An Introduction To Ultraviolet Light

An Introduction To Ultraviolet Light

In order to understand the tanning process of the skin, it is essential that you, the salon owner or operator, understand light and how it works. The influence of light on the development and life-sustaining effects for mankind is not a simple concept. People and animals always have been subjected to various physiological responses due to the effects of sunlight. With the passage of time, researchers are finding that light, whether it be natural or its artificial equivalent, plays a part in many significant physiological and biochemical reactions.

To understand the full consequences of light, it is necessary to have an understanding of the electromagnetic spectrum-a spectrum of a continuous range of radiation spreading from cosmic rays, up through the ultraviolet, visible and infrared regions to radio waves.

Light is a wave-form energy source measured according to the size of its wavelength. A wavelength is the distance between the crests of two consecutive electromagnetic waves and is measured in nanometers. A nanometer is equal to 0.000001 millimeter, which is one millionth of a millimeter. The solar radiation reaching the earth is made up of rays of varying wavelengths.

One portion of the spectrum is visible light, which first was discovered in 1665 by Sir Isaac Newton. At that time, it was thought to be one band of light, but later it was found that it was a combination of many colors. And now, in a rainbow or when a beam of light strikes a prism, it’s apparent that it truly is a combination of many different colors. The multicolored rays spring forth as red, orange, yellow, green, blue and violet. These are known as visible radiation. Visible radiation is that portion of the spectrum between 400 nm and 750 nm.

Ultraviolet light is not visible to the human eye. It is defined as that part of the spectrum below 400 nm. The ultraviolet spectrum can be further divided into four bands: UVA, UVB, UVC and UV Vacuum. UVA rays are the longest ultraviolet rays, while UV Vacuum are the shortest. Since different ultraviolet wavelengths produce markedly different physiological and therapeutic effects, these groupings are based on general biological and physical effects of radiation from each region.

The UVA range abuts visible light and often is referred to as near-UV or “black light.” UVA1 covers the region of 320 nm to 340 nm; UVA2 covers the range of 340 nm to 400 nm in wavelength. UVA light acts primarily to darken melanin pigment granules already present in the skin tissue. In the amount permitted in indoor tanning, it causes little or no perceptible erythema.

Because UVA tans with little or no danger of sunburning, the development of equipment utilizing primarily or exclusively UVA emissions revolutionized the indoor tanning industry. This light accounts for the majority of the UV output of low-pressure equipment and virtually all of the output in high-pressure units.

UVB Light 

UVB is the middle region between 280 nm and 320 nm. It is commonly known as the erythemal UV and is also the band that converts ergosterol in the skin to vitamin D. In addition, ultraviolet light in the UVB range is the light that is predominantly responsible for stimulating increased melanin production. Unfortunately, it is also the range of light that generally causes sunburn, or erythema.

For tanning purposes, UVB light is important in stimulating melanogenesis, but its level must be carefully controlled. In most low-pressure indoor tanning lamps, UVB accounts for 2 percent to 3 percent of the total ultraviolet output of the lamp. In high-pressure units, it is usually filtered out altogether due to the high-output level involved.

UVC Light 

UVC radiation constitutes by the wavelengths between 160 nm and 280 nm, and because of its proven effectiveness in killing single-cell organisms is called germicidal UV. The shorter wavelengths produce ozone in air (oxygen). Solar radiation in the UVC range is absorbed almost entirely by the carbon dioxide and ozone in the atmosphere.

That’s just as well, considering that even short exposure to any quantity of UVC is very harmful to the eyes and causes severe sunburn. Generally speaking, the shorter the wavelength, the more potentially dangerous the ultraviolet radiation.

One place where radiation in the UVC range can be found is in the arc of a welding torch. For that reason, optical damage caused by UVC light is sometimes referred to as “welder’s eye.” UVA and UVB light can cause similar skin and eye damage, but much higher levels and much longer exposure times are required.

The fourth band encompasses all wavelengths below 160 nm to the X-ray region and is called Vacuum UV because its radiation is readily absorbed by the gasses present in the atmosphere. Therefore, the only place it exists is in a vacuum. It is not produced in tanning equipment.

Infrared light is invisible to the human eye. “Near IR ranges 700 nm to 1,000 nm; while IR measures 1,000 nm to 3,000 nm. Infrared light is felt as heat. Most infrared light is absorbed by the atmosphere as well, and there is not much danger to the skin from its rays striking it.

Let’s look at spectrum in relation to a person standing outside receiving the full effects of sunlight. In reality, the wavelengths of radiation that bombard the body are essentially those supplied by the sun after its rays have been filtered by the atmosphere. An important part of the atmosphere is the ozone layer which removes a significant portion of the radiation under 290 nm.

By removing those wavelengths of radiation, the ozone layer screens the most harmful rays from reaching the earth. This is why there is increasing concern over its depletion in recent years from man-made chemicals. In consequence, the solar radiation reaching the earth’s surface consists mainly of the following: 

• Ultraviolet light principally in the range of 280 nm to 400 nm (UVC, UVB, UVA2 and UVA1).
• The visible spectrum in the range of 380 nm to 770 nm.
• The near infrared from about 770 nm to 1,000 nm.
• Wavelengths longer than 1,000 nm which amount to about 20 percent of the solar radiation.