Does the sun in winter have bactericidal effect?

The reason why the sun in winter has sterilization ability is because it uses the ultraviolet rays emitted by the sun light source as sterilization tools. Ultraviolet short-wave ultraviolet rays are extremely destructive to microorganisms. When ultraviolet rays in this band irradiate bacteria, the nuclear protein and deoxyribonucleic acid (DNA) of cells strongly absorb the energy in this band, and the chain between them is opened and broken, which leads to the death of bacteria. For example, air and food are sterilized by ultraviolet mercury lamp or metal halide lamp.

Ordinary bacteria and some viruses will be killed if they are exposed to the sun for half an hour or several hours. For pathogens of various respiratory infectious diseases such as influenza virus and meningococcus, ultraviolet rays in sunlight are natural nemesis, and some bacteria can even be killed within a few hours.

The solar radiation spectrum of the sun is very close to that of a blackbody with a temperature of 5,800 K. About half of the electromagnetic spectrum is in the short-wave range of visible light, the other half is in the near infrared region, and there are some ultraviolet rays in the spectrum. When ultraviolet rays are not absorbed by the atmosphere or other protective coatings, it may lead to sunburn or self-regulation changes of human skin pigments.