Sunlight brings light, heat and energy to people; Make all kinds of plants more lush. For the human body, sunshine plays an important role in sterilization, treating chondropathy and enhancing skin resistance, which is closely related to improving health. However, under certain conditions, it will not only burn people's skin and muscles, but also cause cancer.
Long ago, medical scientists found that people living in areas with strong sunlight and long sunshine hours, as well as fishermen, sailors, herdsmen and farmers who have been engaged in production under the sun for a long time, suffer from more skin cancer than those who work indoors. People with light skin color have more skin cancer, and more skin cancer occurs in exposed parts of the body than in non exposed parts. Later, it was finally found that excessive sunlight and ultraviolet radiation could cause cancer, which was confirmed in animal experiments. It is estimated that hundreds of thousands of people in the world suffer from skin cancer every year.
Why can ultraviolet rays in sunlight cause skin cancer?
The reason is: After skin cells are exposed to excessive ultraviolet radiation, they will damage the genetic material DNA. In the process of DNA repair, or in the DNA of a small number of cells that survive after a large number of cell death, sometimes there will be errors in "genetic information", making the next generation of normal cells become cancer cells. Then, the newborn cancer cells continue to divide and reproduce, so that the offspring cells always maintain the characteristics of cancer cells, and finally form skin cancer.
The wavelength of ultraviolet rays in sunlight ranges from 4900 Angstroms to below 400 angstroms. Ultraviolet rays with a wavelength of 400 ~ 300 angstroms can only cause dark skin. After the action of the ozone layer in the atmosphere, the ultraviolet rays that cause skin cancer only reach the ground with a wavelength of more than 290. So in general, sunlight is not easy to cause skin cancer. On the contrary, people often use the beneficial side of sunlight and ultraviolet rays to enhance their physique, such as sunbathing and other activities. However, air pollution has seriously damaged the ozone layer, increasing the short wave ultraviolet rays exposed to the ground in the sun, and causing more and more skin cancer patients.
It is estimated that every additional 100 modern supersonic jets will reduce ozone by 0.7% and increase skin cancer by 1.4% every year,. Therefore, various measures must be taken to protect the environment and the ozone layer.