What are UV levels and how can you protect yourself?
As the UK faces a period of extreme heat this week, many areas are expected to experience high UV levels.
While some exposure to ultraviolet (UV) radiation is necessary for health, excessive exposure can be harmful and increase the risk of skin cancer.
What is UV and why can it be dangerous?
UV radiation is emitted by the Sun and passes through the Earth's atmosphere.
This radiation enables the skin to produce vitamin D, which is vital for bone health, blood cell function, and the immune system.
However, excessive UV exposure can cause damage. It can harm the DNA in skin cells, leading to skin cancer. UV radiation also contributes significantly to skin ageing, causing wrinkles and loss of skin elasticity.
Additionally, UV exposure has been linked to eye conditions such as cataracts.
"Every exposure to UV, especially every sunburn, increases our risk of skin cancer," says Prof Dorothy Bennett, from St George's, University of London.
"Melanoma, the most dangerous skin cancer, is now the fifth commonest cancer in the UK."
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How is UV measured and what is the UV index?
UV radiation levels fluctuate throughout the day.
The highest UV readings occur during the four-hour period around "solar noon," when the sun is at its peak, typically from late morning to early afternoon.
The UV Index (UVI) is a standardized measure of ultraviolet radiation used internationally.
It starts at zero and can exceed 10. Higher values indicate greater potential for skin and eye damage and shorter time before harm occurs.
What do the different UV levels mean?
In the UK, summer UV index values usually range from 5 to 6, with a maximum of 8 only in rare cases.
Countries near the equator experience consistently high UV levels around midday throughout the year.
For example, Nairobi, Kenya, can have UV levels above 10 year-round, according to the World Health Organization (WHO).
Majorca, Spain, typically reaches a UV index of nine in June and July.
How can you protect yourself from UV radiation?
Using appropriate sunscreen is essential for protection.
The WHO advises that some sun protection is necessary when UV levels are medium (3-5) or high (6-7).
Extra protection is required when UV levels are very high (8-10) or extremely high (11+).
Children are more sensitive to UV radiation than adults and need additional protection at lower UV levels.
The NHS recommends using sunscreen with a sun protection factor (SPF) of 30 or higher and at least 4-star UVA protection.
Sunscreen should be applied to all exposed skin, including the face, neck, ears, and scalp if hair is thinning or absent, ideally 30 minutes before sun exposure.
Adults should apply approximately six to eight teaspoons of sunscreen to cover the entire body.
Reapplication is necessary every two hours or sooner if sweating, swimming, or towel drying.
Additional NHS advice includes:
- Wearing suitable clothing and sunglasses
- Seeking shade during peak sun hours, between 11:00 and 15:00 from March to October in the UK
What should you look for when choosing sunscreen?
What does hot weather do to the body?
When is it too hot to walk your dog?
Can you tan safely?
The NHS states there is no safe or healthy way to obtain a tan.
Dr Bav Shergill, from the British Association of Dermatologists, recommends using self-tanning products instead.
"When you tan, ultraviolet light stimulates your skin cells to produce pigment to try and protect the DNA of skin cells - but that protection is minimal - the equivalent of SPF 4.
That is not much protection at all - so you can still burn very early," he warns.
Can you burn even when it is cloudy and windy?
UV exposure is not related to the air temperature.
"Your skin can burn just as quickly whether it's 30°C or 20°C," warns BBC Weather's Helen Willetts.
"Don't be caught out on cloudy days. UV will still penetrate thin clouds - so even if you don't think it's that sunny, you can still burn."
I have brown skin. Do I need to worry?
Dr Shergill explains that although skin may appear darker, it does not always provide sufficient protection from UV radiation due to genetic factors.
"I have, for example, seen South Asian people with skin cancer and I have seen people with dual-heritage get skin cancer."
Risks of eye damage and immune system effects from excessive UV exposure affect individuals of all skin colors.
