Solar protection factor

To quantify the protective effect of textiles, the solar protection factor (SPF) is determined. The SPF is the ratio of the potential erythemal effect to the actual erythemal effect transmitted through the fabric by the radiation and can be calculated from spectroscopic measurements. The larger the SPF, the more protective the fabric is to UV radiation. In Europe and Austraha, the SPF is referred... 

Table 14.2 Solar protection factors (SPF) of undyed fabrics ...

SPF is the ratio of the length of time of solar radiation exposure required for the skin to show redness (erythema) with and without protection. The term SPF or UPF (ultraviolet protection factor) has been introduced such that a garment of UPF 15 will provide the same amount of protection against solar ultraviolet radiation as a sunscreen of SPF 15. Garments with a UPF value of 20-29 offer high protection (UVR transmission 5.0-3.3%). A UPF value of 30-40 (UVR transmission 3.3-2.5%) offers very high protection and a UPF value of 40 + offers maximum protection with a UVR transmission of 2.5%. 

The major measurement of sunscreen photoprotection is the sun protection factor (SPF), which defines a ratio of the minimal dose of incident sunlight that will produce erythema or redness (sunburn) on skin with the sunscreen in place (protected) and the dose that evokes the same reaction on skin without the sunscreen (unprotected). The SPF provides valuable information regarding UVB protection but is useless in documenting UVA efficacy because no standard systems have been developed to measure UVA protection. Such protocols are needed because more than 85% of solar ultraviolet radiation reaching earth s surface is UVA, which penetrates more deeply into human skin than does UVB and appears to play an important role in photoaging and photocarcinogenesis. 

Book topics include practical aspects of spectrometers and spectrometry, sample preparation, chemometrics, and calibration practices reflectance measurements and standard materials measurements. We have placed an emphasis on reflectance and color measurements due to their common usage in today s spectroscopic laboratories. Methods for selecting a measurement technique are included, as well as solar and color measurements. Spectrometry of new materials, ceramics, and textiles are covered by respective experts in their fields. An appendix of practical reference data for UV-VIS, NIR, IR bench top, IR microspectroscopy, and UV Sun Protection Factor (SPF) measurements is included. 

Often, quality failures are so evident (like, for example, separation of phases, rarefaction of the fat phases, etc.) that users will realise that they should not apply the product. On the other hand, some quality failures do not cause adverse effects on users. For example, an error in the label does not usually cause adverse effects, although it may in certain cases like for instance the wrong sun protection factor labelled on a sunscreen product could give rise to solar erythema in users who would trustingly overexpose themselves to the sun. 

Little is known or understood about the regulation of MAA concentrations within organisms. Is MAA synthesis constitutive or induced Is synthesis stimulated by exposure to solar radiation Is radiation intensity a controlling factor Do particular wavelengths within the solar spectrum stimulate MAA production or accumulation Does UV-induced damage, rather than the perception of UV exposure, trigger the protective response ... 

Figure 14.2 illustrates the relationship between the maximum SPF and the cover factor. Using a SPF value of 50 as the goal, a fabric with a cover factor of 0.98 and composed of fibres that absorb all of the non-reflected UV radiation will provide its wearer with excellent protection against solar UV radiation. 

The reactivity of ultraviolet irradiation which had been an indispensable factor for the origin of life soon became highly dangerous for primitive organisms. Consequently, these early life-forms could only occupy ecological niches which protected them from direct solar radiation. It is, therefore, very probable that the first ecological niches were narrow layers of water two to three meters under the surface of the oceans, a depth by which water has absorbed most of the harmful ultraviolet radiation [1]. The colonization of other habitats, especially land, was not yet possible. 

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