What is the difference between UVA, UVB and UVC and their functions in the tanning process?
Ultraviolet (UV) light is the energy produced by the sun that cannot be seen, but its effects can be observed upon all living things. This light spectrum is organized into three distinct energy ranges – UVA, UVB, and UVC – and the energy is measured in nanometers (nm), with one nanometer equaling one billionth of a meter. The relationship between the length of the light wave and the amount of energy it transports: the longer the wavelength, the lower the energy level.
Typically, the longer the light wave, the less harmful it is to humans exposed to its energy; the shorter the wave, the more intense.
Light in the UV spectrum is organized from the shorter (higher-energy) wavelength (UVC) to the longer (lower-energy) wavelength (UVA). Each UV type has its own location on the electromagnetic spectrum. The length of UVC energy is in the 200-280nm range, the UVB range is 280-320nm, UVA2 is from 320-340, and UVA1 from 340-400nm. Visible light measures in the 400-780nm range.
Typically, the longer the light wave, the less harmful it is to humans exposed to its energy; the shorter the wave, the more intense. Each wavelength has a beneficial purpose. For instance, while UVC is the most powerful of ultraviolet rays and considered harmful to humans, hospitals use UVC (253.7nm) in the form of germicidal lamps to sterilize surgical instruments, water, and the air in operating rooms, because it can destroy bacteria and viruses.
When we spend time outdoors in the natural sun, we primarily are exposed to UVA and UVB light; harmful UVC rays are generally filtered out by the earth’s ozone layer. Some scientists hypothesize that erosion of the ozone layer may be allowing some UVC rays to reach the earth, but the research has not been conclusive.
UVA waves are longer than other ultraviolet waves and can penetrate our skin to the deeper tissue, known as the dermis layer. While it is possible to darken (tan) only existing skin pigment cells with UVA alone, this can only be accomplished with exposure to high amounts of UVA, which may have long-term aging effects on the skin.
Shorter than UVA waves, UVB principally create a reaction in the upper layers of the skin called the epidermis. UVB waves stimulate cells in the epidermis to produce melanin, the pigment that forms a coating around other skin cells to protect them from overexposure to the sun. This process is known as pigmentation. Although UVB cannot penetrate the skin as deeply as UVA waves, the skin is more likely to burn with overexposure to UVB than UVA.
To create a desirable cosmetic tan, a tanning lamp needs a balance of UVA and UVB. UVB stimulates melanin production and can burn the skin if overexposed; UVA2 acts a lot like UVB, with melanin production and some pigment darkening; it is also closely associated with elastosis (photoaging, wrinkles). UVA1 penetrates more deeply past the skin’s surface layer and is primarily responsible for pigment darkening. Newer lamp technology is focused on providing enough UVB to stimulate melanin and aid in production of vitamin D, adequate UVA1, and less UVA2. This combination results in robust pigmentation, very effective bronzing results and a natural protection (SPF) against damage from the sun.
