Progress in the Application of Ultraviolet Germicidal Irradiation for Air Disinfection

35th Meeting: American Society for PhotobiologyProvidence, RI, 16 June, 2010

Edward A. Nardell, MDAssociate Professor, Harvard Medical School

Harvard School of Public HealthBrigham & Women’s Hospital

Division of Global Health Equity(Partners In Health)enardell@pih.org

Ultraviolet Germicidal Irradiation(UVGI) – key concepts:

254 nm UV easily produced by mercury vapor lamps

Low skin/eye penetration because it is so reactive – absorbed by

outer layers – nucleic acids protected Microbes are vulnerable

because of their tiny size – nucleic acids are exposed

UVGI Occupational Exposure Limit

Bactericidal

Photokeratitis

Skin cancer

Skin erythema

Wave length (nm)

Rel

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UVGI is old but still underdeveloped technology Applications of Germicidal, Erythemal

and Infrared Energy, 1946 Matthew Luckiesh, DSc, DE, GE Laboratory

24 other books on light

Ultraviolet Irradiation: its properties, production, measurement, and applications, 1922

Why upper room UVGI? The challenge of airborne infections

What are airborne infections? Why are they so hard to control

with ventilation alone? What are the advantages of UVGI?

Why UV in ducts Why upper room UV?

Where should it be applied?

Current upper room UVGI usage Used in hospital

waiting rooms, clinics, emergency rooms, isolation and procedure rooms

Not considered a substitute for negative pressure isolation or for at least 6 ACH ventilation

Used in shelters, jails, prisons, homeless shelters

Current UVGI fixtures (louvered)

Narrow beam

UV in ventilation ducts or portable room air disinfection devices

Microbial Inactivation

Microbial inactivation characterized by survival curves, based on target theory. Number of survivors decreases by a

constant fractional amount for a given increment of exposure.

Holds for a single “hit”, but multiple “hits” leads to survival curves with a shoulder – commonly seen experimentally.

Limitation common to all air disinfection strategies Ventilation HEPA filtration

Limited by number of air turnovers

UV air disinfection In ducts – same

limitation Upper room –

disinfect large volume at once

0

20

40

60

80

100

120

0 2000 4000 6000 8000

Ventilation, CFM

p

Upper Room UV Air Disinfection uses the entire room as a duct

.

.

UV-C

7 ft. Warm contaminatedair risesDisinfected air

displaced

Paddle fans assure good air mixing

UVGI InvestigationsType: Source: Sample: Utilitiy:

1. Bench-scale

BCG aerosol

Mech. A.S. Culture

UV dose humidity

2. Room-scale

BCG aerosol

Mech. A.S. Culture

Fixtures, Vent/CFD

3. Hospital ward

Human M. tb

Guinea Pig/RFLP

Hospital room UV efficacy

4. Epi Human M. tb

Skin Test Real world UV efficacy

Air flow

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Bench-scale studies

Determination of UV susceptibility of various airborne organisms

Z value

ln N0/NuvµWatt x sec x cm-2Z =

Z is the slope of the plot of the natural logarithm of colony count against UV doseMtb at 50% humidity = 33 (23-42) Erdman

48 (44-55) 199RBM. bovis BCG 37 (33-39) Serratia marcescens 214 (183-245)

Humidity protects the organism

0

10

20

30

40

50

60

70

80

400 800

22-33%49-62%85-91%

% Survival

UV dose (uw.sec/cm2)

Determination of UV susceptibility of various airborne organisms

Z value

ln N0/NuvµWatt x sec x cm-2Z =

Z is the slope of the plot of the natural logarithm of colony count against UV doseMtb at 50% humidity = 33 (23-42) Erdman

48 (44-55) 199RBM. bovis BCG 37 (33-39) Serratia marcescens 214 (183-245)

1 µW/cm2

Permutt analysis - 1Z = 0.0041 = Eq ACH/UV dose = 15 Eq ACH/1 µW/cm2

= 15 ACH

Air Changes per Hour, ACH When a volume equivalent to the

volume of the room enters and is exhausted 1 ACH well-mixed air removes 63% of air

contaminants 2 ACH well-mixed air removes 84% of air

contaminants Any air disinfection method that is

63% effective produces 1 Equivalent ACH

Permutt analysis - 2Z = 0.0041 = Eq ACH/UV dose = 15 Eq ACH/1 µW/cm2

= 15 ACH or 15 AC/60 min =

1 Eq AC/4 min = conc. reducedby 63%

1 µW/cm2

Permutt analysis - 3Z = 0.0041 = Eq ACH/UV dose = 15 Eq ACH/1 µW/cm2

1 µW/cm2

1 Eq ACH = 20 min (5 x 4 min)

20%

Instantaneous mixing

Permutt analysis - 4Z = 0.0041 = Eq ACH/UV dose = 15 Eq ACH/1 µW/cm2

32 µW/cm2 avg.= 480 Eq AC 1 Eq ACH/7.2 sec.

1 Eq ACH = 36 secor 100 Eq ACH

20%

Instantaneous mixing

Permutt analysis - 5Z = 0.0041 = Eq ACH/UV dose = 15 Eq ACH/1 µW/cm2

100% air disinfection

= 25 Eq ACH

20%

25 ACH between upperand lower room

Permutt analysis - 6Z = 0.0041 = Eq ACH/UV dose = 15 Eq ACH/1 µW/cm2

32 µW/cm2 avg.= 480 Eq AC 1 Eq ACH/7.2 sec.

20 Eq ACH in the lower rm

25 ACH mixing

Permutt analysis - 7Z = 0.0041 = Eq ACH/UV dose = 15 Eq ACH/1 µW/cm2

32 µW/cm2 avg.= 480 Eq AC 1 Eq ACH/7.2 sec.

50 Eq ACH in the lower rm

100 ACH mixing

Room-scale studies: Riley-Middlebrook, 1976 - aerosolized BCG

A single 17 W UV lamp added the equivalent of 10 air changes to an unventilated room – air mixing by radiator only

Silent, safe, no drafts, low energy use, low maintenance

Established current dosage guideline 30 W fixture per 200 sq ft area.

Am Rev Resp Dis, 1976, 113:413-18.

Airborne Infection - exposure chamber:

HSPH

Aerosol generator: HSPH

Interior, Large exposure chamber, HSPH

Anderson air sampling, HSPH

Summary: efficacy of upper room UVGI

Riley (1976) Miller (1999) Ko (2000)Microorganism BCG Mycobacterium

parafortuitumBCG

Particle size ( m) 0.5-3 0.65-2.1 1.1-4.7Suspending medium 0.2% BSA DW 10% FCS

Temperature (°C) n/a n/a 15-35 4-26RH (%) 25 20, 40 50-90 41-69

Room size (m3) 61 90 46Mechanical ventilation No Yes Yes

ACH 2 2-4 0 6 6-8 6Mixing fan Yes

(during aerosolization) Yes No

UV output (W) 17 46 99(28) 99(28) 36(10) 59(15)UVoutput/Room size

(W/m3)0.28 0.75 1.1 1.1 0.78 1.3

UV fixture type C1 C1&W CN&C2 CN&C2 C2 C2&W

UV Effectiveness (%) 83 88, 89 98 95 52 64 10

UV effect (ACH) 10 18-19, 33 6-16, 19 9.8 6.4 11.7 7.1

Room Studies – Miller et al, 2002University of Colorado at Boulder, NIOSH contract #200-97-2602

Full scale room studies – 87 m2 test chamber

5 fixtures, tot. 216 W producing avg. 42 µW/cm2 in the irradiated upper zone, only 0.08 µW/cm2 at eye level

3 test organisms: B. subtilis, M. parafortuitum, and M. bovis.

2 types of experiments: constant generation – gives effectiveness decay – gives equivalent room air changes

Miller et al, 2002 (cont.) Results (50% humidity):

Constant generation (effectiveness): B. subtilis 46 – 80% @ 216 W M. parafortuitum 83 – 98% @ 216 W M. bovis 96 – 97% @ 216 W

Decay (release & mix): M. parafortuitum 16 ± 1.2 ACH @ 216 W

6.1 ± 0.8 ACH @ 108 W19% increase @ 509 W

Z value = 1.2 ± 0.15 x10-3 cm2 u.sec-1sec-1

Winter conditions (warm air from ceiling): 25% decrease Photoreactivation

none detected at 40% humidity inconclusive at 100% humidity

Upper room UVGI effect on measles in day schools, (Wells, Am J Hygiene, 35:97-121, 1942)

TUSS – TB UV Shelter Study

Prospective, double-blinded, placebo-controlled trial of upper room UVGI in homeless shelters

Phil Brickner, MD, PI 5 cities:

NYC Birmingham New Orleans Houston - two sites

Indeterminate results due to low infection rates and poor retention of homeless subjects

Lots of data obtained on engineering and safety Safe, reliable, low-maintenance

Experimental Hospital Ward

Riley (Wells) experimental TB wardBaltimore, 1958 - 1962

The Airborne Infections Research (AIR) Facility

Witbank, Mpumalanga Province, SA

Ventilation ducts in patient rooms

Paddle Fans Assure Good Air Mixing

UVGI Fixture Specifications – a test of UVGI, not specific fixtures

• Develop specifications• Advertise bid opportunity in the US and

S. Africa• Review all specifications submitted• Solicit fixtures for laboratory

measurements• Receive and install fixtures

AIR, Experimental Plan

A B

Odd days Even days

3 patient rooms

Plus common areas

Intervention on/off on alternative days

Guinea Pig Air Sampling

Pt. TB

RFLP

Guinea Pig

TB RFLP

UVGI or

other

intervention

Results

UV1      Intervention    ControlTST-1         0                      1TST-2         0                      3TST-3         0                      5TST-4         0                      0TOTAL      0                      9

UV2                 TST-1         3                     

17TST-2       12                    30TST3         0                      1TOTAL*     15                    48 *p<0.0005

Combined hazard ratio 4.9 (CI.95: 2.8, 8.6)

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Critical parameters determining upper-room UVGI effectiveness

• Good UV fixture design – Flood the upper room with

enough 254 nm – Low levels of UV in the

occupied space

• Good air mixing between the lower and upper room

– A slow paddle fan is essential

• Good maintenance of fixtures.

Not all fixtures being sold are well-designed for their application

New Fogarty Application under review – would start Sept, 2010

• $400K for 1 year, multi-institutional, multidisciplinary• Collaborators:

– MIT D-lab, Penn State, U. Colorado, Boulder

• 2 domestic, 1 international fellows• Engineers, architects, public health scientists, MDs• Proposal: “Sustainable Air Disinfection Technology

Innovations for Resource Limited Settings”– one year of intensive study and hands-on research further

developing through innovation and optimization the long-neglected technology of upper room germicidal ultraviolet air disinfection for use in poor settings.

Upper room UV light for the prevention of Upper room UV light for the prevention of airborne airborne

tuberculosis transmissiontuberculosis transmission

R Escombe1,2, R Ramirez3, RH Gilman2,4,6, M Navincopa5, E Ticona5, P Sheen6, C Noakes7, B Mitchell8, D Moore1,2, JS Friedland1, C Evans1,2,4,6.

1. Wellcome Centre for Clinical Tropical Medicine & Department of Infectious Diseases & Immunity, Imperial College London, Hammersmith Hospital Campus, UK.2. Asociación Benéfica PRISMA, Lima, Perú. 3. Facultad de Medicina Veterinaria, Universidad Nacional Mayor San Marcos.4. Johns Hopkins University, Baltimore, USA. 5. Hospital Nacional Dos de Mayo, Lima, Perú.6. Universidad Peruana Cayetano Heredia, Lima, Perú.7. School of Civil Engineering, University of Leeds, UK 8. Agricultural Research Service, USA.

HOSPITAL NACIONAL

“DOS DE MAYO”

Kaplan-Meier survival based on PPD conversionsKaplan-Meier survival based on PPD conversions

Days of study

6005004003002001000

Cum

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1.0

.8

.6

.4

.2

0.0

UV vs. No intervention: Log rank 46 p<0.0001 UVGI reduced TB: 72%Ionizers vs. No intervention: Log rank 20 p<0.0001 Ionisers reduced TB: 58%

UV group

Ionizer group

No intervention group

UV killing and relative humidityUV killing and relative humidity

Relative humidity in Lima 50-95%

Upper room UVGI safety TLV for UVGI (UV-C, 254 nm)

6.0 mJ/cm2 for 8 hr. exposure Continuous staring for 8 hrs. at intensity

of > 0.2 µW/cm2 will cause photokeratitis and skin erythema

Will not cause lens cataracts or skin cancer because of limited penetration

Compare to 240 µW/cm2 for 2 hrs peak sunbathing outside.

Upper Air UVGI

ACGIH: 6.0 mJ/cm2 for 8-hour period

= 0.2 W/cm2 for 8-hour continuous eye-level exposure

10 10 >100 >100 W/cm2

After Bruls, Photochem Photobiol, 1984

% Skin Penetration of UV Depth, m

Skin Layer

254 nm UV-C

297 nm UV-B

365 nm UV-A

0 Surface 100 % 100 % 100 %

10 St. corneum 42 50 80

20 18 25 64

30 Viable layer 5 15 50

50 0.4 6 31

70 0.03 2 19

UVGI – poor design and installationMDR TB Hospital – South Africa

Monitoring Human Exposures to Upper-Room GermicidalUltraviolet IrradiationMelvin W. First, Robert A. Weker, Shojiro Yasui, and Edward A. Nardell

Journal of Occupational and Environmental Hygiene, 2005; 2: 285–292

Biofilm

Chemical photometer

Electronic UV meter

Prof. Melvin First

3 UV detectors:

Personal UVGI monitoring study

Study site: Hospital Room - UV Lamp

Old style fixtures- intensity 10 x 0.2 µW/cm2

Unventilated bldg.

Drug-resistant TB patients

No worker infections

Pt. B - always in bed

Pati ent B 11/ 30/ 01

0.00E+00

3.00E-02

6.00E-02

9.00E-02

1.20E-01

1.50E-01

0 2000 4000 6000 8000 10000 12000 14000 16000 18000

Time (sec)

Irrad

ianc

e (u

W/c

m2)

Peak 1. 49E- 01 uW/ cm2Mean 5. 69E- 02 uW/ cm2

Summary - UV exposure Peak

µW/cm2 Mean µW/cm2

Ratio P/M

Duration/8-hr

Exposure mJ/cm2

8-hr exp. mJ/cm2

% TLV (6 mJ/cm2)

Pt. A 0.124 0.0454 0.37 0.83 1.1 1.3 22

Pt. B 0.149 0.0569 0.38 0.54 0.9 1.6 27

Pt. C 0.190 0.0815 0.43 0.83 2.0 2.2 37

Pt. D 0.767 0.0356 0.05 0.87 0.9 1.0 17

Pt. D 0.847 0.0323 0.04 1.0 0.9 0.9 15

Pt. E 0.313 0.0282 0.09 0.75 0.6 0.8 13

R.N. 0.633 0.0141 0.02 0.60 0.2 0.4 7

Where are we going? UVGI needs:

Better, more efficient fixture designs Wider availability of expertise and UV

technology CAD to plan UVGI installations Greater understanding of human 254

nm exposure

New Guidelines NIOSH. Environmental Control of

Tuberculosis: Basic Upper-Room Ultraviolet Germicidal Irradiation Guidelines for Healthcare Settings . 2009

Recommendations: 30 – 50 µW/cm2 average irradiance 6.3 W total UVGI wattage per cubic

meter room volume treated

Conclusions: UVGI is an old technology with new applications Scientifically sound Safe for room occupants Clinical trials are difficult Applications

Poor countries – TB, influenza Rich countries – influenza, bioterrorism, future

airborne threats Research: air sampling, personal UV monitoring,

and improved fixture designs underway. CAD program under development