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Visible Light and Ultraviolet Light – Introduction

Sunlight is perceived as related to heat and health, and for many years it was considered beneficial to our health. Moreover, tanning is the heart's desire of many, especially young people, who identify it with beauty and health.

 

Indeed, the sun is essential for life on earth.  However, the radiation emitted from the sun is also a health hazard.  Ultraviolet (UV) light, both from the sun's rays and from artificial sources, affects human health in different ways, some beneficial and some harmful.

Sunlight

Sunlight

 

The sun's light and heat are essential for almost all known forms of life.  From the health aspect, insufficient exposure to UVB radiation may lead to Vitamin D deficiency and to the diseases this entails.  UVB radiation may even be beneficial to various skin diseases, such as psoriasis and eczema.

 

Nevertheless, ultraviolet radiation in the UVA and UVB range that penetrates the atmosphere and reaches the earth's surface is also a health hazard, ranging from burning and accelerated aging of the skin, to causing  cataracts and damaging  the conjunctiva of the eye, and through to developing various skin tumors, including malignant melanoma,

 

Ultraviolet radiation is electromagnetic radiation originating from the sun. The wavelengths of ultraviolet (UV) light in the electromagnetic spectrum range from 100 – 400 nanometers, divided into three sub-sectors: UVA, UVB and UVC.  UVA radiation, and part of UVB, are included in the range of non-ionizing radiation wavelengths, while the high frequencies of UVB and UVC are within the range of ionizing radiation.

 

When sunlight penetrates the atmosphere, most UVC radiation and almost 90% of UVB radiation are absorbed by the ozone layer.  Hence, the UV radiation that reaches the earth's surface is mostly (about 95%) in the UVA range, and slightly (about 5%) in the UVB range.

 

In view of the damage and health consequences of this radiation, policies related to UV radiation focus on raising public awareness of the dangers of exposure to radiation, and on providing recommendations to reduce it.  This section reviews policies on UV radiation, and includes:

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