Radiation indicator device

Details Radiation indicator device Radiation indicator device

2000-07-24

2003-01-07

Epps, Georgia (Department: 2873)

Radiant energy

Invisible radiation responsive nonelectric signalling

Optical change type

C250S372000

Reexamination Certificate

active

06504161

ABSTRACT:

TECHNICAL FIELD
A radiation indicator device which provides a visually recognizable indication of exposure to ultraviolet radiation.
BACKGROUND OF THE INVENTION
Sunlight is normally divided into infrared energy, visible light, and ultraviolet light. Infrared energy consists of the portion of the solar spectrum, with wavelength above 760 nanometers. Visible light is defined as radiation with a wavelength between 400 and 760 nanometers. Ultraviolet light consists of radiation with a wavelength below 400 nanometers. Infrared energy is our main source of warmth. Sunlight supplies energy necessary for photosynthesis in living plants. In fact, it is essential for all living things on earth.
In leisure time, some people like to bask in the sun to get a healthy looking tan. Many people like to enjoy months of uninhibited sunshine exposure while participating in other outdoor activities. However, research has found that increased exposure to ultraviolet rays from the sun causes skin cancer, cataracts in human eyes, sunburn, skin wrinkling, possible immune system damage, and leathery skin. It also causes cacti to shrivel, cattle and sheep to develop conjunctivitis, eucalyptus trees to turn yellow, frog population to decline, and fish population to decrease. Humans are among the living beings most vulnerable to the constant shower of ultraviolet radiation. Unprotected by scales or feathers, we face a rising threat of illness related to sunlight exposure. The new health hazard is challenging our desire to spend time outdoors. The incidence of skin cancer has been on the rise steadily for the last 20 years and this disease has become one of the leading causes of death today. One in six Americans might develop skin cancer in their lifetime because sun damage to the skin is cumulative.
Hovering six to 25 miles above the earth, the stratospheric ozone layer is our natural sunscreen, protecting us from some of the sun's harmful rays. Atmospheric scientists at National Aeronautics and Space Administration have used satellites to study the depletion of ozone in the upper atmosphere. There is evidence that a severe depletion of the ozone layer has occurred over the Antarctic, resulting in an ozone hole of about 9 million square miles in 1994 (about 2.5 times the size of the United States of America). The hole in the ozone layer is caused by chlorofluorocarbons (CFCs) which are commonly used as refrigerant and propellant in aerosol sprays. The CFCs undergo a series of chemical reactions in the atmosphere, leading to the production of chlorine monoxide that consumes ozone. Levels of ozone destroying chlorine monoxide in Antarctic are extremely high by August and as a result the ozone shield is destroyed allowing damaging solar ultraviolet radiation to reach the earth's surface. Although the thinning of the ozone layer is most severe over Antarctica, it has been observed as a global phenomenon at all latitudes. According to a report of the United Nations, during the last decade the annual dose of harmful ultraviolet light striking the Northern Hemisphere rose by about five percent.
The solar ultraviolet spectrum is generally considered to consist of wavelengths between 100 and 400 nanometers and the International Commission on Illumination further subdivides this portion of the solar spectrum into UV-A, UV-B and UV-C rays.
UV-A rays have the longest wavelength in the range of between about 400 nanometers and about 315 nanometers and these rays penetrate the skin the deepest. UV-A light is also the most difficult to screen out. These wavelengths of ultraviolet radiation pass readily through the atmosphere and maintain their intensity throughout the day regardless of the position of the sun above the horizon. Heavy clouds can filter this radiation but many traditional sunscreen formulations do not adequately protect against UV-A exposure.
UV-B rays are in the wavelength region of between about 315 nanometers and about 280 nanometers. Although ozone and clouds screen out some of them, many of them do reach the earth. UV-B light is responsible for wrinkling, breaking down the elastic tissue and collagen, and sunburn. UV-B light is probably 100 times more carcinogenic than UV-A light. It causes three types of skin cancer-basal cell cancer, squamous cell cancer, and melanoma. Skin cancers have skyrocketed in the last 20 years, coinciding with our increased outdoor activities and with the depletion of the ozone layer. UV-B light is in large part responsible for the tough leathery look of human skin following prolonged outdoor weathering. However, when the ozone layer is thick enough to function properly, it shields us from most UV-B rays.
UV-C rays have the shortest wavelength of between about 280 nanometers and about 100 nanometers. These rays are the most dangerous ultraviolet radiation but they are filtered out by the atmosphere and do not reach the surface of the earth.
In the United States, the National Weather Service, urged by the Environmental Protection Agency, the Centers for Disease Control, and the American Cancer Society, has begun a new index of UV radiation to warn people against overexposure to the sun. This Ultraviolet Potential Index is based on atmospheric changes and has a scale from 0 to 15. The higher the number, the higher the risk to skin cancer and the faster that outdoor enthusiast will burn. To predict the Ultraviolet Potential Index, the National Weather Service uses satellites and ground equipment to compute the UV levels through a combination of readings from forecasted cloud cover, temperatures, and local ozone amounts. The more ozone present at a location, the less radiation will reach the earth's surface at that area. A rating of 7 means that fair-skinned people should stay out of the sun or risk sunburn and other skin damage associated with high UV exposure.
The new Ultraviolet Potential Index measures potential exposure in five levels according to the National Weather Service and the American Cancer Society:
0 to 2: Minimal risk of ultraviolet radiation; could be in sun unprotected for more than an hour without skin burning;
3 to 4: Low risk; could be in the sun unprotected for 30 minutes to an hour;
5 to 6: Moderate risk; could be in sun unprotected for 20 to 30 minutes;
7 to 9: High risk of skin damage at 13 minutes;
10 to 15: Very-high risk of skin damage occurs at less than 13 minutes.
Although an effective method of defining the risk associated with sun exposure, the Ultraviolet Potential Index has a variety of limitations as a method to protect the population from skin damage due to ultraviolet radiation. As of July 1994, only 85 cities in the United States were given the predicted Ultraviolet Potential Index on a trial basis. It would be very difficult to include all parts of the nation. These predicted index numbers could only serve as general guidelines since the local cloud cover might move away or become thick because weather conditions are unpredictable. Thus, there is a need for a device to be used in situ that would indicate ultraviolet radiation levels and consequently warn outdoor enthusiasts against overexposure to the sunlight anywhere and at any time.
To reduce the ultraviolet radiation exposure to the skin it is advisable to apply sunscreen having a Sun Protection Factor (SPF) of at least 15 and above. The sunscreen contains ultraviolet light absorbers, which are designed to remove part or most of the harmful ultraviolet rays. By applying the sunscreen on the skin, one might mistakenly believe that the skin will not be damaged by the ultraviolet light. In fact, the sunscreen does not completely block all UV-A and UV-B rays in the sunlight. The skin has no natural sensors to ultraviolet radiation exposure other than the delayed and painful effect of skin erythema or “sunburn” which follows excessive exposure.
Various systems and devices have been proposed for monitoring exposure to ultraviolet radiation, such as those disclosed in U.S. Pat. No. 3,449,572 (Sylvester et al) U.S. Pat. No. 3,787,687 (Trumble), U.S. Pat. No. 3,903,423 (Zweig)

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