Will shelter UV fixtures cut back transmission?
Will shelter UV fixtures cut back transmission?
Long-awaited national study finally begins
A national study is under way to determine if germicidal ultraviolet radiation can reduce TB transmission in homeless shelters. Philip Brickner, MD, chief of the Division of Community Medicine at St. Vincent's Hospital in New York City, is in charge of the project.
In one component of the study, UV fixtures are being mounted in a variety of shelters in six cities or regions around the country. Because the shelters encompass such a variety of shapes, sizes, and ventilation characteristics, researchers decided to measure the effect of the intervention by making each shelter function as its own control, by installing placebos that mimic the characteristic deep-purple color of UV fixtures for a portion of the study, says Richard Vincent, project manager, and an architect who specializes in lighting.
In another portion of the study, a Harvard-based team will test how UV reacts in more controlled laboratory settings. UV fixtures already have been installed in shelters in New York City and Birmingham, AL, says Vincent. By late this fall, shelters in New Orleans should be outfitted with the fixtures. Also, efforts are under way to bring shelters on board in Los Angeles, Houston, and the Rio Grande Valley area in Texas, says Vincent.
Since overexposure to UV radiation can cause something akin to sunburn, as well as a transient but unpleasant eye irritation, one of Vincent's biggest challenges has been to design fixtures that takes into consideration the various shapes, sizes, and functions of the buildings involved, he says.
Tailoring fixtures to the building
In one facility, for example, Vincent had to position a stairwell fixture carefully so that shelter clients wouldn't look directly at it as they descended the stairs, he says. Some of the fixtures are the conventional wall- or corner-mounted variety; a pendant-mounted variation resembles "a stack of those old vinyl records," Vincent notes.
Subjects are given a baseline PPD skin test at the time they enroll in the study, and then, if negative, retested every three months. Those who convert to positive are recorded, and retired from the pool of participants, Vincent says.
At Harvard University, researchers are simultaneously conducting research on how UV reacts under controlled conditions. The Harvard team is using a British-made software program called Flow-Vent which uses computational fluid dynamics to look at air flow patterns, says Melvin First, ScD, professor emeritus of environmental health engineering at the Harvard School of Public Health.
The software program "calculates graphically where the air flow directions are, and what the air flow speeds are, in any kind of room or enclosure," says First. Variables that can be adjusted include the size and shape of the room, furnishings that might affect air flow, and air inlets and outlets. The result is a graphic display of air current patterns.
"What interests us is knowing how long it takes for the air to go into the upper part of the room, which is irradiated with UV," says First. "There are two things we need to know: How long are air currents in the beam of ultra-violet irradiation and how intense is the radiation?" The product of those factors - the length of exposure, multiplied by the intensity of the radiation - tells investigators what size dose of UV radiation bacteria are exposed to while in the zone of irradiation, First says.
The Harvard team is also looking at ways to measure the "total irradiance impact" at any given point in a room. In addition, First has constructed a 10-foot cubic chamber on a campus rooftop where he releases surrogate bacteria, and then measures the effects of various doses of UV radiation. "We'll change the intensity of the radiation until we can come up with the length of exposure, the time, and the intensity needed to kill the bacteria," he says. "The point, of course, is that without an adequate dose, you can't kill the bugs; but with too high a dose, you're just wasting energy." Once results from the rooftop lab are incorporated together with the airflow model, the hoped-for result will be a standard that can be applied to real-world conditions, First says.
"It's a worthwhile endeavor, whatever comes of it," First says of the shelter study. "If UV does nothing, why spend time using it? And if it works well, let's proclaim it with good evidence, so others will accept it."
Funding for the project has come from a variety of sources, including the utility industry, the Centers for Disease Control and Prevention, and local health departments. Also, the University of Alabama in Birmingham is donating the services of a doctoral student, who will supervise collection of data for the Birmingham shelters. And, because some of the manufacturers of the UV fixtures are based in New York State, the state has agreed to provide a portion of grant money set aside for small businesses.
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