In the late 1940s and into the 1950s, health officials made statements that the Sun was extremely beneficial to one's health. However, due to the depletion of Stratospheric Ozone recognized in the late 1980s, scientists and health officials have reversed this statement. Ultraviolet radiation is increasingly becoming more intense year by year. It is important to understand the dangers associated with intense UV radiation to minimize long-term health effects.
Ultraviolet Radiation
The Sun emits radiation in what is called the Electromagnetic Spectrum. The EMS is divided into three major bands--shortwave, visible, and longwave. The visible portion is unique to us as it is the type of radiation we can see. Shortwave radiation is the most powerful and longwave is the radiation we can feel and use on a daily basis (i.e. microwaves and radio). Ultraviolet radiation is the last wavelength in the shortwave portion before becoming visible. Although we cannot see it, it is powerful and inflames the skin over a period of time.
UV and the Ozonosphere
As solar radiation enters the atmosphere, it is filtered by stratospheric ozone. This layer of 'good' ozone is important to living species on Earth as it reduces incoming UV. If the ozonosphere did not exist, no plant, animal, or human would be able to survive the intense power it possesses. Essentially, things would burn to a crisp.
UV radiation reacts with ozone by splitting an oxygen atom from the ozone molecule. This process reduces the amount of UV radiation that enters the Troposphere (the layer of the atmosphere we live in).
Ozone Depletion
In the late 1980s, scientists began noticing a hole over the Antarctic continent in October. The production of chlorofluorocarbons (CFCs) in the late 1920s and 30s into the 1980s for use in refrigeration and propellants began to deplete the ozone layer by interacting with the ozone. This depletion has allowed more UV to enter the Earths lower atmosphere. Although the United States passed legislation to cut CFC production, ozone continues to be depleted due to the average 120-year lifespan of CFCs. UV radiation will continue to intensify over the next 30 years.
The UV Index
Ultraviolet radiation sensors have become common within the last 20 years. These sensors measure the amount of UV radiation that enters the lower atmosphere and categorized into the UV Index. The index ranges from 0 (during darkness) to 16 (extreme UV intensity). The index is provided to indicate when people should take precautions. The amount of UV that enters the lower atmosphere is dependent upon the height of the Sun in the sky, the amount of ozone in the stratosphere, and the relative cloud cover over the particular sensor. Clear days can produce high UV values while an overcast sky can reduce the amount of UV received at the surface.
Below is a chart that describes the time it takes the skin to be damaged under the associated UV Index value. This chart should be reviewed before planning extended outdoor activities.
Protecting Yourself
Protecting yourself from harmful UV is important to prevent long-term effects such as skin cancer. If the UV Index is 5 or more, sunscreen that is labeled with a high SPC (SPC 30 or higher) should be worn. Children should wear SPC 45 or higher as their skin is especially susceptible to skin damage. Put the sunscreen on approximately 30-minutes before going outside to allow the skin to absorb the important sun-blocking ingredients. Sunscreen will not last the entire day so multiple applications are necessary. Waterproof and sweat-proof sunscreens are best when outdoor activities include swimming or sporting. Although your activities might be held under shade or open-walled structures, intense UV radiation can still be a problem.
There is a common misconception that tanning beds are safer than outdoor sunbathing. Tanning beds are just as dangerous as tanning outside and the effects are the same. In addition, people think that if they have a tan already that they are better protected from getting a sunburn. No matter how you slice it, UV radiation is harmful to the skin and will cause long-term effects in the future if care is not taken.
Protection from UV radiation can prevent unnecessary visits to dermatologists in the future. Therefore, protect now.
References and Further Information
NOAA UV Index Information Site