Overview

There is ever increasing concern throughout the world about the problems associated with over-exposure to ultraviolet radiation from the sun. Many, many people are now beginning to exercise greater precautions to protect their eyes and skin from the harmful UV rays to which we are exposed on a daily basis. And more and more the public is being advised to avoid prolonged exposure to the sun.

With the rapid depletion of the ozone layer of the earth's atmosphere in recent years, the number of reported cases of skin cancer and other associated health problems have risen dramatically in the last decade. The general consensus of scientists and the medical profession alike is that this problem will continue to escalate in the future. Reports continue to show a reduction in ozone levels. Ultraviolet exposure levels around the globe are expected to be increasingly high in the coming years.

It is generally agreed that serious steps need to be taken to ensure everyone is aware of the problems that may develop if protective measures are not taken. Increased reporting by government, the media and private industry groups has sought to provide the public with information about the causes and effects of UV exposure. It is certain that the concerned public and communities will be further encouraged to undertake more pro-active measures to prevent against problems associated with exposure to the sun's burning rays.

ShadeCorp has put together these UV Facts Pages. Please read them with our compliments - we're pretty sure you'll find them informative and interesting.

What is the Ozone Layer?

The ozone layer forms a thin shield in the upper atmosphere, protecting life on Earth from the sun's ultraviolet (UV) rays. In the 1980s, scientists began accumulating evidence that the ozone layer was being depleted. Depletion of the ozone layer results in increased UV radiation reaching the Earth’s surface, which in turn can lead to a greater chance of overexposure to UV radiation and the related health effects of skin cancer, cataracts, and immune suppression.

What Is Stratospheric Ozone?

Ozone is a naturally occurring gas that is found in two layers of the atmosphere. In the layer surrounding the Earth's surface the troposphere ground-level or bad ozone is an air pollutant that is a key ingredient of urban smog. The troposphere extends up to the stratosphere, which is where good ozone protects life on Earth by absorbing some of the sun's UV rays. Stratospheric ozone is most concentrated between 6 to 30 miles above the Earth's surface.

Ozone Depletion

Until recently, chlorofluorocarbons (CFCs) were used widely in industry and elsewhere as refrigerants, insulating foams, and solvents. Strong winds carry CFCs into the stratosphere in a process that can take as long as 2 to 5 years. When CFCs break down in the stratosphere, they release chlorine, which attacks ozone. Each chlorine atom acts as a catalyst, repeatedly combining with and breaking apart as many as 100,000 ozone molecules during its stratospheric life.

Other ozone-depleting substances include pesticides such as methyl bromide, halons used in fire extinguishers, and methyl chloroform used in industrial processes.

What Is Being Done?

Countries around the world have recognized the threats posed by ozone depletion and adopted a treaty called the Montreal Protocol to phase out the production and use of ozone-depleting substances.

How Ozone Depletion Affects UV Levels

Scientists predict that ozone depletion should peak between 2000 and 2010. As international control measures reduce the release of CFCs and other ozone-depleting substances, natural atmospheric processes will repair the ozone layer around the middle of the 21st century. Until that time, we can expect increased levels of UV radiation at the Earth’s surface. These increased UV levels can lead to a greater risk of overexposure to UV radiation and related health effects.

The Nature of UV Radiation

Ultraviolet (UV) radiation is a specific part of the sun's entire spectrum of wavelengths. UV radiation can be further sub-divided into three parts. 

• UV-C is characterized by wavelengths less than 280 nm. Although highly dangerous to plants and animals, this part of the UV spectrum is completely absorbed by stratospheric ozone and does not reach the earth's surface.

• UV-B ranges in wavelengths between 280 and 320 nm. Ozone absorbs much of the shorter wavelength radiation, but this absorption weakens as 320 nm is approached. Plants and animals are particularly affected by this part of the UV spectrum. UV-B effects to humans are reddening of the skin (erythema) and reduction of vitamin-D synthesis in the short term, development of skin cancer, cataracts and suppression of the immune system in the long term. 

• The wavelengths of UV-A radiation range between 320 and 400 nm. Ozone absorbs very little of this part of the UV spectrum. UV-A radiation is needed by humans for the synthesis of vitamin-D; however, too much UV-A causes photo aging (toughening of the skin), suppression of the immune system and, to a lesser degree, reddening of the skin, and cataract formation.

There are two prices to pay for overexposure to UV radiation: a severe sun burn following an intense short term overexposure, and the more serious skin cancers developing after long term overexposure. Melanoma, the more deadly of the two types of skin cancer occurs when the patient has been subjected to several intense short term overexposures. Non-melanoma skin cancers, which are almost 100% curable, occur in people who are overexposed for very long periods of time, like construction workers, farmers, or fishermen. Long term overexposure to UV radiation has also been linked to the formation of cataracts in the eyes.

United States Steps

In response to the serious public health threat posed by exposure to increased UV levels, the U.S. Environmental Protection Agency (EPA) is working with schools and communities across the nation through what they call the SunWise School Program. The aim of SunWise is to teach children in elementary school and their caregivers about ozone depletion, UV radiation, and how to protect themselves from overexposure to the sun.

See also UV & Children.