With a period of extreme heat forecast across the UK this week, many areas are expected to experience high levels of ultraviolet (UV) radiation. While some exposure to UV is crucial for our overall wellbeing, particularly for the production of essential vitamin D, too much can be profoundly damaging, leading to serious health issues such as skin cancer.
UV radiation, emitted by the Sun, penetrates the Earth's atmosphere and plays a vital role in bone health, blood cell function, and the immune system through vitamin D synthesis. However, its harmful effects are well-documented. Excessive UV exposure can damage DNA in skin cells, directly contributing to the development of skin cancer. It is also a significant factor in skin ageing, causing wrinkles and loss of elasticity, and has been linked to eye conditions, including cataracts. Professor Dorothy Bennett from St George's, University of London, highlights the severity: "Every exposure to UV, especially every sunburn, increases our risk of skin cancer. Melanoma, the most dangerous skin cancer, is now the fifth commonest cancer in the UK."
The intensity of UV radiation varies throughout the day, typically peaking during the four-hour period around "solar noon" – late morning to early afternoon. The UV Index (UVI) is a global standard for measuring this radiation, ranging from zero upwards. A higher UVI indicates a greater potential for damage to skin and eyes, and a shorter time before harm occurs. In the UK, summer UVI typically ranges from 5-6, with exceptional circumstances seeing it reach 8. In contrast, equatorial regions can experience levels above 10 year-round, according to the World Health Organisation (WHO).
Protecting oneself from UV radiation is paramount. The WHO advises sun protection when UK levels are medium (3-5) or high (6-7), with extra precautions necessary for very high (8-10) or extremely high (11+) levels. Children, being more sensitive, require additional protection at lower UV levels than adults. The NHS recommends using sunscreen with an SPF factor of 30 or above, offering at least 4-star UVA protection. This should be applied generously to all exposed skin, including the face, neck, and ears, ideally 30 minutes before sun exposure, and reapplied every two hours, or more frequently if sweating, swimming, or towel drying.
Beyond sunscreen, the NHS advises covering up with suitable clothing, wearing sunglasses, and seeking shade, especially between 11:00 and 15:00 from March to October when the sun is strongest. It is important to note that there is no safe or healthy way to get a tan. As Dr Bav Shergill from the British Association of Dermatologists explains, a tan signifies that UV light has stimulated skin cells to produce pigment in an attempt to protect DNA, but this protection is minimal, equivalent to SPF 4. Furthermore, UV radiation can penetrate thin clouds, meaning that even on cloudy or windy days, skin can burn just as quickly as on a hot, sunny day.