The UV Index, established by the National Weather Service and the United States Environmental Protection Agency (EPA), provides critical information to help you plan your outdoor activities to avoid overexposure to the sun's rays. The UV Index forecasts the risk of overexposure to the sun on a daily basis. It does this by measuring the amount of ultraviolet (UV) radiation that reaches the earth's surface.
Ultraviolet (UV) radiation comes in three main types: UVA, UVB, and UVC. UVA accounts for most of the sun's radiation that reaches the ground - about 90 percent. Only 10 percent of the sun's UVA radiation makes it to the Earth's atmosphere because it is absorbed by oxygen molecules. However, when ozone levels are low, more of this radiation makes its way through to the ground.
UVB radiation is responsible for almost all of the sunburns caused by sunlight. It consists of waves lengthwise along the electromagnetic spectrum, from about 290 nm to 320 nm. Although only 1 percent of solar radiation is UVB, it carries enough energy to reach the upper atmosphere and cause serious damage to living organisms. Human skin is very sensitive to UVB rays; therefore, staying out of the sun's glare is recommended anyway to prevent skin cancer.
UVC radiation is beyond the visible light range and has no effect on humans. It is completely blocked by the atmosphere.
The ultraviolet (UV) index is a measure that represents the strength of the sun's UV radiation. The index was developed by Canadian scientists in the early 1990s and has now been modified for usage worldwide. The UV index ranges from 1 to 11. A number below or at level 0 means there is no risk of exposure-related harm from UV radiation.
The index is calculated based on measurements taken by satellites over large regions of the planet. These measurements indicate how much UV radiation is reaching the ground. The amount of solar radiation that reaches the surface of Earth is greatest when clouds are not present in our atmosphere and least when they are present. Thus, the index takes into account the amount of cloud cover over a large area.
When the index is below or at zero, this means that your exposure to UV radiation is very low. You should therefore not be worried about any effects that might occur as a result of being exposed to these levels of radiation. When the index is greater than or equal to 10, this means that you should take precautions to protect yourself from exposure. At this level, some health problems may arise from too much UV radiation.
These problems include skin cancer, which is caused by rays from the sun that reach the earth's surface.
A UV index of 3 to 5 indicates that there is a moderate risk of injury from unprotected sun exposure. Stay in the shade at midday, when the sun is at its hottest. Wear sun-protective apparel, a wide-brimmed hat, and UV-blocking sunglasses if you're going to be outside. A UV-resistant sunscreen with an SPF of at least 30 should be applied every day you are outdoors. Sunscreen should never be used on babies under one year old because they can't tell us what we should do about our sun protection.
A sun safety expert recommends that people only expose themselves to the sun's rays for up to 15 minutes per day. If you go beyond this time, you increase your chances of developing skin cancer.
The safest way to avoid overexposure to the sun is by staying indoors during sun hours. If you must be out in the sun, wear protective clothing, such as a wide-brimmed hat, long sleeves, and pants. Avoid tanning booths or other ways to obtain a dark skin tone. They aren't safe for everyone, especially if you have darker skin or if you are pregnant.
Sunburn is very painful and could lead to skin cancer. You should always use caution not to get too much sun exposure, especially between 10 a.m. and 4 p.m., when the sun's rays are strongest.
The World Health Organization's Global Solar UV Index rates UV levels from 0 (low) to 11+. (extreme). When UV levels are 3 (Moderate) or above, sun protection is advised. Sunscreen with an SPF of 30 or higher is recommended for full body coverage. Reapply often.
The safest level of exposure is zero exposure. However, because the skin can never get completely protected from the effects of ultraviolet radiation, even those who live in sunny climates develop cancer at some point in their lives. The type of cancer that is most likely to occur after many years of regular exposure to the sun is melanoma. Other types of cancer such as basal cell carcinoma and squamous cell carcinoma may also be caused by prolonged exposure to sunlight. These cancers are called "solar-induced" because they usually appear on areas of the body that are exposed to the sun, such as the nose, ears, neck, and face.
The only way to avoid damage from the sun is not to be outdoors during its peak hours (about 30 minutes before sunrise and after sunset). Use a sunscreen with an SPF of at least 15 if you plan to be outside for more than 10 minutes. Avoid sunburn by using a broad-spectrum sunscreen with an SPF of at least 30.