Why is ultraviolet light important

As a result, distorted proteins can be made, or cells can die. Illustration by David Herring. A special enzyme arrives at the damage site, removes the damaged section of DNA, and replaces it with the proper components based on information elsewhere on the DNA molecule. In addition to their own resiliency, living things and the cells they are made of are protected from excessive amounts of UV radiation by a chemical called ozone.

A layer of ozone in the upper atmosphere absorbs UV radiation and prevents most of it from reaching the Earth. Yet since the mids, human activities have been changing the chemistry of the atmosphere in a way that reduces the amount of ozone in the stratosphere the layer of atmosphere ranging from about 11 to 50 km in altitude.

Without the layer of ozone in the stratosphere to protect us from excessive amounts of UV-B radiation, life as we know it would not exist. Scientific concern over ozone depletion in the upper atmosphere has prompted extensive efforts to assess the potential damage to life on Earth due to increased levels of UV-B radiation. Some effects have been studied, but much remains to be learned. How Much Are We Getting? Sometimes the cells with DNA mutated by the sun's rays turn into problem cells that don't die but keep proliferating as cancers.

The result is skin cancer, the most common form of cancer in the United States. People who get sunburned repeatedly are at much higher risk. The risk for the deadliest form of skin cancer , called melanoma , doubles for someone who has received five or more sunburns, according to the Skin Cancer Foundation. A number of artificial sources have been devised for producing UV radiation. According to the Health Physics Society , "Artificial sources include tanning booths, black lights, curing lamps, germicidal lamps, mercury vapor lamps, halogen lights, high-intensity discharge lamps, fluorescent and incandescent sources, and some types of lasers.

One of the most common ways of producing UV light is passing an electric current through vaporized mercury or some other gas. This type of lamp is commonly used in tanning booths and for disinfecting surfaces. The lamps are also used in black lights that cause fluorescent paints and dyes to glow. Light-emitting diodes LEDs , lasers and arc lamps are also available as UV sources with various wavelengths for industrial, medical and research applications.

Many substances — including minerals, plants, fungi and microbes, as well as organic and inorganic chemicals — can absorb UV radiation.

Absorption causes electrons in the material to jump to a higher energy level. These electrons can then return to a lower energy level in a series of smaller steps, emitting a portion of their absorbed energy as visible light. Materials used as pigments in paint or dye that exhibit such fluorescence appear brighter under sunlight because they absorb invisible UV light and re-emit it at visible wavelengths.

For this reason they are commonly used for signs, safety vests and other applications in which high visibility is important. Fluorescence can also be used to locate and identify certain minerals and organic materials. According to Thermo Fisher Scientific, Life Technologies , "Fluorescent probes enable researchers to detect particular components of complex biomolecular assemblies, such as live cells, with exquisite sensitivity and selectivity.

In fluorescent tubes used for lighting, "ultraviolet radiation with a wavelength of nm is produced along with the blue light that is emitted when an electric current is passed through mercury vapor," according to the University of Nebraska.

The energy from the ultraviolet light is absorbed by the fluorescent coating inside the fluorescent lamp and re-emitted as visible light. Black-light tubes typically use mercury vapor to produce long-wave UVA light, which causes certain dyes and pigments to fluoresce.

The eye waters and vision is blurred. Conjunctivitis is the inflammation of the conjunctiva the membrane that covers the inside of the eyelids and the sclera, the white part of the eyeball ; see Figure 3 which becomes swollen and produces a watery discharge. It causes discomfort rather than pain and does not usually affect vision.

Examples of eye disorders resulting from UV exposure include "flash burn", "ground-glass eye ball", "welder's flash" and "snow blindness" - depending on the source of the UV light causing the injury.

The symptoms are pain, discomfort similar to the feeling of sand in the eye and an aversion to bright light. Maximum absorption by the cornea occurs around nm. Absorption of UV-A in the lens may be a factor in producing cataract a clouding of the lens in the eye. A variety of instruments are commercially available for measuring UV radiation in the laboratory and in the workplace. Specifications and purchasing information can be obtained from suppliers of workplace monitoring equipment.

There are no Canadian regulatory occupational exposure limits for UV radiation. These limits are given below:.

For the UV-A or near ultraviolet spectral region to nm , exposure to the eye should not exceed 1 milliwatt per square centimeter 1. For exposure times less than seconds, the dose total energy should not exceed 1.

Additional exposure limits apply to the amount of UV light exposure to the skin and the eyes. The amount of UV exposure a person can receive on their skin or eyes during an 8-hour period varies with the wavelength of the UV radiation.

UV radiation is invisible and therefore does not stimulate the natural defenses of the eyes. Workers must use eye and skin protection while working with UV radiation sources which present the potential of eye harmful exposure. The selection of eye protection depends on the type and intensity of the UV source. UV radiation is easily absorbed in a variety of materials. Shielding is usually easy to design. Mercury lamps and metal halide lamps have an outer glass cover to stop UV radiation, and are designed such that if the outer glass is broken, the lamp ceases to function.

Certain industrial chemical pollutants in the atmosphere are gradually eroding earth's protective shield ozone layer which stops the sun's UV radiation from reaching the earth. In recent years, there has been growing concern about increasing levels of UV radiation in the sunlight, especially during the summer months. Excessive exposure to ultraviolet rays can cause skin cancer and eye cataracts. Ways to limit exposure to the sun's UV radiation include avoiding working in the sun, wearing protective clothing and hats, and applying sunscreens.

Protective clothing can include long pants, hats, and long-sleeved shirts. Some newer, sun-resistant fabrics are more efficient in blocking UV radiation. Physical sunscreens e. Chemical sunscreens are non-opaque i. Broad spectrum sunscreens are intended to block both types of UV radiation. Sunscreens are rated according to Sun Protection Factor SPF , an index of protection against skin erythema reddening of the skin.

The higher the SPF is, the more protection it offers. For example, sunscreens should be applied 20 minutes before going outdoors, and reapplied every two hours, or more often if perspiring sweating , swimming, or working in water.

Use a broad spectrum lip balm with an SPF of 30 or higher as well. We hear on the radio and read in the newspapers about the UV index as a part of the weather forecast. The UV index is a measure of the intensity of UV radiation in the sunlight that causes reddening of the skin erythema. The UV index can increase the mid-teens at midday in the tropics.

The implications of the UV index are summarized in Table 3. Besides direct sunlight, UV radiation exposure can occur via indirect routes. The following factors must be remembered in this regard:. Add a badge to your website or intranet so your workers can quickly find answers to their health and safety questions.