I spent last weekend in San Antonio for the Annual American Society for Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) conference.  What a nice city!  It was not too hot and the river walk was lovely with great restaurants!  Too bad I spent so much time focusing on UVGI (ultraviolet germicidal irradiation) and not sight seeing (I did get to a yoga class – great one at South Town Yoga Loft).

Aspergillus sydowii

On Saturday I worked on the standards committee for 185.1 “Method of testing UVC lights for use in air handling units or air ducts to inactivate airborne microorganisms.”  This standard establishes a laboratory test method to measure the performance of UVC lights used in ventilation systems for their ability to inactivate airborne microorganisms.  It is the first of its kind and will be published hopefully this year!  One of the issues we wrestled with was what organisms to use in the testing. We decided upon a surrogate for tuberculosis (Mycobacterium parafortuitum) and for air-handling unit contamination (Aspergillus sydowii).  Other options we considered were bioterrorism agents or viruses.

I also attended the Technical Committee meeting for Health Care Facilities (TC 9.6).  I am interested in why more health care facilities are not using UVGI.  I didn’t find many answers here, but there are 2200 hospitals in the US and hospital-acquired infections do happen even though hospitals are vigilant with infection control.  I think there is a role to play for UVGI in health care.  During the TB outbreak in the 80s, the state of AR implemented legislation requiring UVGI to be used in state-owned correctional facilities and health-care clinics that helped to bring the outbreak under control.  To this day they use UVGI in their facilities and I bet they have the most UVGI fixtures installed in the country.

Dr. Jessica Green’s new paper (Jessica was a classmate of mine at Berkeley!) in The ISME Journal  summarizes their results of a microbiome study in an Oregon Hospital.  They found that indoor bacterial communities were very different from outdoors, that many indoor taxa were closely related to potential pathogens, that the relative abundance of potential pathogens was higher indoors and higher in rooms with lower airflow rates and RH.  I mention this paper because it is so interesting and because it shows how the built environment impacts dramatically the microbiome indoors including hospitals.  How would UVGI change the indoor microbiome?

On Monday I gave a seminar talk (Seminar 29) on “Current design standards for upper air UV disinfection installations: Bridging the global gaps,” with my colleague Dr. Richard Vincent.  We summarized what is currently known about designing UVGI installations, based on the CDC/NIOSH Guidelines, the ASHRAE Handbook (chapter 17), and many years experience studying UVGI.  The literature shows that UVGI reduces concentrations of airborne infectious microorganisms by 50->95% depending on the microorganism and dose (upper air and in-duct) (Riley et al 1971a,b,Ko et al 2002, Xu et al 2003, 2005,Tseng and Li 2005, Kujundzic et al 2006, Walker and Ko 2007); interrupts transmission of TB disease (in-duct) (Riley et al 1962,Escombe et al 2009, Dharmadjikar et al 2010); improves worker symptoms in office buildings (AHU) (Menzies et al 2003); improves lung function in asthmatic children (in-duct) (Bernstein et al 2006); alters the spread of measles in schools (upper air) (Perkins et al 1947); reduces ventilator associated pneumonia in NICU (AHU) (Ryan et al 2011); and reduces surface contamination in hospital rooms (in-room) (Rutala et al 2010).

We need to clearly communicate to the global community the current state of upper air UVGI design, and that it is ready for prime time!  There is a critical need for a set of standards, or laws, regarding using UVGI in buildings, without these it is not being used to its full potential.  The lack of standards and variation in its application has lead to resistance in its use, especially globally – in South Africa there us currently a moratorium on using UV.  There is a worldwide epidemic of TB/co-infection with AIDS including South America and Africa — and the use of UV could impact the transmission of disease and public health worldwide.

References can be found here.

World TB Day, South Africa