Ultraviolet radiation (UV) comes naturally from the sun. There are also some man made lamps and tools (welding tools, for instance) that can produce UV radiation. For most of us, however, the sun is the primary source of UV.
UV is divided into at least three different categories based on wavelength:
- UVA wavelengths(320-400 nm) are only slightly affected by ozone levels. Most UVA radiation is able to reach the earth’s surface and can contribute to tanning, skin aging, eye damage, and immune suppresion. UV 400 Protection lenses are engineered to block 100% of all harmful blue light up to 400 nanometers
- UVB wavelengths(280-320 nm) are strongly affected by ozone levels. Decreases in stratospheric ozone mean that more UVB radiation can reach the earth’s surface, causing sunburns, snow blindness, immune suppression, and a variety of skin problems including skin cancer and premature aging.
- UVC wavelengths (100-280 nm) are very strongly affected by ozone levels, so that the levels of UVC radiation reaching the earth’s surface are relatively small.
The effects of UV radiation on earth’s ecosystems are not completely understood. Even isolating the effects of UVA versus UVB is somewhat arbitrary. All UV radiation can be damaging. This knowledge has prompted many manufacturers of sunscreen and sunglasses to offer products that protect against both UVA and UVB wavelengths. While humans can choose various courses of protection, for instance avoiding noon-time sun, plants and animals are not so fortunate. Studies have shown that increased UV radiation can cause significant damage, particularly to small animals and plants. Phytoplankton, fish eggs, and young plants with developing leaves are particularly suspectible to damage from overexposure to UV.
Solar UV radiation levels are highest during the middle of the day. In total, almost half the daytime total UV radiation is received during the few hours around noontime. Clouds, as well as ozone, have a tremendous affect on UV radiation levels. However, cloudy skies generally do not offer significant protection from UV. Thin or scattered clouds can have minor impacts on UV and even, for a short time, increase UV above what it would be on a blue sky day by further scattering the radiation and increasing the levels that reach the surface.
UV effects on human eye:
- excessive watering and blinking
- Burning sensation
- Eyelid swelling
- Photophobia (difficult to look at bright light)
Eye Diseases Associated with Long time Sun Exposure Overexposing to UV rays may have risk to develop following ocular disorders:
- Age-related macular degeneration
- Lid Skin cancer
How to protect your eyes from UV rays effects?
- Wear protective sunglasses. (Find sunglasses that offer both UVB and UVA protection that block at least 99% of UV rays. Make sure to get large lenses that cover the eye area for maximum protection.)
- Wear a hat while out in the sun
- Avoid going out in the sun during the middle of the day (Studies have shown that the main danger period is between 10 AM and 4 PM daily)