TheFeasibilityofImplementingImprovedStovestoMitigate

COPDinCommunitiesoftheGuatemalanHighlands

By

BrentGeraldKlapthor

Athesissubmittedinpartialsatisfactionofthe

requirementsforthedegreeof

MasterofScience

in

HealthandMedicalSciences

inthe

GraduateDivision

ofthe

UniversityofCalifornia,Berkeley

Committeeincharge:

ProfessorJohnBalmes,ChairProfessorSusanIvey

ProfessorMichaelBates

Fall2017

i

TABLEOFCONTENTS

PREFACE II

PART1:LITERATUREREVIEW 1

1:DefiningtheHouseholdAirPollutionProblemanditsImportance 1ABriefHistoryofFireandFuelUse 1TheSpectrumofFuelUseToday 3BiomassCooking&Woodsmoke:What’stheProblem? 7TheGlobalHealthBurdenofHAP 15BeyondtheTraditionalHealthImpacts 27

2:CookstovesasanInterventionforHouseholdAirPollution 28TheHistoryofCookstovePrograms 28TypesofImprovedStoves 30CookstovePrograms:BarrierstoSuccess 35DostovesreduceCOPD? 37

3:ConclusionandResearchQuestion 39

PART2:APILOTSTUDYFORTHEINTERVENTIONOFIMPROVEDCOOKSTOVESINTHEREDUCTIONOFCOPDINTHEHIGHLANDSOFGUATEMALA 40

Introduction 40

Methods 41

Results 50

Discussion 65

Bibliography 68

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PrefaceApproximately40%oftheworld’spopulation-roughly2.8billionpeople-cookswithbiomassfuels,suchaswoodorotherorganicmatter,onadailybasis.1Oftentimesthiscookingoccursonopenfiresindoorscreatinghomeswheretheparticulatematterisoften10timeswhatistypicallyfoundwithintheambientairofhigherincomecountries.Theresultinghouseholdairpollution(HAP)isamajorhealthconcerninlow-andmiddle-incomecountries(LMIC).Thishasbeenwell-documentedwithover200studiesthathaveassessedthelevelsofHAPinthepast30+years.2PartOneofthisthesiswillprovidealiteraturereviewonthedetailsandextentofthisproblemwithafocusonChronicObstructivePulmonaryDisease(COPD)andstoveinterventionsasawaytomitigateHAP.PartTwoofthisthesiswilldocumentoriginalresearchonapilotfeasibilitystudyinvestigatingtheefficacyofusinganimprovedcookstoveinterventiontodelaytheprogressionofCOPDinwomenexposedtobiomasssmoke.

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Part1:LiteratureReview

1:DefiningtheHouseholdAirPollutionProblemanditsImportance

ABriefHistoryofFireandFuelUseTheuseofcookingfiresdatesbacktotheoriginofourspecies.3Manyhavearguedthatcontrolofwoodfiresforcookingwas,infact,oneofthekeyfactorsinthetransformationofhumansasdistinctfromotherprimates,adevelopmentonparwiththedevelopmentoftoolsandblades.2,4Sincefirstusingfiretoharnesstheenergycontainedwithinwood,Halletal4suggestthat“thehistoryofhumanculturecanbeviewedastheprogressivedevelopmentofnewenergysourcesandtheirassociatedconversiontechnologies.”Thisnotioniscapturedintheconceptofafuelorenergyladderinwhichrisingincomesandincreaseddevelopmentleadtotheuseofcleanerfuelsprocessedandcombustedfartherfromtheirpointofuse(Figure1).2

Figure1–TheEnergyLadder.Fromsource5

Atthebottommostrungsofthisladderarebiomassfuelsources,theoldestandmostpollutingoffuelsources.Biomassfuelreferstoorganicmaterialderivedfromlivingorrecentlylivingorganisms.Wood,istheearliestusedofthesebiomassfuels,tracedbackto500,000yearsagowiththePekingman,inwhatisnowChina.6Traditionalbiomassusagecanalsoincludecharcoal,peat,andagriculturalwastes

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liketreeleaves,cropresidues,andanimaldung.2,3,7Thetermsolidfuelsorsolidbiofuelsisalsousedtorefertothesamegroupoffuelsbutwiththeadditionofcoalontopofthetraditionalbiomasssources.aDevelopmentofadvancesinenergysourcesandconversionhasincreasedthestandardsofliving,lifespan,andpopulationofhumans.4However,thosepopulationsatthebottomrungsoftheladdercontinuetoburnbiomassfuelswithintheirownhomesproducinghighlevelsofhouseholdairpollution(HAP),whichisthefocusofthisreview.Asthereaderwillcometoappreciate,movementuptheenergyladderisfarmorecomplicatedthanthepremisethatrisingincomesleadtocleanerfuelsinadirectandlinearfashion.Whileacleartrendexistsbetweenincomesandaccesstomodernfuels,risingincomedoesnotnecessarilyensureaprogressivetransitiontocleanerfuels(Figure2).

Figure2:Therelationshipbetweenhouseholdincomeandaccesstomodernfuelsources.FromSource8

aTraditionalbiomassisnottobeconfusedwithmodernbiofuels(e.g.biodieselorethanol),whichhavebeentoutedaspromisingrenewableenergysources.Inthiscase,biomassisbeingconvertedintoliquidbiofuelsforefficientcombustion.

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TheSpectrumofFuelUseTodayTherangeoftoday’senergysourcesvariesfromharvestedorscavengedbiomass(wood,dung,etc.)tomoreprocessedbiofuelssuchascharcoaltothecommercialfossilfuelsandelectricityusedintheUnitedStates.2Asof2010,theabsolutenumberofpeoplerelyingonsolidfuelshasremainedaround2.8billion.1Whiletheproportionoftheworld’shouseholdsusingsolidfuelshasdroppedfrom53%in1990to41%in2010,theInternationalEnergyAgency(IEA)projectionssuggesttheabsolutenumberofsolidfuel-usinghouseholdswillstayrelativelystablethrough2030.8,1AsFigure3showsbelow,thereislargeregionalvariationinthefractionofpopulationsrelyingonsolidfuels.IndiaandChinacombinedaccountforoverhalfofthispopulation(27%and25%,respectively)withsub-SaharanAfricarepresentinganadditional21%.2Inadditiontotheglobalfuelusevariation,povertyandrurallocationpredictsignificantuseofsolidfuelswithinagivencountry.2Asanexample,Figure4belowshowsthescaleofthisvariationwithinGuatemalaintermsofwoodfuelusageacrossthecountry.Asof2014,only36%ofGuatemala’spopulationhadaprimaryrelianceoncleanfuels,aratethatis2ndonlytoHaitiintheWesternHemisphere.9

Figure3:Proportionofpopulationwithprimaryrelianceoncleanfuels.FromWHOData,2014

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Figure4:Countrywideconsumptionofwoodfuel(leña)inGuatemala.Fromsource10

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AllofthesefactssurroundingpollutinghouseholdenergysourcesledtotheinclusionofHAPwithintheUnitedNation’sSustainableDevelopmentGoals(SDGs).ReleasedinSeptember2015,Goal7includes,“Ensureaccesstoaffordable,reliable,andmodernenergyforall”byatargetdateof2030.11Significanthurdlesstandinthewayofmakingthisgoalhappen.Figure5belowillustratestheprojectionsofKuhnetal.12through2025fortheshareofhouseholdsusingsolidfuel.ThehopeisforagreaterthanlinearreductioninprevalenceofhouseholdHAPexposure.Otherwisewellover10%oftheworld’spopulationwillcontinuetobeexposedtoHAPby2030,despitetheUN’sgoals.

Figure5:Forecastoftheprevalenceofhouseholdsoldfuelexposurethrough2025.Fromsource12

AsilverliningtotheprogresstowardscleanenergyforallisthatconnectednesstoelectricityhasactuallygrownfasterthanWorldEnergyOutlookprojectionsoverthelast10to15years.TheIEA’s2004WorldEnergyOutlookpredicteda10-yeargrowthforglobalaccesstoelectricityto78%by2014from73%in2004.13However,mostrecentestimatesshowedthat84%oftheworld’spopulationhadaccesstoelectricityin2014.13Inplaces,regionalgrowthwasevenhigher.Indiawentfromhaving44%electricityaccessin2002tomorethan80%in2004,farsurpassingprojectionsof60%.Analystscredittheroleofstrongpolicybythefederalandstategovernmentsforthissuccess.InAfrica,wherethepolicyenvironmentdidnotchangesignificantly,realitylargelymatchedthepessimisticprojectionsof2004.13

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However,asFigure6belowreveals,accesstocleancookingatagloballevelactuallyunderperformedtheIEA’salreadytemperedprojectionsfrom2004.Thecleancookingcommunitymaybeabletolearnfromthesuccessandfailuresofpolicydecisionsaroundelectricityaccess.Whileaccesstoelectricitycanbedrivenbygovernment-levelpolicydecision,ensuringcleancookingcanbeafarmorecomplicatedissue.7Movementawayfromtraditionalfuelsforhouseholdheatingandcooking(where90%ofbiomassfuelsareconsumed)isahousehold-leveldecision.Inruralareas–wherehalfofhumanitylives–household-levelenergyusedominatestotalfueldemand.7Thepredominantfactorbehindthisisthatbiomassfuelssourcessuchasfirewood,cropwaste,etc.areoftenfarlessexpensive–orevenfree–ascomparedtoelectricity,afarmoreexpensivesourceofenergy.

Figure6:Comparisonsof2004projectionsandto2014estimatesfortheWEO’s10-yearelectricityandcleancookingprojections.Fromsource13

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BiomassCooking&Woodsmoke:What’stheProblem?Asthissectionwillbegintoexplain,householdairpollutionfromtheburningofsolidfuelswithinthehomeisamajorhealthconcerninlow-andmiddle-income(LMIC)countries.Thishasbeenwell-documentedwithover200measurementstudiesthathaveassessedthelevelsofHAPinthepast30+years.2Thetendencytominimizeanytoxiceffectsfromsolidfuelsmokehasbeenacommonsentimentbecausetheuseofbiomassfuelsforcookingandwarmthhasalongandintimatehistorywithhumandevelopment.Theprimaryreasonthatsolidfuelsmokecanbetoxicisincompletecombustion,orsaidanotherway,poorcombustionefficiency.3,14ThishighlightswhyresearchershavereframedtheproblemasHAPfromitsoriginallabelasindoorairpollution,whichimpliesthatsimplyinstallingachimneyorventing,cansolvetheproblemcompletely.1However,inmanycasesambientpollutants–indoorsornot–areatlevelssufficienttobedamagingintheirownright.Harmisnotlimitedtothekitchensofsolidfuel-burninghomes.Thegreatestdangersareofcourseconcentratedwithinhomeswherehighlevelsofpollutionarebeingreleasedinlocationswherepeoplearenearlyalwayspresent.Heretheintakefractionmeasuringtheportionofpollutionreleased,whichisactuallyinhaledbypeople,isdramaticallyhigherthanoutdoorsources.7,15Whenthisiscombinedwiththefactthatexposuresareoftenfor3to7hoursdailyformanyyears,thehealtheffectscausedbythecumulativeexposuresarenotparticularlysurprising.14Sowhatexactlyarethesepollutantsinthecaseofwoodsmoke?

Figure7:Chemicalequationforthecompletecombustionofagenerichydrocarbon

Woodisprimarilycomposedofthehydrocarbonpolymerscelluloseandlignin(70and30%byweight,respectively).Otherbiomassfuelsalsoprimarilycontainthesecompoundsinadditiontosmallerorganiccompoundssuchasresins,waxes,andsugars.7Thecombustionefficiencyofbiomasscompoundsisoftenquitepoor(80%comparedto99%forgaseousfuels)meaningtheabovechemicalequationwithwaterandcarbondioxideassoleendproductsisoftenincomplete.Hundredsofpartiallyoxidizedorganiccompoundsandsideproductsresult,and6to20%offuelmaybeconvertedintotoxicsubstancesinatypicalsolidfuelstove.2,7Woodsmokehasbeenfoundtocontainupwardsof4,000solid,liquid,andgaseousconstituentswhichvariesdependingonthespecificfuelusedandcombustionconditions(stovetype,temperature,oxygenavailability,humidity,etc.)alongwithotherfactors.7Figure8belowsummarizestheseconstituents.Thetopthreemosthealthdamagingcontentsofwoodsmokeare:respirableparticulatematter,carbon

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monoxide(CO),andnitrogenoxides(NOx).Ofthese,particulatematterandcarbonmonoxidearethemosteasilyandcommonlymeasuredpollutants.2

Figure8:Pollutantsfromthecombustionofbiomassandfossilfuels.FromSource2

TheHealthEffectsofRespirableParticulateMatterinHAPRespirableparticulatematter(PM)isamajorhealthconcernandprobablythesinglemostdamagingconstituentofwoodsmoke.7Sincethe1993“HarvardSixCitiesStudy”,firstfoundthestrongassociationbetweenfineparticulateairpollutionandmortality,manyadditionalepidemiologicstudieshavefoundanassociationbetweenfineparticulatematterandbothacuteandchronicmortality.16,17Specifically,total,cardiovascular,andlungcancermortalitywereallpositivelycorrelatedwithambientPMconcentrationswhileitsreductionwasassociatedwithdecreasedmortalityrisk.17Thespecificpathogenicityofparticlesisdependentontheirsize,composition,origin,solubilityandabilitytoproducereactiveoxygenspecies(seeFigure10).18Particlessmallerthan10microns(μm)havebeenfoundtobeparticularlydamagingduetotheircapacitytoenterandlodgethemselveswithinthelowerrespiratorytractofthelung.3Airqualitystandardstypicallyfurtherdividetheseparticlesbetweenthefraction,whichissmallerthan10μm,PM10,andthose,whicharesmallerthan2.5μm(PM2.5).PM2.5,alsocommonlyreferredtoasfinePM,isconsideredtobemoredamagingastheirdiametersallowalveolardeposition.Ultra-fineparticles(withdiameterssmallerthan0.1μmarebelievedtoallowthediffusionofdamagingchemicalsacrossthelungs,intotheblood,andthroughout

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body.18PMcancauserespiratoryinflammationthatimpactslungfunction,exacerbatesasthma,andpromoteslungcancer.18However,thedamageisnotlimitedtotherespiratorysystem,asincreasedcardiovasculardiseaseandmortalityhavealsobeenidentified.19Potentialmechanismsofcardiovasculartoxicityinclude,a)spilloverofPM-inducedoxidativestressandinflammatoryresponsesinthelungsintothesystemiccirculationthatmightinduceendothelialdysfunctionandatherosclerosis;b)increasedriskofthrombosisduetothesameresponses;andc)lungnosioceptivesignalsthatimpaircardiacautonomicfunction.19,20

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Figure9:types,andsizedistributioninmicrons(μm),ofatmosphericparticulatematter.SourceWikipedia(from:GFDL,https://en.wikipedia.org/w/index.php?curid=48987967)

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TheUSEnvironmentalProtectionAgency(EPA)hasestablishedregulatorystandardsforambientPM2.5andPM10displayedbelowinFigure10(alongwithadditionalpollutants).Regulatorystandardsareseparatelyspecifiedfor24-handannualtimeperiods,abovewhichthegivenPMlevelsaredeemedtobedangerouslyhigh.

Figure10:AirpollutantstandardsfromtheUSEPA.FromSource21

In2000,expertsestablisheda7µg/m3annualmeanforPM2.5concentrationasthepointwherehealthrisksbegin.1UnsurprisinglythePMlevelsmeasuredduringtheuseofbiomasscookinginsidethehomearedramaticallyhigherthanboththisnumberandEPAstandards,atlevelsofupto100timeshigherandroutinely30timeshigherthanWHOairqualityguidelines.22–24Theaverageofparticulateexposurewithuseofindoorcookstovesisintherangeofmilligramspercubicmeter(notethe100foldchangeinunitsfromµgtomg)withpeaklevelsreachingover10–30mg/m3.3Ina2010studyofthewomenandchildrenin63Guatemalanhouseholdsusingacombinationofopenwoodfiresandwoodcookstoveswithchimneys,Northcrossetal.24measuredPM2.5concentrationsof900µg/m3overa48-haveragingtimewithinhomesusingopenfires,avaluethatisover128timesthepointwherehealthrisksarebelievedtobegin.Personalmonitoringofthemothersfoundvaluesof270and220µg/m3foropenfiresandchimneystoves,respectively.Concentrations

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measuredoninfantsandchildrenwere30to40%lower,butstillwellwithinthedangerouslevel.Figure11belowshowsanexamplecurvefordisease(ischemicheartdisease)bydoseforannualaveragePM2.5exposure.Theshapeofthiscurve,knownasanintegratedexposure-responsefunction,suggeststhatamongstthoseinthesolidfuelzoneofPM2.5exposure(attheplateauedportiontothefarrightofthecurve)drasticreductionsinPM2.5levelswouldbenecessarytomeaningfullyreducerelativerisk.25Forexample,evenhalvingannualaveragePM2.5from300to150µg/m3wouldhaveminimaleffectsonareductionoftherelativeriskofischemicheartdisease.

Figure11:RelativeriskofischemicheartdiseasebyaveragePM2.5concentration.FromSource2

WhilenosystematicworldwidemeasurementsforPMlevelsexist,Smithetal.2havepositedthatdatashowthefollowingmeanvaluesbasedonfueltype,

• dung:7,800±11,200µg/m3• charcoal:3,900±8,400µg/m3• wood:2,100±3,900µg/m3

PMvaluesinhomesusingkeroseneareapproximatelyanorderofmagnitudelower,whilethoseinhouseholdsusingexclusivelygasorelectricityareevenlower.

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TheHealthEffectsofCarbonMonoxideinHAPThetoxiceffectsofcarbonmonoxide(CO)havebeenwelldocumentedviaitsinteractionwithhemoproteinsandoxygenbindingwithintheblood.26Theformationofcarboxyhemoglobin(COHb)whenCOcombineswithhemoglobin(Hb)resultsinadecreasedabilitytobindoxygenleadingtodiminishedbloodoxygenlevelsandultimatelydecreasedoxygendeliverytoallofthebody’stissues.WithhighenoughCOconcentrationsthiswillleadtodeath.TheUSEPAsetslimitsforCOconcentrationsatamaximumof9ppmover8hourswhile35ppmisthemaximumallowableoutdoorconcentrationforaone-hourperiodinanyyear(https://www.epa.gov/criteria-air-pollutants/naaqs-table).TheUSCDCandOSHAdefine1,500ppmastheconcentrationwhichisimmediatelydangeroustolifeorhealth(from:https://www.cdc.gov/niosh/idlh/630080.html).InoneofmanypapersfromtheseminalRESPIREstudySmithetal.27foundbaselineaveragesofCOtobe10.2ppmwithinGuatemalankitchensusingopenfirecookingwhilepersonaldevicemonitoringfound48-hlevelstobe3.4ppmforboththemotherandchildren(seeFigure12).

Figure12:FromRESPIREdata,showingtrendsin48-hCOlevelsbygroupassignmentovertime(months).Dashedlinesrepresentpoint-wise95%confidenceintervals.Tickmarksabovex-axisindicateindividualmeasurementsattime(months)relativetotheintervention.Fromsource27.

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TheHealthEffectsofNitrogenOxidesinHAPNitrogenoxides(NOx)isaHAPconstituent,thoughmorelikelytobeproducedbythehighertemperaturesofLPGcombustionandmotorvehicles.28Thesenitrogenoxidescanbeahealthdetrimentinandofthemselves,aswellasbeingamajorcomponentofphotochemicalsmog.Bythemselves,thedamagingeffectsoccurviaoxidativedamageandfreeradicalization.29Inreviewingtheresultsofchallengestudiesofhealthysubjectsandsmokers,Bernsteinetal.30notedthatNO2exposure(2-6ppm)resultedinamildinflammatoryresponsecharacterizedbyincreasedneutrophilsanddecreasedlymphocytes.GiventherelativelowintensityofNO2-inducedairwayinflammationatambientlevels,theprimaryroleofthispollutantmaybeasasensitizingagentforinhaledallergensratherthanadirectactor.Whennitrogenoxidesandvolatileorganiccompoundsmixwithsunlightandheatintheatmosphereozonesmogresults(Figure13,below).31Whilethisisofgreaterconcerninurbancenters,HAPisnotexclusivelyaruralissue.ResearchonthehealtheffectsofNO2haslargelyoccurredinhigh-incomecountrieswheretherobustassociationshavebeenbetweenNO2exposureandasthmaoutcomes.32

Figure13:Thecomponentsandreactionsresultingintheproductionofphotochemicalsmog.Fromsource33

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TheGlobalHealthBurdenofHAPTheGlobalBurdenofDiseaseprojectisanenormousinternationaleffortseekingtoestimatethedeath,disease,andinjurybyage,sex,anddiseasefor21worldregions,whichhasoccurredin1990,2005,2010,andmostrecentlyin2015.WhilethemostrecentGBDresultshaveyettobefullyanalyzed,theGBD-2010wasusedfortheproductionofaseriesofComparativeRiskAssessments(CRAs)toestimatetheportionoftheburdenattributabletoeachofroughly60riskfactorsinthe21globalregions.Limetal.’s34comparativeriskassessmentfortheGBD-2010,attributed3.5to4milliondeathstodirectexposuretoHAP,identifyingitasthe3rdmostdangerousriskfactortohealth,behindonlyhighbloodpressureandtobaccosmoking,includingsecondhandsmoke(seeFigure14below).34,35

Figure14:Burdenofdiseaseattributableto20leadingriskfactorsin2010,expressedasapercentageofglobaldisability-adjustedlife-year.Fromsource34.

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BeforeIcontinue,abriefasideshouldbemaderegardingtheunitofthedisability-adjustedlifeyear(DALY)asameasureofdisease.Historically,simplemortalitydataor,whereavailable,prevalenceand/orincidenceofdiseasehadbeenusedasmeasuresofdiseaseburden.36Forthefirsttime,in1993,theworlddevelopmentreportutilizedDALYsasameasureofdiseaseburden.Itscalculationattemptstoquantifynotonlythenumberofliveslostfromdiseasebutalsothedurationoflifelostandlengthofdisabilityincurredforagivendiseasetodeterminethosediseaseswiththegreatestburdenontheglobalpopulation.Basedonastandardizedlifeexpectancy(82.5forfemalesand80formales),DALYsareametricthatquantifiesliveslostand/ordisabilityusingstandardizedratesofdisabilitydiscounting(seeFigure16).36Ina1994BulletinoftheWorldHealthOrganizationMurrayjustifiedthisdecisionstating(emphasismyown)36:"[T]heintendeduseofanindicatoroftheburdenofdiseaseiscriticaltoitsdesign.Atleastfourobjectivesareimportant.

•toaidinsettinghealthservice(bothcurativeandpreventive)priorities;•toaidinsettinghealthresearchpriorities;•toaidinidentifyingdisadvantagedgroupsandtargetingofhealthinterventions;•toprovideacomparablemeasureofoutputforintervention,programmeandsectorevaluationandplanning.

Noteveryoneappreciatestheethicaldimensionofhealthstatusindicators…Nevertheless,thefirsttwoobjectiveslistedformeasuringtheburdenofdiseasecouldinfluencetheallocationofresourcesamongindividuals,clearlyestablishinganethicaldimensiontotheconstructionofanindicatoroftheburdenofdisease.36”WhileDALYscontinuetobewidelyusedasthefundamentalunitofdiseaseburdeninglobalhealthandpolicy-makingdecisions,thepracticeisnotwithoutcontroversy.Chiefamongtheobjectionsisperhapstheuseofstandardizedlifeexpectanciesacrosscountries.Impliedinthisdecisionistheideathathealthinterventionsalonecoulderasethedifferenceinlifeexpectancybetweenhighandlow-incomenationswithadisregardforbroadersocialdeterminantsofhealthandwellbeing.Yet,thealternativeofusingdifferinglifeexpectanciesacrossnationsisarguablyevenmoreproblematicforobviousreasons.37

Figure15:ThedefinitionsfordisabilityweightinginthecalculationofDALYs.Fromsource36

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Withthatsaidandtheirvariousproblematicfeatures,DALYscontinuetobethedefactounitofmeasurefordiseaseburdeninglobalpublichealth,andasFigure14aboveillustrated,HAPisresponsiblefor4.5%ofthetotalDALYslostglobally.34Ina2014reviewarticleSmithetal.1,elaboratedonthecomparativeriskassessmentusedinGBD-2010,breakingoutthehealthburdenofHAPacrossage,sex,andregion,comparingHAPagainstotherenvironmentalriskfactors(seeFigure16).BasedonGBD-2010,HAPwasresponsiblefor119millionDALYsand3.89milliondeaths.OftheseDALYs,38.6%weresufferedbymen,28.0%bywomen,and33.7%bychildrenundertheageof5.IndescendingorderofimpactthetopsixdiseasesattributabletoHAPare:LowerRespiratoryInfections,Stroke,IschemicHeartDisease,COPD,LungCancer,andCataracts.IwilldiscusseachofthesebrieflywithmentionoftheroleofHAPinthepathogenesisofeachdisease.

Figure16:AdjustedtotalHAPburden-of-diseasefromtheanalysisofGBD-2010.Fromsource1

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AcuteLowerRespiratoryInfections(ALRI)AcuteLowerRespiratoryInfections(ALRI)arethemostsignificantcauseofglobalmortalityinchildrenundertheageof5.1Intermsofmortalityanddisability,childrenarethepopulationmostaffectedbyHAP-causedALRI.Forarespiratoryinfectiontooccur,thecellsofthebody’sinnateimmunesystemmustfirstbeevaded.Whenapathogenisdetected,“justright”immuneresponsemustoccurwhichissufficienttokillofftheinvaderbutwithoutgeneratingunnecessaryanddamaginginflammation.ThespecificsofhowHAPinterfereswiththismechanismarenotfullyunderstood,butitisbelievedthatPMinsomewayinterfereswiththebody’sabilitytoclearpotentialpathogens.38A2014whitepaperreviewonWHO’sIndoorAirQualityguidelinesregardingthestateoftheevidenceforthehealtheffectsofHAPpooledtheresultsof26studiestofindapooledORof1.73(95%CI=1.47,2.03)fortheeffectofHAPonALRI.39However,thelandmarkRESPIREstudyin2011remainstheonlyRCTshowingthatreducedexposuretoHAPcanreduceriskofearlychildhoodALRI.Itfoundthata50%reductioninCOexposurewassignificantlyassociatedwithareductioninphysician-diagnosedseverepneumonia(RR0.82,0.70–0.98).40Additionalreviewsincludeonein2011fromPoetal.41ontheeffectsofsolidbiomassfuelexposureonthehealthofruralwomenandchildrenwhichfoundthepooledORforALRItobe3.53(95%CI1.94to6.43)basedontheanalysisof25studies.Morerecentlyina2015pooledanalysisassessingtherelationshipbetweencookingpracticesandALRIinsub-SaharanAfrica(n=56,437),BuchnerandRehfuessfoundsignificantlyincreasedoddsofALRIinhomesusingkeroseneorsolidfuels(ORkerosene:1.64,CI:0.99,2.71;coalandcharcoal:1.54,CI:1.21,1.97;wood:1.20,CI:0.95,1.51).42ResearchonHAPandALRIhasgenerallyfocusedonchildren,butconsideringthattobaccosmokingisariskfactorforpulmonarytuberculosis,HAPmayalsoincreasetheriskoftuberculosis.35However,mostrecentlythe2017CookingandPneumoniaStudyofover10,000childreninMalawifailedtoshowareducedincidenceofpneumoniainaninterventiongroupgivenbiomass-fueledimprovedcookstovesversusacontrolgroupusingtraditionalopenfireswithanincidencerateratio(IRR)of1.01(95%CI0.91–1.13;p=0·80).43Thestudyinvestigatorshavenotyetreportedwhethertheimprovedstoveactuallyreducedexposurestobiomasssmoke.

CardiovascularDiseaseAdversecardiovascularevents(myocardialinfarction,stroke,etc.)areamajorhealthconcernregardingHAPexposure.Unfortunately,therearelittlepublisheddataontheassociationbetweenHAPexposureandcardiovasculardisease(CVD),largelybecauseHAPexposuretendstooccurinlow-resourcesettings.However,analysishasshownthatthereisaconsistent,nonlinearrelationshipbetweeninhaleddoseofPM2.5andcardiovasculardiseasemortalityoverseveralordersofmagnitudeofdosefromcigarettesmoking,secondhandsmoketobaccosmoke(SHS)exposure,andambientairpollution(seeFigure17;notelogscaleofthex-axis).44,45

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Figure17:Adjustedrelativerisks(95%confidenceintervals)ofcardiovascularandcardiopulmonarymortalityandestimateddoseofPM2.5acrossstudiesofoutdoorairpollution,secondhandsmoke(ETSabove),andactivecigarettesmoking.FromSource44,45

DuetothegapinevidencefortherelationshipbetweenHAPPM2.5andCVD,theHAP-basedCVDdiseaseburdenfortheGBD-20101reliedoninterpolationforthelevelsofPM2.5typicallymeasuredinHAPonanintegratedexposure-responsecurvethatincludesothercombustionsourcesofPM2.5.TheHAPPM2.5levelsfallbetweenthelevelsofPM2.5knownforcigarettesmokingandSHSexposure.BasedonthisandpreviousobservationalevidenceforoutdoorPM2.5,a2010publishedstatementfromtheAmericanHeartAssociation46indicatedthatshort-termPM2.5exposureincreasestheriskofCVD-relatedmortalitywhilelonger-termexposureoverthecourseofafewyearsincreasestheriskevenmore.ProposedmechanismsforhowthispathologymanifestsareshowninFigure18below.Moreconcretely,ina2012studyofover14,000ChineseadultsLeeetal.47foundthathouseholduseofsolidfuelswasassociatedwithincreasedriskofself-reportedcoronaryheartdisease(oddsratio[OR]:2.58,95%confidenceinterval[CI]:1.53to4.32).Additionally,comparingthehighesttertileofdurationofsolidfuelusewiththelowesttertilefoundasignificantassociationwithahistoryofstroke(OR:1.87,95%CI:1.03,3.38).

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Figure18:ProposedmechanismsfortherelationshipbetweenHAPandCVD.FromSource48

LungcancerTheWHO’sInternationalAgencyforResearchonCancer(IARC)firstevaluatedthecarcinogenicityofHAPin2006.49,50Coal-basedHAPwasclassifiedasaGroup1carcinogenindicatingdefinitecarcinogenicity.BiomassfuelusemeanwhileisGroup2(a)designatingitasaprobablecarcinogen,citingarelativelackofepidemiologicalevidence.1Smithetal.’sreview1,showedanoddsratioof1.18(1.03,1.35)forbiomassfueluseleadingtolungcancer.Ina2016studyof606lungcancercasesamongstnever-smokersinNepalwithmatchedcontrols,Raspantietal.50foundincreasedriskoflungcanceramongstthoseexposedtoHAP(OR:1.77,95%CI:1.00–3.14).

CataractsCataractsaretheleadingcauseofblindness,globally,withincreasedratesinthosecountrieswithhighsolidfueluse.1Ameta-analysisofsevenstudiesreportingontheriskofcataractwithexposuretosolidbiomassfuelinthehomeshowedapooledORof2.46(1.74,3.50).39

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ChronicObstructivePulmonaryDiseaseChronicObstructivePulmonaryDisease(COPD)isofsignificantandgrowingimportanceintermsofitsshareofglobalmortalityandmorbidity.Formerlyseenasprimarilyasmoking-relateddiseaseindevelopedcountries,by2020projectionsshowthatCOPDwillbethe3rdleadingcauseofglobalmortalityandmorbidity.1,51The2005NHANESIIIstudyfoundthatnearly25%ofcasesofCOPDintheUSareinnever-smokers,andthatnumbermaybeinexcessof70%inlow-incomenationswhereratesofsolidfuelusearehigh.14WhilesmokingremainsamajorriskfactorforthedevelopmentofCOPD,HAPhasreplaceditastheworld’stopriskfactorglobally.14,52ThegreatestshareofHAP-relatedprematuredeathscomesintheformofnonsmokingwomenwithCOPD.53ThepathogenesisofCOPDisaslowandprogressiveprocessduetochronicexposurestodamagingparticlesorgasesinageneticallysusceptiblesubsetofthepopulation.51,54Itisatypeofobstructivelungdiseasecharacterizedbychronicrespiratorysymptomsandairflowlimitationduetoairwayand/oralveolarabnormalitiesusuallycausedbysignificantexposuretonoxiousparticlesorgases.55Exposuretothesesubstancescauseschronicinflammationandoxidativestressleadingtoirreversibledamagewithtwoseparatebutoftenoverlappingphenotypes:emphysemaandchronicbronchitis.Chronicbronchitisischaracterizedbysmallairwaysobstructionduetoincreasedmucousproduction(seeFigure20).55,56Theemphysemaphenotypeoccursthroughthedestructionoflungparenchyma55,56HAP-derivedlungdiseasetendstobelesscommonlyassociatedwiththeemphysemaphenotypethantobaccosmoking.52

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Figure19:ThepathogenesisofchronicbronchitisprecedingthedevelopmentofCOPD.AdaptedfromSource57

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Whilealsoundertheheadingofobstructivelungdiseases,asthmaisdistinctfromCOPDinhavingreversiblebronchospasmafteradministrationofinhaledbronchodilatorwhiletypicalCOPDwillbelargelynon-reversible(seeFigure20)..

Figure20:Theoverlapofchronicobstructivelungdiseases.Fromsource56

Whileamoredetaileddiscussionofthemechanismsbehindthepro-inflammatorymechanismsofbiomasssmokeleadingtothedevelopmentofCOPDisbeyondthescopeofthisreview,Figure21belowfromSilvaetal.54providesasummary,whichmaybehelpfulinshowingsomeofthepro-inflammatorybiomarkersinvolved.

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Figure21:Thepro-inflammatorymechanismsofbiomasssmoke.Fromsource54

ThedevelopmentofsevereCOPDischaracterizedbyarapiddeclineinthelungs’forcedexpiratoryvolumeover1second(FEV1)throughthedestructionofterminalbronchiolesanddiminishedairways.58COPDprogressionoftenoccursinfitsandstartsratherthanonesmoothcurvebecausetherateofdeclineofFEV1isdictatedbytherateofdestructionofterminalbronchioles.58Ramirez-Venegasetal59showedthisintheir2014studyofacohortofCOPD-patientsover15years.

HAP&COPD,theStrengthofAssociationA2010systematicreviewbyKurmietal.51soughttoquantifythehealthriskandstrengthofassociationbetweenCOPDandtheuseofsolidfuels.Onthewhole,positiveassociationswerefoundbetweentheuseofsolidfuelsandCOPD(OR=2.80,95%CI1.85to4.0)andchronicbronchitis(OR=2.32,95%CI1.92to2.80).Ina2011systematicreviewandmeta-analysisPoetal.41focusedonrespiratorydiseaseduetosolidbiomassfuelexposureinruralwomenandchildren.ForchronicbronchitisinwomentheyfoundanORof2.52(95%CI1.88to3.38)whileforCOPDtheyfoundanORof2.40(95%CI1.47to3.93).A2010meta-analysisbyHuetal.60foundthatbiomasssmokeexposurewasclearlyidentifiedasariskfactorfordevelopingCOPDinbothwomen(OR,2.73;95%CI,2.28-3.28)andmen(OR,4.30;95%CI,1.85-10.01).

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However,afairbitofheterogeneitywasfoundacrossthestudiesincludedinthesesystematicreviewsandmeta-analyses.OnereasonnotedthatcouldhavebeenbehindthisisalackofstandardizationacrossthedefinitionsofCOPDand/orchronicbronchitis.51TheGlobalInitiativeforChronicObstructiveLungDisease(GOLD),AmericanThoracicSociety(ATS)andtheEuropeanRespiratorySociety(ERS)havealltriedtoresolvethisissuewithstandardizedcriteriaforCOPDdiagnosis.55,61Thishingesontheuseofspirometry,definingCOPDasapost-bronchodilatorFEV1/FVCratiooflessthan0.70.55,62However,thisdoesnotchangethefactthatspirometry,especiallywhendoneinthefieldinlow-resourcesettings,canbeachallengingdiagnostictest.Alternatively,symptom-baseddiagnosisofchronicbronchitisisalsousedbasedontheMedicalResearchCouncil(MRC)standardwhichdefinesitasahistoryofcoughwithphlegmproductionformorethanthreemonthsayearforatleasttwoconsecutiveyears.63However,heretooissuesarisewithrecallbiasandthelackofasimplediagnostictest.Ina2015,nonsystematicreviewAssadetal.52,describedCOPDoutcomessecondarytoHAPfromthecombustionofvarioustypesofindoorsolidfuel.Clinicalevidenceofthisassociationhasbeenwelldocumentednowforover30years,butitwasmentionedthatmoredataonexposure–responserelationshipsfromlongitudinalstudiesareneeded.Furthermore,datafromlow-incomecountriesremainlimited.52ThestudiesontheassociationbetweenHAPandCOPDhighlightedbyAssadetal.52included,

• A2006studybyRegaladoetal.64fromruralMexicofoundthatbiomassusewasassociatedwitha4%decreaseinFEV1/FVCratio.Additionally,anincreaseinkitchenparticulateconcentrationof1,000mg/m3wasassociatedwitha2%reductioninFEV1.64

• A2008prevalencestudyofCOPDacrossfivecitiesand5,500ColombianadultsperformedbyCaballeroetal.65foundanORof1.5(95%CI,1.22–1.86)fortheassociationbetween10ormoreyearsofbiomassstoveuseandspirometry-diagnosedCOPD.

• Amorerecent2013studybyKurmietal.66of1,600youngadultsinNepalfoundanORof2.1fortheassociationbetweenGOLDcriteriaCOPDandexposureto(unquantified)biomasssmoke.66

• A2011studyof900womeninIndiafound1.4foldincreaseinCOPDprevalenceinbiomassvs.cleanfuelusers.67

• InBrazil,across-sectionalstudyfoundtheprevalenceofCOPDdefinedbyGOLDcriteriainbiomasssmoke-exposednonsmokerstobe20%,aratethatwassimilartotheprevalenceinsmokerswhocookwithcleanfuel.68

• Asmentioned,longitudinalstudiesoftheimpactofbiomasssmokeexposureonthedevelopmentofCOPDarelacking,butRamirez-Venegasetal69lookedattheassociationbetweenCOPDassociatedwithbiomasssmokeexposure

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andmortality.Theirsurvivalanalysisover7yearsoffollow-upfoundwomenwithCOPDduetobiomasssmokehadmortalityratessimilartomenwithCOPDduetotobaccosmoking.

• A2015studybyJaganathetal.70acrossadiversecross-sectionofPeruviancommunitiesfoundthatdailybiomassfueluseforcookingamongwomeninruralcommunitieswasassociatedwithCOPDwithaprevalenceratioof2.22(95%CI1.02–4.81).Thepopulationattributablerisk(PAR)ofCOPDduetodailyexposuretobiomassfuelsmokewas55%.

Returningtotheabovementioned2010systematicreviewbyKurmietal.51,Figure22belowshowsaforestplotsummarizingtheeffectsizeoftheassociationbetweenGOLD-standarddiagnosedCOPDandvariousbiomassfuelexposures.Notethegradientofeffectsacrossfueltypeswithwoodsmokebeingassociatedwiththelargesteffect.

Figure22:ForestplotshowingtheeffectsizeofCOPDduetoexposuretofueltypes(forstudiesbasedonlungfunctiondiagnosis).N/A=notavailable.Fromsource51

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TheExposure-ResponseRelationshipofHAP&COPDAnadditionalgapintheresearchregardingHAPandCOPDisthecharacterizationofanexposure-responserelationship.52Suchacharacterizationisvitaltodeterminingwhenandhowaninterventioncouldbeimplemented,andtowhatextentsuchaninterventioncouldpreventtheprogression–orevenreverse–theeffectsofHAP.Whenbiomasssmokeexposurehasbeenquantifiedbyhour-years,aassociationhasbeenfoundwithFEV1.68,71Thissuggestsagreateramountofexposuretobiomasssmokeisassociatedwithgreaterrespiratoryimpairment.AnotherstudylookedattheindividualcomponentsofthismetrictoshowthattheORforCOPDisgreaterinsubjectswitheitheragreaternumberofyearsofexposureormoreheavyexposureintheformofhoursperday.72

BeyondtheTraditionalHealthImpactsWhilelargelybeyondthescopeofthisreview,therearealsonumerousotherimpactsofHAP,whichmayaffecthealthmorebroadly.

RiskofPhysicalandSexualViolenceGirlsandwomenarenearlyalwaysresponsibleforthecollectionoffirewoodandseveralstudieshaveshownthisresponsibilitymayexposethemtotheadditionalrisksofphysicaland/orsexualviolencewhilewalkingmilesfromhome.3,73,74Thiscanbeparticularlyproblematicinrefugeecrisissituations.StudieshaveshownincreasedincidencesofviolenceandrapeofwomenduringfirewoodcollectioninAfricanrefugeecampsacrossChad,Uganda,andSouthSudan.75

TimeBurdenThetimeburdenoffuel-collectionandcookingcanbeamajorsourceofgenderinequalityinthesecommunitiesasgirlsaremorelikelytodropoutofschoolatearlieragesthantheirmalepeerstohelpwiththelabor-intensivecookingprocess.73ClimateChangeTheemissionsofHAPareknowncontributorstoglobalwarming.3Infact,theblackcarbonemittedfromopenfiresisperhapsthe2ndleadingcauseofatmosphericcarbon.76Additionally,therecentrecognitionofcleanercookingasamajorleverinreducinggreenhousegasemissionsfromlowerincomecountrieshasresultedinarenewedeffortonthepartofdevelopmentagenciestoscaleupcleancookingprograms.77

DeforestationOntopofclimatechange,theconsumptionofwoodleadstodeforestationandtheassociatedcascadeofsocial,environmental,andclimateconsequencestocomewithit.3

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2:CookstovesasanInterventionforHouseholdAirPollution

TheHistoryofCookstoveProgramsAsof2014,therewereatleast160improvedcookstoveprogramsgloballywhichhasproducedavastandsomewhatdisorganizedbodyofliterature.6Eventhebasicterm“improvedcookstove”isusednonspecificallyintheliteratureandwidelytoutedbypromoterswithlittleconsensusonwhatisthefocusoftheimprovement.78Thishascreated,attimes,duelingprioritiesonwhichfactorsofimprovementshouldbeoffocus:fuel-efficiency,HAP,cost-savings,etc.79Intoday’sliteratureimprovedcookstove(ICS)simplyreferstobiomass-burningcookstoveswhichhavesoughttoimproveontraditionaldesigntoimprovecookingefficiencyandreduceHAP.80Though,itshouldbenotedthatICSsdonotnecessarilyreduceemissionstomeetWHOairqualityguidelines.81Oftenseenastheworld’sleadingexpertoncookstoveprograms,researcherKirkSmithwroteonthe“DialecticsofImprovedStoves”in198979presentingthehistoryofimprovingstovetechnologywithhumandevelopment.WhilehumanshadalwaysbeenimprovingstovetechnologiesSmithcitesthe20thcenturyasbeinguniquewiththefirstof“self-conscious”stoveimprovementmovements.IndiaservedasthebirthplaceofICSprogramswithfuel-andcost-savingsbeingtheprimarydriver.ManyoftheseprogramsoriginsgrewoutoftheGandhieraoftheearly20thcentury.HAPwasformallyidentifiedasacauseofhealthproblemsinIndiaasearlyasthe1950s,andbythe1970sformalscientificresearchandengineeringstovedesignhadturnedattentiontoICSdevelopment.6Throughthistime,anerawhichSmithhastermedthe“energyperiod,”thefocusonICSdevelopmentwasdrivenby“aglobalinterestinappropriatetechnology,oilshortages,anddeforestation.79”Asmentioned,thiscreatedtheduelingprioritiesoffuel-efficiencyvs.smokelessstovedesign.Infact,evenupuntiltheturnofthemillenniumICSdesignprioritizedenergyefficiencyoverHAPreduction.78InadditiontoIndia,ICSswereintroducedtotheSahelregionofAfricainthewakeofanextremedroughttotheregion.6CentralAmericaalsosawitsfirstICSprograminthistimeaftertheGuatemalanearthquakeof1976.82Smithcalledtheemergingphaseofthe1980sthe“Phoenixphase”whereexperiencesfromearlystoveprogramscouldinformthereemergenceofsuccessfulprogramswithafocusonHAP.79Issuescloselyassociatedwithtraditionalstovesuchas“women-empowerment,enhancementoflivelihoods,andnaturalresourceconservation”gainedtractionforthefirsttime.6Thelate1980sintothe1990susheredinathirdphaseofcookstovedevelopmentwithgovernment-backedprogramsinIndiaandChinabeingtwoofthemajorevents:6,83

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• From1982to1992theChineseNationalImprovedStoveProgram(NISP)becamethelargestandmostsuccessfulcookstoveprograminhistory,introducingapproximately129millionnewstoveswhilefocusingonenergyefficiencythroughtheuseofchimney-basedcookstoves.78,83,84Evenasgovernmentfundingfortheprogramdriedup,privatecompaniesemerged,continuingtoproduceindoorpollution-reducingstoves.83

• FollowingtheleadofChina,theIndianMinistryforNewandRenewable

Energylaunchedanambitiousnationalcookstoveprogramin1985thatperformedwellbelowexpectations.83Itwasconcludedthattheruralpopulationbeingtargetedhadhigherpriorityneedsthanthegovernment’sconcernfordeforestation.Additionallyrecognizedinfluenceofsocio-culturalfactorshighlightedtheneedforimprovedassessmentofcookstoveprogramswithsurveysandevaluationofculturalbarriers.

However,withhindsight,Barnesetal.85concludedthatthestoveprogramsuptothispointwere,onthewhole,notassuccessfulastheycouldhavebeenforanumberofreasons.Amajorissuewas–andIwouldarguecontinuestobe–alackofcoordinationbetweentheinnumerableICSprogramsinexistence.AdditionallyitwasemphasizedthatallprogramsshouldunderstandthediscreteroleofICSprogramsinfacilitatingaclearenergytransition.Astheysaid,“Theimprovedbiomassstoveshouldbeconsideredanewsteppingstonebetweenthetraditionalbiomassstovesusedbyruralandurbanpoorfamiliesandthemodernfuelsandappliancesmainlyusedbyurban,betteroffhouseholds.”TheunfortunaterealityisthatafulltransitionuptheenergyladdertocompleteelectrificationorcleanfuelusesuchasLPGmaybedecadesawayformuchoftheworld’spoor(seeFigure23,below).3ICSprogramsshouldaimtoalleviatethehealthburdenofHAPwhilethispopulationcontinuestorelyonbiomassfuels.

Figure23:PercentageofpeoplehavingaccesstoICSinsomelow-andmiddle-incomecountriesasof2009.Fromsource6

Inthenewmillennium,thehealthimpactsofHAPhavebeenmorefullyrecognizedashasbeenthoroughlydocumentedabove.ThishassetthestageforenormousforeignaidinvolvementonthepartoftheUnitedStates.In2002,theU.S.EPA

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launchedthe“PartnershipforCleanIndoorAir.”ThiswasfollowedbytheU.S.DepartmentofStateandEPA’sco-launchof“TheGlobalAllianceforCleanCookstoves”inconjunctionwiththeUnitedNationsFoundationin2010.TheAlliance’sgoalcallsfor100millionhomestoadoptcleanandefficientstovesandfuelsby2020.Ithassoughttounitemorethan12USgovernmentalagenciesandover600partnersinthecreationofglobalmarketforcleanercookstoves.6

TypesofImprovedStovesTodatecountlessICSdesignshavebeenproduced,avarietyofwhicharepicturedbelowinFigure24.

Figure24:Cookstovesfromaroundtheworld.Fromsource35

Becauseofthegreatvarietyofstovedesigns,manyschemasexistforwaysinwhichtocompareandcontrastthembasedonconstructionmaterial,size,fueltype,combustion,etc.80Themostrecentadvancesincookstovetechnologiesmakesupanewclassofstovesknownasadvancedbiomasscookstoves(ABS).6,80OftheseABSstovestherearetwoprimarycategories:RocketandGasifierstoves.80Gasifierstovesrelyontwo-stagecombustion,meaningthewood(orotherfuelmaterial)isfirstheatedtothepointofthereleaseofvolatilegases.6,86Thesegasesarethenburned.Gasifierstoveshaveshowntoproduceadrasticreductioninemissionsascomparedtotypicalsingle-stagecombustionsystemwherethegasesmaybereleasedupthechimneybeforebeingfullycombusted.Gasifierstovesare

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availablewithorwithouttheuseofafansystemtoassistairflow.6Thetwomostwell-knownGasifiertypestovesarecurrentlythe“Oorja”ofIndiaandthe“Philips”stoves(showinFigure25below).6,86

Figure25:SchematicofaPhilipsforceddrafttypecookstovewithabattery-operatedfan.FromSource87

Theso-called“Rocketstoves”applythedesignprinciplesdevelopedbyDr.LarryWiniarskiin1980intoacharacteristicL-shapeddesign(seeFigure26below).87,88Asaclass,RocketStoveshaveprovenreliableandattimeshaveperformedevenbetterthanGasifierstoves.6Stilletal.89summarizedacoupleofthekeydesignprinciplesas,

• theuseofaninsulatedandtremendouslyhotcombustionchamber(over1,100F)toimprovethemixingoffuelandflameresultinginimprovedcombustionefficiency,aswellas

• aninsulatedchimneycreatingaverystrongnaturaldraft

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Figure26:ASchematicoftheRocketStoveDesign.Fromsource83

Ina2010publicationbyMacCartyetal.81thefueluseandemissionsperformanceof50differentcookstoveswereinvestigated.Asaclass,theRocket-typestovesreducedfuelconsumptionby33%,COemissionsby75%,andPMemissionsby46%ascomparedtothethree-stonefirecookstove.OneofthemostsuccessfullyiterationsoftherocketstovedesignistheONILcookstoveproducebyHELPSInternational,aninternationalnot-for-profitfoundedtoprovidemedicalcareforthepoorinCentralAmerica.90TheONILstovewasdesignedtomeettheneedsofitsusersthroughinterviewswith60womenoftheGuatemalanhighlands(showninFigure27below).91TheONILcookstoveshavenowbeendisseminatedinGuatemala,Honduras,andMexicoatacostofabout$125perstove.90,92Intheir2014reviewofcookstoveperformancesKshirsagaretal.6foundtheONILstovetobehigh-performing,low-polluting,andverysafetooperate.

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Figure27:OnilStove.Fromsource90

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Anadditionalplancha,rocket-stovedesignistheEcostufawhichisproducedinMexicoatacostofabout$200(seeFigure28below).92,93.SeveralthousandEcostufashavebeendistributedacrossseveralMexicanstates.93

Figure28:Ecostufa.Source:Author'spersonalphoto

Liquefiedpetroleumgas(LPG)Aboveimprovedbiomasscookstovesontheenergyladderarethe“modernfuels,”generallyconsideredtoincludeliquefiedpetroleumgas(LPG),naturalgas,andelectricity.94Ofthese,LPGstoveshavebeenmostthoroughlyinvestigatedasatoolforHAP-reductioninlow-incomecountries.Thusfar,oftheimprovedbiomasscookstoveoptions,nonecanreachthecleanlinessofLPG.Whilecontinueddevelopmentoffan-assistedgasifierstovesmaygetclosetoLPG-likeHAPperformance,eventhebestofimprovedbiomassstovesremainatleastanorderofmagnitudemorepollutingthanLPG.95Invirtuallyallcases,levelsofrespirableparticulatematterfollowthefollowingtrendacrossfuelsources96:

Dung>Cropresidue>Wood>Charcoal>Kerosene>LPG>ElectricityInastudyofmorethan400households,thepersonalexposuretorespirableparticulatematter(PM10)wasfoundtobeabout70μg/m3forhouseholdsusingLPGorkerosenecomparedto2000μg/m3forthoseusingbiomassasfuel.96TheevidenceisclearthatLPGhasunrivaledairqualitybenefitsascomparedtobiomassfuels.95,97Inthelongterm,itisgenerallythoughtthatmodernfuelswillbetheanswertotheHAPproblem.TheIEAhasidentifiedthiswithits“UniversalModernEnergyAccess”goalfor2030.13However,thecurrentrealityseemsthatLPGisunlikelytobeanear-

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termfixasitremainunaffordableforthepoorofmuchoftheworld.87Fueldistributionisalsoasignificanthurdlefortheruralpoor.95BrazilhasbeenacasestudyofsuccesswiththepromotionofLPG.A30-yearprogramtherebroughtsignificantpenetrationofLPGandkerosenethroughsubsidiesonthesemodernfuels.97However,theappropriateroleoffuelsubsidiesinencouragingfuelswitchingisadebatedtopicindevelopmentaleconomics.97,98IthasbeenarguedthatpublicsubsidiesofLPGfueluseinaplacelikeGuatemalawouldberegressive.BysubsidizingcurrentLPGfuelconsumption,fundsareallocatedawayfromtheexpansionofmodernenergyaccesstothosewhoarethemostrural,themostpoor,andleastlikelytohavemodernenergyaccess.98Anadditional–andoftenunderestimatedaspect–ofLPGfueluptakeistheprofileofagivenhousehold’scookingneeds.Forexample,inGuatemalaamajorcomponentoffoodpreparationisthecookingofnixtamal(tortilladough),whichrequirescorntobeslowlycookedinlargepotsoverseveralhours.10Preferenceandtraditionhasoftenmadebiomassthefuelofchoiceforthistypeofcooking,leavingLPGtofillthenicheofbreakfastandfoodre-heatingfuel.10

CookstovePrograms:BarrierstoSuccessAsmentionedabovewiththediscussionofincompletefuelswitchingwithregardstoLPG,so-called“stovestacking”hasbeenamajorbarriertosuccessintheabilityofICSandLPGstoveprogramstoreduceHAPasmuchashoped.Inconsideringtherealityoffuelstacking,themodelofanenergyladderwithsimplelinearprogressionbreaksdownbecauseamoveuptoanewfuelisnotalwaysaccompaniedbyamoveawayfromthegreaterHAP-producingfuelsofthelowerrungs.98Householdstendtouseeverycombinationofstovesforthetasksthatbestfulfilltheirneeds(seeFigure29below).99

Figure29:Aschematicrepresentationofapossiblestove-stackingscenario.Atleftisahouseholdwithasinglefuelcookingpractice.Afteracquiringnewstoves,theoriginalcookingsystemtransformsintoanewsystemofthreestovesandtwofuels(right).Thenewstovesfindanicheinthecookingpracticesofmakingtortillasandreheatingfood,whiletheoldoneisstillusedtoboilwater.Fromsource78

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Heltberg94,98hasstudiedthisfuelstackingphenomenonthroughoutthedevelopingworldandspecificallywithinGuatemalafromabehavioraleconomicspointofview.Figure30belowshowsthatinGuatemalatherelationshipbetweenthenumberofdifferentfuelsusedbyahouseholdandwelfareissomewhatU-shaped.Asincomerises,sotoodoesthenumberofdifferentcookingfuelstypesused.Asincomerisesfurther,especiallyinurbanareas,thereisatransitionbacktowardsasingle(modern)fuel.Asaresultofthisphenomenon,firewoodandLPGisacommonfuelcombinationinGuatemalawhereitisusedby26%and16%ofurbanandruralhouseholds,respectively.94

Figure30:TherelationshipbetweentheaveragenumberoffuelsourcesutilizedbyruralandurbanGuatemalanhouseholdsandpercapita,perdayfuelexpenditures.FromSource98

Acommonshortcomingofstoveprogramsisthatrelativelylittleefforthasbeendevotedtounderstandinghowwellstovesaretrulyadoptedandiftheiruseissustainedovertime.78However,duetothefrequencyofthestove-stackingphenomenon,quantitativeassessmentofstoveusagehasbecomeanecessityofhighqualitystoveprograms.Directobservationofcookingactivitieshasbeenconsideredthegoldstandardbutmaychangeparticipantbehaviorandisademandinguseofresources.99SimpletemperaturesensorsknownasStoveUseMonitors(SUMs)havelargelyreplacedquestionnaires,diaries,surveys,interviewsandobservationsasawaytoeasilyquantifyadoptionandfuelstacking.99

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Inadditiontothequestionofwhetherstovesarebeingusedasexpected,thereisthequestionofwhetherthefieldperformanceofanICSmatcheslaboratorytestsofthestove.A2015reviewfromThomasetal.100soughttodothisandfoundquiteheterogeneousresults.Amongstthoseincludedinthereview,thestudywiththelongestfollow-uptime(4years)failedtoshowHAPreductionbeyondoneyear.In2017theMalawi-basedCAPSstudybecamethelargesttrialofacookstoveinterventiononhealthoutcomesinhistorybutfailedtofindaneffectontheprimaryoutcome(childhoodpneumoniaincidence),anoutcomethatseemstobeattributabletostovesthatwerenotasreliableoreffectiveaslaboratorytestssuggested,aswellastofairlywidespreadstacking.43,101AkeyconclusionofWHO’s2014indoorairqualityguidelines(IAQG)wasthatwhilestoveprogramsmayproducenotablerelativereductionsofHAPby50-80%,inmanycasestheabsolutePMlevelsremainwellabovetheWHOinterimtarget(PM10of35µg/m3annualmean)whereitisestimatedthatsignificanthealthimprovementswouldresult.102,103Basedonthesefindings,ithasbeensuggestedthatperhapsexclusive,community-wideuseofcleanfuelsistheonlywaytoreachthePM2.5guidelineandmaximizehealthbenefits.102,104

DostovesreduceCOPD?Relativelyfewstudieshaveinvestigatedthelong-termeffectsofdecreasedHAPthroughcookstovesprogramsonlungfunctionandobstructivelungdisease.Ina2005studyinXuanwei,China,Chapmanetal.105comparedtheincidenceofself-reportedCOPDbetweenpeoplewhoinstalledchimneysagainstthosewhousedonlyunventedstovesinaretrospectivecohortstudy.TheriskofCOPDdecreasedwithlengthoftimesinceinstallation(seeFigure31below).

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Figure31:Productlimitsurvivalplotsshowingprobabilityofnothavingchronicobstructivepulmonarydisease(COPD)byageinyearsinwomenaccordingtowhethertheyhadachimney(redsolidline)ordidnot(bluedashedline),Xuanwei,China,1976-92.Fromsource105

Zhouetal.106performeda9-yearprospectivecohortstudyontheeffectsofinstallingimprovedbiomassstovesand/orexhauststoimprovekitchenventilation.Participantschoseforthemselveswhichinterventiontheywantedtoadopt(biogasfuel,akitchenventilationfan,both,orneither).Theuseofthecleanerbiogas(methane)fuelwasassociatedwithareduceddeclineinFEV1by12ml/y(95%CI,4to20ml/y)comparedtothosewhotookupneitherintervention.106Anexposure-responserelationshipwasalsoseenasthelongerdurationofcleanfuelusewasassociatedwithaslowerdeclineinFEV1,aswasthecombineduseofbiogasandthekitchenfan.Inacookstoveinterventioninvolvingover500Mexicanwomen,Romieuetal.107(2009)failedtoobserveadifferenceinsymptomsorlungfunctionbetweentheinterventionandcontrolgroupsattributedtolowadherencetouseoftheimprovedstove.However,self-reporteduseoftheimprovedstovewassignificantlyassociatedwithareductioninbothsmoke-relatedsymptomsandFEV1declineover1yearoffollow-up.AsapartoftheRESPIREstudy,Smith-Sivertsenetal.108(2009)alsoreportedthattheimprovedchimneystovewassignificantlyassociatedwithareducedriskofrespiratorysymptomsinanintention-to-treatanalysis,butnosignificanteffectonlungfunctionwasobserved.However,inalaterexposure-responseanalysisofthesamestudyparticipants,reducedexposuretoCOwasassociatedwithaslowerdeclineinlungfunction.109

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3:ConclusionsandResearchQuestionsUltimatelythequestionsof,

• Howcleandoesacookstovehavetobetoreduceand/oreliminateHAP-associateddisease?

• And,whathouseholdenergytechnologywillgetusthere?remainincompletelyanswered.110Imbeddedwithinthefirstquestionistheelucidationoftheexposure-responseforHAPandobstructivelungdisease(chronicbronchitisandCOPD).AmorecompleteunderstandingofthisphenomenonisnecessarytounderstandwhethertheprogressionofCOPDduetoHAPmaybestopped–orevenreversed.Thesearethebeginningstepstounderstandinghowthemosteffectivecookstoveinterventionshouldbedesigned.Perhapsaphysicianinalow-incomecountrywillonedaybeabletodefinitively“prescribe”new,cleanerstovestoCOPDpatients.

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Part2:APilotStudyfortheInterventionofImprovedCookStovesintheReductionofCOPDintheHighlandsofGuatemala

IntroductionApproximately40%oftheworld’spopulation-roughly2.8billionpeople-cookswithbiomassfuels,suchaswoodorotherorganicmatter,onadailybasis.1Oftentimesthiscookingoccursonopenfiresindoorscreatinghomeswheretheparticulatematterisoften10timeswhatistypicallyfoundwithintheambientairofhigherincomecountries.Theresultinghouseholdairpollution(HAP)isamajorhealthconcerninlow-andmiddle-incomecountries(LMIC).Thishasbeenwell-documentedwithover200studiesthathaveassessedthelevelsofHAPinthepast30+years.2IntheGlobalBurdenofDisease’sComparativeRiskAssessment,4.5%ofthedisabilityadjustedlife-yearslostareattributedtoHAPduetoacutelowerrespiratoryinfectionsinchildrenandchronicobstructivepulmonarydisease(COPD),lungcancer,cataracts,andcardiovasculardiseaseinadults.2,34COPD,specifically,isofsignificantandgrowingimportanceintermsofitsshareofglobalmortalityandmorbidity.Formerlyseenasprimarilyasmoking-relateddiseaseindevelopedcountries,projectionsshowthatby2020COPDwillbethe3rdleadingcauseofglobalmortalityandmorbidity.1,51Womentendtohavethehighestlevelsofbiomasssmokeexposure,andnumerousepidemiologicstudiesofwomenindevelopingcountrieshaveshownstrongassociationsbetweentheuseofbiomasscookingfuelandchronicbronchitisand/orCOPD.24,72,111–115Improvedstovesincludebothdesignswhichusechimneysystemstoremovesmokefromthehomeandliquidpetroleumgas(LPG)stoves,whichgiveoffdramaticallylessparticulatematterintotheair.Specifically,therehaveyettobeanylongitudinalstudiesallowingforthequantificationoftheeffectofbiomasssmokeexposuresontherateofdeclineinlungfunction.Norhavetherebeenstudiesontheefficacyofdifferentimprovedstovedesignstoslowtherateofdeclineinlungfunctionduetobiomasssmoke.52,53Toobtainpreliminarydatathatcouldserveasastepping-stonetowardsamuchlargerstudy,wecarriedoutapilotfeasibilitystudyofstoveinterventionsinacohortofwomenwithchronicobstructivepulmonarydisease(COPD)orchronicbronchitisandexposuretoHAPfromtheuseofbiomassfuelsintheruralGuatemalanhighlands.

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Methods

EthicalConsiderationsAllresearchdiscussedhereinwasapprovedbytheResearchEthicsCommitteesattheUniversitiesofCalifornia-SanFrancisco,California-Berkeley,anddeGuatemalaValle.

OverviewThisisastudyofacohortofwomenwithCOPDand/orchronicbronchitisandexposuretoHAPfromtheuseofbiomassfuelsfollowedprospectivelyforsixmonths.ThestudywasconductedintheDepartmentofQuetzaltenango,Guatemalawhere40participantswererandomizedintooneoffourstoveinterventionstrategiesintendedtoreduceHAPexposure:(1)anEcostufa,improvedwood-burningstovewithchimneydesign,(2)aHelps-Onil,improvedwood-burningstovewithchimneydesign,(3)aliquefiedpetroleumgas(LPG)Supercocinastove,and(4)anidenticalLPGstovewithasubsidyfor50%ofhouseholdpropaneuse(seeFigure32below).

Figure32:Thefourstovegroups

Stove Groups 1. Ecostufa

2. Onil

3. LPG

4. LPG w/ Subsidy

42

Thegoalofthispilotstudywastoevaluatethefeasibilityofcarryingoutalargerstoveinterventionstudytoinvestigatewhetheranimprovedstoveinterventioncanslow–orevenreverse–theprogressionofCOPDinwomenexposedtobiomasssmoke.Thisgoalgeneratesthreemainresearchquestions:

1. Isitfeasibletoconductalarge-scalestudytotesttheeffectivenessofastoveinterventiontodelaytheprogressionofCOPDinwomenexposedtobiomasssmoke?

2. WhichofthefourinterventionsevaluatedinthispilotstudyhasthegreatesteffectivenessinreducingexposuretoHAP?

3. Whichofthefourinterventionsevaluatedinthispilotstudyhasthegreatestacceptabilityforuse?

Thestudyareaincludes10municipalitiesaroundthecityofQuetzaltenangointhewesternhighlandsofGuatemala(Almolonga,Cantel,ConcepciónChiquirichapa,LaEsperanza,Olintepeque,Salcajá,SanJuanOstuncalco,SanMartínSacatepequez,SanMateo,Zunil).Illiteracyiscommoninthisregion,especiallyamongstwomen.MamisthefirstlanguageofmostpeoplewhileSpanishisspokenatvariablelevelsoffluencyfromalmostnotatalltofullyfluent.Priorworkhereshowedboththatwomenspendanaverageof5hoursdailyinaroomwithalitfireandthattobaccosmokinglevelsareverylowamongMamwomen.116,117TimelineRecruitmentanddatacollectionforthisstudywereperformedbetweenOctober2015andMay2017.Inthemannerdiscussedbelow,studysubjectswererecruitedandbaselinemeasureswereobtainedonthosewhoprovidedconsent.Repeatmeasureswerethentakenatboth3and6monthspost-stoveinstallation.Followingcompletionofdatacollectionatapproximately6monthsafterinstallation,participantswerefreetokeepthestovesanddowiththemastheywished(seeFigure33below).

43

Figure33:ProjectTimeline

ParticipantInclusionCriteria&TargetNumberAsoriginallydesigned,inclusioncriteriaforthisstudywere:

• non-smokingwomen• over40yearsofage• whowerebiomasssmoke-exposed,

o duetoeither:§ theuseofanopen-firestovewithoutachimneyor§ theuseofabiomass-burningstovewithachimney,whichwas

inpoorconditionwithobviousstructuraldamageandsignificantsmokeleakingintothecookingspace

• experiencingsymptomsofchronicrespiratorydisease,includingo cough,o phlegmproduction,ando shortnessofbreath

• withaspirometry-confirmeddiagnosisofCOPDaccordingtotheATS-GOLDcriteria55ofanFEV1/FVCratiolessthan0.70.

Aftersixmonthsofpersistentrecruitmentdifficulties,thefinalcriterionofspirometry-confirmedCOPDaccordingtoGOLDcriteriawasrelaxedtoasymptom-baseddiagnosisofchronicbronchitisaccordingtotheMedicalResearchCouncil(MRC)standard63,definedasahistoryofcoughwithphlegmproductionformorethanthreemonthsayearforatleasttwoconsecutiveyearsplusadequatequalityspirometry.Duetotheexpansionoftheinclusioncriteria,ourstudypopulationconsistedof20womenwithGOLDcriteriaCOPDand20womenwithMRC-standardchronicbronchitis.

44

Asapilotstudy,40wasseenasapracticableandsufficientlylargesamplesize,givenlimitedstudyresources.Statisticalpowerwasnotaconsiderationinsamplesizedecisions,becauseitwasnotourobjectivetodetermineanassociationbetweenexposureandoutcome.

RecruitmentRecruitmentforparticipationinourstudyoccurredbetweenFall2015andFall2016.TheinitialrecruitmentplanwasthatwomenwithchronicrespiratorysymptomswouldbeidentifiedamongpatientshospitalizedinorattendingtheoutpatientclinicoftheSanJuandeDiosHospitalortheRodolfoRoblesHospitalinQuetzaltenango.However,thisapproachyieldedveryfewparticipantsbecause

• themajorityofpatientsvisitingthesehospitalsinthisurbancenterwerenotusingopenfirestoves,and

• ofthosewhowereusingsuchstoves,manyarrivedatthehospitalwithsevereCOPDexacerbationsandweretoosicktoparticipateinthestudy.

Asaresult,additionalwomenwithchronicrespiratorysymptomswereidentifiedthroughrecordsofhealthservicesineachmunicipalityandthroughhomevisitsincoordinationwithstaffofthesehealthservices.Toenhancerecruitmentacombinationofdoor-to-doorandwordofmouthpromotionaswellascommunityhealtheventsheldatlocalschoolswerealsoutilizedintherecruitmentprocess.

ParticipantScreeningScreeningofpotentialparticipantsforeligibilityaccordingtoinclusioncriteriawasperformedusingasimplequestionnaireofdemographicvariables,exposure,andsymptomsassociatedwithCOPD.ThequestionnairewasdevelopedbasedonscreeningquestionnairealreadytestedinEnglishandtranslatedintoSpanishbyaqualifiedtranslator.QuestionnaireswereadministeredbyabilingualMam-andSpanish-speakingteamoffieldworkers,whocarriedoutallinteractionswithstudyparticipants.If,accordingtothescreeningquestionnaire,candidatesforthestudyhadoneofthefollowing:

• coughmultipletimesadayoverthemajorityofdaysandnightsforthelastthreemonths,

• phlegmproductionthemajorityofdaysandnightsforthelastthreemonths,Or

• shortnessofbreathduringphysicalactivitythattheygaugedtobeworsethanotherstheirage

andmetthefirstthreeelementsofthepreviouslydefinedinclusioncriteria(non-smokingwomen,over40yearsofage,biomasssmoke-exposed),theywerereferredforthespirometryscreeningdescribedbelow.

SpirometryScreeninglungfunctiontestingbyspirometrywascarriedoutonthecompletionofapositivescreeningquestionnaire.Standingheightwithoutfootwearwasmeasured

45

inthefieldusingastadiometer.Weightwasmeasuredinlightclothingusinganelectronicscale.SpirometrywasthenperformedinaccordancewithEuropeanRespiratorySociety/AmericanThoracicSocietyguidelinesusingtheEasyOneSpirometer(nddMedicalTechnologies,Andover,MA,USA).Calibrationchecksofthespirometerwereundertakenatthebeginningofeachdayofuse.Forspirometry,participantswereseatedwithoutnoseclips.Alltestswereperformed10minutesaftertheadministrationof90μgofalbuterolusingaspacerdevice.Pre-bronchodilatorspirometrywasnotcarriedout.Measurementswereclassifiedasacceptableifthewomanhadatleastthreegoodexhalations,andifbestandsecond-bestvaluesofbothFVCandFEV1didnotdifferbymorethan0.20L.Twolocalbilingual(MamandSpanish)field-workersperformedthespirometrytesting.Asdiscussedabove,thefirst20participantswerewomenwhoproducedabaselinespirometrywithanFEV1/FVCratiolessthan0.70.Forthenext20participants,womenwhoscreenedpositivelyforMRC-standardsymptomsofchronicbronchitisandwereabletoproduceacceptablespirometrywereincluded,eveniftheydidnotmeetGOLDcriteriaforCOPD.Thewomenwhoparticipatedinthestudyhadspirometrytestingatthreetimepoints:atbaseline(priortonewstoveinstallation)aswellas3monthsand6monthspost-stoveinstallation.

Allspirometrysessionswerereviewedbyanexperiencedpulmonologist(Dr.JohnBalmes)forqualitygrading,accordingtomodifiedATS/ERSperformancecriteria,asfollows:

• 3:Allpartsoftheexpiratoryflow-volumecurveareacceptableandallparameterscanbeused

• 2:Minorissuesmayexist(e.g.,evidenceofcough)butallparameterscanbeused

• 1:Qualityissuesexistattheendoftest,butthemajorityofthecurveisacceptable.OnlytheFEV1valueisacceptable

• 0:NoportionofthecurveisacceptableAdditionally,theEasyOnespirometrysoftwareappliedagradeofreproducibilityforeachsessionwheregradesareasfollows:

• A:>=3acceptabletestsANDthedifferencebetweenthebest2FEV1&FVCis<=100ml

• B:>=3acceptabletestsANDthedifferencebetweenthebest2FEV1&FVCis<=150ml

• C:>=2acceptabletestsANDthedifferencebetweenthebest2FEV1&FVCis<=200ml

• D:>=2acceptabletestsBUTresultsarenotreproducibleORonly1acceptabletest

• F:Noacceptabletests

46

Aselaboratedbelowinthestatisticalmethodssection,analysisofspirometrydataoccurredintworounds:

1. AllacceptableFEV1values(withoutconsiderationforreproducibility)2. SensitivityanalysisusingallsessionswithreproducibilitygradesofA,B,orC,

whereatleasttwocurveswerefoundtobeacceptable

StoveGroupRandomizationandInstallationWomenwhomettheaboveinclusioncriteriaandprovidedinformedconsentwererandomizedtooneofthefourstovegroupsasindicatedabove.Thefieldteamwaskeptindependentoftherandomizationofstovetypes.TheMam-andSpanish-speakingfieldteamwasresponsibleforstoveinstallation.Inadditiontotheinstallationvisit,participanthomeswereagainvisitedwithin48hoursofinstallationtoensurethestovewasworkingproperlyandthattheparticipantswerefamiliarwithitsproperuseandmaintenance.

Demographic,RespiratorySymptoms,&CookingHabitsQuestionnaireInformationonhouseholddemographics,currentstoveuse,andfueltypeswasobtainedviaaninterviewer-administeredquestionnaire.QuestionsaboutchronicrespiratorysymptomswerefromtheCOPDAssessmentTest(CAT),whichwastranslatedintoSpanish.118TheCATconsistsofscoringeightsymptomsofCOPDonascaleof0(nonexistent)to5(verysevere).Additionalquestionsregardinghealthoutcomes(e.g.,recentillnessandexacerbations)werealsoincludedinthequestionnaire.AllinterviewerswerebilingualinbothMamandSpanish.WhilethequestionnairewaswritteninSpanish,theinterviewerprovidedMamclarificationasneeded.Thedemographic,CAT,andcookinghabitsquestionnairewascompletedatthesamethreetimepointsasspirometry:atbaseline(priortonewstoveinstallation),3months,and6months.

BloodSampleCollectionBloodsampleswerecollectedbystandardphlebotomyatbaseline(priortonewstoveinstallation)andsixmonthspost-installation.FivemLofwholebloodweredrawnfromparticipantsanddividedbetweentwotubes:oneforserumandoneforwholeblood.Oncecollectedfromthefield,bloodsamplesweretransportedincoolerstothelaboratoryatSanJuandeDiosHospitalinQuetzaltenango.Labpersonnelpreparedserum,plasma,buffycoat,andFlindersTechnologyAssociates(FTA)cardsamples(Whatman,Inc.,Clifton,NewJersey).TheFTAcardsampleswerekeptatroomtemperaturewhileothersamplesweremaintainedat-20°Cwhileinthehospitallab.BiweeklytransportofcollectedsampleswasmadetotheUniversityofGuatemala-VallelaboratoryinGuatemalaCity.HeretheFTAcardscontinuedtobestoredatroomtemperaturewhileothersamplesweremaintained

47

at-80°C.Uponcollectionofallsamples,bulkshipmentwasmadetoEmoryUniversityinAtlantaforanalysis.Atthedateofwriting,thisanalysishasnotbeencompleted,butwillbeincludedinafuturemanuscript.

StoveusagemeasurementWeutilizedThermochroniButtons1921G(MaximIntegratedProducts,Sunnyvale,CA)temperaturedataloggersasStoveUseMonitors(SUMs)todeterminestoveusageandobtaincountsofthedailymealsfromthetemperaturesignals.Thesebutton-sized,battery-operateddevicesdidnotdisruptcookingactivities.TwoweekspriortonewstoveinstallationSUMswereplacedontheoriginalstove(s)and/oropenfiresusedforcookinginparticipanthomes,fortwofullweeksofdatacollection.AdditionalSUMsdatawerecollectedatthreeandsixmonthspost-installationwhentheSUMswereplacedontheinterventionstovesaswellastheoriginalstovesand/oropenfires.Eachofthethreeperiodsofstovetemperaturelogginglastedtwoweeks.DuringperiodsofSUMstemperaturemonitoring,returnvisitsweremadeafteroneweektoensuretheSUMswerefunctioningcorrectly.SpikesintemperatureasmeasuredbytheSUMswereusedtocountcookingeventsanddeterminethepercentofcookingeventsusingthenewvs.oldstove(s).Thisanalysiswillbeincludedinafuturemanuscript.

Exposuremeasurement

KitchenmonitoringForparticulatematter(PM)measurementsinallparticipantkitchens,theUCBParticleMonitorandTemperatureSensor(UCB-PATS),aPMmonitorbasedonlightscattering,wasusedwithatemperaturesensor,whichhasbeenvalidatedinthelaboratoryandinthefieldandwidelyusedbyresearchersinIndia,Nepal,Guatemala,Chinaandelsewhere.119–122TheUCB-PATShasbeenwidelyusedinareasinGuatemalaaroundthesiteofthisstudy.MeasurementsofPMwithamassmediandiameter≤2.5μm/m3(PM2.5)inthekitchensofallparticipantswerecarriedoutusingastandardmonitorlocationprotocol,placingtheUCB-PATS1.5metershighonthewallandmorethan1meterawayfromanydoororwindow.Asampleofone-thirdofparticipatinghouseholdswassystematicallyselectedalsotohavePM2.5concentrationsmeasuredinthekitchenusingagravimetricmonitorwithaTUFFTMPersonalSamplingPump(Casella,Bedford,UK),anSKCimpactor(http://www.skcinc.com/pumps.aspz)andpre-weighed37mmfilters.COmeasurementsweremadewithaLascarmonitor(EL-USB-CO300).ThesegravimetricPM2.5andCOmonitorswereco-locatedintheareawiththeUCB-PATSmonitors.Wetookthesegravimetricmeasurementsintwo24-hourperiodsduringthestudy:oncebeforeinstallationoftheinterventionstoveandthesecondtimeatthreemonthsafterinstallation.ThesemeasurementswereusedforthecalibrationoftheUCB-PATSmonitors.Pre-andpost-measurementofCasellafilterweights

48

wereperformedinthesamemicro-scale(withmicrogramaccuracy)atHarvardUniversitySchoolofPublicHealthlaboratoryinaroomwithenvironmentalcontrol.Atthedateofwriting,analysisofkitchen-basedexposuremeasureshasnotbeencompletedandwillbeincludedinafuturemanuscript.

PersonalmonitoringAllparticipantsreceivedpersonalPM2.5gravimetricmonitoringinthree24-hourperiods(beforeinstallationoftheinterventionstove,at3monthsandat6months)usingthesameCasellaTUFFTMgravimetricmeasurementdevicesasabove.Flowsweresetto1.5LPMusingarotameterforcalibration.ALascarCOmonitorwasplacedinconjunctionwiththePM2.5personalmonitorandatthesametimewhenCOmonitorswereplacedinthekitchen.Bothdevicesweresetfor24hoursofdatacollectionandfittedwithinavestwornoutsideofthewoman’sotherclotheswhereeachmonitorsatintheupperchestarea.Willingnesstoundergopersonalmonitoringwasaconditionofparticipationassessedinourconsentprocedures.Participantswereinstructedtogoabouttheirdaysasnormallyaspossiblewhilewearingthevestwiththemonitorsatalltimes.Theywereinstructedtoplacethevestwithmonitorsattheheadofthebedduringsleepingperiods.WhiletheLascarCOdataareanalyzedhere,analysisofthegravimetricPM2.5datawillbeincludedinafuturemanuscript.

DataManagementInitialquestionnairedatainthefieldwererecordedonpaper.DatawerethenenteredintoEpiInfo2000software(CDC,Atlanta,USA)beforebeingexportedtospreadsheets(MicrosoftExcel2011;MicrosoftCorporation,Redmond,WA).SpirometrydatawerehandledintheEasyWaresoftware(nddMedicalTechnologies,Andover,MA,USA)beforebeingexportedtoadatabase(MicrosoftAccess2011;MicrosoftCorporation,Redmond,WA).

StatisticalanalysisTheanalysiscomponentofthisprojectwashandledinExcelandR(RDevelopmentCoreTeam,2005).Excelwasusedtocheckfordataentryconsistency,whileRwasusedtoexecutealldatacleaning,statisticalanalyses,anddatavisualizations.

BaselineAssessmentofNormalityandRandomizationAllbaselinevariableswereexaminedtocheckfornormalityandrandomizationoftheirdistributionsacrossthestovegroupsusingappropriatestatisticaltests(chi-squaredtestforcategoricalvariablesandanalysisofvariancetestingforcomparisonofmeanvalues).

BaselineAnalysisUsingmeasurescollectedatbaseline(priortostoveinstallation),thefollowinganalyseswereperformed:

49

1. AssociationbetweensymptomburdenandmeanpersonalCOlevelatbaseline

2. AssociationbetweenspirometrymeasuresandmeanpersonalCOlevelatbaseline

Agewasconsideredasacovariateineachoftheaboveanalysesandmultiplelinearregressionswereperformed.

LongitudinalAnalysisUsingchangesinmeasuresfrombaselineto6months,thefollowinganalyseswereperformed:

3. AssociationbetweenchangeinmeanpersonalCOlevelandstovetype

4. Associationbetweenchangeinsymptomburdenandstovetype

5. AssociationbetweenchangeinspirometrymeasuresandstovetypeAsimplelinearregressionwasusedinanalyses3to5.

50

Results

SociodemographiccharacteristicsandbaselinemeasuresTable1showsdataonprincipalbackgroundcharacteristicsaswellasbaselinemeasuresofsymptomburden,COexposure,andspirometry,stratifiedbystoveassignmentgroups.Anindicationofdifferencesbetweenstovegroupswasfoundonlyinoneinstance:weeklyuseofthetemescal.bBecausethestovegroupswereassignedrandomly,thisdifferenceislikelytobearesultofchanceandwouldnotbelikelytooccurinastudywithalargersamplesize.Temescaluseisunlikelytohavebeeninfluencedbythetypeofstoveaparticipantwasassigned,butisalikelysourceofincreasedCOexposure.Approximately48%ofthewomencookedusinganopenfire(n=19)whiletheotherscookedonastovedeterminedtobeinpoorconditionwithasignificantlydamagedornon-functionalchimney.

bA‘‘temescal’’isasauna-likestructureinwhichawoodfireisfirstlittoheatwaterandrocks.Whenthefireisout,thepeopleenterthesteamyenvironmenttobathe.Theinteriordimensionsareabout1.5mlongby1mwideby1mhigh.BathinginthetemescalistypicallydoneonceperweekandmaybeasignificantsourceofHAPexposure

51

Table1:Sociodemographiccharacteristicsstratifiedbystoveassignmentgroup.

†indicatesmissingdata;n=9forthismeasure

Ecostufa, mean

(SD)orn(%)

Onil, mean(SD)orn(%)

Gas, mean(SD)orn(%)

Gas Subsidy, mean(SD)or

n(%)

p

n 10 10 10 10 Characteristics of Women

Age 63.20 (13.44)

59.60 (6.70) 58.50 (9.40) 59.90 (11.44)

0.78

Have Open Fire? 2 (20.0)

5 (50.0)

6 (60.0)

6 (60.0)

0.23

Hours Per Day in Kitchen

4.00 (1.69)

5.80 (1.55)

5.30 (2.06) 4.30 (1.16)

0.081

Years of Education 0.67 (1.32)

0.70 (1.25)

0.70 (1.06) 0.60 (1.26)

1.0

Baseline CAT Burden Score Cough 2.90

(1.29) 2.90

(0.88) 2.10 (0.99) 2.60

(1.17) 0.33

Phlegm 2.80 (1.03)

2.90 (0.99)

2.70 (1.25) 3.10 (1.45)

0.89

Chest Pressure 3.30 (0.67)

2.90 (1.20)

2.50 (1.08) 3.20 (0.79)

0.26

Shortness of Breath 3.30 (0.82)

3.20 (0.79)

2.90 (1.20) 3.20 (1.14)

0.83

CAT Burden Sum 23.20 (6.86)

21.89 (5.67) 20.40 (6.60) 23.10† (6.30)

0.74

HouseholdCharacteristicsSmoker in Home? 2

(20.0) 1

(10.0) 1

(10.0) 0

(0.0) .53

Use a Temescal Weekly?

6 (66.7)

2 (20.0)

5 (50.0)

8 (80.0)

.046*

Electricity in Home 9 (90.0)

10 (100.0)

9 (90.0)

8 (80.0)

.53

People Living in Home

5.00 (3.43)

6.00 (3.71)

6.20 (3.85) 5.10 (2.77)

.82

Baseline ExposureMeans 24h mean personal

CO at baseline (ppm)

0.96 (1.08)

1.85 (1.72)

2.08 (2.03) 3.08 (3.66)

0.26

52

Ecostufa, mean

(SD)orn(%)

Onil, mean(SD)orn(%)

Gas, mean(SD)orn(%)

Gas Subsidy, mean(SD)or

n(%)

p

BaselineLungFunctionMeasuresn 6 8 7 9

FEV1 1.81 (0.57) 1.95 (0.41) 1.59 (0.45) 1.58 (0.44)

0.33

FVC 2.21 (0.64)

2.65 (0.45) 2.10 (0.53) 2.16 (0.46)

0.16

FEV1/FVC Ratio .82 (0.04)

.74 (0.10)

.76 (0.11

.73 (0.09)

0.32

***p<0.001,**p<0.01,*p<0.05

53

BaselineAnalysis

1. AssociationbetweensymptomburdenandmeanpersonalCOlevelatbaselineAstrong,positiverelationshipcanbeseenbetweenageandsymptomburdenatbaseline.Therelationshipofagetoourdependentvariable,symptomburden,canbeinterpretedasa0.31pointincreaseeveryyear,or3.1pointseverydecade(i.e.worseningsymptomswithincreasingage)ascanbeseenbelowinTable2andFigure34.Inthecontextofthe40-pointCATscore,a2to3-pointchangehasbeendemonstratedtobeclinicallysignificant.123WhilepersonalPM2.5isconsideredthegoldstandardofwoodsmokeexposure,ithasbeenshownthatpersonalCOexposurecorrelateswellwithexposuretoPM2.5inthispopulationofwood-fuelusers;somehavemadethecaseforitsuseasaproxyforPM2.5exposure.24However,analysisonforthcomingPM2.5datawillbeperformedtovalidatethisassumption.Carbonmonoxideconcentrationsdidnothaveasignificantrelationshipwiththeparticipants’symptomburden(Β=-0.28;p-value=0.45).Thismodel’sfindingssupportexpectedhealthtrendswithsymptomburdenincreasingwithage(andpresumedyearsofHAPexposure)butdonotestablishadirectlinkbetweencurrentCOexposureinthehouseholdandrespiratoryhealthatbaseline.

Table2:RegressionofCATsymptomburdenonageandmeanpersonalCOlevelsatbaseline

***p<0.001,**p<0.01,*p<0.05

Coefficient

(Β)

SEB t-value P-value

Intercept 3.98 5.46 0.73 0.47

COPPM -0.28 0.37 -0.76 0.45

Age 0.31*** 0.08 3.62 <0.01

R2 0.31

Num.obvs. 39

RMSE 5.34

F-statistic 7.93** <0.0001

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Figure34:LinearRegressionPlotofSymptomBurdenbyAgeatbaseline.

2. AssociationbetweenspirometrymeasuresandmeanpersonalCOlevelatbaseline

Whiletheexpecteddecrementsinlungfunctionparametersbyagewereobserved,therewerenostatisticallysignificantassociationsbetweenmean24-hpersonalCOlevelsatbaselineandlungfunctionmeasures(FEV1,FVC,orFEV1/FVCratio)(Table3).Table3:RegressionoutputfortheassociationbetweenspirometrymeasuresandmeanCOlevelsandageatbaseline

DependentVariable

FEV1 FEV1(sens) FVC FEV1/FVCRatio

Intercept 3.65*** 3.97*** 3.88*** 1.04***

(0.47) (0.49) (0.73) (0.14)

PPMbaseline 0.02 0.02 0.07 0.00

55

(0.03) (0.03) (0.06) (0.01)

Age -0.03*** -0.04*** -0.03* 0.00

(0.01) (0.01) (0.01) (0.00)

R2 0.46 0.51 0.30 0.16

Num.obvs. 30 28 26 26

RMSE 0.36 0.35 0.47 0.09

F-Statistic 11.45*** 13.05*** 4.95* 2.11

***p<0.001,**p<0.01,*p<0.05

Thef-statisticsinthefirstthreemodelsindicatethatatleastoneofthepotentialpredictorvariablesisassociatedwiththeresponsevariables.Asexpected,theeffectestimatesshowthatagehasastrong,negativerelationshipwithlungfunction:HoldingCOlevelsconstant,

• FEV1decreasedby0.03Lforeveryyearincreaseinage• FEV1(sensitivityanalysis)decreasedby0.04Lforeveryyearincreaseinage• FVCdecreasedby0.03Lforeveryyearincreaseinage

TheR2valueincreaseswhenmovingfromthemoreinclusiveFEV1model1tosensitivitymodelwithstricter(lessinclusive)useofFEV1values.AgeandCOexposureseemedtohavelittletonoassociationwiththeFEV1/FVCratio.Theactualestimateforagewas-0.004withamarginallysignificantp-value,indicatingaweaknegativerelationshipaswouldbeexpected.AnoutlierinCOconcentrationswaspresentinthefirstthreemodels,buttheremovalofthisoutlierdidnothavemuchofaneffectontheanalysisresults.Furthermore,theoutlierwaswithinreasonablelevelsforCOlevelsinthepopulation.

56

LongitudinalAnalysis

3. AssociationbetweenchangeinmeanpersonalCOlevel(baselineto6months)andstovetype

Theoutcomevariablewasthedifferenceinmean24-hCOlevelfrombaselinetosixmonths,andtheexposurevariablewasthetypeofstoveinstalledinthehousehold.Table4:Asummaryof24hpersonalCOmeasures(ppm)acrosstimeinthestudy

Exposure Means Ecostufa, mean

(SD)orn(%)

Onil, mean(SD)orn(%)

Gas, mean(SD)orn(%)

Gas Subsidy, mean(SD)or

n(%)

p

24h mean personal CO at baseline (ppm)

0.96 (1.08)

1.85 (1.72)

2.08 (2.03) 3.08 (3.66)

0.26

24h mean personal CO at 3

months (ppm)

0.88 (0.48)

1.09 (0.59)

1.12 (0.75) 1.28 (0.89)

0.65

24h mean personal CO at 6

months (ppm)

1.57 (1.17)

2.08 (0.99)

1.74 (1.56) 2.77 (3.61)

0.60

Change in CO from baseline to

6m (ppm)

0.61 (2.00)

0.23 (2.09)

-0.34 (2.92) -0.31 (5.73)

0.92

Themodelwas: COdifference~stovetype+errorTheEcostufastovewasusedasthereferencegroupbecauseitwasconsideredtobetheleastlikelytoreduceCOexposureandleastpopularofthefourand,therefore,mostsimilartotheoriginalstovesthatwereinthehomes.

57

Table5:RegressionoutputfortheassociationbetweenchangeinCOlevelsandstovegroupsover6months.

***p<0.001,**p<0.01,*p<0.05

ThenullhypothesiswasthattherewasnochangeinCOdifferenceacrossthestovetypes,andthereisinsufficientevidencetorefuteit.Anestimateof0.61anditsassociatedp-valueof0.59failtoindicateanon-zerovaluefortheintercept.Theestimatesforthethreeotherstovetypesareallslightlynegative;however,thestandarderrorsarelargeenoughtocreateconfidenceintervalsthatspan0,andthep-valuesarewellabove0.05.Aswasanticipatedgiventhesmallcookstovegroupsamplesizesinthispilotproject,themodelhaddifficultyfindinganythingmorethanaweaksignalinthedata.TwooutliersexistedwiththeGasSubsidygroup,ascanbeseeninthefollowinggraph:

DeltaCO(6mo-baseline)inPPM

Coefficient

(B)

SEB t-value P-value

Intercept(Ecostufa) 0.61 1.11 0.55 0.59

Onil -0.37 1.58 -0.24 0.81

Gas -0.95 1.58 -0.60 0.55

GaswithSubsidy -0.92 1.58 -0.58 0.56

R2 0.01

Num.obvs. 40

RMSE 3.52

F-statistic 0.17 0.91

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Figure35:DotplotbystovetypeforthechangeinCOlevelsover6months.

Whilethedistributionisevenlydispersedaround0forthefirst3groups,thefourthhasanoutlierineitherdirection,bothbeingwellbeyondtwostandarddeviationsfromthemean.Removingtheoutlierswasfoundtohavenosubstantialchangeonthedescriptivepoweroftheregressionmodel.Thepresenceoftwooutliersisimportanttonote,butgiventhesamplesizeonlytrendsarenoted,withorwithouttheoutliers.ItwasdiscoveredthatthereisanoticeabledifferenceinthechangeofCOlevelsatthreemonthscomparedtobaselineandsixmonths(Table4andFigure36).Therewasastatisticallysignificantreductionat3monthsacrossallstovetypesthenactuallyaslightincreaseover6months,withthe6-monthchangefailingtobesignificant.RemovingtheextremevaluesthatcanbeseenintheGaswithSubsidygroupreducesthemagnitudeofthischange,buttheregressionmodelstillsupportsthesignificanceofthischange.Thesefindingsareinterestingandcouldbesupplementedbymoreinformationonstoveuse.Perhapsstoveswereusedinitiallyduetothenoveltyofthem,butoldcookinghabitsreturnedovertime

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Table4:RegressionoutputofoverallchangeinCOlevelsovertime.

COPPM COPPM(outliersremoved)

Intercept 1.99*** 1.73***

(0.29) (0.20)

3Months -0.90* -0.64*

(0.42) (0.28)

6Months 0.05 0.04

(0.42) (0.28)

R2 .05 .06

Num.obvs. 120 118

RMSE 1.86 1.23

F-Statistic 3.33* 3.77*

***p<0.001,**p<0.01,*p<0.05

Figure36:ChangeinCOfrombaselinethrough6months

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4. Associationbetweenchangeinsymptomburden(baselineto6months)andstovetype

Linearregressionwasusedasthemodeltoanswerthisquestion.TheoutcomevariableherewasthechangeinCATsymptomscorefrombaselineto6months.Themodelwas: Deltaburdensum~stovetype Table5:Regressionoutputofchangeinsymptomburdenbystovetype

***p<0.001,**p<0.01,*p<0.05

Theoverallmodeldoesshowaslightdecreaseinthesymptomburdenaftersixmonthsasisindicatedbytheeffectestimatecoefficients.TheEcostufa,representedbytheintercept,hasthecoefficientof-3.30(p-value=0.08)whiletheotherstovecoefficientsareinrelationtothe-3.30-interceptestimate.Itisworthnotingthedecreaseshownbytheinterceptestimateandconsideringitinthecontextofoursmallsamplesize.Perhapsaclearersignalcouldbedetectedinalargerstudy.Thefollowingplotshowsthedispersionoftheoutcomevariableacrossthestovegroups:

DeltaSymptomBurden

Coefficient

(B)

SEB t-value P-value

Intercept(Ecostufa) -3.30 1.85 -1.78 0.08

Onil -0.37 2.69 -0.14 0.89

Gas 0.70 2.62 0.27 0.79

GaswithSubsidy -0.10 2.62 -0.04 0.97

R2 <0.01

Num.obvs. 39

RMSE 5.87

F-statistic 0.06

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Figure37:Dotplotbystovetypeforthechangeinsymptomburdenover6months.

Clearly,thereisalotofvariabilityintheCATscoreoutcomevariable,buteachstovegrouphasanegativescore,whichreflectsaslightdropinsymptomburdenoversixmonths.Apairedt-testwasconductedexaminingthemeanscoreatbaselineandsixmonths:Pairedt-testt=3.57 Df=38 p-value=<.00195%ConfidenceInterval 1.40 5.06 MeanofDifference 3.23

Thereisevidencetosupporta3.23-pointdecrease(95%confidenceinterval:1.40,5.06)insymptomburdenaftersixmonthsoftheimprovedstovesbeinginstalledinthehouseholds.Whilethismaynotbeproofofacausalrelationshipbetweentheimprovedstovesandrespiratoryhealth,thedeclineinsymptomburdenisencouraging.

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5. Associationbetweenchangeinspirometrymeasures(baselineto6m)andstovetype

Althoughourstudywasnotpoweredtodetermineanysignificantdifferencesbetweenthestovegroupsregardingtheirabilitytoimprovepulmonaryfunctionaftersixmonthsofuse,wewereinterestedinassessingwhethertherewasanydirectionalchange.ThefouroutcomevariablesofinterestwerechangeinFEV1,FVC,andFEV1/FVCRatio.Theregressionmodelswere: DeltaFEV1~StoveGroup DeltaFEV1(sensitivityanalysis)~StoveGroup DeltaFVC~StoveGroup DeltaFEV1/FVCRatio~StoveGroupWhichwereusedtogenerateTable6below.Table6:Regressionoutputofchangeinspirometrymeasuresbystovetype

DependentVariable DeltaFEV1 DeltaFEV1

(sens)DeltaFVC Delta

FEV1/FVCRatio

Intercept(Ecostufa)

0.00 0.00 -0.09 0.04

(0.12) (0.13) (0.18) (0.04)Onil -0.03 -0.03 0.13 -0.08 (0.17) (0.17) (0.24) (0.05)

Gas 0.02 0.04 0.15 -0.04 (0.18) (0.19) (0.26) (0.05)

GaswithSubsidy

-0.24 -0.29 -0.26 -0.01

(0.17) (0.18) (0.26) (0.05)

R^2 0.11 0.15 0.13 0.13Num.obvs. 30 28 26 26RMSE 0.33 0.33 0.45 0.09

F-Statistic 1.04 1.38 1.08 1.07***p<0.001,**p<0.01,*p<0.05

Norelationshipsprovedstrongenoughtohavestatisticalsignificanceatthealpha=0.05level.OnetrendisthatoftheGaswithSubsidygroup,whichmaintainedanegativeestimateacrossthefourmodels.Ecostufaisthereferencegroup,sothis

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negativeestimateisrelativetotheInterceptestimate.Thisistheoppositeofwhatwouldbeexpectedifthegasstovewasbeingusedproperlyandfrequently,andfurtherexaminationshowsthatthismaybeduetoaparticularoutlierinthatgroupwithalargenegativevalue.Removingthisoutlierdidnotsubstantiallyimprovethefitofthemodel,butdidreducethedegreeofthatnegativerelationshipobservedintheregressionoutputtable.Thenumberofobservationsuseddecreasesfromlefttorighttoreflecttheincreasingstringencywithwhichthespirometrywasgraded.BothFEV1testscanbeseenbelow:

Figure38:(Left)DotplotofoverallchangeinFEV1after6monthsbystovetype.(Right)Anidenticalplotusingasensitivityexcludingspirometrytrialswithpoorreproducibility.

ItseemstheremovalofthetwospirometrytrialswithpoorreproducibilityinthesensitivityanalysishadlittleeffectonthechangeinFEV1.OnepointwasremovedfromtheGasgroupandonefromtheGaswithSubsidygroup,causingslightshiftsintheirmeans.Inbothmodels,theGasgroupperformedthebest.ThethirdcolumnintheregressionoutputtabledenotestheFVCmodel.Forcedvitalcapacityshouldhaveincreasedifthestoveswerehavingaremedialinfluenceontheparticipants.

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Figure38:DotplotofoverallchangeinFVCafter6monthsbystovetype

TheOnilandGasgroupsimprovedslightly,whileGaswithSubsidywasthelowestgrouponceagain.TheremovaloftheoutlierdoesnotproduceapositiveDeltaFVC.Ultimately,allvaluesareveryclosetozero,indicatingthestovesdidnothaveamarkedeffectonFVC.Asimilartrendisseeninthefinalplot,wherethevaluesareallclosetozero.Thedistributionsaremorehomogenousinthisplotcomparedtotheotherthree.Incontrasttowhatwasseenintheotherthreetests,theGaswithSubsidygroupshowedaslightimprovementaftersixmonths.

Figure39:DotplotofoverallchangeinFEV1/FVCratioafter6monthsbystovetype

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Unfortunately,thedatadidnothaveastrongsignaltoit,andtheevidenceforarealimprovementinlungfunctionintheGaswithSubsidygroupisminimal.AninterestingobservationfromthesefourplotsisthattheGasgroupdemonstratedaslightimprovementineverysingletest.Thisistheeffectexpectedifthestoveswereusedproperlythroughoutthesixmonths.MoreinformationonstoveusefrequencymayshedlightonwhytheGaswithSubsidygroupdidsopoorlyincomparisontotheGasgroup.

DiscussionThisisthefirststudyofitskindtolookatfourstoveinterventionsinaprospective,randomizedfashionwithwell-measuredexposureandoutcomedata.Despitebeingafeasibilitypilotstudywithoutsignificantstatisticalpowertherewerenotablefindings.While24h-personalCOlevelsfailedtoshowareductioninexposureoversixmonths,astatisticallysignificantreductionwasseenatthreemonths.Additionallytherewasa3.23-pointdecrease(95%CI:1.40,5.06)inCATsymptomburdenoversixmonthsacrossallstovetypes.Whilenosignificantchangeswereseeninspirometrymeasures,oursix-monthtimeframewaslikelytooshorttoobservemeaningfulchangesinspirometry.ForthcomingdataonPM2.5.exposure,SUMsstoveusagemeasures,andbloodworkmeasuresofinflammatorybiomarkersshouldfurtherbolsterourresults.WhatisseenwithCOlevelsdroppingthenrisingagainisanotableresultthatisconsistentwithevidenceintheliteraturesurroundingstovestacking.99,122,124ItwillbenecessarytoconfirmthesefindingswithSUMsdata,butseveralstudiesincludingonesinIndiaandMexicohaveshownreductionsininterventionstoveuseovertime.124,125Inoneofthelargestandlongestmeasuresofstoveusagetodate,Pillarisettietal.124foundthatusageofinterventionstovesdeclinedcontinuously overthefirst200daysoftheinterventionatwhichpointusagestabilized.InastudyofMexicanindigenouswomenthepatternwassomewhatdifferentwithstoveusageincreasinguntilmonth4atwhichpointusagedeclinedbeforeplateauing.125BasedonCOdataitispossiblethatpatternsofuseinthisstudymimickedthelatter.ForthcomingSUMsandPM2.5datawillbeevaluatedtofurtherelucidatethesepatterns.124,126Thisstudywasabletodetectasmallbutclinicallysignificantreductioninsmoke-relatedsymptomsbutasexpectedgivenoursamplesizeandtimeframenosignificantspirometrychangesweredetected.Thesefindingareconsistentwitha2009cookstoveinterventioninvolvingover500Mexicanwomen.107InthisstudyRomieuetal.failedtoobserveadifferenceinsymptomsorlungfunctionbetweentheinterventionandcontrolgroupsattributedtolowadherencetouseoftheimprovedstove.However,increasedself-reporteduseoftheimprovedstovewassignificantlyassociatedwithareductioninbothsmoke-relatedsymptomsandFEV1declineover1yearoffollow-up.Thesmallsamplesizeofourstudywilllikelylimitourabilitytofurtherinvestigatesymptomandspirometrychangeswhenweanalyzestoveusage.

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Thispilotstudywasnovelbecauseitproducedacombinationofexposureandoutcomedataacrossfourseparatestoveinterventioninawaythathasnotpreviouslybeenachievedinasingleproject.Strengthsofthestudyincludethequantitativenatureandbreadthofboththeexposureandoutcomedata.Whilesomeanalysisisyettooccur,thefinalresultswillinclude:

• bothpersonal(24h)-andkitchen-COandPM2.5,• SUMsstoveusagedata,• post-bronchodilatorspirometry,• thewellvalidatedCOPDAssessmentTest(CAT)ofrespiratorysymptoms• bloodbiomarkersofinflammation.

Anotherstrengthwasthecollectionoffielddatabyalocal,multilingualteamthatwaswellknowninthecommunitiesstudied.Ashasbeennoted,thesmallsamplesizeandpilotnatureofthisstudywerelimitationstoproducingstatisticallysignificantfindingsbeyondtheoriginallydesiredknowledgeregardingfuturefeasibilityofalarge-scaleproject.Additionally,therewasnotruecontrolgroupofhouseholdscontinuingtraditionalstoveuse,whichwouldbeimportantforafuturelarge-scaletrial.Thequestionofvaliditysurroundingself-reportedsymptomscoringisalsoanimportantone.PriorworkinasimilarGuatemalanpopulationsuggests“socialdesirability”biashasalikelybutunknowableinfluenceonparticipantresponse.99Allstovesinthisstudyweregivenfullyfreeofcharge.EvidencefromIndiahasshownthatstovesgivenfreeofchargedevaluetheirperceivedvalueandpotentiallyreducetheiruseovertime.127WhileparticipantsinthisstudywerelimitedtoarelativelysmallgeographicareainthedepartmentofQuetzaltenango,theywerespreadacrossmorethanfivedistinctcommunities.Inanaforementionedstudyinarural,largelyindigenousMexicanpopulation,highlevelsofheterogeneitywasseeninstoveadoptionacrossvaryingcommunities.107Community-levelstratificationonstoveuseandexposuresisnotpossiblegivenourdatabutwouldbeofinterestinafuturestudy.Thisraisesthequestionofneighborhoodorvillage-levelpollutionlevels.Thisisanimportantbutchallengingquestionabouthowsignificantlyasinglehousehold’sexposurescanbereducedwithanimprovedcookstovewhilebeingsurroundedbyhomescontinuingtousetraditionalstoves.Tryingtodocumentthenumberofimmediateneighborsusingbiomassfuelscouldbeaworthwhileeffortintryingtoaccountforalikelyconfounder.HAP-associatedobstructivelungdisease(chronicbronchitisandCOPD)isanimportantandincreasingsourceofglobalmorbidityandmorality.Amorecompleteunderstandingoftheexposure-responserelationshipforHAPandobstructivelungdiseaseisvitaltoknowingwhethertheprogressionofCOPDduetoHAPmaybestopped–orevenreversed.Thispilotstudyprovidedproofofconceptforthecollectionofhigh-qualitydataonemissions,stoveuse,fieldspirometry,andbloodsamplesinafuturelarge-scaleRCTonstoveinterventionsasatreatmentforHAP-relatedchroniclungdiseaseinGuatemala.Inconductingthispilotstudy,wealso

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showedthatimprovedstovesmayproduceaclinicallysignificantreductionintherespiratorysymptomsoverasix-monthperiod.AllofourresultshavepushedforwardthequestionofhowthemosteffectivecookstoveinterventionshouldbedesignedinGuatemala.Workremainstobedone,butperhapsaGuatemalanphysicianwillonedaybeabletodefinitively“prescribe”new,cleanerstovesforthetreatmentofCOPD.

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