紫外綫(xiàn)是(shì)太陽光(guāng)中不可見(jiàn)的輻射(shè)光。根(gēn)據(jù)波(bō)長及(jí)其(qí)生(shēng)物效(xiào)應，可劃分(fēn)為UVA，UVB和(hé)UVC三(sān)個(gè)主(zhǔ)要(yào)波段(duàn)。雖然(rán)過度暴露於(yú)紫外綫會對皮膚(fū)造成(chéng)損害(hài)，但適量接觸亦對(duì)人體(tǐ)健(jiàn)康(kāng)具有(yǒu)重(zhòng)要(yào)價值(zhí)。

「紫外綫的(dí)光譜(pǔ)特(tè)性與(yǔ)皮膚(fū)影(yǐng)響(xiǎng)」

1，UVA（315-400nm）作(zuò)為長波(bō)紫外綫，穿(chuān)透(tòu)力很(hěn)強，不(bù)僅(jǐn)能(néng)直(zhí)達皮(pí)膚(fū)真皮(pí)層，也(yě)可(kě)輕易(yì)穿(chuān)透(tòu)普(pǔ)通(tōng)玻(bō)璃(lí)。這意味著即使(shǐ)在(zài)室內靠(kào)窗位置，皮膚(fū)仍會受(shòu)到UVA輻射。UVA深入(rù)真(zhēn)皮層(céng)後，會(huì)產生(shēng)活性氧(yǎng)簇(cù)等(děng)自由基，攻擊(jī)並(bìng)降(jiàng)解膠(jiāo)原蛋白(bái)和彈性(xìng)纖(xiān)維這些(xiē)關(guān)鍵(jiàn)結構蛋(dàn)白——膠(jiāo)原(yuán)蛋(dàn)白和彈性纖維。長期且反復的UVA暴(bào)露，會(huì)導(dǎo)致(zhì)真(zhēn)皮(pí)層(céng)結(jié)構(gòu)塌陷(xiàn)，表現(xiàn)為皮膚(fū)出(chū)現深皺(zhòu)紋(wén)，鬆(sōng)弛(chí)，失去彈性。

上(shàng)一期我們介紹過(guò)，針(zhēn)對(duì)UVA的(dí)防(fáng)護，我們(mén)需(xū)要關注防曬產品(pǐn)上的PA標識，PA值越高，防(fáng)護效果(guǒ)越好。

2，UVB（280-315nm）作(zuò)為中波(bō)紫(zǐ)外(wài)綫，主要影(yǐng)響表皮層。當(dāng)皮膚暴露(lòu)於過量UVB時(shí)，表(biǎo)皮細胞會直(zhí)接受損(sǔn)。身(shēn)體為應對此(cǐ)損(sǔn)傷，會(huì)啟(qǐ)動炎症(zhèng)反應，皮膚表(biǎo)麵(miàn)形成肉(ròu)眼可見的(dí)紅斑，即(jí)曬傷，並增(zēng)加(jiā)患(huàn)皮膚癌的(dí)風險。SPF值(zhí)專(zhuān)門標示(shì)對(duì)UVB的(dí)防護(hù)等級(jí)，日常使用SPF30即可(kě)阻擋約97%的UVB。

3，UVC（200-280nm）雖然能量很(hěn)強(qiáng)，但絕大多數被大氣(qì)層吸收(shōu)，自然環境(jìng)中(zhōng)不(bù)對人體構成威(wēi)脅(xié)。但(dàn)需注意(yì)，人工(gōng)UVC光源（如殺菌燈）不可直接照(zhào)射人(rén)體(tǐ)，其(qí)短時(shí)照射(shè)即可灼(zhuó)傷(shāng)皮(pí)膚與(yǔ)眼睛(jīng)，需嚴格(gé)規範(fàn)使(shǐ)用。

「紫(zǐ)外綫(xiàn)的積(jī)極(jí)作用與(yǔ)生活應用(yòng)」

適(shì)量(liáng)紫外(wài)綫(xiàn)對人體健康(kāng)至(zhì)關(guān)重(zhòng)要。UVB能促(cù)進(jìn)皮膚合成(chéng)維(wéi)生(shēng)素D，這(zhè)一過程對鈣質吸收和骨骼(gé)健(jiàn)康(kāng)具有不可替代的(dí)作用。

UVA憑借其(qí)出色(sè)的(dí)穿(chuān)透(tòu)與熒(yíng)光(guāng)激(jī)發能力(lì)，常(cháng)用於錢及證(zhèng)件防(fáng)偽鑒定(dìng)，刑偵(zhēn)取證，其光(guāng)固(gù)化特性(xìng)也廣泛(fàn)應用於(yú)牙(yá)科修復(fù)，電子產(chǎn)品塗層和印(yìn)刷(shuā)油墨的(dí)快速(sù)固化(huà)。

UVB在(zài)醫(yī)療領(lǐng)域中，窄譜UVB是(shì)治(zhì)療銀屑病等皮膚病(bìng)的有(yǒu)效(xiào)方法；在農業(yè)上，可(kě)用(yòng)於提(tí)高溫室作(zuò)物(wù)中(zhōng)維(wéi)生(shēng)素(sù)D的含(hán)量。

UVC因其高(gāo)效的(dí)殺菌(jūn)消毒(dú)能(néng)力(lì)，被廣泛(fàn)用(yòng)於飲用(yòng)水淨化，空(kōng)氣(qì)消毒(dú)及(jí)醫療器械(xiè)的無菌(jūn)處理。

這些應(yīng)用充分(fēn)體現了紫外(wài)綫的“雙(shuāng)麵(miàn)性(xìng)"：科學利(lì)用(yòng)可造(zào)福(fú)人類(lèi)，過度暴露(lòu)則(zé)會造成(chéng)傷(shāng)害(hài)。我(wǒ)們既(jì)不應過度恐(kǒng)懼(jù)紫(zǐ)外綫，也要(yào)避(bì)免(miǎn)無防(fáng)護的(dí)長時間暴露。通過(guò)合理的(dí)防曬措(cuò)施(shī)，在享受戶外(wài)生活(huó)的同(tóng)時，盡可(kě)能(néng)限(xiàn)度降低紫(zǐ)外綫對皮膚的(dí)傷(shāng)害，實(shí)現人(rén)與紫外綫(xiàn)的(dí)和(hé)諧共(gòng)存。

Ultraviolet Radiation: From Skin Health to Practical Applications

Ultraviolet (UV) radiation is an invisible component of sunlight. Based on wavelength and biological effects, it is divided into three main bands: UVA, UVB, and UVC. While excessive exposure to UV radiation can damage the skin, moderate exposure also holds significant value for human health.

「Spectral Characteristics of UV Radiation and Its Effects on the Skin」

1. UVA (315–400 nm), as long-wave ultraviolet radiation, has the strongest penetrating ability. It can reach the dermis layer of the skin and easily pass through ordinary glass. This means that even indoors near a window, the skin remains exposed to UVA radiation.

Upon penetrating the dermis, UVA generates free radicals such as reactive oxygen species, which attack and degrade key structural proteins—collagen and elastic fibers. Long-term and repeated UVA exposure leads to the breakdown of the dermal structure, manifesting as deep wrinkles, skin laxity, and loss of elasticity.

As discussed in our previous issue, protection against UVA requires attention to the PA rating on sunscreen products. A higher PA value indicates better protective efficacy.

2.UVB (280–315 nm), as medium-wave ultraviolet radiation, primarily affects the epidermal layer. When the skin is exposed to excessive UVB, epidermal cells are directly damaged. In response, the body triggers an inflammatory reaction, resulting in visible erythema (sunburn) on the skin surface and an elevated risk of skin cancer. The Sun Protection Factor (SPF) specifically indicates the level of UVB protection. Daily use of SPF 30 can block approximately 97% of UVB radiation.

3.UVC (200–280 nm), although the most energetic, is largely absorbed by the atmosphere and does not pose a threat in the natural environment. However, it is important to note that artificial UVC sources (e.g., germicidal lamps) must not be directly exposed to the skin or eyes, as even brief exposure can cause burns. Strict safety protocols are essential when using such devices.

「Positive Effects and Practical Applications of UV Radiation」

Moderate UV exposure is crucial for human health. UVB stimulates the skin’s synthesis of vitamin D, a process indispensable for calcium absorption and bone health.

Thanks to its strong penetrating and fluorescence-inducing properties, UVA is widely used in anti-counterfeiting technologies for banknotes and official documents, as well as in forensic investigations. Its photopolymerization characteristics are also applied in dental restorations, electronic product coatings, and the rapid curing of printing inks.

In the medical field, narrowband UVB therapy is effective in treating skin conditions such as psoriasis and vitiligo. In agriculture, it can be used to enhance vitamin D levels in greenhouse-grown crops.

UVC’s potent germicidal properties make it valuable for disinfecting drinking water, purifying air, and sterilizing medical equipment.

These applications highlight the "dual nature" of UV radiation: when used scientifically, it benefits humanity, but overexposure can cause harm. We should neither fear UV radiation excessively nor neglect protection during prolonged exposure. With reasonable sun protection measures, we can minimize skin damage while enjoying outdoor activities, achieving a harmonious coexistence with ultraviolet radiation.