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Ultraviolet
Radiation (UV)
UV lies between X-rays and visible light on
the electromagnetic spectrum. UV wavelengths range from 100 to 400
nanometers. A nanometer (nm) is one billionth of a meter. About 6% of
the energy that reaches the earth from the sun is UV. The amount of UV we
get from the sun depends on elevation, cloud cover, time of day, and
season. Other sources of UV include tanning beds, black lights, germicidal
lamps, welding arcs, and UV lasers, among others.
Scientists divide UV into three regions:
UVA (near): 400 to 315 nm
UVB (medium): 315 to 280 nm
UVC (far): 280 to 100 nm
Air absorbs UV from 100 to 180 nm, a region known as vacuum UV. Therefore, UV exposure only occurs at wavelengths greater
than 180 nm.
The ozone layer absorbs the UVC and most of
the UVB emitted by the sun before it reaches the surface of the
Earth. However, there are many artificial sources of UV-C. Some of
these UVC sources are used to disinfect air and surfaces, for example to kill
the COVID virus.
US Regulations:
The Food and Drug
Administration (FDA) regulates UV from sunlamps and sunlamp products
(tanning beds and booths) in 21CFR Part 1040.20. Some states
regulate tanning salons. In North Carolina the Department of Health
and Human Services Radiation Protection Section regulates
tanning salons.
There is no Occupational Safety and Health
Administration (OSHA) standard for UV exposure. Scientific and safety
groups that provide UV exposure limits and other information include:
International
Commission on Nonionizing Radiation Protection (ICNIRP)
Centers for Disease
Control (CDC)
UV
Health Effects:
Too much UV exposure
can cause:
Sunburn
Early skin aging
Melanoma and other
types of skin cancer
Cataracts (dark
spots in the lens of the eye) and other types of eye damage
Reduced immune
system strength. In the case of cold sores, it can no longer keep the virus
Herpes simplex [HSV1] under control, reviving the infection.
Because these symptoms are usually delayed,
you may not notice excessive UV exposure until its too late.
These EPA links provide further information
on UV health effects.
EPA: Sunscreen - The Burning Facts: Information on UV
rays and sunscreen.
EPA: Prevent Eye Damage - Protect Yourself from UV
Radiation
While too much UV exposure is harmful,
smaller amounts of UV aids good health. For example, UV helps the body
to make vitamin D. By reducing the bodys immune response, moderate
amounts of UV can also help fight chronic inflammation
Minimize
Your Risk:
You can
protect yourself from the harmful UV effects in the following ways:
Don't use indoor tanning devices; see this FDA
Consumer Update
Don't let your skin burn.
When outdoors on sunny days
Check the UV index for your area,
and take proper action when outside during days when the UV index is high.
Limit outdoor
activities between 10 am and 2 pm.
Wear a full brim hat
with brim at least 7 cm (3 inch) wide
Use sunscreen with
SPF of 30
Wear woven
shirts/blouses. Dark blue was best in some studies. If using clothing with
assigned UV protection factors (UVP), choose 50+ clothing.
Outdoor UV levels depend on the time of
day, time of year, latitude, altitude, and weather conditions. The
Environmental Protection Agency explains how these factors affect the UV Index.
Many medications, supplements, cosmetics, and
foods can make you more sensitive to UV effects. Click here for a list
of photosensitizing
agents.
International
Perspective:
World Health
Organization International Agency for Research on Cancer (WHO/IARC): Exposure
to Artificial UV Radiation and Skin Cancer
UK Health Security Agency: What
You Need to Know About UV (ultraviolet) Radiation
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