Control of viral and bacterial pathogens in the built environment is an important aspect of indoor environmental quality with severe personal and economic consequences. Diminished quality of life, premature mortality, decreased worker productivity, and increased healthcare costs are all possible outcomes. Healthcare environments are particularly at risk due to the state of health of patients and the prevalence of increasingly drug-resistant pathogens. The World Health Organization (WHO) estimates that in developed countries, 7% hospital patients overall and roughly 30% of intensive care unit patients will contract at least one healthcare acquired infection (HAI) during their stay. The role of heating, ventilation, and air-conditioning systems in an infection control program is to prevent exposure through a combination of ventilation, pressurization, compartmentalization, and air treatment. By lowering airborne loadings of infectious aerosols, a beneficial effect may be achieved with respect to both inhalational and intermediate surface (fomite) transmission. These measures are becoming of greater importance as the ability to stop infections with drug therapy (e.g., the use of antibiotics for bacterial infections) decreases. Conventional approaches include the use of large quantities of outside air and high air change rates, which increase energy use in combination with high efficiency filters. It has been known for nearly a century that certain wavelengths of light have germicidal capability that is not affected by drug resistance. In particular, optical radiation in the UVC band, particularly 254 nm UVC produced by low pressure mercury vapor lamps has been used to good effect not only for air disinfection, but also as an adjunct to surface disinfection using oxidants and other cleaning materials. This presentation summarizes the state of the art with respect to technology and applications, surveys available evidence of effectiveness, and discusses the potential of future developments. The context is primarily healthcare facilities, but with applicability to other types of residential and non-residential facilities.

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BUILT ENVIRONMENT FACING CLIMATE CHANGE
Current Status and Future Prospects for
Infection Control with Optical Radiation
Authors: William P. Bahnfleth, PhD, PE
Affiliation: The Pennsylvania State University, USA
Session: Plenary #6/29 May 2019
Diamond sponsors

2. OUTLINE
• Motivation
• Infectious diseases
• Infection control
• Existing UVC-based environmental controls
• Emerging optical radiation disinfection technologies
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3. WHY THIS TOPIC?
• Infectious diseases are a major cause of
morbidity and mortality
• Most infectious disease transmission by
occurs in indoor environments
• Building and building system design and
operation affect infection risk
• Protection of building occupants from
disease is a sustainability goal
• Effective low energy methods for
reducing risk are needed
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4. INFECTIOUS DISEASES – BIG PICTURE
(WORLD HEALTH REPORT, WHO 2013)
• 17 million deaths globally per year (all causes – 52 million)
• 1.5 million new pathogen-caused cancer cases (all causes ~10 million)
• Drug resistance of major killers is increasing
• 30 new diseases, some with no treatment in past 20 years
• Current conditions of increase likelihood of dispersion and exposure
• Population growth and urbanization
• Mobility and displacement
• Re-emergence due to complacency or public health system failure
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5. MOST DEADLY DISEASES – AIRBORNE AND
FOMITE TRANSMISSION
( WO R L D H E A LT H R E P O RT, W H O 2 0 1 3 )
Disease Annual Mortality (1995 data)
Acute lower respiratory infections 4.4 million
Diarrhoeal diseases 3.1 million
Tuberculosis 3.1 million
Measles >1 million
Pertussis 355,000
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Transmission commonly occurs indoors due to
proximity and favorable environment for pathogens

6. HEALTHCARE ASSOCIATED INFECTION
• Infections not present or incubating
at time of admission
• Hospitalized patients acquiring at
least one HAI (WHO)
• 7 per 100 in developed countries,
~30% of intensive care unit
patients, much higher rates in
developing countries
• Millions of cases per year
• Attributable annual deaths (WHO)
• Europe 37,000
• US 99,000
• Direct costs per year (WHO)
• Europe €7 billion (16 million extra
hospital days)
• US $6.5 billion
(CDC estimates ~$30 billion)
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7. HEALTHCARE ASSOCIATED INFECTIONS
• Most important HAI types associated with equipment
and procedures (US CDC)
• Central Line-associated Bloodstream Infection
(CLABSI)
• Catheter-associated Urinary Tract Infections (CAUTI)
• Surgical Site Infection (SSI)
• Ventilator-Associated Pneumonia (VAP)
• Others may not be related to specific medical
interventions
• Surfaces, air, water, people are potential reservoirs for
HAI pathogens
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Govt. has certain rights

8. HEALTHCARE ASSOCIATED INFECTION
• Many microbes may be pathogenic to immune compromised patients
• Some are more generally pathogenic and also have antimicrobial
resistance
• Methicillin-resistant Staphylococcus aureus (MRSA)
• Clostridium difficile (CDI)
• Mycobacterium tuberculosis (MDR-TB)
• Vancomycin-resistant Enterococci
• Gram-negative Bacteria
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VRE
(Source: CDC)

9. INFECTION CONTROL
• Transmission modes
• Droplet
• Airborne
• Fomite
• Direct
• Vector
• Infection control program based on
risk assessment
• Source control
• Administrative controls
• Environmental controls
• Personal protection
• Vaccination
• Antibiotic prophylaxis or treatment
• Must be multi-modal
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10. INFECTION CONTROL
• Control of microbial infections with
antibiotics was once routine and effective
• Overuse/misuse of antibiotics has created
resistant pathogens that are difficult to
treat while reducing symbiotic microbes
• Formerly minor infections are now life
threatening
• Increased importance of prevention by
other means
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Source: Pharmaceutical Microbiology www.pharmamicroresources.com

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Source: MMWR, July 30, 1999
Infectious Disease Death Trends
• Rate for developed countries is
much lower than a century ago
• Sanitation has had the largest
impact
• Antibiotics and vaccines
responsible for most
improvement since 1940
• Incidence has bottomed out,
may rise as antibiotic resistance
increases, prevalence of vector-
borne disease increases

12. ENVIRONMENTAL CONTROLS
• ASHRAE Position Document on airborne
infections diseases identifies three controls
demonstrated to reduce risk
• Ventilation/exhaust
• Filtration
• UVGI
• Surfaces require chemical cleaning or
irradiation
• Ventilation/media filtration can have high
energy use and life cycle cost
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13. OPTICAL RADIATION (1 nm – 1mm)
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State of the art is based on 254 nm UVC
“Ultraviolet Germicidal Irradiation” (UVGI)

14. DNA DAMAGE THROUGH
THYMINE DIMER FORMATION
GERMICIDAL ACTION SPECTRUM
(UVC 100 – 280nm, UVB 280 -315 nm)
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UVC PRINCIPLES
ASHRAE Handbook 2016 HVAC Systems and Equipment
Martin Hesseling, Hochschule Ulm

15. UVC PRINCIPLES
• Microbial survival after UVC exposure
• S = surviving fraction of initial
population
• k = deactivation rate constant
(cm2/µW-s)
• I = UV fluence (µW/cm2)
• t = duration of exposure (s)
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( )expS kIt= −

16. UVC PRINCIPLES
• Sources currently are mainly low pressure Hg vapor lamps that emit ~254 nm
UVC…fluorescent lamp technology
• LEDs are emerging as the next generation source
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17. UVC FOR HAI CONTROL
• UVC can be effective against antibiotic resistant bacteria because it
works on a different principle
• Antibiotic mechanisms
• Prevent cell wall growth
• Prevent essential protein synthesis
• Damage DNA by a different mechanism than UVC
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18. UVC FOR HAI CONTROL
• Ways in which UVC can be used to
reduce exposure
• Room surface disinfection
• Air treatment
• Medical instrument disinfection
• Surgical site disinfection
• Complementary to other measures
and methods
• Oxidants
• Antimicrobials
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19. UVC TECHNOLOGIES
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Portable room disinfection unit Equipment disinfection cabinet

20. UVC TECHNOLOGIES
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Upper room air treatment “In duct” air treatment

21. UVC TECHNOLOGIES
• Caveats
• Importance of line of sight
• Relative contribution to risk
• Status of standards
• Material degradation
• Risk to occupants
• Byproducts
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22. OVER 90 YEARS OF STUDIES
INDICATING EFFECTIVENESS OF UVGI
• Historical highlights:
• 1927 – Quantification of bactericidal action of UV
• 1937 – Application in schools to control measles outbreaks
• 1957 – Demonstration of effectiveness in controlling tuberculosis
• 1994 – Effectiveness forTB control recognized by CDC
• 2000 – US Army recommends UVGI for disease isolation
• 2007 – Demonstrate effectiveness for reducing surgical site
infections
• (Kowalski,W. 2009. Ultraviolet Germicidal Irradiation Handbook. Springer.)
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American Journal of Hygiene (1942)

23. REPORTED EFFECTIVENESS – AIR
DISINFECTION
• Wells,Wells, andWilder (1942)
• Interventions in two schools in 1937
• Upper air UVGI
• Tracking of infectious disease outbreaks
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Am. J. Hygiene (1942)

24. REPORTED EFFECTIVENESS – AIR
DISINFECTION
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25. REPORTED EFFECTIVENESS – ROOM
DISINFECTION
• Review of room disinfection studies
using UVC and hydrogen peroxide
(Weber, et al., 2016)
• Reviewed studies reduced surface
loadings of HAI pathogens by as
much as 4 logs with ~1hour or less
exposure
• Room disinfection strategies reduced
infections 10-30% across clinical trials
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26. REPORTED EFFECTIVENESS – ROOM
DISINFECTION
• Comparison of normal cleaning and UVC
room decontamination no HAI pathogens
(Wong, et al. 2016)
• Conventional cleaning (peroxide and
detergent) or automated UV
• Cleaning - no significant change in number
of rooms where contamination was
detected
• UV – large reduction in contaminated
rooms and in counts
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27. REPORTED EFFECTIVENESS – ROOM
DISINFECTION
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After conventional cleaning, little change in contamination; large change post-UVC irradiation

28. REPORTED EFFECTIVENESS -
INSTRUMENTS
• Stethoscope disinfection device
(Messina, et al., 2015)
• UV LED – 255-280 nm
• One minute exposure
• 87.5 – 94.9% reduction in four
common bacteria including S.
aureus and E. faecalis
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29. REPORTED EFFECTIVENESS -
INSTRUMENTS
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30. FUTURE OF DISINFECTION WITH
OPTICAL RADIATION - LEDS
• LEDs should take over much of the
market
• Long life
• Configuration flexibility
• More wavelength options
• Dimmable
• Cycleable
• Better in typical thermal
environments
• No mercury
• Current market barriers
• Low output (mW)
• Cost
• Durability
• Standards
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31. PERFORMANCE OF AVAILABLE LEDS
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Source: International Light Technologies

32. MERCURY VAPOR VS. LED OUTPUT AS A
FUNCTION OF TEMPERATURE
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0
20
40
60
80
100
0 20 40 60 80
Lamp Surface Temperature [ο
C]
UVOutput[%]
UV lamp output vs. cold spot temperature LED output vs. junction temperature

33. FIVE LOG REDUCTION OF VIRUSES,
BACTERIA, AND FUNGI
(Kim And Kang 2018)
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Appl. Env. Microbiology vol. 84(17), Sept. 2018
S. aureus

34. FUTURE OF DISINFECTION WITH
OPTICAL RADIATION – VISIBLE LIGHT
• Extensive studies of blue visible light
(400-470 nm) in past decade
• Evidence of effectiveness from
multiple studies, including HAI
pathogens
• Potential for continuous irradiation
of occupied spaces
• Reduced risk from consequences of
exposure to UVC
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35. SUMMARY
• Infectious diseases are a major global health issue
• Prophylaxis and treatment are becoming less effective, better prevention needed
• Environmental controls in buildings are a key part of a prevention strategy
• Optical radiation in UVC range is used in a variety of ways to reduce exposure via
HVAC systems in in spaces
• Emerging LED technology for UVC and visible wavelength disinfection have great
potential to expand use of optical radiation in disinfection and reduce infection risk
to building occupants
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36. THANK YOU!
wbahnfleth@psu.edu
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