What do you mean by "ultraviolet index" in weather forecast and "sun protection factor" of sunscreen? What's the use for us?

Brief introduction of ultraviolet index

1. What is the UV index?

The ultraviolet index refers to the degree of possible damage to human skin caused by ultraviolet radiation in the solar rays reaching the earth's surface when the sun is at the highest position in the sky (usually around noon, that is, from 10 to 3 pm). The variation range of the ultraviolet index is represented by a number of 0- 15. Usually, the ultraviolet index at night is 0, and the ultraviolet index in tropical, plateau and sunny days is 15. The higher the UV index, the more serious the erythema damage to human skin caused by UV radiation. Similarly, the higher the ultraviolet index, the greater the damage to the skin in a short time.

Second, understanding and needs.

In recent years, due to the increasingly serious destruction of stratospheric ozone, the amount of ultraviolet radiation received by the ground has increased, which has aroused widespread concern. Therefore, environmental scientists all over the world remind people to attach great importance to the harm of ultraviolet radiation to human body and take necessary preventive measures.

When skin is irradiated by ultraviolet rays, melanocytes in human epidermis begin to produce melanin to absorb ultraviolet rays, thus preventing skin from being damaged. Long-term ultraviolet radiation will cause a large amount of melanin to deposit on the epidermis and become a permanent "tanning" trace.

It is now widely recognized that skin cancer and cataracts are easily caused by excessive exposure to ultraviolet radiation.

It is reported that the incidence of skin cancer in Australia is 800 out of 65,438+10,000 people. There are 250 out of 65,438+people in the United States; In Japan, it is estimated that there are about 5 people in the current population of 654.38 million+. Japanese environmental and medical experts warn that it may not be long before Japan reaches the incidence of skin cancer in Europe, America and Australia, and it is only a matter of time before this dangerous situation appears. In China, although there is no exact estimate and report on the incidence of skin cancer so far, foreign experiences and lessons tell us that we must pay full attention to it.

In addition, ultraviolet radiation will accelerate the chemical decomposition and aging of various organic and inorganic substances; The plankton in the ocean will also be affected by ultraviolet radiation and even die; Ultraviolet radiation brings serious harm and influence to the physiology, growth and development of various animals and plants, including people.

According to different wavelengths, ultraviolet radiation can be divided into three bands: UV-A (3 15-400 nm), UV-B (280-3 15 nm) and UV-C (below 280 nm). Because the atmospheric ozone layer absorbs little UV-A, the change of UV-A radiation has nothing to do with the change of ozone layer. And UV-C is completely opposite to UV-A, it is almost completely absorbed by the ozone layer, so it basically does not reach the ground; The amount of UV-B radiation is closely related to the change of ozone layer. Therefore, we can study the change of atmospheric ozone layer and the influence of ultraviolet radiation on the environment and human body through direct measurement and analysis of UV-B.

Nanjing is a big city with rapid development. With the continuous improvement of people's living standards and quality of life, people urgently need to understand and master the environmental changes and various factors that are closely related to their normal life and health, so as to take various countermeasures and measures to protect the environment and protect themselves.

Third, why do you want to release the ultraviolet forecast?

The destruction of the ozone layer is developing. Not only the ozone hole appeared over the Antarctic, but also the ozone hole was found in the Arctic. In addition, the thinning of the ozone layer has also been found in other parts of the earth where we live. In the future, the destruction of the ozone layer will further develop. In this way, among the ultraviolet radiation, the UV-B which has the greatest influence on human body in the future will increase. It will have a greater impact on people. This has prompted people all over the world to pay great attention to ultraviolet rays.

Because the influence of ultraviolet rays on human body is accumulated for many years, it is for the future to pay attention to prevention from an early age. According to the ultraviolet index forecast and related knowledge, people can take active actions to prevent it, and they can also use ultraviolet forecast to take countermeasures in their own lives. Combined with daily weather forecast, ultraviolet index forecast can popularize all kinds of knowledge about ultraviolet rays among the people. Therefore, the prediction of ultraviolet index and ultraviolet knowledge are useful knowledge to improve people's understanding of ultraviolet.

Four, how to correctly understand and use the ultraviolet index forecast.

Ultraviolet index forecast is a very useful forecast in daily life. According to the ultraviolet index published in the forecast, some measures can be taken to prevent ultraviolet rays. Of course, ultraviolet is not a terrible thing, and we should not be unilaterally affected by ultraviolet forecast.

According to the published ultraviolet index, it is necessary to take effective measures to prevent excessive ultraviolet radiation and make effective use of ultraviolet radiation in a suitable time. The intensity of ultraviolet radiation is not constant in a day, and the most important time in a day is from 10 to around 3 pm. Of course, according to the weather changes, the amount of ultraviolet radiation is also changing, so we should also pay attention to the daily weather changes, and pay attention to which time period we should be particularly careful according to the weather changes.

If you want to draw a natural and beautiful makeup, you must first know how to care for your skin. The hot summer is here, and there should be new measures for maintenance! Do you know enough about sun protection? Do you know what UVA, UVB or UVC are? Before choosing a sunscreen product that suits you, I will take you to understand the influence of ultraviolet rays on the skin and the meaning of labels in sunscreen care products.

Ultraviolet rays will not only make the skin black, sunburn, long spots and wrinkles, but also cause skin cancer in severe cases. Also, because ultraviolet rays are so harmful to the skin, it is even more important to take protective measures against sun exposure.

How big is the influence of ultraviolet rays on the skin? What's the difference between UVA, UVB and UVC?

Light can be divided into three parts: ultraviolet light, infrared light and visible light, and ultraviolet light can be divided into three parts: UVA, UVB and UVC. Among them, UVC has been absorbed and scattered by the ozone layer in the atmosphere because of its short wavelength, so the wavelength of UVB can't reach the ground, and UVA with long wavelength can only reach the epidermis of the skin, which will go deep into the skin and damage the dermis of the skin, leading to skin aging.

According to the statistics of the Environmental Protection Agency, May to June is the rainy season in Taiwan Province Province every year. During this period, when there is no rain, the ultraviolet index often reaches the standard level (the human body will get sunburned if exposed to the standard level for 20 minutes), and after the rainy season, it officially enters summer. In summer, the proportion of days when ultraviolet rays exceed the standard level is as high as 77%, and the proportion of days when dangerous levels appear (people will get sunburned when exposed to dangerous levels 15 minutes).

What is SPF? What is PA?

Most sunscreen products are marked with SPF or PA, SPF (sun protection coefficient) is a numerical value indicating the sunscreen effect of preventing UVB injury, and PA (UVA protection) is an indicator of the degree of UVA prevention.

Most people are familiar with SPF, but because dermatologists keep warning that UVA is not easy to burn the skin, it will cause skin aging and lesions, so PA label has been paid more and more attention.

The value of SPF is suitable for everyone, and its calculation method is: assuming that the intensity of ultraviolet rays will not change with time, a person without any sun protection measures will turn red in the sun for 20 minutes, and when he uses SPF 15 sunscreen, it means that the time can be extended by 15 times, that is, his skin will turn red after 300 minutes.

PA is the "standard for measuring the preventive effect of UVA" published by Japan Cosmetics Industry Federation 1996, and it is the most widely used standard in Japanese products at present. The defense effect is divided into three grades, which are PA+, PA++, PA++, PA++ means effective, pa++ means quite effective and pa++ means very effective.

With the above understanding of ultraviolet rays, you should also know how to choose the right skin care products so as not to fail!

Sun protection coefficient:

SPF is the abbreviation of sun protection coefficient, and the so-called SPF is the index marked by the time to prevent sun exposure.

Due to the different nature of human skin, the degree of defense against ultraviolet rays is also different. SPF is used to indicate the degree to which sunscreen protects the skin from ultraviolet rays.

Take SPF 15 as an example. If your skin is exposed to the sun for 10 minutes without sunscreen, SPF 15 can protect your skin from turning red after 10 minutes * 15(SPF)= 150 minutes.

As we all know, people should protect themselves from the sun all the year round. Sun protection is more popular in summer ... Generally speaking, the sun protection index of the lowest-grade sun protection products is SPF 2 ~ 6, the sun protection index of the middle-grade sun protection products is SPF2~6 ~ 8, the sun protection index of the high-grade sun protection products is SPF6~8 ~ 12, and the SPF value is in the range of 12 ~ 20. ...