Sources of UV Light

Ultraviolet Light (or UV) is a part of the light spectrum that is damaging to human tissue. This is because UV rays are able to penetrate the skin more deeply than other light rays, and can even cause mutation of the skin cells in some cases. Because UV light is potentially hazardous, it is important to recognize the sources that generate UV rays.

The Sun

• The Sun is the single largest natural source of UV light that we have. Any time the sun is shining, UV rays are bombarding the surface of the planet. Some of these rays are deflected by the Earth's magnetic field, and others scatter across the outer atmosphere and back out into space; however, a small percentage of them fall directly onto the surface of the planet and onto anything that is on the surface.

  Even on cloudy days, UV rays penetrate the cloud cover and pose a threat to living tissue. Wearing sunscreen and sunglasses with a UV rating helps protect you from dangerous exposure. However, the best protection is to limit the time you spend in direct sunlight.

Street Lights

• Arc Lamps that are powered by either mercury or xenon will produce UV light. These lights are commonly referred to as "discharge lamps" and are powered by using a fused quartz arc tube. This tube is then housed inside a globe. Sometimes the globe is clear glass, sometimes it contains a phosphor powder coating inside. The outer globe serves as a thermal insulator, and is the only part of the lamp that provides protection from UV light.

  These lights are most commonly used in utility street lights. Although not all street lights use mercury or xenon, those that do will create ultraviolet light. This light comes in doses much smaller than what is generated by the Sun, but exposure should still be limited, and staring directly into the light should be avoided.

Fluorescent Lights

• Fluorescent lights are commonly referred to as discharge tubes. Some forms of fluorescent lights are powered by being filled with gas atoms, which are then heated. This is the general principle behind all fluorescent light, including neon lights.

  If a light is filled with gas atoms of hydrogen, deuterium or mercury, there is a chance that the lights will produce a small amount of UV light spectrum. This largely depends on whether or not the internal energy levels of the bulb reach an energized state that matches or exceeds that of the UV wavelength.