Why is ultraviolet radiation important

However, the amount of UVB exposure needed to obtain a benefit depends on several factors, such as: the amount of vitamin D in your diet, skin color, sunscreen use, clothing, where you live latitude and altitude , time of day, and time of year. UV radiation, in the form of lasers, lamps, or a combination of these devices and topical medications that increase UV sensitivity, are sometimes used to treat patients with certain diseases who have not responded to other methods of therapy.

Also known as phototherapy, this method of UV exposure is performed by a trained healthcare professional under the supervision of a dermatologist. Studies suggest that phototherapy can help treat unresponsive and severe cases of several diseases, including:.

Phototherapy involves exposing a patient to a carefully monitored dose of UV radiation on a regular schedule. While this type of therapy does not eliminate the negative side-effects of UV exposure, treatment is carefully supervised by a doctor to ensure that the benefits outweigh the risks. UV rays are strongest in areas close to the equator. Because the sun is directly over the equator, UV rays only travel a short distance through the atmosphere to reach these areas.

UV radiation is also the strongest near the equator because ozone in these areas is naturally thinner, so there is less to absorb the UV radiation. UV exposure is lower in areas further from the equator because the sun is farther away. UV exposure is also greater in areas of snow, sand, pavement, and water due to the reflective properties of these surfaces. Altitude is another contributing factor to the amount of UV. Higher altitudes have greater UV exposure because there is less atmosphere to absorb UV rays.

During the summer months the sun is in a more direct angle, resulting in a greater amount of UV radiation. UV is most intense at noon when the sun is at its highest point in the sky, and UV rays have the least distance to travel through the atmosphere. Especially in the hot summer months, it is a good idea to remain indoors during the peak sun hours of 10am and 4pm. Many people believe that you cannot get sunburned on a cloudy day; this is simply not the case.

Even under cloud cover it is possible to damage your skin and eyes, and cause long-term damage. It is important that you protect yourself with sunscreen, even in cloudy weather. Some surfaces, such as snow, sand, grass, or water can reflect much of the UV radiation that reaches them. The daily UVI forecasts the amount of UV reaching your area at noon when the sun typically reaches its highest point in the sky. Many illustrations of the UVI use a system of colors to designate levels of UV exposure for a particular area on the map.

What is UV radiation? How is radiation classified on the electromagnetic spectrum? 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. Although every effort is made to ensure the accuracy, currency and completeness of the information, CCOHS does not guarantee, warrant, represent or undertake that the information provided is correct, accurate or current.

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UV radiation is divided into three wavelength ranges: Figure 1 - Electromagnetic spectrum. Table 1 Workers at Potential Risk from Exposure to UV Radiation Food and drink irradiators Salon workers and patrons Laboratory workers Lighting technicians Lithographic and printing workers Forensic experts Dentists and assistants Dermatologists and pediatricians General freight truckers Outdoor workers Construction workers Contractors and surveyors Paint and resin curers Physiotherapists Plasma torch operators Welders Agriculture, forestry, fishing Photolithography Table 2 Some Devices Emitting UV Radiation Bactericidal lamps Black light lamps Carbon, xenon and other arcs Dental polymerizing equipment Fluorescence equipment Hydrogen and deuterium lamps Ultraviolet nail curing lamps Metal halide lamps Mercury lamps Plasma torches Phototherapy lamps Printing ink polymerizing equipment Welding equipment Counterfeit currency detectors.

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?