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UV light zaps undiagnosed TB
NIOSH offers guide to effective use
New guidelines promote the use of ultraviolet light in hospitals as an effective way to reduce the risk of tuberculosis transmission from the undiagnosed case. The National Institute for Occupational Safety and Health (NIOSH) released its publication, Environmental Control for Tuberculosis: Basic Upper-Room Ultraviolet Germicidal Irradiation (UVGI) Guidelines for Healthcare Settings, to provide detailed recommendations for the use of UV germicidal irradiation (www.cdc.gov/niosh/docs/2009-105/).
"It is a promising technology to help prevent transmission of TB where the source is not recognized," such as in emergency departments or clinic waiting areas, says Jennifer Topmiller, MS, team leader in the Engineering and Physical Hazards Branch of NIOSH in Cincinnati. She adds that "the UVGI is intended to be a supplement to personal protective equipment."
Not all organisms are as vulnerable to UV radiation as tuberculosis, but the technology still might provide some benefits in reducing risk of transmission of emerging infectious diseases, says Shelly Miller, PhD, associate professor of mechanical engineering at the University of Colorado, Boulder, and the lead researcher in UVGI studies.
"We need so many tools in our back pocket to fight infectious disease," she says. "The more we can have, the better."
The Centers for Disease Control and Prevention recommended UV light as an effective engineering control as part of its updated tuberculosis guidelines in 2005, noting that "using additional air-cleaning technologies (such as UVGI) should be considered to increase the equivalent air changes per hour."
The new guidelines outline the specifications that create the best germicidal effect. For example, air mixing is essential to maximize the effectiveness of the technology, says John Whalen, MS, MSA, microbiologist and a contractor with the Division of Applied Research and Technology at NIOSH in Cincinnati.
"If you've got a person in the lower portion of the room coughing, you need to be able to get the TB bacteria into the upper portion of the room," he says.
UVGI emits UVC light, which is a wave length of UV solar radiation that is blocked by the earth's ozone layer. Its germicidal effect apparently occurs because it damages the cell's nucleic acids, affecting its ability to replicate or causing cell death.
With a short wavelength, UVC is considered to be safer than UVA and UVB, the components of sunlight that are associated with tanning, sunburn, and skin cancer. But UVC still has the potential to cause eye and skin damage.
The NIOSH guidelines provide a recommended exposure limit for UVGI. People who are photosensitive should either avoid exposure to UVGI or use personal protective equipment, NIOSH states.
Proper maintenance of the lamps will help reduce the risk of overexposure, says Whalen. "You've got to keep your lamps clean. You've got to keep your fixtures clean," he says. "You should measure in the lower portion of the room to make sure you're not getting too much radiation in the lower portion.
Proper location and maintenance of UVGI also are essential, says Miller. The Colorado research team assessed the use of UVGI at three hospitals in Denver and found that only one was using it effectively, she says. The other two did not have strong enough lamps or did not place the fixtures in the optimal location, she says.
NIOSH also recommends education of health care workers who are exposed to UVGI and warning signs on the fixtures or on the door of rooms with unshielded fixtures.