Richard L. Vincent

The application of ultraviolet germicidal irradiation to control transmission of airborne disease: bioterrorism countermeasure

Bioterrorism is an area of increasing public health concern. The intent of this article is to review the air cleansing technologies available to protect building occupants from the intentional release of bioterror agents into congregate spaces (such as offices, schools, auditoriums, and transportation centers), as well as through outside air intakes and by way of recirculation air ducts. Current available technologies include increased ventilation, filtration, and ultraviolet germicidal irradiation (UVGI) UVGI is a common tool in laboratories and health care facilities, but is not familiar to the public, or to some heating, ventilation, and air conditioning engineers. Interest in UVGI is increasing as concern about a possible malicious release of bioterror agents mounts. Recent applications of UVGI have focused on control of tuberculosis transmission, but a wide range of airborne respiratory pathogens are susceptible to deactivation by UVGI. In this article, the authors provide an overview of air disinfection technologies, and an in-depth analysis of UVGI-its history, applications, and effectiveness.

Safety of Upper-Room Ultraviolet Germicidal Air Disinfection for Room Occupants: Results from the Tuberculosis Ultraviolet Shelter Study

Objectives. We evaluated the safety of room occupants in the Tuberculosis Ultraviolet Shelter Study (TUSS), a double-blind, placebo-controlled field trial of upper-room ultraviolet germicidal irradiation (UVGI) at 14 homeless shelters in six U.S. cities from 1997 to 2004. Methods. Data collection involved administering questionnaires regarding eye and skin irritation to a total of 3,611 staff and homeless study subjects. Results. Among these subjects, there were 223 reports of eye or skin symptoms. During the active UV period, 95 questionnaires (6%) noted such symptoms, and during the placebo period, 92 questionnaires (6%) did so. In the 36 remaining cases, either the UV period when symptoms took place was unknown or the symptoms spanned both periods. There was no statistically significant difference in the number of reports of symptoms between the active and placebo periods. One definite instance of UV-related keratoconjunctivitis occurred, resulting from a placement of a bunk bed in a dormitory where a single bed had been used when the UV fixtures were first installed. Conclusions. These findings demonstrate that careful application of upper-room UVGI can be achieved without an apparent increase in the incidence of the most common side effects of accidental UV overexposure.

Fundamental Factors Affecting Upper-Room Ultraviolet Germicidal Irradiation—Part I. Experimental

The objective of this research was to study the factors that relate to the effectiveness of upper-room ultraviolet germicidal irradiation for inactivating airborne microorganisms. The work was conducted in a room-sized chamber designed and furnished for investigations of this nature. Nebulized Serratia marcescens, Bacillus subtilis spores, and vaccinia virus were used as test aerosols. Most data were collected from steady-state experiments comparing the number of viable organisms in the chamber air remaining with UV lamps turned on to the number with UV lamps turned off, but some decay experiments were conducted to compare the two methods. UV power level had a strong influence but was fully effective only in the presence of air mixing that produced vigorous vertical air currents. A conclusion of the study is that an upper-room ultraviolet installation is a complex system that requires careful integration of UV luminaires, UV power, and room ventilation arrangements.

Spatial distribution of fluence rate from upper-room ultraviolet germicidal irradiation: Experimental validation of a computer-aided design tool

A commercial computer-aided design tool used by the lighting industry was modified to predict fluence rates for upper-room ultraviolet germicidal irradiation. Experimental validation based on more than 1600 measurements and 3 types of commercial ultraviolet fixtures, which was done in an experimental chamber and in a homeless shelter having fixtures in continuous use for over 7 years, showed differences in measured and predicted average upper-room fluence rates of less than 10%. The computer-aided design tool, however, was not very successful at predicting fluence rates at specific room locations, a capability that is needed for mating computational fluid dynamics with ultraviolet germicidal irradiation. Although not an objective of this study, it was also found that the three types of fixtures used in this study have surprisingly significant differences in efficiency based on fixture ultraviolet power output and electrical input. One fixture type had an efficiency that was more than five times that of another. For comparison purposes, a standard method for measuring and reporting fixture efficiency is needed.

Latent tuberculosis and active tuberculosis disease rates among the homeless, New York, New York, USA, 1992-2006.

We conducted a retrospective study to examine trends in latent tuberculosis infection (LTBI) and TB disease rates among homeless persons in shelters in New York, NY, 1992–2006. Although TB case rates fell from 1,502/100,000 population to 0, a 31% LTBI rate in 2006 shows the value of identifying and treating TB in the homeless.

Influenzalike illness among homeless persons.

To the Editor: We report rates of influenzalike illness (ILI) and influenza vaccination among homeless persons at 3 shelter clinics in New York City examined from 1997 through 2004. Little is understood regarding the prevalence and transmission of influenza among the homeless (1). Further inquiry on this topic is timely because of concern over a possible influenza pandemic, because of US goals to increase vaccination rates among high-risk groups (2), and because of the potential threat to persons who live and work in shelters. Homeless shelters are paradigmatic congregate settings and thus likely sites for transmission of airborne pathogens such as influenza viruses and tubercle bacilli, shown in part by numerous tuberculosis outbreaks among the homeless (3). Homeless persons experience high rates of pneumonia (4) and related death (5,6). This outcome indicates that the homeless also have high rates of influenza because pneumonia is a common complication of influenza. Depending upon patients age and sex, death rates attributed to pneumonia or influenza among homeless adults ranged from 1.6 to 6.3 (95% confidence interval 0.4–24.1) in one study (7). The New York City Departments of Health and Mental Hygiene and Homeless Services reported in December 2005 that 1% of hospitalizations and 3.4% of deaths of homeless adults in New York City from 2001 to 2003 were caused by influenza or pneumonia (8). We analyzed 4,319 medical charts of persons who received medical services in 3 New York City homeless shelter clinics during influenza seasons (i.e., October 1 through May 30) from 1997 through 2004. This study was approved by the St. Vincents Hospital Research Committee and Institutional Review Board. This analysis identified 59 recorded cases of ILI, defined as temperature >100°F (37.8°C) and cough, sore throat, or both (Table). ILI is accepted as an indicator of influenza by the Centers for Disease Control and Prevention and others (9). Table Cases of influenzalike illness (ILI) among homeless persons by influenza season, New York City, 1997–2004 The overall medical chart review also showed that less than one fourth of all persons examined and one third of those >65 years of age had evidence of influenza vaccination noted in their charts. Vaccinations are available from many sources, but those given at shelter clinics accounted for a large percentage, and vaccination rates varied widely by homeless shelter clinic site. This study has some limitations. Because vaccinations are offered at numerous health centers, rates of vaccination based on the medical charts we studied may be underestimated. Moreover, since only those homeless persons at shelters who attended the medical clinic provided data, the findings cannot be used to make generalizations regarding ILI or influenza vaccination rates among the general population of the shelters. Nonetheless, these numbers can serve as a basis for more rigorous inquiry. The implementation of an appropriate public health response is critical in maintaining the health of homeless persons. Controlling influenza transmission within shelters may benefit the broader public in the same way that reducing the rates of tuberculosis among homeless persons is regarded as essential in preventing transmission to the general population. The decision to receive an influenza vaccination is influenced by many factors. These factors include concern with related side effects, belief that the vaccine is not required, previous bad reactions, dislike of injections, and doubts about vaccine efficacy (10). Understanding how these factors affect vaccination rates among the homeless would be valuable in planning healthcare interactions and quality improvements. Similarly, since the New York City Departments of Health and Mental Hygiene and Homeless Services recommend that influenza immunizations be provided to all sheltered homeless adults and shelter staff (8), further inquiry would help determine the risk-benefit balance of such an approach.

Numerical Investigation of Upper-Room UVGI Disinfection Efficacy in an Environmental Chamber with a Ceiling Fan†

This study investigated the disinfection efficacy of the upper‐room ultraviolet germicidal irradiation (UR‐UVGI) system with ceiling fans. The investigation used the steady‐state computational fluid dynamics (CFD) simulations to solve the rotation of ceiling fan with a rotating reference frame. Two ambient air exchange rates, 2 and 6 air changes per hour (ACH), and four downward fan rotational speeds, 0, 80, 150 and 235 rpm were considered. In addition, the passive scalar concentration simulations incorporated ultraviolet (UV) dose by two methods: one based on the total exposure time and average UV fluence rate, and another based on SVE3* (New Scale for Ventilation Efficiency 3), originally defined to evaluate the mean age of the air from an air supply opening. Overall, the CFD results enabled the evaluation of UR‐UVGI disinfection efficacy using different indices, including the fraction of remaining microorganisms, equivalent air exchange rate, UR‐UVGI effectiveness and tuberculosis infection probability by the Wells–Riley equation. The results indicated that air exchange rate was the decisive factor for determining UR‐UVGI performance in disinfecting indoor air. Using a ceiling fan could also improve the performance in general. Furthermore, the results clarified the mechanism for the ceiling fan to influence UR‐UVGI disinfection efficacy.

Upper-room ultraviolet germicidal irradiation (UVGI) for air disinfection: A symposium in print

Upper-room ultraviolet germicidal irradiation (UVGI) has several applications, its most important use is to reduce tuberculosis transmission in high-burden, resource-limited settings, especially those dealing with epidemics of drug-resistant disease. The efficacy of upper-room (UVGI) to reduce the transmission of airborne infection in real-world settings is no longer in question. International application (dosing) guidelines are needed, as are safety standards and commissioning procedures. A recent symposium to build consensus on guidelines discussed specifications for affordable UVGI fixture designs, safety, performance, computer-aided design (CAD) for UVGI, maintenance, dosimetry, gonioradiometric measurement and innovation using germicidal LEDs.

In-Place Testing of In-Duct Ultraviolet Germicidal Irradiation

This paper reports results from a field study designed to demonstrate a method for evaluating a buildings in-duct ultraviolet germicidal irradiation (UVGI) system using naturally occurring airborne microorganisms and to evaluate its potential effectiveness against selected airborne microorganisms. Forty-eight 64 in. (1.63 m) long ultraviolet germicidal lamps were installed perpendicular to airflow and upstream of the cooling coils in a heating, ventilating, and air-conditioning (HVAC) system for a retail space in a large New York City office building. A portable in-duct UVGI apparatus was used to benchmark ultraviolet susceptibility of naturally occurring airborne microorganisms. Benchmarking was accomplished by measuring the portable apparatuss efficiency for inactivating UVGI-resistant microorganisms in the laboratory at various operating conditions. Inactivation efficiency for both the in-duct UVGI-equipped HVAC system and portable in-duct UVGI apparatus were then measured simultaneously using naturally occurring microorganisms. If the UVGI-equipped HVAC system had higher inactivation efficiency than the portable in-duct UVGI apparatus, then the UVGI-equipped HVAC systems efficiency for inactivating the UVGI-resistant microorganisms used in the laboratory would be expected to be higher than the efficiency of the portable in-duct UVGI apparatus. Based on the results for the tested UVGI-equipped HVAC system, the expected efficiency was at least 88% for Bacillus subtilis var. niger spores, a common surrogate for Bacillus anthracis spores.

A Radiometry Protocol for UVGI Fixtures Using a Moving-Mirror Type Gonioradiometer

Ultraviolet germicidal irradiation (UVGI), 254 nm UV-C, is increasingly used as an infection control strategy to reduce the spread of airborne pathogens such as tuberculosis (TB), influenza viruses, and measles. With the appearance of multidrug-resistant TB and emerging infectious disease such as severe acute respiratory syndrome (SARS) and H1N1 influenza viruses, engineering controls using 254 nm UV-C lamps within specialized luminaires, herein designated UVGI fixtures, are being installed in high-risk settings such as homeless shelters, hospitals, jails and prisons, and schools. Studies have established that a relatively uniform spatial distribution of UV-C in the upper room can effectively cleanse the air of aerosolized pathogens. However, for planning purposes, the placement of multiple UVGI fixtures in a space, to achieve uniformity of UV-C energy distribution using currently available lighting software, is not yet practical because no industry-wide standard method exists for radiometric measurement of commercial UVGI fixtures. In this article, standard methods for photometry and reporting of general fluorescent lighting luminaire photometric data are adopted to provide UVGI fixture spatial emission distribution data in an electronic file format. The ultimate expectation of the authors is that the results will lead to a software program for fixture placement, comparable to and as easy to use as the corresponding software used for general interior lighting applications. To accomplish this goal, a radiometry measurement system is developed to obtain the radiant intensity distributions of UVGI fixtures in a three-dimensional space. This system includes a moving-mirror Type C goniometer, a mirror, a radiometer, a desktop computer, the mechanical control hardware, and the data acquisition/presentation software. Repeated measurements were made on each of three exemplary UVGI fixtures, and measurement variation did not exceed ± 2.0%.