latest research on uvc: focus on bioaerosols foarde latest uvc.pdfcellular repair mechanisms...
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RTI International is a trade name of Research Triangle Institute
3040 Cornwallis Road ■ P.O. Box 12194 ■ Research Triangle Park, North Carolina, USA 27709 e-mail: [email protected] phone: (919) 541-8018
Latest Research on UVC: Focus on Bioaerosols
Karin K. Foarde
September 22, 2006
Outline
§ Brief Review of UVC and Microorganism Basics
§ Some UVC uses and applications
§ RTI research and testing projects
§ ASHRAE UVC activities
Electromagnetic Spectrum
Breakdown of UV Spectrum
Inactivation by UVC
§ Damages DNA § Formation of thymine dimers
§ Distortion of DNA strand
§ Unable to replicate
Cellular Repair Mechanisms (Potential to Overcome Damage)
§ Photoreactivation with near UV or visible light § 330 – 480 nm
§ Works for fungal spores, bacteria, and viruses, as well as animal and plant cells
§ Excision repair or dark repair § Dual enzyme system
§ #1 excises the dimers; #2 replaces the excised regions by copying the undamaged strand
§ SOS repair § Extremely complex
§ Results in a high level of mutations increasing chances of survival
§ Viruses – host or infected cell repair
Uses of UVC
§ Upper Air Disinfection CDC Guidelines for Preventing the Transmission
of Mycobacterium tuberculosis in Healthcare Facilities, 2005
§ Air Ducts § Airstreams § Coils, etc.
§ Air Cleaners
§ Others § Biosafety cabinets, etc.
Some Adverse Health Effects Caused by Bioaerosols
§ Infectious diseases § TB
§ Biowarfare
§ Allergy
§ Asthma
Infectious Disease
§ Bacterial diseases
§ Tuberculosis
§ Strep throat
§ Diphtheria
§ Legionellosis
§ Bacterial meningitis
§ Bacterial pneumonia
§ Viral diseases
§ Influenza
§ “Colds”
§ Hepatitis
§ SARS
§ Viral meningitis
§ Viral pneumonia
Capable of being transmitted by infection with or without actual contact
Scenario
Requirements for Control by UVC
1. The infectious disease is transmissible by inhalation,
2. The infectious agent reaches the duct,
3. The infectious agent is transported to the lights, and
4. There is a sufficient dose of radiation.
Parallels for Filtration
1. The infectious disease is transmissible by inhalation,
2. The infectious agent reaches the duct,
3. The infectious agent is transported to the filter, and
4. There is a sufficient filtration efficiency.
Bacterial Shapes Important for Filtration
Microbe Groups Susceptibility to UVC
most susceptible
least susceptible
Lipid viruses
Vegetative bacteria
Fungi
Non-lipid viruses
Mycobacteria
Bacterial spores
least resistant
most resistant
Fungal Spores
Inactivation Efficiency vs. Dose
§ Inactivation Efficiency = Effectiveness of agent to inactivate organism to a given level § 90% inactivation – 1 log increase
§ 99% inactivation – 2 log decrease
§ 99.9999% inactivation - 6 log decrease
§ Dose = the amount of radiation to which something has been exposed § Irradiance X Contact Time
UVC Inactivation Equation
§ “k” depends on microbial organism susceptibility
§ Eeff = f( I, T, H) § I = Irradiance § T = temperature of lamp, affected by air temperature and
velocity § H = humidity
§ “Dt” is exposure duration
§ Nt / N0 = exp (- k Eeff Dt)
Dose Calculation
§ Estimated using model
§ Calculated using inactivation
UU
n
ii
n
= =å
1
( )k
NNlnDose 0t-=
Beyond Reaching the Lights
RTI Research and Testing Projects
§ Lessons from testing UVC inactivation in a full-scale test duct. § Results of 2 projects
§ Other Projects § K value comparison
§ Coil surface kill
Projects Using a Full-Scale Test Duct
§ ARTI project (2002) § Defining the Effectiveness of UV Lamps Installed in
Circulating Air Ductwork (Project 610-40030) § http://www.arti-
research.org/research/completed/finalreports/40030-final.pdf
§ EPA Homeland Security Research - Technology Testing and Evaluation (TTEP) (2006) § Bioaerosol Inactivation Efficiency by HVAC In-Duct
Ultraviolet Light Air Cleaners
§ http://www.epa.gov/nhsrc/abouttte.htm
Full Scale Equipment
Full Scale Test System 300 - 3000 CFM test duct
•Meets ANSI/ASHRAE 52.2 specs
Use of Surrogates/Simulants
§ Testing with actual agents is rarely practical § Expensive because require high level of containment
§ Organisms themselves are often fragile
§ Often utilize surrogates or simulants § Compatible with bioaerosol technical issues
§ Match inactivation/removal mechanisms under test
Simulant Selection Criteria
§ Range of susceptibilities to the device to bracket those of the actual agents.
§ Susceptibility of the organisms to UVC kill or inactivation
§ Appropriate physiological characteristics to reflect those of the infectious agents.
§ Appropriate physical characteristics that reflect those of the BWA. § Reflect natural diversity of size and shape
§ Laboratory containment compatible with biohazard of simulant.
Factors to Consider
§ Physical
§ Lamp type, power, age
§ Lamp location & orientation/ configuration
§ Duct reflectance
§ Air flow
§ Air Temperature
§ Air Humidity
§ Microbial
§ Organism
§ Dose (irradiance x time)
§ Protective factors § Relative Humidity § Literature inconsistent on effect
of RH § Organic matter § Dust or other organisms § Body fluids
Test Organisms
Group Test Organism Susceptibility to UVC
Size (µm) & Shape
B. subtilis spores Moderate 0.9; ellipsoidal
P. fluorescens High 0.7 X 2.8; rod
S. epidermidis High 0.5 -1.5; sphere Bacteria
S. marcescens High 0.5 X 1.0; rod
A. versicolor Low 2 - 3.5; globose
P. chrysogenum Low 3 X 3.8; globose Fungal spores
C. sphaerospermum Low 3 x 7; subglobose
Virus MS2 Moderate - High 0.03; sphere
% Inactivation Bacterial Spores (Bacillus)
# Protection Factors
0 1 2
Protection Factors
55% RH 85% RH or 55% RH + Broth
85% RH + Broth
# Lights 3 6 3 6 3 6 % Inactivation 43 83 43 83 46 89
% Inactivation Fungal Spores (Aspergillus)
# Protective Factors 0 1 2
Protective Factors
55% RH 85% RH or 55% RH + Broth
85% RH + Broth
# Lights 3 6 3 6 3 6
% Inactivation 7 23 7 36 14 47
% Inactivation Vegetative Bacteria (Staphylococcus)
# Protective Factors
0 1 1 2
Protective Factors
55% RH 85% RH 55% RH + Broth
85% RH + Broth
# lights 1 <1 1 <1 1 <1 1 <1
% Inactivation
99 69 74 15 86 19 63 0
Calculated k Values
k values, cm2/mW-s, at indicated humidity Test Organism
55% RH 85% RH Vegetative Bacteria
S. epidermidis 2.4 ± 2.0 (n=18)
0.8 ± 0.2 (n=12)
Bacterial Spore
B. subtilis 0.2 ± 0.06 (n=14)
0.2 ± 0.06 (n=14)
Fungal Spore
A. versicolor 0.03 ± 0.02 (n= 12)
0.06 ± 0.03 (n=12)
Bacillus spp. k values
1.00E-05
3.00E-05
5.00E-05
7.00E-05
9.00E-05
1.10E-04
1.30E-04
Bs oran
ge
Bs crea
m
B.stearo
therm
ophilu
s
B. pum
ilus
B. meg
ateriu
m
B. cereu
s
B. thurin
giensis
B.a. ste
rne
k va
lues
Environmental Technology Verification Program (ETV)
§ EPA Office of Research and Development created ETV in 1995
§ Goals § To accelerate the entrance of new environmentally
beneficial technologies into marketplace § To provide potential purchasers and permitters
with an independent and credible assessment of what they are buying and permitting
§ EPA works with partners to verify products
www.epa.gov/etv
RTI ETV Related Programs
Program IAQ Document/tests Program Date ETV - Indoor Air Pilot Protocol and Test/QA plan for
filters (particulates only), tests to verify protocol
1995-2002
ETV - Safe Buildings (homeland security)
Protocol and test/QA plan for filters (includes bioaerosols), verified 14 filters
2002-2004
TTEP (Technology Test and Evaluation Program) – homeland security
Developing test/QA plan for UV lights, verified 9 products
2004-2006
APCT indoor air program
Draft test/QA plan 2005-present
Results for UV Devices (TTEP)
Device Lamps Measured Dosage
µW-s/cm2 Power
(w) BG %
SM %
MS2 %
1 1 247 (208 – 304) 53 4 99 39 2 4 295 (249 - 363) 94 0 99.8 46 3 4 582 (490 - 716) 169 9 > 99.96 75 4 12 7,651 (6,443 – 9,416) 755 71 > 99.98 98
5 8 3180 (2678 - 3914) 568 40 > 99.98 82 6 5 16,439 (13,843-20,223) 944 93 > 99.97 99 7 6 19,826 (16,696– 24,401) 421 96 > 99.96 99 8 6 42,342 (35,656– 52,113) 748 99.9 99.9 99.9 9 12 447 (376 – 550) 6480-6720 6.9 99.8 59
Dosage, # Lamps, % Inactivation
spore vegetative bacteria
247 1 4 99 39582 4 9 > 99.96 75
3,180 8 40 > 99.98 827,651 12 71 > 99.98 98
16,439 5 93 > 99.97 9919,826 6 96 > 99.96 99
% InactivationCalculated Dosage
µW-s/cm2 Lampsbacteria
virus
APCT Center Focus
§ PM, NOx, VOCs, and Hazardous Air Pollutants.
§ Completed protocols: § Paint overspray arrestors § Baghouse filter products § NOx controls § Dust suppressants for unpaved roads § Mobile source retrofit controls (3 protocols) § Biofiltration systems for VOC control § Indoor Air Pollutant Products
Test Options for Devices that Work in Ducts
§ Tests § American Society of
Heating Refrigeration and Air-conditioning Engineers (ASHRAE) 52.2 test (inerts 0.3 – 10 µm)
§ RTI/ETV-HS inerts test (0.03 – 10 µm)
§ RTI/ETV-HS bioaerosol test (0.03 – 10 µm)
§ Overview § Stakeholder developed
plans from § ETV Pilot § Homeland security
verifications
§ Methods and procedures developed through EPA programs
§ In-duct systems - filters, UV systems, electronic cleaners, etc.
Aspergillus versicolor on Coil
ASHRAE Activities
§ New TC2.UVAS (Technical Group - UltraViolet Air and Surface Treatment)
§ SPC 185 MOT (Special Project Committee-185 Method Of Test UVC Lights for use in air handling units or air ducts to inactivate airborne microorganisms)
TC2.UVAS
§ Chuck Dunn (Lumalier) TC Chair
§ Karin Foarde (RTI) Research Subcom. Chair
§ Steve Martin (CDC) Program Subcom. Chair
§ Terri Wytko (ARI) Standards Subcom. Chair
§ Derald Welles (Sterli-Aire) Handbook Subcom. Chair
§ Rick Larson (Trane) Website
Research Subcommitee
§ Top Research Ideas
§ Ultraviolet lamp (UVGI) effectiveness for maintaining clean HVAC cooling coils
§ Ability of UVC to penetrate the entire depth of aluminum fin & tube heat exchangers
§ Study the degradation of typical HVAC materials and filters irradiated by UVC
§ Air Disinfection on the Fly
§ Levels of UVC Energy Needed to Keep Coil Clean (Surface)
§ Efficacy of UVC Field Systems
§ Other ideas
§ Extent of coil fouling and impact of cleaning
§ Effect of bioaerosol on coil/energy efficiency
§ Degradation and benefits of surface filter irradiance (interface of UVC & filters, pressure drop)
SPC 185 Roster (*voting members, + Chair, ++ Vice Chair)
Chuck Dunn Lumalier [email protected]
Karin Foarde*++ RTI [email protected]
Rick Larson Trane [email protected]
Steve Martin* CDC/NIOSH [email protected]
Shelly Miller* University of Colorado [email protected]
John Putnam EDYN [email protected]
Dean Saputa UV Resources [email protected]
Richard Vincent* St. Vincent's Hospital [email protected]
Derald Welles*+ Steril-Aire [email protected]
Dave Witham* UVDI [email protected]
Terri Wytko* ARI [email protected]
Willie Young Freudenberg [email protected]
SPC 185 Methods
§ SPC 185.1 – Air § Chair – Derald Welles, Vice Chair – Karin Foarde
§ Starting with ASHRAE 52.2 as basis
§ Incorporating as needed from ETV/TTEP method
§ SPC 185.2 - Surface § Chair - Dean Saputa, Vice Chair - TBD
§ Investigating available surface methods
Summary
§ A lot of research and testing of UVC has been done and is underway.
§ With sufficient dose, UVC has the potential to be effective in controlling microorganism.
§ UVC is being used in buildings in a variety of applications.
§ ASHRAE has a TG and is developing methods for testing efficacy.
UVC
1. Organism must reach the lamps.
2. Expect High Variability for Inactivation § Microorganisms are part of a
population § Natural distribution of
resistance § Inherent dose variability for
aerosols in a duct
3. 90% inactivation efficiency may not be enough.
4. Irradiance and residence time must be sufficient to achieve needed dose.
Filters
1. Organism must reach the filter.
2. Expect High Variability for Inactivation
§ Microorganisms are part of a population § Natural distribution of
shapes and sizes
§ Inherent dose variability for aerosols in a duct
3. 90% filtration efficiency may not be enough.
Factors to Consider when Using:
to Control Microorganisms