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Stay Safe in the Sun - Beware of Ultraviolet Radiation

8 May 2025

Ultraviolet Radiation and Health

The sun emits radiation of different wavelengths, including ultraviolet (UV) radiation, which is invisible and cannot be felt.

A moderate amount of sun exposure helps our body to produce vitamin D, which is important for keeping our bones healthy.

Excessive exposure to UV radiation may cause painful sunburn, wrinkling and premature ageing of the skin, as well as an increased risk of skin cancers and cataracts.

The UV Index and Forecast

The Hong Kong Observatory measures and forecasts UV intensity, adopting the scheme provided by the World Health Organization (WHO) to calculate the UV Index and classify it into the corresponding exposure level.

The UV Index is a measure of the potential harm of UV radiation on human skin. The higher the number, the greater the potential for damage to the skin. In Hong Kong, the UV index value can often exceed 10 on a sunny day in the summer.

The UV Index and the corresponding exposure level defined by the WHO are shown in the table below:

    UV Index

    Exposure Level

    0-2

    Low

    3-5

    Moderate

    6-7

    High

    8-10

    Very High

    >11

    Extreme


Protective Measures against UV Radiation

  1. To reduce the harm caused by UV radiation, it is of utmost importance to minimise direct exposure of the skin and the eyes to sunlight.
  2. Avoid staying outdoors for prolonged periods on days with a high UV Index value (6 or above).
  3. If it is necessary to stay outdoors for activities, take the following precautions:
    • Check the latest UV Index reading and forecast. The UV Index value may remain high even during cloudy periods.
    • Choose a broad-spectrum water-resistant sunscreen product with a sun protection factor (SPF) of at least 30 or higher when doing outdoor activities and apply liberally; reapply every two hours if you need to stay outdoors for a prolonged period, or after swimming, sweating or toweling off.
    • Seek shade.
    • Wear a wide-brimmed hat that covers the back of your neck.
    • Wear UV blocking sunglasses.
    • Wear long-sleeved and loose-fitting clothing.
    • Use an umbrella.


Sun Safety Tips for Children

Children are at a higher risk of UV damage than adults, and therefore require special protection. To enjoy the sunshine with them, parents/carers should consider the following tips:

  1. Encourage children to play in the shade.
  2. Make sure children wear appropriate clothing (e.g. a hat and sunglasses) when they go outdoors.
  3. Help children apply sunscreen products liberally, with special attention paid to their exposed body parts (e.g. their faces, necks, shoulders, arms, backs and knees, as well as the dorsum of their feet).
      Safety under the Sun "Protect Yourself against UV Radiation"            Proper Use of Insect Repellents;

(Revised in 2025)