Low that is less than 2
Moderate that is from 3 to 5
High that is anything and above 7
Very high that is anything above 8
Extreme that is beyond 11
It is a fact that cataracts rise and so does incidence of cancer as there is a rise in the index and immunosuppression increases. An oncologist can explain you more about this.
What are UV rays?
UV radiations are of three types. VIBGYOR is the term by which we usually call them and so the ones, which are beyond the range of violet, are called ultraviolet rays. In the visible light spectrum, the ones which are close to it are UVA, the B and the C. A is the closest to visible light and C is the farthest. All of these UVCs are fully absorbed and 90% of the UVB rays are absorbed by ozone, water vapour, oxygen, carbon dioxide and the clouds as the sun passes through the atmosphere. Mainly UVA rays and very few B rays consist of the UV ray that reaches the earth surface.
The UVA ray is actually responsible for ageing, wrinkles and to some extent, cancers too. Sunburns and skin cancers are caused by the UVB ray. There is no need to worry about the UVC rays as they do not generally penetrate the atmosphere.
About 90% of UV rays get reflected after penetrating over the clouds and they are received between 10 am to 2 pm. We all worry about UV rays as there is a general rule that there are no safe UV rays.
How UV radiation causes skin cancer?
Melanin is contained in different quantities in the different skin types in human. So, it is normal that their response to UV exposure also differs. The skin has been categorized by The United Nations and WHO into four types which are the burner, the tanner, the naturally brown and the naturally black. This is based on the minimum exposure rates without doing any harm.
We Indians come under group 3, naturally brown. It makes us highly vulnerable to the effects of UV rays as our skin is exposed to a UV index of 10 or above. In such instances, usage of shade, sunscreen, shirts and cap is recommended by a cancer specialist. The risk categories are further divided based on low rays, medium rays, high rays and very high rays. We Indians are in the very high-risk category at present.
The UV rays are filtered by the ozone layer. In the present days, it is a very worrisome fact as the ozone layer is depleting. The main factor that causes skin cells to become cancer cells is exposure to UV radiation.
Too much UV radiation from the sun or other sources such as solaria (solariums, sunbeds and sunlamps) cause almost all skin cancers (95% of melanoma skin cancers and approximately 99% of non-melanoma skin cancers).
In the cells in the epidermis (the top or outer layer of the skin), skin cancer develops. UVA and UVB rays make up UV radiation. They cause permanent damage to the cells as they are able to penetrate the skin.
UVA causes genetic damage to cells, photo-ageing (wrinkling, blotchiness, etc.) and immune-suppression as it penetrates into the skin.
UVB causes damage to the cells as it penetrates into the epidermis (top layer of the skin). A significant risk factor for skin cancer, especially melanoma, is sunburn. For this, UVB is responsible.