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Ultraviolet
Radiation: UV
radiation
is a type of radiation with
wavelengths from 200 to 400 nanometers. A nanometer is one billionth of a
meter. Ultraviolet radiation is part of the invisible radiation that
comes from the sun.
About 6% of the energy that reaches the earth from the sun is UV energy.
Other sources of UV
radiation include tanning beds, black lights, welding arcs, and UV
lasers.
Ultraviolet is classified into:
UV-A (near) with a wavelength of 400 to 320 nm
UV-B (medium) with a
wavelength of 320 to 280 nm
UV-C (far) with a wavelength of 280
to 100 nm.
All of the UV-C emitted by the sun is absorbed by the ozone layer before it
reaches the surface of the Earth. However,
there are manmade sources of UV-C that are used medically and commercially
for its germicidal properties.
The biological effect of UV-A and UV-B
on skin is to induce melanin production from melanocyte cells to cause sun
tanning of skin. Vitamin D is produced on the skin by a radical reaction
initiated by UV radiation.
US Regulations:
The Food and Drug Administration regulates UV radiation from sunlamps and
sunlamp products (tanning beds and booths) in
21CFR Part 1040.20. Tanning facilities are
additionally regulated at the state level. In North Carolina, tanning
facilities are regulated by the Department of Health and Human Services,
Radiation Protection Section per
15A NCAC Section .1400. Visit the
North Carolina Tanning
Program
website for more information regarding the regulation of tanning facilities
in North Carolina.
There is no Occupational Safety and Health
Administration (OSHA) standard for exposure to ultraviolet light, but the
National Institute for Occupational Safety and Health (NIOSH) recommends
that the time of exposure to an intensity of 100 microwatts per square
centimeter at wavelength 254 nanometers not exceed 1 minute. When averaged
over an eight-hour work day, this value is 0.2 microwatts per square
centimeter.
International Perspective:
See
a summary of international policies in the IARC/WHO report on Exposure to
Artificial UV Radiation
Appendix: European and international positions regarding
artifical sources of UV radiation
Scientific/Medical:
Ultraviolet light can cause burns to skin,
skin damage, premature
aging, melanoma, and other types of skin cancer. It can also cause cataracts
and other types of damage to the eyes.
UV light can be particularly hazardous because there are usually no
immediate symptoms of overexposure. The Center for Disease Control (CDC)
warns of the effects of exposure to ultraviolet radiation on their
CDC UV Information
page.
UV-A and UV-B are technically
non-ionizing, but all UV wavelengths can cause photochemical reactions that
to some extent mimic ionization. For example, ultraviolet light, even in the
non-ionizing range, can produce free radicals that induce cellular damage and can cause skin cancer. UV radiation is characterized
by the International Agency of Research on Cancer (IARC) as a known human
carcinogen.
The
World Health Organization and International Agency of Research on Cancer
published a report in 2006,
WHO/IARC Exposure to Artificial UV
Radiation and Skin Cancer.
The WHO/IARC press release for this report states, "combined
analysis of over 20 epidemiological studies shows that the risk of cutaneous
melanoma is increased by 75% when the use of tanning devices starts before
age 30. There is also sufficient evidence of an increased risk of ocular
melanoma associated with the use of tanning devices. Studies in experimental
animals support these conclusions and demonstrate that ultraviolet radiation
(UVA, UVB, and UVC) is carcinogenic to humans.
These findings reinforce current recommendations by the World Health
Organization to avoid sunlamps and tanning parlours and to protect yourself
from overexposure to the sun."
Additional Information on UV-A, UV-B, and the effects of artificial tanning
from the
World Health Organization
NTP 12th Report on
Carcinogens, Ultraviolet Section:
Minimize Your Risk:
Skin specialists
recommend that people protect the skin from both kinds of ultraviolet
radiation (UV-A and UV-B). You can do this by:
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Not using indoor
tanning devices.
FDA
Consumer Update
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Not allowing your
skin to burn.
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Minimizing outdoor activities between 10 am
and 2 pm.
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Wearing a full brim hat with brim at least
7 cm.
-
Using
sunscreen with SPF of 30.
-
Wearing
tightly woven shirts/blouses (dark blue was best in some studies) or, if using clothing with assigned UV
protection factors (UVP), by using 50+.
-
Getting
Vitamin D from safe
sources (food, supplements).
How much UV radiation you are exposed to
outdoors depends on a number of factors including time of day, time of year,
latitude, altitude, and weather conditions. The Environmental
Protection Agency explains how these factors affect the
UV Index
Tool which can be used to determine your risk for UV exposure at any give
time and location.
A number of
different medications, supplements, cosmetics, and foods can make you more
sensitive to the effects of UV radiation. Click here for a list of
photosensitizing agents.
Professional Resources:
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