Ultraviolet
(UV) Radiation
UV radiation of significance falls between 200
and 400 nm. Air, water and window glass are transparent for wavelengths in the
300 to 400 nm range and ordinary window glass and skin absorb wavelengths from
200 to 320 nm. The ozone layer absorbs much of the UV energy from the sun in
the wavelengths below 290 nm.
Classification
of UV radiation:
UV-A ...... wavelengths from 315 to
400 nm
UV-B ...... wavelengths from 280 to
315 nm
UV-C ......wavelengths from 200 to
280 nm
Wavelengths from 200 to 315 nm (Actinic UV
region) are of greatest concern in safety and health.
UV Radiation
Sources:
Sun is the most notable source of UV radiation.
Other sources include heliarc
welding, mercury and xenon discharge lamps, lasers .
Hazards:
Skin burns or erythema
(reddening)
l
< 280 nm is absorbed by outer layer of skin
Exposure at 320 nm > l > 280 nm levels cause deeper skin
penetration
380 nm > l > 320 nm is absorbed by outer layer of
skin
Skin cancer, skin aging
Keratitis
(inflammation of the cornea) UV is absorbed by the cornea (dangerous level is
around 280 nm (UV-B). It feels like sand in the yes; watery and eye lids may
swell.
Controls:
Limit exposures
Use absorbing materials
Protective coating (suntan lotion)
Examples:
Welders are exposed to high levels
of UV radiation and they must wear appropriate eye and skin protection.
Sunlamp users must wear protective
eye wear.
Standards:
American Medical Association (Recommends
limiting UV exposures)
ACGIH(American
Conference of Government Industrial Hygienists) Maintains exposure standards
based on exposure time, irradiance and wavelength.
FDA Regulates sunlamps and ultraviolet
lamps (21 CFR 1040.20) and high intensity mercury vapor discharge lamps.(21 CFR 1040.30).
Measurement:
Ultraviolet detection devices convert radiation
that arrives at a sensing device to analog or digital display images. Conversion
can be done:
Electrical (photovoltaic cells)
Thermal (thermopile)
Chemical (photographic plates)
For most devices selective filters determine
what wavelengths arrive at the sensor.
LINKS
UV Radiation
and Ozone Depletion
Last Update:
By: Serdar Z. Elgun