latest research on uvc: focus on bioaerosols foarde latest uvc.pdfcellular repair mechanisms...

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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 cdunn2@lumalier.com

Karin Foarde*++ RTI kkf@rti.org

Rick Larson Trane rlarson@trane.com

Steve Martin* CDC/NIOSH smartin1@cdc.gov

Shelly Miller* University of Colorado shelly.miller@colorado.edu

John Putnam EDYN edyn@earthlink.net

Dean Saputa UV Resources dean.saputa@uvresources.com

Richard Vincent* St. Vincent's Hospital rvincent@svcmcny.org

Derald Welles*+ Steril-Aire dwelles@ix.netcom.com

Dave Witham* UVDI davew@uvdi.com

Terri Wytko* ARI tytko@ari.org

Willie Young Freudenberg willie.young@freudenberg-nw.com

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