimmed hat, and sunglasses.
- New generation photostable UV filters are now available in Europe and many parts of the world and are beginning to enter the US market.
- UV protection factor is a UV protection rating for fabrics. Several chemical treatments can increase the natural UV protection factor.
- Glass that filters out more than 99.9% of UV from 300–380 nm is now commercially available.
- Sunglass standards, mandatory in Australia and voluntary in the United States, specify a maximum percentage of light allowed to be transmitted and a minimum vertical dimension of sunglasses.
With increased attention to physical fitness and outdoor recreational activities, daily exposure to sunlight is common. Although sun exposure may have beneficial effects such as mood elevation and vitamin D3 photosynthesis, unwanted effects are well known. Acute effects of sun exposure include sunburn and delayed tanning. Chronic sun exposure is strongly associated with photoaging, actinic keratoses, and squamous cell carcinoma; intermittent sun exposure is associated with basal cell carcinoma and melanoma. Complete avoidance of sun exposure is neither necessary nor practical, nor will it be accepted by the general public. As such, behavioral modification of seeking shade during peak ultraviolet B (UVB) hours of 10:00 am. to 2:00 pm and the use of photoprotective measures, such as sunscreen, clothing, wide-brimmed hat, and sunglasses, and when appropriate, intake of vitamin D supplements, have become the public health message to deliver. This chapter discusses the currently available, commonly used photoprotective measures.1
The first UVB filter, PABA (para-aminobenzoic acid), was patented in 1943, and the first UVA filter, a benzophenone, was introduced in 1962. In 1972, the US Food and Drug Administration (FDA) reclassified sunscreens from cosmetics to over-the-counter (OTC) drugs, resulting in more stringent regulation. In 1979, long UVA filters, dibenzoylmethane derivatives, became available. In 1990s, the need for protection against UVA, as well as against UVB, was recognized, which led to further development of UVA filters.
The sun protection factor (SPF) was first developed by an Austrian, Franz Greiter, in 1962 and was adopted by the FDA in 1978.2 Current FDA guidelines specifically require that products be tested using a solar simulator with emission spectrum covering the wavelength range of 290–400 nm, and that the sunscreen product be applied at a concentration of 2 mg/cm2.
By definition, SPF is the ratio of minimal erythema dose (MED) of a subject's sunscreen-protected skin over the MED of the unprotected skin. Because the end point is erythema, SPF is a reflection of protection against the biologic effect of UVB (290–320 nm), and to a lesser extent, UVA2 (320–340 nm) (see Chapter ...