UVA Radiation: Effects, Risks and Sun Protection

What is UVA Radiation?

UVA radiation is a form of ultraviolet (UV) light spanning wavelengths from 320 to 400 nanometers (nm). It accounts for approximately 95% of all UV radiation that reaches the Earth's surface. Unlike UVB radiation (280–320 nm), UVA intensity remains relatively constant throughout the day and across all seasons. It can also penetrate window glass and clouds, making year-round exposure a concern.

Properties and Skin Penetration Depth

Due to its longer wavelength, UVA radiation penetrates significantly deeper into the skin than UVB. While UVB mainly affects the outermost layer of the skin (epidermis), UVA reaches the deeper layer known as the dermis, where it damages collagen and elastin fibers, contributing to premature skin aging.

• Penetration depth: reaches the dermis
• Intensity: relatively constant year-round and throughout the day
• Penetrates: clouds, window glass, and thin fabrics
• Share of total UV radiation at the Earth's surface: approx. 95%

Biological Effects on the Skin

UVA radiation produces several biological effects on the human body, particularly the skin:

Premature Skin Aging (Photoaging)

UVA radiation is the primary driver of photoaging – premature aging of the skin caused by UV exposure. It indirectly damages DNA in skin cells through reactive oxygen species (free radicals) and degrades collagen and elastin, leading to wrinkles, pigmentation spots, and loss of skin elasticity.

Pigmentation and Tanning

UVA radiation activates existing melanin in the skin, producing an immediate but short-lived tan. This so-called immediate pigment darkening offers little to no protection against further UV damage.

DNA Damage and Skin Cancer

Although UVA causes less direct DNA damage than UVB, it can trigger indirect DNA mutations through oxidative stress. These mutations can contribute to the development of skin cancer, including the most dangerous form, malignant melanoma.

Immunosuppression

UVA radiation can weaken the skin's immune defenses by damaging Langerhans cells and reducing local immune responses, making the skin more vulnerable to infection and malignant changes.

UVA Radiation and Tanning Beds

Tanning beds (sunbeds) primarily emit UVA radiation to produce rapid skin tanning. However, their use is associated with significant health risks. The World Health Organization (WHO) and major cancer research institutions classify sunbed use as carcinogenic (Group 1) and strongly advise against it, particularly for individuals under 18 years of age.

Protection Against UVA Radiation

Effective protection against UVA radiation is important throughout the entire year, not just in summer:

• Broad-spectrum sunscreens: Use products with a high SPF and explicit UVA protection (UVA seal or PA+++ system)
• Protective clothing: Wear clothing with a UV protection factor (UPF), wide-brimmed hats, and UV-blocking sunglasses
• Seek shade: Especially during midday hours when UV radiation is strongest
• UV window films: Apply to office or car windows, as UVA radiation passes through glass

UVA Radiation in Medicine

UVA radiation is also used therapeutically in a treatment known as PUVA therapy (Psoralen plus UVA). In this approach, a photosensitizing agent (psoralen) is combined with controlled UVA exposure to treat skin conditions such as psoriasis, vitiligo, and eczema. This therapy is always performed under strict medical supervision.

References

1. World Health Organization (WHO) – Ultraviolet radiation and health. WHO, Geneva. Available at: https://www.who.int/news-room/questions-and-answers/item/radiation-ultraviolet-(uv)
2. International Agency for Research on Cancer (IARC) – IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 100D: Radiation. IARC, Lyon, 2012.
3. Matsumura Y., Ananthaswamy H.N. – Toxic effects of ultraviolet radiation on the skin. Toxicology and Applied Pharmacology, 2004; 195(3): 298–308.