UV Forecasts and safety
What are the different types of UV radiation rays?
UV radiation is classified into three primary types: ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC). These groups are based on the measure of their wavelength, which is measured in nanometers (nm= 0.000000001 meters or 1×10-9 meters).
| Wave Type | UVA | UVB | UVC |
|---|---|---|---|
| Wavelength | 315- 399 nm | 280-314 nm | 100-279 nm |
| Absorption Level | Not absorbed by the ozone layer | Mostly absorbed by the ozone layer, but some does reach the Earth’s surface | Completely absorbed by the ozone layer and atmosphere |
All of the UVC and most of the UVB radiation is absorbed by the earth’s ozone layer, so nearly all of the ultraviolet radiation received on Earth is UVA. UVA and UVB radiation can both affect health. Even though UVA radiation is weaker than UVB, it penetrates deeper into the skin and is more constant throughout the year. Since UVC radiation is absorbed by the earth’s ozone layer, it does not pose as much of a risk.
Benefits
Beneficial effects of UV radiation include the production of vitamin D, a vitamin essential to human health. Vitamin D helps the body absorb calcium and phosphorus from food and assists bone development. The World Health Organization (WHO) recommends 5 to 15 minutes of sun exposure 2 to 3 times a week.
Risks
- Sunburn is a sign of short-term overexposure, while premature aging and skin cancer are side effects of prolonged UV exposure.
- Some oral and topical medicines, such as antibiotics, birth control pills, and benzoyl peroxide products, as well as some cosmetics, may increase skin and eye sensitivity to UV in all skin types.
- UV exposure increases the risk of potentially blinding eye diseases, if eye protection is not used.
- Overexposure to UV radiation can lead to serious health issues, including cancer. Skin cancer is the most common cancer in the United States. The two most common types of skin cancer are basal cell cancer and squamous cell cancer. Typically, they form on the head, face, neck, hands, and arms because these body parts are the most exposed to UV radiation. Most cases of melanoma, the deadliest kind of skin cancer, are caused by exposure to UV radiation.
Anyone can get skin cancer, but is more common in people who:
- Spend a lot of time in the sun or have been sunburned.
- Have light-color skin, hair, and eyes.
- Have a family member with skin cancer.
- Are over age 50.
To protect yourself from UV radiation:
- Stay in the shade, especially during midday hours.
- Wear clothes that cover your arms and legs.
- Consider options to protect your children.
- Wear a wide brim hat to shade your face, head, ears, and neck.
- Wear wraparound sunglasses that block both UVA and UVB rays.
- Use sunscreen with sun protection factor (SPF) 15 or higher, for both UVA and UVB protection.
- Avoid indoor tanning. Indoor tanning is particularly dangerous for younger users; people who begin indoor tanning during adolescence or early adulthood have a higher risk of developing melanoma.
Please visit CDC’s Radiation and Your Health website for more information.