| 摘要: | 受大氣臭氧層破壞及地表暖化影響，人類遭受日光紫外線及濕熱危害之暴露風險日增，國民使用防護措施之意識亦逐步提升。本論文旨在探討於日常活動中，遭受熱危害因子及自然紫外光暴露時，使用防曬乳液與否對人體皮膚生理反應變化之影響及影響幅度，並應用建立之生理指標評估紫外線所用防護乳液於濕熱地區如我國之適用性。研究所選定之皮膚生理指標包含：皮膚微血流變化量(skin blood flow change, SBFC)、經皮水分散失度(transepidermal water loss, TEWL)、皮膚溫度、皮膚濕度、紅斑生成指數(erythema-index, E-index)與黑色素沉澱指數(melanin-index, M-index)；主觀熱舒適感則以美國冷凍空調技師協會Standard 55標準問卷為基礎發展之中文問卷調查。研究包括二主要階段：戶外日光實驗測量受試者在日光曝曬下或戶外陰涼處之立即性皮膚生理反應；暴露艙實驗於人工氣候環境暴露艙內模擬不同環境溫濕度狀況。兩階段實驗皆評估實驗組(使用防曬乳液)與控制組(未使用防曬乳液)受試者皮膚生理指標與人體熱舒適感隨不同環境物理因子改變所產生之變化，以分析生理指標與熱暴露間之劑量－反應關係、生理指標間之反應－時程關係、以及主、客觀指標間之可能差異。戶外日光實驗過程同時收集每日台中地區即時紫外光指數作為評估日光紫外光短期與累積輻射量之基準。
研究結果顯示：SBFC為反應環境物理因子影響之高敏感、先期皮膚生理指標。戶外日光實驗結果發現：TEWL、皮膚濕度、以及E-index為警示因遭受短期(急性)紫外線輻射生成健康危害之較佳皮膚生理指標。皮膚障壁功能減低與紅斑生成現象於低劑量紫外光暴露(紫外光指數<6)時即可發生，並明顯反應遭受日光曝曬時皮膚使用防曬乳液與否所產生之生理變化差異，為評估乳液效能之良好指標。暴露艙實驗結果顯示：SBFC、TEWL、及皮膚溫度顯著地隨環境溫度改變而變化，但較不受環境相對濕度之作用；皮膚濕度為各生理指標中唯一可同時反應環境溫度與相對濕度影響者。上述指標間之反應－時程關係為：人體散熱需求增加時，皮膚微血流量增加以將熱量帶至表皮，而後表皮濕度顯著上升。隨皮膚濕度漸趨飽和，TEWL增加以排出水分。散熱後皮膚溫度與周邊熱環境達到平衡。防曬乳液在皮膚表面形成類薄膜屏障，提供皮膚保溼效能，亦對皮膚與外界熱環境之直接接觸產生隔離，因此遲滯SBFC與TEWL對外界熱環境變化之反應。熱感知投票值隨環境溫濕度上升而增加，尤以溫度效應最為明顯，且熱感知投票值與皮膚溫度之相關性最高(R2 > 0.75)。
With the deterioration of atmospheric ozone and global warming continuing, the risks of exposure to solar UV radiation and heat stress have exacerbated in the last decades, and people nowadays have become increasingly familiar with the use of protective mechanisms. The research described in this thesis quantitatively investigated the physiological changes in the sunscreen- protected vs. -unprotected human skin in response to exposure to solar UV radiation and thermal stress. The skin physiology-based indicators were also applied to evaluate the effectiveness of sunscreen rendering protection when used in hot and humid areas such as Taiwan. The physiological indicators selected in the study included skin blood flow change (SBFC), transepidermal water loss (TEWL), skin temperature, skin moisture, erythema (E-index), and melanogenesis (M-index). Subjective thermal sensation was also gauged, using a standardized questionnaire developed by the American Society of Heating, Refrigerating, and Air-conditioning Engineers Standard 55. The research was conducted in two successive stages, the first being conducted outdoors to evaluate the immediate/prolonged changes in skin physiology of the subjects under the sun or in the shadow (the solar UV study) and the second to examine the patterns of physiological adjustment in response to alteration in thermal microclimate (the exposure chamber study). In both studies, the physiological indicators and thermal sensation of the treatment group (using sunscreens) and control group (not using sunscreens) were simultaneously assessed to develop dose-response relationships between dermal indicators and physical variables and to investigate any variations between physiological and psychological indicators, particularly as a result of sunscreen application.
The results of the solar UV study show: SBFC was a physiological indicator highly sensitive to change in solar irradiation and microclimatic factors, thus serving well as a pre-clinical indicator. TEWL, skin moisture, and E-index well indicated the acute health hazard resulting from short-term solar UV irradiation. TEWL and E-index among all physiological indicators best differentiated the efficacy of sunscreen protecting against solar UV radiation at a level of UV Index 6 or less. As observed in the exposure chamber study, SBFC, TEWL, and skin temperature responded linearly to the alteration in environmental temperature, but less to the influence of relative humidity (RH). In contrast, skin moisture was the only indicator responded to influences from both environmental temperature and RH. Among the physiological indicators, skin temperature first changed in response to alteration in environmental temperature, and then SBFC increased to circulate the excess body heat to skin surface for dissipation. The skin moisture increased next to expel the heat absorbed in skin moisture to the skin surface. Once the moisture in the skin saturated, TEWL dramatically rose to evaporate water in stratum corneum. The heat dissipation cycle ended with the skin temperature being re-equilibrated with the thermal environment. As for the psychological indicator, the thermal sensation votes (TSVs) of the participants were influenced proportionally by alterations in the examined thermal factors, particularly the environmental temperature. The TSV was most significantly correlated to skin temperature (R2 > 0.75). |
