UV radiation is split into three types: UVA, UVB, and UVC. UVC doesn't reach Earth's surface because the ozone layer blocks it. UVA and UVB both penetrate skin, but they work differently. UVB causes direct DNA damage and burns, while UVA penetrates deeper and contributes to aging and skin cancer risk over time.
The UV Index measures radiation intensity on a scale from 0 to 11+. Higher numbers mean greater risk. The index shifts throughout the day, peaking between 10 a.m. and 4 p.m., and varies by season, location, and cloud cover. Reflective surfaces like water, sand, and snow amplify exposure.
Vitamin D production requires some UV exposure. Most people get adequate levels through casual sun exposure, but dermatologists warn that intentional tanning or extended unprotected time outdoors carries serious risks. Cumulative UV damage causes premature skin aging, cataracts, and melanoma and non-melanoma skin cancers.
Protection strategies include applying broad-spectrum sunscreen with SPF 30 or higher, reapplying every two hours, and wearing UV-blocking clothing, hats, and sunglasses. Seeking shade during peak hours reduces exposure significantly. People with darker skin tones still need sun protection; while melanin offers some natural defense, skin cancer still develops in these populations, often at later stages when diagnosis becomes harder.
The WHO and American Academy of Dermatology recommend checking daily UV Index forecasts to plan outdoor activities strategically. Regular skin checks and professional dermatological screening catch early changes before they become serious.