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Be Safe in the Sun - Beware of Ultraviolet Radiation

22 June 2022

Ultraviolet Radiation and Health

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

A moderate exposure to the sun helps our body to produce vitamin D, which is important for maintaining healthy bones.

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

The UV Index and Forecast

The Hong Kong Observatory adopts the UV Index and its corresponding exposure levels defined by the World Health Organization (WHO).

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

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

    UV Index

    Exposure Level








    Very High



Protective Measures against UV Radiation

  1. To reduce the harm from UV radiation, the most important thing is to minimize direct exposure of the skin and the eyes to sunlight.
  2. On days when the UV Index is high (6 or above), you should avoid staying outdoors for prolonged periods.
  3. If you must be out in the sun, take the following precautions:
    • Check the latest UV Index and its forecast.
    • Seek shade.
    • Use an umbrella.
    • Wear long-sleeved and loose-fitting clothing.
    • Wear a wide-brimmed hat.
    • Wear UV blocking sunglasses.
    • Use a broad-spectrum sunscreen lotion of a Sun Protection Factor (SPF) 15+ generously. Apply again if you stay out in the sun for more than two hours and after swimming, sweating, or towelling off.

Sun Safety Tips for Children

Children are at a higher risk of suffering UV damage than adults, and therefore require special protection. To enjoy fun in the sun with children, parents / carers should bear in mind 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 lotion generously and pay particular attention to the exposed body parts (e.g. face, neck, shoulders, back, knees and tops of feet).