The Invisible Killer: Ultraviolet (UV) Rays in Sunlight

Know more to be smarter!

Moderate exposure to sunlight helps the body produce vitamin D, which makes bones stronger and, in the case of mature adults, reduces the chance of fractures.

However, it should be noted that the ultraviolet rays in excess sunlight can lead to sunburn and cause skin aging, wrinkles, and increase the risk of skin cancer and cataracts. Types of UV rays and their effects It turns out that there are three types of ultraviolet rays: UVA, UVB and UVC, all of which are invisible to the human eye. Ozone in Earth's atmosphere absorbs all UVC (the shortest wavelength, most dangerous ultraviolet) and most UVB, but not UVA. Therefore, most of the ultraviolet rays reaching the ground are UVA and a small part of UVB. Although UVB only accounts for 2% of the ultraviolet rays reaching the ground, it is much more harmful to the human body than UVA. The World Health Organization estimates that about 80% of skin cancers are caused by excessive sun exposure. Studies have shown that UVA causes skin aging, wrinkles and tanning, and may also lead to skin cancer. In addition to causing sunburn on the skin, excessive absorption of UVB is one of the main causes of skin cancer. Ultraviolet rays are invisible killers. They don't make the skin feel hot, but they can cause sunburn. The heat we feel in the sun is infrared light from the sun, not ultraviolet light. So even if you don't feel the heat of the sun, there's still a chance of getting a sunburn.

UV Index The UV Index is a measure of the possible damage caused by the sun's ultraviolet rays to human skin. The higher the UV index, the higher the chance of skin and eye damage, and the less time it takes to cause damage. During the summer in Hong Kong, the UV index usually rises above 10 on sunny days. The UV Index and its corresponding exposure class defined by the World Health Organization are shown below. UV Index Exposure Class 0-2 Low 3-5 Medium 6-7 High 8-10 Very high =>11 Extremely high UV monitoring The Hong Kong Observatory began to measure and publish the UV index in 1999, and began to predict the highest UV index for the next day in 2006.

The UV index published in the weather forecast is based on clear skies and does not take into account clouds, rain, pollution or reflectors. The index is obtained by estimating the expected maximum UV Index value for the day from the ozone level figures given by computer simulations.

Usually, the index value is lower when the sun angle is lower in the morning and evening, so the estimated maximum value of the day is generally the index value around noon. When the measured or predicted UV index is 11 or above, the Observatory will remind the public to avoid prolonged outdoor exposure. UV protection Using sun oil is one of the effective ways to reduce UV damage. The sun protection factor (SPF) shown on a product at the time of purchase is a measure of UV-B protection. Simply put, it has to do with how long it takes to get a UVB sunburn in the sun. For example, if you use SPF15 sun oil, it means that if there is a visible sunburn in 10 minutes without sun oil, it will be extended to 150 minutes.

SPF also works with other sun protection measures. Generally speaking, a sombrero has an SPF of around 3 to 6, compared to 6 to 7 for regular summer clothes. It can be seen that their sunscreen efficacy is lower than that of sun oil.

Regarding the protection of UVA, there is still no unified indicator, and it is more commonly expressed in the value of PA (Protection Grade of UVA) in Asia. This indicator is divided into three levels: PA+, PA++ and PA+++, with more plus signs representing higher sun protection efficacy. So when one buying sun block he should pay attention to SPF and PA value at the same time.

Reminder to friends

Although sunlight is good, mature adults need to be careful to avoid the harmful effects of ultraviolet rays, properly and take appropriate protective measures. Even in cold temperatures, or when there are clouds, UV rays can harm you. In short, pay attention to the UV index, do not expose to the sun for too long, and properly use sunglasses, sun blocks, wear protective clothing and hats, etc. EGA Lifestyle!