Ultraviolet Radiation: Effects, Risks and Protection

What Is Ultraviolet Radiation?

Ultraviolet (UV) radiation is a form of electromagnetic radiation with wavelengths ranging from 100 to 400 nanometers (nm). It sits in the electromagnetic spectrum between visible light and X-rays and is invisible to the human eye. The primary natural source of UV radiation is the sun. Artificial sources such as tanning beds, UV disinfection lamps, and welding equipment also emit UV radiation.

Classification of UV Radiation

UV radiation is divided into three ranges based on wavelength:

• UV-A (315–400 nm): Penetrates deeply into the skin, causes premature skin aging, and contributes to the development of skin cancer. UV-A radiation reaches the surface of the Earth almost entirely unfiltered.
• UV-B (280–315 nm): Responsible for sunburn, but also stimulates vitamin D synthesis in the skin. A large proportion is absorbed by the ozone layer.
• UV-C (100–280 nm): Biologically the most harmful range, but completely absorbed by the atmosphere and does not reach the surface of the Earth under natural conditions. UV-C is used artificially for disinfection purposes.

Beneficial Effects on the Body

In moderate amounts, UV radiation also has health benefits:

• Vitamin D production: UV-B radiation stimulates the synthesis of vitamin D in the skin, which is essential for bone health, the immune system, and numerous metabolic processes.
• Mood enhancement: Sunlight can promote the release of serotonin, positively influencing mental well-being.
• Treatment of skin conditions: In dermatology, controlled UV exposure (phototherapy) is used to treat conditions such as psoriasis, atopic dermatitis, and vitiligo.

Health Risks and Damage from UV Radiation

Effects on the Skin

Excessive UV exposure is one of the leading causes of skin damage:

• Sunburn (erythema): An acute inflammatory skin reaction resulting from excessive UV-B exposure.
• Photoaging: Chronic UV-A exposure leads to wrinkle formation, pigmentation spots, and loss of skin elasticity.
• Skin cancer: UV radiation is considered the most important risk factor for basal cell carcinoma, squamous cell carcinoma, and the dangerous malignant melanoma.

Effects on the Eyes

• Short-term overexposure can cause photokeratitis (snow blindness).
• Long-term exposure increases the risk of cataracts and other eye diseases.

Factors Influencing UV Intensity

The intensity of UV radiation reaching the surface of the Earth depends on several factors:

• Time of day: UV radiation is strongest between 10 a.m. and 4 p.m.
• Season: UV levels are higher in summer than in winter.
• Geographic latitude: UV exposure is greater near the equator.
• Altitude: UV intensity increases by approximately 10–12% per 1,000 meters of elevation.
• Ozone layer: A thinner ozone layer allows more UV-B radiation to pass through.
• Reflection: Snow, water, and sand can strongly reflect UV radiation, increasing exposure.

UV Index

The UV Index (UVI) is an internationally standardized measure of the intensity of UV radiation at the surface of the Earth. It ranges from 1 (low) to above 11 (extreme). Health authorities recommend protective measures starting at a UV Index of 3.

Protective Measures

To minimize the harmful effects of UV radiation, health organizations recommend the following precautions:

• Apply sunscreen with an adequate Sun Protection Factor (SPF) that covers both UV-A and UV-B radiation.
• Wear protective clothing, wide-brimmed hats, and UV-protective sunglasses.
• Avoid midday sun between 10 a.m. and 4 p.m.
• Regular skin examinations by a dermatologist for early detection of skin changes.
• Avoid tanning beds, especially for children and adolescents.

References

1. World Health Organization (WHO) – Ultraviolet radiation and health. Available at: https://www.who.int/news-room/fact-sheets/detail/ultraviolet-radiation
2. International Commission on Non-Ionizing Radiation Protection (ICNIRP) – Guidelines on limits of exposure to ultraviolet radiation. Health Physics, 2004.
3. Moan J, Grigalavicius M, Baturaite Z, Juzeniene A, Dahlback A – The relationship between UV exposure and incidence of skin cancer. Photodermatology, Photoimmunology & Photomedicine, 2015.