英语翻译During recent years there has been a growing interest on

英语翻译
During recent years there has been a growing interest on sunscreen technology.The well known harmful effects of UVB and UVA radiation from the sun and artificial sources have led to the development of new and innovative filters.So far,sunscreens have been designed to protect against erythema,that is mainly an UVB effect,but there is a number of sunscreens that can also protect against the long wavelengths of the UVA range.The customary use of sunscreens in the condition of exposure is recommended in order to reduce significantly the level of UV irradiation.Actually the official and internationally accepted method for sunscreen tests is the in vivo sun protection factor (SPF) method based on the COLIPA standard .The in vivo method is expensive and time consuming,factors that make it difficult to adopt in routine quality control.Moreover,in vivo tests to assess UVA protection,such as PPD or IPD ,often result in not reproducible and controversial results.As a consequence,a lot of efforts have been devoted to the development of in vitro techniques for assessing the photo-protection ability of sunscreen products.A sunscreen in vitro test is based on absorbance or reflectance measurements of sunscreen applied on suitable UV transparent substrates.These methods produce estimates of protection factors which correlate with the results obtained in in vivo photo-testing of human subjects.In principle,the substrate should have optical and physical—chemical properties close to those of the skin.Most commonly adopted substrates are Transpore,Vitro-Skin,Roughened Quartz Plate and PMMA Plates .Studies performed using Excised Human Stratum Corneum and Excised Human Epidermis have been reported,but the biological nature of these materials introduces practical
problems.The choice of the substrate is a very critical issue as sunscreen tests performed on different substrates are not always reproducible ,especially when the substrate/sunscreen is irradiated
before or during the tests.Moreover,when a particular substrate is used other parameters can affect the final in vitro SPF value.It is well known that the correlation between in vitro and in vivo
data depends on the quantity of applied product and also from the formulation of the sunscreens.To obtain the correspondence between in vitro and in vivo SPF data,an initial calibration must be performed for different sunscreen products labeled by different SPF values.Calibration should be performed for each instrumentation used,each method adopted (substrates,sunscreen amount applied,etc.),and each type of sunscreen formula (lait,gel,etc.).However,different substrate materials can be suitable for in vitro tests.This paper describes the performance of a material,Teflon (PTFE),that has never been considered for SPF and photo-stability testing.