UV radiation emitted by the sun penetrates Earth’s atmosphere and enables the skin to produce vitamin D, which supports bone function, blood cell development, and immune system health. However, overexposure to ultraviolet radiation poses significant health risks.
Excessive UV exposure can damage DNA in skin cells, leading to skin cancer. Melanoma, identified as the most dangerous form of skin cancer, is now the fifth most common cancer in the UK, according to Prof Dorothy Bennett from St George’s, University of London. UV radiation also contributes substantially to skin aging, causing wrinkles and skin laxity, and has been linked to eye problems including cataracts.
UV radiation levels vary throughout the day, with the highest readings occurring in the four-hour period around solar noon, typically from late morning to early afternoon. The UV Index measures ultraviolet radiation on a scale starting at zero and potentially exceeding 10. In the UK, summer UV levels typically range from 5-6, with a maximum of 8 only in exceptional circumstances. Countries near the equator experience significantly higher levels year-round, with Nairobi, Kenya regularly recording UV levels above 10 and Majorca, Spain typically reaching nine during June and July.
The World Health Organization indicates that sun protection is essential when UK UV levels are medium (3-5) or high (6-7), with additional protection required at very high (8-10) or extremely high (11+) levels. Children require additional protection at lower UV levels than adults. The NHS recommends sunscreen with SPF 30 or above and at least 4-star UVA protection applied to all exposed skin approximately 30 minutes before sun exposure. Adults should apply approximately six to eight teaspoons of sunscreen to cover the entire body and reapply every two hours or more frequently after sweating, swimming, or towel drying. Additional protective measures include wearing suitable clothing and sunglasses, seeking shade between 11:00 and 15:00 from March to October in the UK, and avoiding tanning.
UV exposure risk is not determined by ambient temperature, as skin can burn equally quickly at both 30 degrees Celsius and 20 degrees Celsius. UV radiation penetrates thin clouds, so overcast conditions do not eliminate burn risk. Skin cancer risk affects individuals across all skin colors, as does broader immune system damage from excessive UV exposure.
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