Evaluation of Window-Tinting Films for

Sunlight Phototherapy

by Hendrik J Vreman1 Tina M Slusher2 Ronald J Wong1 Stephanie Schulz1 Bolajoko O Olusanya3 and David K Stevenson1

1Division of Neonatal and Developmental Medicine Department of Pediatrics Stanford University School of Medicine

Stanford CA 94305-5208 USA2Center for Global Pediatrics University of Minnesota Minneapolis MN 55414-1932 USA3Department of Community Health and Primary Care College of Medicine University of Lagos Lagos State Nigeria

Correspondence Hendrik J Vreman Tel thorn1 650-7235-5859 Fax thorn1 650-725-7724 E-mail lthenkvremanstanfordedugt

Summary

We evaluated nine semi-transparent plastic window-tinting films for their ability to block ultraviolet

A (UVA) and infrared (IR) radiation and transmit therapeutic blue light (400ndash520 nm) for treating

jaundiced newborns For indoor testing three light sources (TL52 special blue fluorescent Black Light

UVA and IR heat lamps) were positioned above each film and measured successively using a thermo-couple thermometer UVA radiometer and blue light irradiance meter placed below each film

For outdoor testing the same setup was used with the sun at zenith and a cloudless sky Compared

with unfiltered radiation blue light transmission through films ranged from 24 to 83 UVA trans-mission was 01ndash71 and reductions in IR heat were 6ndash12C and 5ndash10C for heat lamp and sun

respectively The data suggest that most of the relatively low-cost window-tinting films tested can

effectively reduce sunlight UV and IR and offer a range of significant attenuations of therapeutic

blue light

Key words bilirubin Jaundice Hyperbilirubinemia Newborn Phototherapy

Introduction

Sunlight phototherapy (PT) has been investigated asa treatment for hyperbilirubinemia because of itsability to reduce jaundice and serum total bilirubinlevels in infants with hyperbilirubinemia [1ndash3]However direct sunlight is undesirable for treatmentbecause it has a number of significant clinical and

practical disadvantages [4] For instance harmfulultraviolet (UV) radiation (100ndash400 nm) in sunlightcan seriously and permanently damage human skin[5] Furthermore sunlight also contains warming in-frared (IR) radiation which can cause hyperthermiaand dehydration with insufficient cooling especiallyin vulnerable neonates [6] For these reasons theAmerican Academy of Pediatrics does not recom-mend its use for treating hyperbilirubinemia [7]Mitigating these risks is likely to make sunlight safeand effective as a low-cost alternative to artificiallight PT Technological methods using pigmentscoatings and films exist for blocking UV and IR ra-diation and some will allow transmission of desirableportions of the solar energy spectrum One innov-ation (already used in vehicles and buildings) isthe application of semi-transparent plastic tintingfilms to windows However it is not known if anyof these films would permit the transmission of suf-ficient therapeutic levels of blue light (400ndash520 nm)necessary to treat hyperbilirubinemia in newbornsThis study investigates nine such films for theirblocking ability of UV and IR radiation andthe transmission of therapeutic blue light to

Acknowledgements

The authors received editorial support from John JMahoney They express their thanks for offers of ex-pertise and donation of samples of window-tintingfilms by Tom King of V-KOOl Inc Houston TX(V-KOOl 55 and 70) and Tammy OrsquoMeara ofWindow Innovations Inc Brentwood CA (HuperOptik Select Sech)

Funding

This work was supported by the Mary L JohnsonResearch Fund the Christopher Hess Research Fundand the HM Lui Research Fund

JOURNAL OF TROPICAL PEDIATRICS VOL 59 NO 6 2013

The Author [2013] Published by Oxford University Press All rights reserved For Permissions please email journalspermissionsoupcom 496doi101093tropejfmt062 Advance Access published on 23 July 2013

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determine the feasibility of using any of the films forsunlight PT

Materials and Methods

FilmsRepresentative samples of nine metalized (M) andmetal oxynitride (S) films [TAP R-20 (M) Titanium(M) Gila Platinum (M) V-KOOl 55 (S) Gila Light(M) Huper Select (S) TAP R-50 (M) V-KOOl 70 (S)andAir Blue 80 (S)] were obtained from the companieslisted in Table 1 Presently Solutia Inc (St LouisMO) owns these brands The retail price of the filmstested range from US $050 (for M-type film) to $200(for S-type film) per 30 30 cm (or 1 sq ft)

Laboratory Bench TestsBecause the radiation properties of sunlight cannot beeasily reproduced in the laboratory by any one light

source three light sources were used for the benchtests (Fig 1) For IR testing a reflector IR heatlamp (115ndash125 V 250 W General Electric FairfieldCT) powered with 80VAC from a Variac transformerwas clamped to a laboratory stand 23 cm (a) above arectangular wire film support positioned 75 cm (b)above a thermocouple thermometer (Type KEA11A Extech Instruments Melrose MA) thatwas placed 25 cm (c) above an insulating layer of1-cm polyester batten and 5-cm thick polystyrenefoam The heating effect of the lamp with no filmpresent was measured Temperatures were recordedas C Ambient temperature was kept constantFor UVA testing a black light fluorescent lamp

(F15T8-BLB General Electric) with a spectral rangeof 315ndash400 nmwas clamped to the laboratory stand ata 2-cm distance (a) above the film support with 0-cmdistance (b) from the film to the meter UVA intensitywas measured as mWcm2 using a UVA meter(Goldilux RadiometerPhotometer with a GAP-1

TABLE 1Light (T) and heat (IR) transmission (C) for lamp- and sunlight through nfrac14 9 flexible window-tinting

films with attached liner

Lightsource

Film (Type) Bluea (400ndash520 nm)mWcm2nm (Tb)

UVAc (315ndash400 nm)mWcm2 (Tb)

IRd C (Te) tfrac12 (min)f

Lamp

No Film 215 (100) 2226 (100) 36 (0) NDg

1 TAP R-20 (Mh) 71 (33) 9 (04) 245 (115) ND2 Gila Titanium (M) 93 (43) 8 (04) 245 (115) ND3 Gila Platinum (M) 101 (47) 157 (71) 24 (12) ND4 V-KOOl 55 (Si) 123 (57) 1 (01) 24 (12) ND5 Gila Light (M) 125 (57) 11 (05) 26 (10) ND6 Huper Select (S) 129 (60) 1 (01) 265 (95) ND7 TAP R-50 (M) 140 (66) 12 (05) 28 (8) ND8 V-KOOl 70 (S) 154 (71) 2 (01) 24 (12) ND9 Air Blue 80 (S) 179 (83) lt1 (lt01) 30 (6) ND

Sunj

No Film 114 (100) 1526 (100) 36 (0) 401 TAP R-20 (M) 28 (24) 8 (05) 26 (10) 1002 Gila Titanium (M) 38 (33) 7 (04) 265 (95) 1023 Gila Platinum (M) 44 (38) 75 (49) 27 (9) 744 V-KOOl 55 (S) 60 (53) 4 (02) 28 (8) 805 Gila Light (M) 64 (56) 8 (05) 29 (7) 1026 Huper Select (S) 66 (53) 4 (02) 29 (7) 777 TAP R-50 (M) 68 (60) 13 (08) 31 (5) 808 V-KOOl 70 (S) 78 (68) 4 (02) 29 (7) 729 Air Blue 80 (S) 91 (79) 2 (01) 30 (6) 47

NotesaBlue Light Tl 20W52 (Philips Amsterdam The Netherlands) measured by BiliBlanket Meter IIbT is the percentage of light transmitted by a film relative to the light presented to that film (no filmfrac14 100)cUVAfrac14 Black light F15T8-BLB (General Electric Hartford CT) measured by Goldilux UVA photometerdIRfrac14 Heat Lamp 115VAC 250W powered at 80VAC (General Electric) measured by a thermocouple thermometereAmbient temperatures for lamp and sun experiments were 20C and 18C respectivelyfThe tfrac12 is the number of minutes required for the bilirubin concentration to decrease to half its original valuegNDfrac14 not determinedhMfrac14metalizediSfrac14 spectrally selective transition metal oxynitridejSunlight zenith cloudless sky

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Probe Oriel Instruments Stratford CT) with the topof the photometer at 25 cm (c) above the insulatinglayer This meter has a spectral sensitivity range of315ndash400 nm with peak sensitivity at 365 nm

For therapeutic blue light (spectral range of400ndash520 nm) testing a fluorescent lamp (TL20W52 Philips Electronics Amsterdam TheNetherlands) fitted with a Clip-On Reflector (3MInc Minneapolis MN) was clamped to the labora-tory stand 23 cm (a) above the film support and a23-cm distance (b) from film to meter Light intensity(irradiance) was measured as mWcm2nm with thetop of the meter 25 cm above the insulating layer (c)using a BiliBlanket Meter II (GE HealthCareTechnologies Waukesha WI) which has a spectralsensitivity range of 400ndash520 nm and peak sensitivity

at 450 nm Light intensity (irradiance) is a measure ofradiometric flux per unit area (or flux density) It istypically expressed as Wcm2 (watts per squarecentimeter) or mWcm2nm (microwatts per squarecentimeter per nanometer) by clinically used irradi-ance metersFor each indoor bench test the appropriate lamp

was first powered on and allowed to equilibrate for30 min The appropriate detector was then placed atthe center of the radiation footprint and the controlresponse level (ie no film) was recorded Withoutmoving the detector various films (22 28-cmsheets) with their protective liners attached wereplaced in succession on the film support with theliner facing the lamp The filtered radiation intensitywas then recordedFor outdoor sunlight testing a similar experimen-

tal procedure was used except that the lamps werereplaced by sunlight at zenith (1100ndash1400 hr) in acloudless sky on a roof at the Stanford UniversityMedical Center (latitude 37 2600800 N longitude122 100260 0 W) The experimental setup was shieldedas much as possible from air currents without inter-fering with sunlight delivery Ambient temperatureswere also recorded

Determinations of tfrac12The method and calculations for the determinationof tfrac12 (min) for bilirubin photodestruction to diazo-negative compounds were performed as previouslydescribed [8] In summary sets of (nfrac14 3) hematocrittubes containing 25 ml of a bilirubinhuman serumalbumin (BRHSA 25mgdl4 HSA in buffer)solution were exposed at 37C to filtered sunlightThe remaining BR concentrations were quantitatedusing a diazo-reaction assay The rate of BR photo-degradation (t12) was then determined throughinterpolation of plotted BR degraded vs time(min) We found that the t12s (efficacy) for anumber of artificial light PT devices ranged from 16to 67 min (in Table 3 ref 8)

Data AnalysisPercent transmission (T) for blue and UVA radi-ation was calculated for each film using the equation[Tfrac14 (FilmNo Film) 100] The transmission ofIR is expressed as the difference [ (delta) T] in tem-perature (C) between unfiltered and filtered sunlight

Results and Discussion

The results of testing the films with the three types ofradiation are shown in Table 1 with the dataarranged in order of increasing T of therapeuticblue light (rangefrac14 33ndash83) relative to unfilteredlamp light The sunlight T values for the filmswere similar but relatively lower (range 24ndash79)than for lamplight This is likely due to the meterrsquosresponse to the broader-spectrum and higher-

Light Source

Detectors (UV-A Blue IR)

Film Support

Insulated detector stage

(a)

(b)

(c)

FIG 1 Bench test system used for evaluating samplesof window-tinting films The setup consists of a lightsource (IR UVA or blue lamp) clamped separatelyto a laboratory stand or the sun under which a wireframe is positioned to support the 22 28-cm sheetsof film To make the measurements each detector(ie a thermocouple thermometer a UVA photom-eter or a blue light irradiance meter) was placed inturn on the insulating layer so that its sensor waslocated 25 cm above the insulation For IR UVABlue lamps and sun the distances for (a) were 23 223 cm and infinity (b) were 19 0 23 and 5 cm and(c) were all 25 cm

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emission peak (gt600 nm) of sunlight compared withthe narrow-spectrum and lower-emission peak(450 nm) of the specialized TL52 blue light lamp[8 9] Blue light irradiance from unfiltered sun atzenith ranges from 100 to 150 mWcm2nm in acloudless sky but only lt25 mWcm2nm in an over-cast sky (measured with the BiliBlanket II Meterunpublished observations) Significant attenuationof blue light might be desirable depending on geo-graphical latitude season and the time of day Thusunder clear skies when an attenuated transmission ofblue light is desirable Gila Titanium film would be agood choice because it transmits only 33 (or po-tentially up to 33ndash50 mWcm2nm) of therapeutic bluelight [10] However under overcast sky this filmtransmits a barely effective irradiance of 8mWcm2nm When maximum blue light transmission isdesired (eg under an overcast sky) the Air Blue80 film (79T) would still transmit 20mWcm2nm which is comparable with standard PT used indeveloping [11 12] and developed countries [13] Thepresent data suggest that most of the tested window-tinting films can effectively reduce sunlight UV andIR and offer a range of clinically significant attenu-ations of therapeutic blue lightExcept for Gila Platinum film UVA transmission

for the films was lt1 Therefore UV radiation iseffectively blocked by all but one of the tested filmsBecause UVA light (315ndash400 nm) is more likely topass through organic films than UVB (280ndash315 nm)or UVC (100ndash280 nm) light it can be inferred thatthese forms of UV irradiation will also be blockedIR measurements show the greatest difference in

magnitude between lamp- and sunlight Howeverthere also exists a corresponding relationship forthis parameter with the sunlight values being lowerthan lamplight by an average of 3C It is possiblethat air currents or the broader sunlight IR spectrum[9] affected the results Nonetheless the data showthat all films reduced heat transmission and thatthe metalized (M) films were more effective at redu-cing temperature compared with the spectrally select-ive transition metal oxynitride (S) films Relativetemperature reduction is important for designingclinical field studies In areas where sunshine is abun-dant but ambient temperatures are relatively low(eg at high altitudes or latitudes) films with suffi-cient heat transmission would probably be needed tomaintain patient thermostasisThe tfrac12 data demonstrated the effectiveness of sun-

light toward bilirubin degradation UnfilteredStanford sunlight produced a very short tfrac12 of 4min whereas the filtered light showed a range oflonger tfrac12s (range 47ndash102 min) However com-pared with our earlier results [8] even the film withthe longest tfrac12 (Gila Titanium tfrac12frac14 102 min) wasmore effective than the artificial electric light devicessuch as the BiliBed [Medela McHenry IL (tfrac12frac14 18

min)] or the Wallaby Term (Senior) (PhilipsHealthcare Monroeville PA tfrac12frac14 67 min)Because the films were studied with their liners

(which protect the sticky or window applicationside from dust) in place we also tested if there waspolarity to the films but no difference in T wasdetected whether the active layer of the films or theliner faced the light source (data not shown)Consequently liners were left attached to serve asan additional protective layer when panels of thefilm were handled and studied or installed overcanopies and exposed to sun rain wind and dustWe recommend that the films be mounted with theliner side facing the sun so that the active layer ismaximally protected from being damagedThe ideal sunlight PT film should (i) block UV

radiation to lt1 that of unfiltered sunlight(2000mWcm2) (ii) block IR sufficiently to main-tain patient thermostasis (iii) transmit sufficient levelof therapeutic blue light and (iv) be transparent tofacilitate visibility of the patient for purposes of clin-ical management Optimally effective blue light ir-radiance levels have not yet been established but itis believed that levels between 30 and 70 mWcm2nm(as measured with the BiliBlanket Meter II) consti-tute intensive and effective PT for jaundiced new-borns [7] CriglerndashNajjar syndrome patients arefrequently treated with 100mWcm2nm [14] Thepresent data suggest that most of the tested win-dow-tinting films can effectively reduce sunlight UVand IR and offer a range of clinically significantattenuations of therapeutic blue lightData from the developing world suggest that

severe newborn jaundice and its progression to ker-nicterus is a leading cause of newborn deaths anddisabilities [15] Many of these same locales areunderserved clinical settings where electrical energyis not reliably available or where hospitals cannotafford the purchase of effective PT devices [3] Forexample in Nigeria there is a shortage of modern PTunits and only intermittent electric power is availableto run these devices [13 16] Thus in such localesdevelopment of inexpensive sunlight PT methodsmight alleviate both cost and health burdens If oneor more of the films tested in this study can be shownto be clinically safe and effective more patients mightreceive lifesaving PT treatment and avoid serious life-long health consequences (ie kernicterus) or deathClinical studies are in progress to confirm the safetyand efficacy of some of these films for sunlight PT[10] Therefore the use of window-tinting films mightbe a viable option for advancing the delivery of safeand effective PT to patients in these areasWe envision that the applicability of the films

to physical treatment facility configurations will be3-fold (Fig 2)

1 Portable individual treatment configurationwhere the patient receives PT in a bassinet or

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basket which is placed in sunlight filtered with arelatively small panel of film (60 90 cm)draped over a simple (wire) frame (Fig 2A)

2 Portable group or community treatment facility(Fig 2B) This type of configuration is presentlybeing studied in Nigeria where the mothersseated in comfortable seats can hold and bondwith their babies as well as nurse while interact-ing with other mothers and infants [10]

3 Permanent hospital-based treatment facility Thistype of facility is economically more expensiveand involves the building of a more or less per-manent PT facility with optimal orientation tothe daily and seasonal course of the sun [17] andmaximum and optimally placed overhead andvertical windows covered with carefully selected

window-tinting film attached to or affixed nextto the inside window surfaces Moreover itsnon-window surfaces should be painted white tomaximally reflect the incoming light throughoutthe room An advantage of a permanent structureis the ability to receive sunlight PT withoutdisruption of care during rain

A significant limitation of sunlight PT is that sun-light radiation levels can and do change hourly dailyand seasonally [3] It is therefore likely that sunlightPT will be most practical in medical facilities nearthe equator where sunlight is relatively plentifuland intense and where ambient air temperaturesare sufficiently high to keep the nearly nakedpatientrsquos body temperature within safe levels Itmay also be a sustainable alternative PT option forworldwide applicationFinally filtered sunlight PT could be a particularly

powerful therapeutic tool when it is combinedwith solar panel energy-capturingstorage systemsand efficient light-emitting diode-based PT devicesfor treatment when sufficient sunlight is not avail-able [18]

References

1 Cremer RJ Perryman PW Richards DH Influence oflight on the hyperbilirubinaemia of infants Lancet195811094ndash7

2 Dobbs RH Cremer RJ Phototherapy Arch Dis Child197550833ndash6

3 Salih FM Can sunlight replace phototherapy units inthe treatment of neonatal jaundice An in vitro studyPhotodermatol Photoimmunol Photomed 200117272ndash7

4 Stevenson DK Should sunlight be used to lower biliru-bin level Consult Prim Care 19913115ndash6

5 Harrison SL Buettner PG MacLennan R Why domothers still sun their infants J Paediatr ChildHealth 199935296ndash9

6 Hall JY Hartenberger C Garcia C et al Inappropriatetreatment of newborn jaundice by exposure to sunlight(heliotherapy) recommended by clinicians and families(Abstract) E-PAS2008 2008584429

7 American Academy of Pediatrics Clinical practiceguideline Management of hyperbilirubinemia in thenewborn infant 35 weeks of gestation Provisionalcommittee for quality improvement and subcommitteeon hyperbilirubinemia Pediatrics 2004114297ndash316

8 Vreman HJ Wong RJ Murdock JR et alStandardized bench method for evaluating the efficacyof phototherapy devices Acta Paediatr 200897308ndash16

9 Sunlight solar spectrum httpenwikipediaorgwikiSolar_spectrum

10 Slusher TM Vreman HJ Wong RJ et al Selectivelyfiltered sunlight phototherapy is safe and efficacious fortreatment of neonatal jaundice in Nigeria (Abstract)New Orleans LA American Academy of PediatricsNational Convention and Exhibition 2012

11 Pejaver RK Vishwanath J An audit of phototherapyunits Indian J Pediatr 200067883ndash4

FIG 2 Possible applications of sunlight filters(A) Photograph of a simple portable individual sun-light PT setup using a rugged wire canopy for sup-port of a 60 90-cm sheet of Air Blue 80 (for usewith an overcast sky) (B) An example of a low-costportable canopy (240 240-cm footprint 180 cm inheight) for group or communal sunlight PT con-structed from polyvinyl chloride (PVC) irrigationtubing The canopy frame was covered with a panel(240 360 cm) of Gila Titanium window-tinting filmfor use with clear-sky sunlight PT Note the shadowcast by the film which transmits 33 of the sunrsquostherapeutic blue light

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12 Cline BK Vreman HJ Faber K et al Phototherapydevice effectiveness in Nigeria Irradiance assessmentand potential for improvement J Trop Pediatr 2013May 10 [Epub ahead of print]

13 van Imhoff DE Hulzebos CV van der Heide M et alHigh variability and low irradiance of phototherapydevices in Dutch NICUs Arch Dis Child FetalNeonatal Ed 201398F112ndash6

14 Strauss KA Robinson DL Vreman HJ et alManagement of hyperbilirubinemia and prevention ofkernicterus in 20 patients with Crigler-Najjar diseaseEur J Pediatr 2006165306ndash19

15 Slusher TM Zipursky A Bhutani VK A global needfor affordable neonatal jaundice technologies SeminPerinatol 201135185ndash91

16 Owa JA Ogunlesi TA Why we are still doing so manyexchange blood transfusion for neonatal jaundice inNigeria World J Pediatr 2009551ndash5

17 Barss P Comfort K Ward design and neonatal jaun-dice in the tropics report of an epidemic Br Med J(Clin Res Ed) 1985291400ndash1

18 Vreman HJ Wong RJ Stevenson DK PhototherapyCurrent methods and future directions Semin Perinatol200428326ndash33

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