WHO ResidentialHeatingWoodCoalHealthImpacts

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Abstract

Residential heating with wood and coal is an important source of ambient (outdoor) air pollution; it can alsocause substantial indoor air pollution through either direct exposure or inltration from outside. Evidencelinks emissions from wood and coal heating to serious health effects such as respiratory and cardiovascularmortality and morbidity. Wood and coal burning also emit carcinogenic compounds. The results presentedin the report indicate that it will be difcult to tackle outdoor air pollution problems in many parts of the world

without addressing this source sector. A better understanding of the role of wood biomass heating as amajor source of globally harmful outdoor air pollutants (especially ne particles) is needed among national,regional and local administrations, politicians and the public at large.

Keywords

AIR POLLUTIONBIOMASSHEALTH POLICYHEATING

INDOOR AIR QUALITY

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ISBN 978 92 890 50760


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Contents

Authors .................................................................................................................. Acknowledgements ...............................................................................................

Abbreviations and denitions ................................................................................

Executive summary ................................................................................................

1. Introduction and context........................................................................

2. Use of solid fuels for residential heating as a major source of air

pollution.................................................................................................

3. Health effects of solid fuel heating emissions........................................

4. The burden of disease attributable to ambient air pollution fromresidential heating with wood and coal..................................................

5. Interventions shown to decrease emissions, improve outdoor andindoor air quality and improve human health.........................................

6. Regulatory and voluntary measures available to reduce emissions

from wood heating in developed countries............................................7. Policy needs regarding future use of biomass for heating and energy

production.............................................................................................

8. Co-benets for health and climate of reducing residential heatingemissions...............................................................................................

9. Conclusions...........................................................................................

10. References.............................................................................................

Annex 1. Residential wood combustion contributions to ambient PMconcentrations.......................................................................................

References.............................................................................................

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List of boxesBox 1. New WHO indoor air quality guidelines...................................................... 2

Box 2. Residential heating with coal...................................................................... 8

Box 3. Residential cooking with solid fuels............................................................ 9

Box 4. Intake fraction............................................................................................. 10

Box 5. Constituents of pollution from residential biomass and coal combustion.. 13

Box 6. DALYs.......................................................................................................... 19

Box 7. Pellet stoves................................................................................................ 28

List of gures

Fig. 1. Residential use of wood in Finland, 1970–2012, according to nationalenergy statistics........................................................................................... 5

Fig. 2. Emissions of PM 2.5 from residential sources in the EU-28, 1990–2030....... 11

Fig. 3. Baseline BC emissions from the common major sources in the EU-28,1990–2030................................................................................................... 12

List of tables

Table 1. Examples of government incentives and subsidies for residential heatingwith wood.................................................................................................... 4

Table 2. Focus of the report...................................................................................... 6

Table 3. Residential heating contribution to outdoor PM 2.5 and burden of disease,selected regions, 1990 and 2010................................................................ 18


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Authors

Zoë Chafe , University of California, Berkeley, United States of AmericaMichael Brauer , University of British Columbia, Vancouver, Canada

Marie-Eve Héroux , WHO Regional Ofce for Europe, Bonn, Germany

Zbigniew Klimont , International Institute for Applied Systems Analysis (IIASA),Laxenburg, Austria

Timo Lanki , National Institute for Health and Welfare, Kuopio, Finland

Raimo O. Salonen , National Institute for Health and Welfare, Kuopio, Finland

Kirk R. Smith , University of California, Berkeley, United States of America


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Acknowledgements

This publication was prepared by theJoint WHO/United Nations EconomicCommission for Europe (UNECE) Long-range Transboundary Air Pollution(LRTAP) Convention Task Force on Health

Aspects of Air Pollution according to theMemorandum of Understanding betweenUNECE and the WHO Regional Ofce forEurope. The Regional Ofce thanks the

Swiss Federal Ofce for the Environmentand the French Ministry of Social Affairsand Health for their nancial support ofthe work of the Task Force. The TaskForce’s work is coordinated by the WHORegional Ofce for Europe’s EuropeanCentre for Environment and Health, Bonn,Germany.


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1 All denitions are taken directly or adapted from the draft European Commission Directive on requirements for solid fuelboilers (available at:

BC black carbonBTU British Thermal UnitCCME Canadian Council of

Ministers of the EnvironmentCH4 methaneCI condence intervalCO carbon monoxideCO2 carbon dioxideCOPD chronic obstructive

pulmonary diseaseCSA Canadian Standards

AssociationDALY disability-adjusted life-yearEC elemental carbonEC JRC European Commission

Joint Research CentreEPA United States Environmental

Protection AgencyEU European UnionGAINS Greenhouse Gas and Air

Pollution Interactionsand Synergies [model ]

GBD Global Burden of Disease(Study)HEPA high-efciency particulate airIIASA International Institute for

Applied Systems AnalysisLPG liqueed petroleum gasNO2 nitrogen dioxideNOx oxides of nitrogenNSPS new source performance

standardOC organic carbon

PAH polycyclic aromatic hydrocarbonPM particulate matterPM2.5 PM with an aerodynamic

diameter of less than 2.5micrometres

PM10 PM with an aerodynamicdiameter of less than 10micrometres

SO 2 sulfur dioxide VOC volatile organic compound

Abbreviations and denitions 1

biomass biodegradable products, waste and residues from agriculture,forestry, sheries and related industries, as well as thebiodegradable fraction of industrial and municipal waste

fossil fuel carbon rich fuel other than biomass, including anthracite, browncoal, coke, bituminous coal and peat

hydronic heater wood-red boilers, often located outside the building (in a shed,for example) from which the heat is being generated and thencirculated into the building as heat source

solid fuel a fuel that is solid at normal indoor room temperatures, includingbiomass and coal

solid fuel boiler a device with solid fuel heat generator(s) that provides heat toa water-based central heating system, with heat loss of


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Executive summary

Wood, coal and other solid fuelscontinue to be used for residentialcooking and heating by nearly 3 billionpeople worldwide at least part of theyear, including many in Europe andNorth America. Residential heating withwood and coal is an important sourceof ambient (outdoor) air pollution; itcan also cause substantial indoor airpollution through either direct exposureor inltration from outside. The specicmagnitude of the problem varies greatlyby geography, prevalence of solid fueluse and the technologies used.

Across Europe and North America,central Europe is the region with thehighest proportion of outdoor particulatematter with an aerodynamic diameter ofless than 2.5 micrometres (PM 2.5 ) thatcan be traced to residential heating withsolid fuels (21% in 2010). Evidence linksemissions from wood and coal heating to

serious health effects such as respiratoryand cardiovascular mortality andmorbidity. Wood and coal burning alsoemit carcinogenic compounds. Each year61 000 premature deaths are attributableto ambient air pollution from residentialheating with wood and coal in Europe,with an additional 10 000 attributabledeaths in North America.

Measures are available to reduceemissions of solid fuels for residential

heating in most places. Encouraging fuelswitching (away from coal and other solid

fuels) and use of more efcient heatingtechnologies (such as certied replacesor pellet stoves) can reduce the emissionsfrom residential wood and coal heatingdevices. Educational campaigns mayalso be useful tools to reduce emissionsfrom residential solid fuel heaters.Furthermore, lters may reduce healtheffects from indoor air pollution.

Existing regulatory measures includeecodesign regulations and labels in the

European Union (EU) and technology-based emission limits in the UnitedStates of America and Canada. Financialfuel switching and technology change-out incentives – as well as targeted “noburn” days and ecolabelling – are othertools available to policy-makers.

Given the substantial contributions toair pollution from residential heating withsolid fuels, it will be difcult to tackleoutdoor air pollution problems in manyparts of the world without addressingthis source sector. Nevertheless, theuse of solid fuels for heating is expectedto persist and probably even expand,especially within the EU, in the comingdecades as a result of climate policies thatfavour wood burning. Better alignment istherefore needed between climate andair pollution policies in many countries.Information campaigns – especiallythose that increase knowledge about the

energy efciency of heating options – areencouraged.


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Introductionand context

Residential heating is an essentialenergy service required by many peopleworldwide. Even with widespreadavailability of electricity and naturalgas, the use of solid fuels for residentialheating continues to be common practicein many places, including within Europeanand North American countries. Solidheating fuels consist primarily of woodand coal but can also include forestry andagricultural residues and even garbage.Most fuels are burned in small-scalecombustion devices, such as householdheating stoves or small boilers for singlehouses, apartment buildings or districtheating. Open replaces are popular inmany parts of the developed world butdo not actually provide net heating inmost circumstances; they are thereforeoften characterized as for recreationaluse rather than space heating.

Currently, most burning of solid fuels for

space heating is done in devices thatincompletely combust the fuel owingto their low combustion temperatureand other limitations. This results inrelatively high emissions per unit of fuel,

including many products of incompletecombustion such as PM 2.5 and carbonmonoxide (CO) – two major air pollutants.Small-scale solid fuel combustion is alsoan important source of black carbon (BC)emissions. BC is a component of PM 2.5 that warms the climate. When coal isused for residential heating it can alsoresult in emissions of sulfur and othertoxic contaminants found in some typesof coal; even with good combustion thesecontaminants are not destroyed.

The amount of heating fuel needed in aparticular climate is dependent on thefuel efciency of the stove, as well as thecharacteristics of the housing in which itis used (such as insulation inltration –inltration through the building envelope),an issue this publication does not addressfurther. In developed countries nearly allspace heating devices have chimneys; insome developing countries much space

heating is done with open stoves insidethe house. In both cases most of theemissions end up in the atmosphere andcontribute to outdoor air pollution, whichis the focus of this report (see Box 1).

1.


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The dangers of coal burning forresidential heating in cities in developedcountries were slowly recognized overcenturies, but a major policy responsewas triggered by the Great Smog ofLondon in December 1952, whichcaused thousands of premature deathswithin a short period (Brimblecombe,

2012) due to smoke from householdheating with coal. Wood heating, whilestill a common practice even in someurban areas, has not received the sameattention as coal, although it is also amajor source of ambient air pollutionduring the heating season in nearly allparts of the world where wood is available(see Annex 1). For example, wood spaceheating was responsible for 11% ofCalifornia’s annual average PM 2.5 and

22% of the state’s winter PM 2.5 emissions

in 2012 (Air Resources Board, 2014). Inthe Helsinki Metropolitan Area, Finland,the contribution of wood heating to PM 2.5emissions for the six-month cold seasonin 2005–2009 was 19–28% at urban and31–66% at suburban monitoring sites(Saarnio et al., 2012).

Residential heating with wood is a sectorin which PM 2.5 and BC emissions canpotentially be reduced with greater cost–effectiveness than many other emissionreduction options. Nevertheless, withinEurope and North America only a fewcountries or states have set legal limitsfor minimum combustion efciency ormaximum emissions of PM and harmfulgaseous compounds like CO and gaseousorganic compounds (see section 6).

Box 1. New WHO indoor air quality guidelines

WHO recently released indoor air quality guidelines for householdfuel combustion (WHO, 2014a). The guidelines describe the householdcombustion technologies and fuels (and associated performance levels)needed to prevent the negative health effects currently attributable to thissource of air pollution. Recommendations pertinent to household spaceheating include:

• setting emission rate targets (see the guidelines for specic target values)for both vented and unvented household stoves (for PM 2.5 and CO);

• encouraging governments to accelerate efforts to meet air quality guidelines,in part by increasing access to and encouraging sustained use of cleanfuels and improved stoves, including maintenance and replacement of thestoves over time;

• preventing use of unprocessed coal as a household fuel, given that indooremissions from household combustion of coal are carcinogenic to humans,according to the International Agency for Research on Cancer (IARC, 2010)– note that unprocessed coal is distinguished here from so-called “clean”or “smokeless” coal, for which less research on health effects has beendone;

• discouraging household combustion of kerosene since there is strongevidence that heating with kerosene leads to indoor concentrations ofPM2.5, nitrogen dioxide (NO 2 ) and sulfur dioxide (SO 2 ) that exceed WHOguidelines, and household use of kerosene also poses burn and poisoninghazards;

• encouraging governments to maximize health gains while designingclimate-relevant household energy actions.


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measures, with a focus on BC reductions,primarily because of the strong climaticinuence of BC and the opportunity to“provide benets for human health andthe environment” (UNECE, 2012).

Parties to the United Nations EconomicCommission for Europe’s Convention onLong-Range Transboundary Air Pollutionadopted emission reduction targets forPM2.5 in participating countries in 2012.They decided to prioritize PM 2.5 mitigation

countries in North America and Europeare actively encouraging residentialheating with wood and other biomass(see Table 1). Biomass is touted, in somecases, as a renewable fuel that canassist with climate change mitigationand contribute to energy security.For example, the United Kingdom’s

Renewable Heat Incentive, introducedin 2014, explicitly includes paymentto households using biomass boilersas part of the strategy to reduce thecountry’s greenhouse gas emissions by80% (from 1990 levels) by 2050 (Ofgem,2014). Biomass fuels were also includedin the European Commission’s strategyfor reaching the “202020” targets (20%reduction in greenhouse gas emissions,20% of nal energy consumption fromrenewable energy and 20% increasein energy efciency by 2020), althoughmuch new biomass use in the EU hasbeen for electricity production rather thanhousehold heating (ECF, 2010).

The main reason for concern fromresidential heating using wood andcoal is the effect it has on ambientair pollution and health. The types offuel used for residential heating are animportant determinant of both outdoorand indoor air quality in many countries.Burning solid fuel in homes produces

more neighbourhood-level PM pollutionthan using electricity, gas or liquid fuelsfor heating. Burning conditions are ofteninefcient and household-level emissioncontrols or regulations are often lacking.

WHO reports that 3.7 million prematuredeaths from exposure to ambientparticulate air pollution occurred in 2012,including 482 000 in Europe and 94 000in Canada and the USA (WHO, 2014b).Household use of solid fuels for heating is

a contributor to this outdoor air pollution(see section 3).

Another reason for concern arisesfrom climate and energy policies. Many

Reasons for concern


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Household wood combustion for heatingseems to be rising in some countriesthanks to government incentives andsubsidies, the increasing costs ofother energy sources and the publicperception that it is a “green” option (seeTable 1 and Fig. 1). As in many areas

emissions from other sources (suchas ground transportation, industry andpower plants) are already controlled orlegislation is in place to reduce them,residential biomass combustion isexpected to gain prominence as a sourceof PM 2.5, especially if no efforts are madeto encourage (or incentivize) use ofmodern and efcient residential wood-heating devices. The World Bank noted in2013: “there is an urgent need to designand implement an effective approach

to limiting black carbon emissions fromhome heating sources as their usecontinues to rise” (Pearson et al., 2013).

Further reasons for concern areeconomic downturns and fuel switching.Some families revert to heating with solidfuels (such as discarded furniture, wood

scrap and coal) in response to economichardship; this has happened recently inGreece and other European countries(Saffari et al., 2013). A 2012 study by theInternational Energy Agency concludedthat, even in the absence of a globalclimate change agreement, biomassuse in the residential energy sector willincrease (quoted in Pearson et al., 2013).In the USA the number of households(especially low – and middle-income

Table 1. Examples of government incentives and subsidiesfor residential heating with wood

Country (scheme) Incentive/subsidy Notes on implementation

Denmark(Incentive to scrap pre-1980wood boilers)

Grant of €2000 or €2500 whencombined with solar panels

The programme is more thana decade old; designatedfunding has been adjusteddownwards in some years.

Norway (Ban on electrical and oil

heating in new buildings; 40% of heat demand in new buildings must be supplied by non-grid electricity or non-fossil fuel energy)

Subsidies of 20% forpurchase of a new pellet

stove (


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Motivated by the threat of increasingemissions from a push for more bioenergycombustion driven by renewable energyand energy security considerationsand climate change mitigation policies(without proper consideration of health

effects), this report addresses severalconcurrent factors:• persistent levels of emissions from

residential solid fuel combustion forheating (section 2);

• evidence of health effects fromexposure to PM from this source sectorin epidemiological studies (sections 3and 4);

• measures available and policy needs

to reduce emissions of solid fuel usefor residential heating in most places(sections 5-8).

This publication does not representa full systematic review of all relevant

literature; the authors relied primarily onrecent comprehensive reviews, reportsand WHO guidelines to present a generalpolicy-relevant overview of these topics.Seasonal space heating with wood iscommon in mountainous regions of manymiddle-income and poor countries – Chileand Nepal, for example – and coal is usedfor space heating in the parts of middle-income countries lying in temperatezones, such as Mongolia and China.

households) heating with wood grew34% between 2000 and 2010 – faster

than any other heating fuel – and in two

states the number of households heatingwith wood more than doubled during this

period (Alliance for Green Heat, 2011).

Structure of the report

Fig. 1. Residential use of wood in Finland, 1970–2012, accordingto national energy statistics

Note: A petajoule is 10 15 joules.

Source: personal communication from Dr Niko Karvosenoja, Finnish Environment Institute (SYKE). Figureprepared on the basis of public data provided by Statistics Finland (2014).

1970

P e

t a j o u

l e s

/ Y e a r

Year1980 1990 2000 2010

80

70

60

50

40

30

20

10

0


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America, however, this report focuses onEurope and North America (see Table 2).

Owing to time and resource constraints,combined with the relative lack of dataon usage and emissions in Asia and Latin

Table 2. Focus of the report

Category Main focus Less emphasis

Geographical scope(regions)

Europe and North America Other countries whereresidential heating is required,including China and India

Type of fuel Wood and coal Other solid fuels, such ascharcoal, peat, agriculturalwaste and garbage

Type of heating Single-home residential

heating

District heating

Type of exposure Population-level exposureto ambient air pollution fromheating appliances

Indoor (in-home) air pollution;emissions from cooking withsolid fuels


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Residential heating with wood and coal is a signicant source of ambient air pollution;it can also cause substantial indoor air pollution, through either direct exposure orinltration from outside. The specic magnitude of the problem varies greatly bygeography, prevalence of solid fuel use and the combustion technologies used.Nevertheless, use of solid fuels for heating is expected to persist and probably evenexpand within the EU in the coming decades as a result of climate policies that favour

wood burning.

Use of solid fuels forresidential heatingas a major sourceof air pollution

2.

from biomass heating, while most of therest comes from household coal burningfor heating (see Box 2). (These gures donot include district heating.)

Worldwide, less than 10% of totalambient PM 2.5 (from both primary PMemissions and secondary PM formation)comes from residential heating stovesand boilers; about half of that comes

Residential combustion of solid fuels:a major source of PM 2.5


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While the residential sector as awhole represents about 40% of globalanthropogenic PM 2.5 emissions, themajority of this portion (about 80% ofthe PM 2.5 produced directly by householdcombustion) comes from cooking ratherthan heating stoves in developingcountries (see Box 3). In several specic

regions of the world, however, residential

combustion of solid fuels (biomass andcoal) for heating makes a substantialcontribution to total ambient PM 2.5 emissions, including Europe (13–21% in2010, central Europe being the highest),the USA and Canada (10%) and central

Asia (10%) (Chafe et al., in press) (seesection 4).

Box 2. Residential heating with coal

Coal has been used for residential heating for centuries. In the 1960s coaland coke (a coal derivative) were the residential heating fuels of choice inGermany (84% of energy use in the residential sector) and France (68%),and were second only to oil in Denmark (33%) and Canada (22%). By the1980s, however, residential coal/coke use was virtually nonexistent (


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In Austria during the winter months of2004 wood smoke caused about 10%of PM 10 near Vienna and around 20%at rural sites in two densely forestedregions (Salzburg and Styria) (Caseiroet al., 2009). A study in a small villagein the Czech Republic – where the onlymajor wintertime source of particulate airpollution was residential combustion ofwood, coal and household waste – foundthat average winter PM 10 was higherin the village (around 40 µg/m 3 ) than inPrague (around 33 µg/m 3 ) in 1997–1998and 1998–1999 (Braniš & Domasová,2003).

In Seattle 31% of PM 2.5 measured atan outdoor monitoring site close toresidential areas was apportioned towood combustion and other vegetativeburning (Kim & Hopke, 2008). Duringheating season the contribution hasbeen as high as 62% at neighbourhoodmeasurement sites (Larson et al., 2004).

In areas where wood combustion forresidential heating is prevalent, studieshave found relatively high short-termPM2.5, PM with an aerodynamic diameterof less than 10 micrometres (PM 10 )and volatile organic compound (VOC)concentrations.

In some places wood combustion is themajor source of ambient PM 2.5, especiallyduring the heating season (see Annex 1).Source apportionment studies, whichidentify the types of emission sourcecontributing to measured air pollutionlevels, generally indicate that woodcombustion accounts for 20–30% of localheating-season ambient PM 2.5 levels,although this estimate varies greatly bylocation. For example, a study in Italyfound that in 2008 residential heatingwith wood caused 3% of PM 10 in Milan,18–76% in seven other urban areas and40–85% in three rural areas (Gianelle etal., 2013).

Box 3. Residential cooking with solid fuels

Approximately 40% of the world’s population – some 2.8 billion people –cook with solid fuels (Bonjour et al., 2013). The resulting household PM 2.5 air pollution, which shares the same constituents produced by residentialheating with solid fuels, is associated with an estimated 3.5 million deathsper year. In addition, residential cooking accounts for approximately 12% ofall outdoor PM 2.5 pollution worldwide (with a much higher proportion in someregions) and about 370 000 premature deaths each year from exposure tooutdoor PM 2.5 pollution from this source worldwide (Chafe et al., 2014).

In two regions – east Asia (including China) and south Asia (including India) –a large proportion of PM 2.5 comes from both residential heating and cooking.When considered alongside their high population numbers, these two regionsrepresent high-priority areas for shifting people away from residential solidfuel use and towards grid (electricity) connections or access to piped natural

gas or liqueed petroleum gas (LPG).

Observed outdoor pollution levels fromresidential heating

Role of inltrationSince residential wood combustion, byits nature, occurs in residential areas inclose proximity to where people live, thereis high potential for elevated exposure

via emissions from a household’s ownappliance and/or those of neighbouringhomes. Such exposure largely occursindoors (due to indoor emissions from


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Modern wood stoves and replaces,when operated according to themanufacturers’ instructions, releasesome PM and gaseous pollutants directlyinto indoor air, although in most casesthe evidence for substantial indooremissions from these modern stoves is

very limited. With poor operation, poorventilation or backdrafting, however,elevated concentrations of combustionproducts (such as PM, CO, VOCs, NO xand aldehydes) may result indoors. AcuteCO poisoning, which can sometimeseven be fatal, may occur due to indoor

wood burning and inltration of dirtyambient air), especially during thewinter. A household with wood-burningappliances is likely to be surroundedby other homes with wood-burningappliances, and wood burning also tendsto aggregate temporally; thus, on cold

evenings and nights most homes in thearea may be burning wood.

Given that most wood burning occursin cold locations where homes are wellinsulated, buildings are expectedto have low inltration (meaning thatrelatively small amounts of outdoorair pollution, including wood-burningsmoke, enter the house and contributeto indoor air pollution), especially duringthe heating season. Comparisons inEuropean cities, however, do not showa strong relationship between annualclimate and annual average inltration:the infiltration rate does not varymuch according to the climate when

averaged over a year (Hoek et al., 2008).

In North America heating-season outdoortemperature is an important determinantof inltration, and inltration levels aregenerally lower in the heating than thenon-heating season, when doors andwindows are likely to be open more (Allenet al., 2012). In British Columbia the meaninltration fraction of PM 2.5 in winter wasfound to be 0.28, compared to 0.61 insummer, although inltration factors forindividual homes in winter ranged from0.1–0.6 (Barn et al., 2008); another studyreported similarly low mean inltrationlevels of 0.32 ±0.17 during the winter(Allen et al., 2009). Combustion of woodin residential areas and often undercold, calm meteorological conditionscan nonetheless lead to high exposurecompared to other pollution sources,owing to the principle of intake fraction(see Box 4).

Indoor pollution levels

Box 4. Intake fraction

Intake fraction describes the fraction of released emissions inhaled byhumans; it is expressed in terms of the proportion of a pollutant taken in by

humans of a given amount of a pollutant emitted. This fraction is dependenton the proximity of the population to the emitting source (and thus potentialfor dilution) and the density of the population exposed to the source (Bennettet al., 2002).

An analysis for the urban area of Vancouver, Canada, indicated a high intakefraction for wood smoke during the heating season (Ries et al., 2009), inpart driven by the high population density in areas where wood was burned.Winter intake fractions of 5–13 per million were estimated, which is similar toestimated intake fractions for trafc emissions in North America. An analysisof the wood smoke intake fraction conducted for the entire population ofFinland, however, reported a considerably lower intake fraction (2.9 permillion compared to 9.6 per million for trafc sources), probably due to lower

population density (Taimisto et al., 2011).


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In general, if current trends continue,the relative contribution of primary PM 2.5 emissions from biomass combustion

for household heating are expected toincrease in the future, although decliningin absolute terms (see Fig. 2).

emissions of wood combustion productswhen ventilation of the wood-burningappliance is not managed properly. Insome situations exposure to ultraneparticles (PM with a diameter of less than100 nanometres) may be high as well.

Indoor wood combustion sources areoften closer to recipients than some

outdoor sources; as a result, the intakefraction is higher. The composition ofparticles is different because of theshorter mixing time for atmosphericreactions and the typically higher indoorthan outdoor temperatures. Exactlyhow these factors modify exposure and

subsequent health effects is unclear.

America. This last sector has historicallygenerated a signicant amount of PM 2.5(now partially controlled) and continuesto be a major source of air pollutants,

including those that contribute to theformation of tropospheric ozone (Chafeet al., in press).

The fraction of total PM 2.5 emissions due toresidential heating with solid fuels greatlyincreased in many regions between 1990and 2005. This was due partly to much

increased use of biomass fuels and partlyto a reduction in emissions from othersources like industry, power plants andground transportation in Europe and North

Residential heating emissions comparedto other sectors

Future trends in residential biomass emissions

Fig. 2. Emissions of PM 2.5 from residential sources in the EU-28,1990–2030

Notes: EU-28 is countries belonging to the EU after July 2013; current legislation scenario as in Amann etal. (2014), using the Greenhouse Gas and Air Pollution Interactions and Synergies (GAINS) model (Amannet al., 2011).

Source: reproduced with permission from the International Institute for Applied Systems Analysis (IIASA).

M i l l i o n

t o n n e s

Year

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

1990 2000 2010 2020 2030

Residential – biomass

Residential – fossil fuels

Residential combustion

Total


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current inefcient stoves and boilers.These PM 2.5 emissions include BC, whichis a potent climate-warming substance(see Fig. 3). The net warming impact ofBC-emitting sources, however, dependson the concurrent emissions of coolingaerosols, such as organic carbon (OC).

fuels is generally much lower than 100%(WHO, 2014a).

The less than ideal combustion conditionsin most household replaces and stoves –including low combustion temperatures,suboptimal air circulation/oxygenavailability, overloading of the reboxwith wood, moist biomass fuel, and heatloss – cause emissions of harmful PM andgaseous compounds often referred to as“products of incomplete combustion”.

(see Box 5).

The reasons for this include the push forclimate change mitigation (with biomassconsidered a renewable fuel undersome climate policies), the potentialfor economic hardship to increasedependence on solid fuels, slow adoptionof state-of-the-art technologies and the

lack of strong incentives for exchanging

Most residential stoves and boilersin use today are relatively inefcient,compared to the best models availablefor sale. Under ideal burning conditions,all the carbon in wood and other typesof biomass, coal, kerosene, LPG, naturalgas, diesel and gasoline would becompletely converted to carbon dioxide(CO2 ) while releasing energy. This isknown as 100% combustion efciency.Unfortunately, combustion efciency ofsimple household stoves burning solid

Fig. 3. Baseline BC emissions from the common major sourcesin the EU-28, 1990–2030

Note: EU-28 is countries belonging to the EU after July 2013; current legislation scenario as in Amann etal. (2014), using the carbonaceous particles module (Kupiainen and Klimont, 2007) of the GAINS model(Amann et al., 2011).

Source: reproduced with permission from IIASA.

Other sources

Transport

Residential combustion

Total

M i l l i o n

t o n n e s

Year

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0.001990 1995 2000 2005 2010 2015 2020 2025 2030


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Box 5. Constituents of pollution from residential biomassand coal combustion

Particles: PM 2.5 , BC, OC

PM2.5 is one of the major air pollutants produced by burning solid fuels. Fineparticles are generally considered to a good indicator of the health impactsof wood combustion sources: they have been the most broadly studied andare the focus of most emissions regulations.

BC is one constituent of PM 2.5 that has been associated with adverse healtheffects (see section 3) and is recognized as an important short-lived climateforcer (Bond et al., 2013; Janssen et al., 2012). (See section 8 for more onthe climate implications of residential solid fuel use for heating.) As emissionsfrom wood stoves or long-wood burners cool or “age”, a series of gaseoushydrocarbons adsorb onto the BC. When used correctly to optimize airow,pellet stoves produce a much lower level of BC and polycyclic aromatichydrocarbons (PAHs) than conventional wood stoves (Eriksson et al., 2014).

OC is another PM component that is emitted directly from combustion ofmany solid fuels; it also forms as a secondary pollutant. The organic andsome inorganic emissions undergo rapid physicochemical transformation,followed by more delayed reactions in the atmosphere (Kocbach Bølling etal., 2009; Naeher et al., 2007). The speed of many reactions depends on theavailability of sunlight (ultraviolet radiation) and on atmospheric temperature,which means that they are much slower in the cold and dark heating seasonthan in the much brighter warm season of the year. In contrast to BC, whichis light in colour, OC aerosols tend to be cooling for the climate.

Even as combustion efciency of small-scale heaters is improved, the amountof BC emitted from a given amount of fuel will remain nearly constant. Morecomplete combustion, however, will result in a much smaller amount oforganic compounds and an increase in inorganic salts such as potassiumsulfates, chlorides and carbonates and zinc, depending on the type ofbiomass (Larson & Koenig, 1994; Lighty et al., 2000).

Gases: CO, NO x, PAHs, SO 2, VOCs

Wood (and other biomass) smoke also contains gaseous air pollutants linkedwith a range of potential health outcomes like CO, NO x and VOCs such asacrolein, formaldehyde, benzene, gaseous and particulate PAHs, as wellas other organic compounds including carboxylic acids, multiple saturatedand unsaturated hydrocarbons, aromatics, PAHs and oxygenated organiccompounds such as alhedydes, quinones, phenols and organic acids andalcohols. Combustion of biomass that contains chlorine, for example, whichhas been treated or transported via saltwater, can also emit chlorinatedorganic compounds. Burning coal often causes emission of SO 2 owing to

its potentially high sulfur content (see Box 2).


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Box 5. Contd

Levoglucosan

Levoglucosan is a tracer of biomass combustion and is often used as anindicator to determine exposure to biomass fuels or for source apportionmentresearch. While it has proved useful as a marker of biomass combustion,more research is needed to evaluate the quantitative relationship betweenlevoglucosan levels and PM mass concentration, given scenarios involvingdifferent wood types and combustion devices (Mazzoleni et al., 2007).

Other emissions

Burning coal can release elements and compounds that are particularlyharmful to human health, such as uorine, arsenic, selenium, mercury andlead; burning coal at the household level can release these into the indoorenvironment (see Box 2). When economic conditions are acutely bad, peopleoften resort to burning furniture, plastics and garbage. Combustion of theseproducts causes emissions that are of special concern to human health,

such as dioxins and lead.


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Hundreds of epidemiological time-seriesstudies, conducted in different climatesand populations, link daily increasesin outdoor PM concentration withincreased mortality and hospitalization.

Long-term (years) PM exposure appearsto inuence health outcomes morestrongly than short-term (days) exposure,although fewer studies have been doneon longer-term exposure. Exposure toPM leads not only to acute exacerbationof disease, these studies suggest, butmay also accelerate or even initiatethe development of chronic diseases(WHO Regional Ofce for Europe, 2013).Long-term high-level exposure to woodsmoke in low-income countries hasbeen associated with lower respiratoryinfections (including pneumonia) inchildren; chronic obstructive pulmonary

disease (COPD), reduced lung functionand lung cancer in women; stillbirthsand low birth weight of newborn babies(Smith et al., 2011; WHO, 2014a).

Although relatively few studies on

the health effects of residential woodcombustion specically in developedcountries have been undertaken, there isevidence of an association between woodcombustion and respiratory symptoms.

Ambient levels of particulate air pollutionfrom wood combustion appear tobe associated with exacerbation ofrespiratory diseases – especially asthmaand COPD (Gan et al., 2013) – andincluding bronchiolitis (Karr et al., 2009)

and otitis media (beginning as upperrespiratory infection) (MacIntyre et al.,2011). A review of the health effects

Evidence links emissions from wood and coal heating to serious health effects. Bothshort-term and long-term exposures to wood and coal smoke are harmful to health:they contain cancer-causing compounds and appear to act in the same way as PMfrom other sources. Respiratory problems are a common concern associated withexposure to wood smoke. Recent studies suggest that exposure to wood and coalsmoke may also harm cardiovascular health. Studies of other biomass burning (suchas forest res) can help improve understanding of the health effects of residential woodburning.

Short-term exposure to particles fromwood combustion appears to be asharmful to health as exposure to particlesfrom the combustion of fossil fuels. Atleast 28 pollutants present in smokefrom solid fuel use have been shownto be toxic in animal studies, including14 carcinogenic compounds and fourcancer-promoting agents (Smith et al.,2014). Undifferentiated PM was recentlydeclared carcinogenic by the International

Agency for Research on Cancer, includingfrom household combustion of coal and

household use of solid fuels (Loomis etal., 2013). The results of studies such

as these were taken into account inthe development of the WHO indoorair quality guidelines (WHO, 2014a;see Box 1) and are summarized in theirsupporting documents.

Several approaches have been takento understand the effects of solid fuelheating emissions on human health.These include epidemiological studiesthat track the health effects of airpollution in human populations, studiesof other biomass burning such as forestre smoke and toxicological and clinicalexposure studies.

Health effects of solidfuel heating emissions3.

Epidemiological studies


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is consistent with the associations foundwith urban air pollution (Dennekamp &

Abramson, 2011). Smoke from landscaperes causes an estimated 339 000 deathsannually (Johnston et al., 2012).

Burning of agricultural residues alsoseems to produce respiratory effects. In

Winnipeg, Canada, a group of peoplewith mild to moderate airway obstructionreported symptoms (cough, wheezing,chest tightness, shortness of breath,breathing trouble) during a smoke episodecaused by burning of straw and stubble(Long et al., 1998). Burning of residuesfrom rice farming in Iran was associatedwith increased prevalence of, amongothers, asthma attacks, use of asthmamedication, cough and decreased lung

function (Golshan et al., 2002).Few studies have been done on theeffects of long-term or prenatal exposureto residential wood smoke in developedcountries. Exposure to wood smokeduring pregnancy (number of days),however, was associated with smallsize for gestational age (Gehring et al.,2014); exposure to wildre smoke duringpregnancy slightly reduced average birthweight in infants (Holstius et al., 2012).

The particles in wood smoke cause harmto human health through oxidative stress,direct cellular toxicity, impaired renewalof damaged cells, lung damage withsecondary inammation and genotoxicity(causing increased risk of respiratorycancer). Pulmonary inammation mayfurther lead to systemic inammation.Particulate PAHs and their derivativesmay cause many of these effects.

Fewer controlled human exposurestudies have focused on residentialwood combustion than have examinedthe effects of PM 2.5 or PM 10 exposurefrom diesel engine exhaust. Theparticulate concentrations used in thesestudies (200−500 µg/m 3 PM2.5 or PM 10 )correspond to the highest hourly levelsmeasured during wintertime temperatureinversions in suburban residential areas

of particles from biomass combustionconcluded that there was no reason toconsider PM from biomass combustionless harmful than particles from other urbansources, but that there were few studieson the cardiovascular effects (Naeheret al., 2007). Recent epidemiological

studies suggest that short-term exposureto particles from biomass combustion isassociated with not only respiratory butalso cardiovascular health (McCrackenet al., 2012; WHO Regional Ofce forEurope, 2013).

The health effects of ambient PM exposurefrom residential wood combustion canbe assumed to resemble those of openbiomass burning – including forest, brushand peat res – because of the similarfuels. In many studies wildres havebeen associated with severe respiratoryeffects, including:• increased rates of respiratory hospital

admissions and emergency room visits(Arbex et al., 2007; Duclos & Sanderson,1990; Hanigan et al., 2008; Jacobs &Kreutzer, 1997; Johnston et al., 2007;Mott et al., 2005; Ovadnevaité et al.,2006);

• eye irritation and respiratory symptoms,such as cough and wheezing amongchildren and teenagers (Kunii et al.,

2002; Mirabelli et al., 2009);• increased use of COPD medication

and decreased lung function from PMexposure (Caamano-Isorna et al., 2011;Jacobson et al., 2012).

People with asthma or COPD seem tobe especially threatened. A review of therespiratory effects of wildres found anassociation between respiratory morbidity

and exposure to bushre smoke, which

Learning from other types of biomass burning

Toxicological and clinical exposure studies


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In 2010 an estimated 61 000 prematuredeaths in Europe were attributable tooutdoor PM 2.5 pollution originating fromresidential heating with solid fuels (woodand coal) – about the same number asin 1990 (Chafe et al., in press). Thisrepresents 55% of all deaths worldwidethat can be attributed to exposure tooutdoor air pollution from residentialheating with wood and coal. Outdoorair pollution from household heatingwith solid fuels also is estimated to beresponsible for 1 million DALYs (see Box

Across Europe and North America, central Europe is the region with the highestproportion of outdoor PM 2.5 that can be traced to residential heating with solid fuels(21% in 2010). Each year 61 000 premature deaths are attributable to ambient air

pollution from residential heating with wood and coal in Europe, with an additional10 000 attributable deaths in North America.

Household space heating with biomass-based solid fuels (wood, crop residuesand similar) creates outdoor air pollutionthat in turn results in an important publichealth burden (both in terms of prematuredeaths and in healthy life-years lost)across many regions of the world. Europeis among the regions with the mostserious challenges in this regard: theproportion of outdoor PM 2.5 caused byhousehold space heating with wood andcoal is especially high across many partsof Europe (see Table 3).

The burden of diseaseattributable to ambientair pollution fromresidential heatingwith wood and coal

4.

Region PM 2.5 fromresidentialheating (%)

PM 2.5 fromresidentialheating (µg /m 3 )

Prematuredeaths/year Disability-adjustedlife-years(DALYs)/year

1990 2010 1990 2010 1990 2010 1990 2010

Central Europe 11.1 21.1 3.5 3.4 18 000 20 000 370 000 340 000Eastern Europe 9.6 13.1 2.0 1.4 24 000 21 000 480 000 410 000Western Europe 5.4 11.8 1.3 1.7 17 000 20 000 280 000 290 000

High-incomeNorth America 4.6 8.3 0.9 1.1 7 500 9 200 140 000 160 000

Central Asia 9.9 8.3 2.4 1.6 5 500 4 200 180 000 110 000

Global 3.0 3.1 0.9 0.7 120 000 110 000 2 800 000 2 200 000

Table 3. Residential heating contribution to outdoor PM 2.5 andburden of disease, selected regions, 1990 and 2010


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pollution also caused 160 000 DALYs in2010, up slightly from 140 000 in 1990.Reducing the use of biomass for spaceheating or reducing emissions throughbetter combustion or pollution capturewould lessen this burden.

weighted PM 2.5 concentrations of 1.7,3.4 and 1.4 µg/m 3, respectively. Incomparison, 8% of the total ambientPM2.5 in North America (Canada and theUSA) comes from household heating withsolid fuels (1.1 µg/m 3 ).

6) across Europe in 2010 (47% of theglobal total), down from 1.3 million DALYsin 1990.

In North America exposure to outdoorPM2.5 pollution from residential heatingwith solid fuels resulted in 9200 deaths in2010, an increase from 7500 in 1990. This

Globally, Europe has the highestproportion of outdoor PM 2.5 emissionsattributable to household heating withsolid fuels at 12% of total PM 2.5 inwestern Europe, 21% in central Europeand 13% in eastern Europe in 2010.This corresponds to average population-

Box 6. DALYs

DALYs are a combined unit composed of mortality (premature death) inthe form of years of life lost plus morbidity (injury and illness) in the form ofyears of life lost to disability in order to fully understand the ill health causedby a risk factor or disease. In the case of morbidity, a disability weight is

assigned to each year lived with a specic afiction.


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country as a result of background healthand pollution conditions.

An important consideration is to whatextent results from epidemiological

studies on urban PM can be generalizedto PM from residential wood combustion.In the WHO air quality guidelines (WHORegional Ofce for Europe, 2006) it wasconcluded that there was little evidencethat the toxicity of particles from biomasscombustion would differ from thetoxicity of more widely studied urbanPM. This same approach was followedin the analysis presented in section 4and in the recent GBD Study (Lim et al.,

2012), in which all combustion particles,regardless of source, were considered tobe hazardous depending on the exposurelevel. This was based on the integratedexposure response curves developed forthe GBD Study, which linked exposures tocombustion particles across four sources– ambient air pollution, secondhandtobacco smoke, household air pollutionand active smoking – to the healthoutcomes ischaemic heart disease,stroke, COPD, lung cancer and childpneumonia (Burnett et al., 2014).

The analysis in section 4 combinesenergy use and emissions estimatesfrom the GAINS model hosted by IIASA,secondary PM formation calculated withTM5-FASST software at the EuropeanCommission Joint Research Centre (ECJRC), and health impact data from the2010 Global Burden of Disease (GBD)Study (Amann et al., 2011; IIASA, 2014; ECJRC, 2014; Lim et al., 2012). All ambientair pollution estimates are populationweighted and account for other sourcesof PM, such as open biomass burning(forest res, agricultural burning) anddust. Health impacts are estimated bytaking a proportion of the total impactsfrom outdoor air pollution, based on theproportion of total air pollution attributableto residential solid fuel combustion forheating. This procedure is in line withthe approach taken by the Global Energy

Assessment (Riahi et al., 2012) and aWorld Bank report on the burden ofdisease from road transportation (Bhallaet al., 2014). Although health impactsare presented by region here, the healthbenets of reducing exposure to outdoor

air pollution will vary signicantly by

Methodology


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and that the results were thereforebiased away from the null; however,the reanalysis still showed a signicantdecrease in respiratory mortality (Dockeryet al., 2013). The work also showed that,where the ban was extended to otherIrish cities, signicant improvements

in air quality were detected, as werereductions in morbidity and mortality,especially for respiratory outcomes. Asnoted earlier (Box 2), the WHO indoorair quality guidelines for householdcombustion now strongly recommendagainst the use of unprocessed or rawcoal as a household fuel (WHO, 2014a).

One successful intervention inLaunceston, Tasmania, combined fuelswitching (via replacement of wood

stoves with electricity) with communityeducation and enforcement ofenvironmental regulations (Johnston et

Encouraging fuel switching (away from coal and other solid fuels) and use of moreefcient heating technologies (such as certied replaces or pellet stoves) can reducethe emissions from residential wood and coal heating devices. Filters may reduce

health effects from indoor air pollution. Educational campaigns may also be usefultools to reduce emissions from residential solid fuel heaters.

National, state/provincial and localregulatory agencies have implementeda large number of regulatory air qualitymanagement efforts targeted atreducing ambient concentrations ofpollutants emitted from residential woodcombustion. These include actionsfocused on fuel switching, combustion

technology (stove exchange), introductionof district heating and in-home high-efciency particulate air (HEPA) ltrationand educational efforts addressingburning practices. Comparatively fewstudies have assessed the effectivenessof these actions, and only a subsection ofthese assess the resulting health benets.

One study in Ireland found that banningthe marketing, sale and distributionof coal (specically bituminous coal)improved both air quality and health,and reduced deaths from respiratoryand cardiovascular causes. Averageconcentrations of black smoke (ne PM

measured by its blackening effect onlters) in Dublin declined by 35.6 µg/m 3 (70%) when coal sales were banned;adjusted non-trauma death ratesdecreased by 5.7%. Respiratory deathsfell by 15.5% and cardiovascular deathsby 10.3%. About 116 fewer respiratorydeaths and 243 fewer cardiovasculardeaths were seen per year in Dublin afterthe ban (Clancy et al., 2002).

In a subsequent reanalysis the original

authors concluded that the statisticalapproach did not adequately control fora downward long-term trend in mortality,

Fuel switching

Interventions shownto decrease emissions,improve outdoor andindoor air quality andimprove human health

5.


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Ward et al., 2008; 2010; 2011). Lower

ambient PM 2.5 was also associated withreduced likelihood of reported respiratoryinfections. Compared to a two-yearbaseline period established prior tothe stove exchange, the interventionproduced a 26.7% (95% CI: 3.0% to44.6%) reduced odds of reported wheezefor each 5 μg/m 3 decrease in PM 2.5 inschoolchildren.

A source apportionment studyconducted in Golden, British Columbia,

found that wood smoke-associatedsource contributions to ambient PM 2.5 levels decreased by a factor of fourfollowing a wood stove change-outprogramme (Jeong et al., 2008). Duringthe programme the proportion of homes

al., 2013) to reduce the proportion ofhouseholds heating with wood from 66%to 30%. Wood heating accounted for85% of PM emissions at the beginning ofthe 13-year study; mean wintertime PM 10 dropped 39% (from 44 to 27 µg/m 3 ) withthe interventions.

This improvement in air quality wasassociated with reductions in annualmortality, after adjustment for generalregional improvements in health that werecharted in a nearby location (Hobart) overthe course of the study. In winter months

only, borderline signicant reductions incardiovascular (−19.6%; 95% condenceinterval (CI):−36.3% to 1.5%) andrespiratory (−27.9%; 95% CI: −49.5% to3.1%) mortality were observed. Largerand statistically signicant reductionsin all-cause (−11.4%; 95% CI: −19.2%

to 2.9%), cardiovascular (−17.9%; 95%CI: −30.6% to −2.8%) and respiratory(−22.8%, 95% CI: −40.6% to 0.3%)mortality were also observed in malescompared to the whole population.

A successful community wood stove

exchange programme in Libby,Montana, replaced 95% (n = 1100) ofolder (not certied by the United StatesEnvironmental Protection Agency(EPA)) wood stoves with EPA-certiedappliances or other heating sourcesover the course of four years. Beforethe exchange, residential wood stovescontributed about 80% of ambient PM 2.5 in the airshed (part of the atmospherethat behaves in a coherent way withrespect to the dispersion of emissions)in winter months. Compared to thepre-intervention winter, average winterPM2.5 mass was reduced by 27% andsource-apportioned wood smoke-relatedPM2.5 by 28% (Ward & Lange, 2010;

Heater and wood stove exchanges


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While household or individual-levelstrategies are not typically part of airquality management programmes, twostudies from Canada indicate that in-home HEPA ltration might reduce healthimpacts from wood smoke. An initialsingle-blind randomized crossover studyof 21 homes during winter, in an areaaffected by residential wood combustionas well as trafc and industrial sources,reported a mean 55% (standard deviation= 38%) reduction in indoor PM levelswhen HEPA lters were operated (Barnet al., 2008). This study was followedby a randomized intervention blindedcrossover study, which included bothexposure measures and assessment ofpotential health benets associated with

EPA has set up a “Burn wise” programmeto educate people to burn the right wood(dry, seasoned hardwood; no trash)

HEPA lter operation (Allen et al., 2011).Use of the HEPA lters reduced indoorPM2.5 and levoglucosan concentrationsby 60% and 75%, respectively. Useof HEPA ltration for one week wasassociated with improved endothelialfunction and decreased levels ofbiomarkers of inammation in healthadults (impaired endothelial function andsystemic inammation are predictorsof cardiovascular morbidity). Noassociations were observed for urinarymarkers of oxidative stress. Thesestudies indicate the potential for portableroom air cleaners to reduce exposureand the health impacts associated withresidential wood combustion.

the right way (hot and not smoulderingre, not overloading the appliance, notwhen outdoor air quality is poor) in the

HEPA ltration

Educational campaigns

District heating is a system for distributingheat generated in a centralized locationfor residential and commercial heatingrequirements such as space heatingand water heating. It was introduced forhealth, efciency and comfort reasonsin Sweden in the 1940s, both to avoidthe use of coke and sulfur-containing oilclose to where people live in cities andtowns and to support the production ofelectricity (combined heat and powerproduction). It was estimated in the 1970sthat levels of SO 2 were two to ve timeslower in towns where district heatingwas common compared to similartowns without district heating (Boströmet al., 1982). Since then, heavy oil as afuel has been abandoned because ofsulfur, energy and carbon taxes. Withstringent emission controls, a numberof different fuels have been introduced –predominantly biofuels. Today, Swedishdistrict heating and cooling is mainlybased on the use of excess heat fromthe production of electricity or industrial

processes; it is considered one of themost environmentally friendly ways touse biofuels. Other energy sources arealso used, such as heat pumps that useheat from sea/river or sewage water.

The most common heating method inmultifamily dwellings and nonresidentialpremises in Sweden is currently districtheating. As a result of this and otherchanges, the ambient air concentrationof soot in the second largest city,Gothenburg, has decreased from almost50 µg/m 3 in 1965 to about 5 µg/m 3 in 1995(Areskoug et al., 2000). Another exampleis from central Stockholm, where SO 2levels were dramatically reduced fromover 200 µg/m 3 in 1965 to below 25 µg/ m3 in 1990. The environmental aspectsof district heating have been describedin detail and it has been estimated thatthe total energy requirement for heatingin the EU could be met by using excessenergy from power production for districtheating (Frederiksen & Werner, 2013).

District heating


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increasing awareness of the health risksof wood combustion does not alwayscause benecial changes in behaviour(Hine et al., 2007; 2011).

Educational campaigns may fail if theyonly provide information on risks but donot try to affect the positive image ofwood combustion. Many associate woodcombustion at home with innate feelingsof comfort, goodness, happiness andwarmth (Hine et al., 2007). Decisionson whether to burn wood or not – whenan individual has the ability to choose –may be based rather on intuitive positivefeeling than on logical calculation of risks.Wood smoke seems to be perceived asless health-threatening than many otherenvironmental stressors, although thereis little evidence for or against this notion.Increasing the perception of health risksassociated with solid fuel heating canbe one motivation to change behaviour,although awareness of risks does notautomatically lead to benecial changesin behaviour. Tobacco smoking, however,is an encouraging example of an activitywhose image has been altered, at leastin part, by active campaigning. Banson smoking in bars have been shownto lead to benecial changes in therespiratory and cardiovascular healthof populations (Bartecchi et al., 2006;Goodman et al., 2007).

right efcient appliance. Educationalcampaigns run at the city, county andnational levels can also encourageswitching to alternative energy sourcesand avoiding unnecessary recreationalcombustion.

A study conducted in Armidale, a smalluniversity city in Australia with high PMpollution levels due to wood-burningheaters, found an educational campaignsignicantly decreased visible wood smokeemissions among 316 study participants(Hine et al. 2011); unfortunately, no airpollution measurements were taken. Themain barriers to reducing wood smokeidentied by the study were poor operationof wood heaters, mismanagement ofrewood and lack of knowledge aboutthe health effects of wood smoke. Thecampaign did not succeed in increasingknowledge among the study participantsof the health risks of wood combustion.

In general, environmental educationalcampaigns have only moderate successin generating pro-environmental behaviourand there is little evidence of theireffectiveness in peer-reviewed literature.No quantitative estimates describehow improved wood-burning practices– without exchanging combustionappliances – can reduce the healthimpacts of wood combustion. Veryfew studies have evaluated why even


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Box 7), indoor and outdoor wood boilers,furnaces and heaters. The EPA has hadvoluntary qualication programmes inplace for hydronic heaters since 2007and for replaces since 2009. Phase 2qualications of hydronic heaters is at0.32 pounds parts per million British

Thermal Unit (mmBTU) heat output andPhase 2 qualications for replaces is 5.1g/hr. The proposed NSPS revisions alsoinclude masonry heaters (2.0 g/h dailyaverage; 0.32 lb/mmBTU (around 0.14g/megajoule).

A hydronic heater is a wood-red boiler,often located outside the building forwhich it is generating heat – in a shed,for example – that heats a liquid (water orwater/antifreeze mix) and then uses this tocirculate heat. To promote the productionand sale of cleaner and more efcientoutdoor hydronic heaters, EPA currentlyruns a voluntary certication programmefor manufacturers. Certied outdoorhydronic heaters at the most stringentcertication level (“phase 2”) are about90% cleaner than uncertied models.Even outdoor hydronic heaters qualifyingfor phase 2 certication, however, stillemit one to two orders of magnitude more

PM2.5 on an annual average emission ratebasis than residential oil or gas furnaces.Under the proposed revisions to theNSPS, a limit of 0.32 lb/mmBTU (around0.14 g/megajoule) for indoor and outdoorhydronic heaters is proposed for 2015and of 0.06 lb/mmBTU for both indoorand outdoor hydronic heaters in 2020.

A number of state and local jurisdictionshave also adopted setback distances(distances from buildings or other

structures deemed to need protection)of 30–150 m, depending on emissionscertication, for outdoor hydronic heaters.

All the above standards are focusedon PM emissions, but the proposed

American standard also includesminimum efciency and CO testing andreporting requirements for wood-burningappliances, with the aim of also reducingCO emissions.

requirements for solid fuel boilers 3 andthe energy labelling are expected to savearound 18 petajoules (0.4 Mtoe) of energyeach year – corresponding to about 0.2million tonnes of CO 2 – and resulting inannual reductions of 10 kilotonnes ofPM, 14 kilotonnes of organic gaseous

compounds and 130 kilotonnes of CO.Some countries in Europe (including

Austria, Denmark, Germany, Norway andSweden) have issued national emissionstandards for small residential heatinginstallations, which are already in effect.The most comprehensive at this time is aGerman law of 2010 (quoted in Bond etal., 2013).

Canada also has countrywide standards

in effect, limiting emissions for PM 2.5 andozone pollution levels, and residentialwood burning has been prioritized as asector in which contaminant emissionscan be reduced. CCME participatedin an initiative to update the CanadianStandards Association (CSA) standardsfor new wood-burning appliances(CSA Group, 2010). These standardswere adopted in 2010, lowering the PMemission rate to 4.5 g/h for noncatalyticwood-heating appliances and to 2.5 g/hfor catalytic wood-heating appliances.They also established emissions limitsof 0.4 and 0.13 g/megajoule for indoorboilers/furnaces and outdoor hydronicheaters, respectively.

In the USA, EPA established a newsource performance standard (NSPS)limiting emissions for residential woodstoves under the Clean Air Act in 1988(7.5 g/h for noncatalytic wood-heatingappliances and 4.1 g/h for catalytic wood-heating appliances). This is expected tobe updated in 2015 to reect current bestsystems of emission reduction.

Note that the 1988 NSPS cover onlynew wood stoves and not devicesinstalled prior to implementation of thestandards, nor do they encompass manyincreasingly popular residential wood-burning devices, including replaces,masonry heaters, pellet stoves (see

3 The proposed draft regulation sets a PM emission limit value of 40 mg/m 3 for automatic and 60 mg/m 3 for manual solidfuel boilers by 2020.


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Box 7. Pellet stoves

Pellet stoves use processed biomass (in pellet form) as a fuel. Someare equipped with automatic pellet-feeding systems, which often run onelectricity but are occasionally gravity-fed and require little attention from theuser. They were developed in the 1980s and have become quite popular inEurope, although less so in the USA and Canada.

Signicant growth in the installation of pellet stoves and boilers in residentialand commercial sectors has been observed in several European countriesover the last decade. Annual sales growth rates of 20–30% per year havebeen reported in Austria, France, Germany, Italy, Sweden (currently thelargest market in the world) and Switzerland, varying a little from year to yearowing to changes in the price of fossil fuels compared to stove pellets (UNEP& WMO, 2011).

Pellets were originally produced in some European countries as a way ofusing the waste products from sawmills. Pellet production increased fourfoldin the EU between 2001 and 2009 and trade is uid both within the EU and

with external producers, particularly Canada, the Russian Federation and theUSA (FAO, 2010). There is some concern about the overall carbon footprintof heating with pellets in Europe as many pellets are currently produced inNorth America or other regions and exported to Europe to sustain its thrivingpellet market.

Pellet stoves are cleaner than many other options (Kjällstrand & Olsson,2004; Olsson & Kjällstrand, 2006), but they may not be cost-effective forusers who harvest their own wood for fuel. Prices for these kinds of stoveare in the range of US$ 1000–3000. One estimate suggests that the cost–effectiveness of reductions for replacement of a wood stove ranges from US$130/megagram PM for a noncatalytic stove to almost US$ 1000/megagramPM for a pellet stove, but is highly dependent on the fuel price and the typeof stove or boiler being replaced (Bond et al., 2013; Houck & Eagle, 2006).

In Sweden a 52% CO 2 tax on fossil fuels shifted consumer choice and ledto increased penetration of modern biomass boilers and pellet stoves. Inaddition, public incentive programmes in several countries support modernbiomass heating in households to reduce greenhouse gas emissions. Forexample, in France value-added tax on pellet stoves and boilers was reducedfrom 19.4% to 5.5%, a tax refund of up to 50% of the installation costs wasmade available and public campaigns were organized. Subsidies in Germanyfor the installation of pellet boilers of >150 kW were increased in 2008from €1500 to >€2000 or even €2500 when combined with solar panels

(UNEP & WMO, 2011).

Fuel switching

Several nancial incentives for fuelswitching are in place in Europe. In Austriabiomass combustion (in pellet or woodchip boilers) is incentivized by a at rate

of €120/kW for 0–50 kW appliances and€60/kW for every additional kW up to amaximum of 400 kW. A maximum of 30%

of the purchase value of the installationmay be covered by this policy.

Germany provides grants for buyers ofwood-burning appliances, with incentivesto guide the purchase of automaticallyfuelled pellet-burning devices. Minimum


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California limits wood burning on dayswhen air pollution approaches unhealthylevels. Santa Clara County, near SanFrancisco, uses a two-stage system toissue burn bans: at stage 1 residentscan only use certied stoves; at stage 2they may only use a wood stove if it is aprimary heat source (EPA, 2014).

Voluntary “no burn” advisories are alsoin place in the USA. Lagrande, Oregon,

asks for voluntary curtailment of woodstove use for heat based on dailyadvisories. The Yolo-Solano Air QualityManagement District has initiated avoluntary programme called “Don’t LightTonight”, which encourages residents notto use wood stoves and replaces whenair pollution approaches unhealthy levels.The district also encourages cleanerburning techniques and switching tocleaner burning technology (EPA, 2014).

rebates are in the range of €500–2500 forpellet ovens and boilers, depending onthe specic model.

In Northern Ireland a grant of


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Several European countries, such as Austria, Germany and Sweden, haveintroduced voluntary ecolabelling ofstoves with standards for efciency andemissions (Bond et al., 2013), such as theNordic Swan label in Sweden (Pearson etal., 2013).

The 1999 Gothenburg Protocol under theConvention on Long-Range Transboundary

Air Pollution, as amended in 2012, alsoincludes recommendations on PM emission

limit values for residential combustioninstallations with a rated capacity of lessthan 500 kW hours. The recommendedemission limit values for PM depend onthe type of fuel (wood: 75 mg/m 3; woodlogs: 40 mg/m 3; pellets and other solidfuels: 50 mg/m 3 ) (UNECE, 2012).

The Wood Stove Decathlon, an initiativeof the Alliance for Green Heat, wasorganized in 2013 to focus creativity andresources on designing next generationwood stoves. The main goal was tochallenge teams of combustion engineers,engineering students, inventors and stovemanufacturers to build wood stoves that arelow-emission, high-efciency, innovativeand affordable, in a common process thatmay point to commercially attractive nextgeneration stove production (Alliance forGreen Heat, 2013).

A model by-law and code of practiceare in place in Canada. CCME produceda code of practice for residential wood-burning appliances; this focuses onreducing the impacts of emissions to airquality and climate, while recognizingthe appliances’ importance for domesticheating. The code includes a model by-law that municipalities or provinces canadopt for regulatory purposes, as well asguidance on wood-burning curtailmentin response to air quality advisories,emissions testing for individual sourcesand complaint response strategies. Thecode provides advice and regulatoryguidance for six best practices forconsideration by jurisdictions in designingpolicies and programmes to reduce woodsmoke emissions:• regulating appliance efciency;• air quality advisories and “no burn”

days;• limits on installation or operation of

wood-burning appliances;• incentives to change;• public outreach and education;• performance management – planning

for and measuring success.

Other regulations and voluntary measures

stoves and EPA-certied wood stovesbe installed in remodelled or newlyconstructed buildings. Emissions labelling

for rewood, wood logs and wood pelletssold is also required (BAAQMD, 2014b).


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rapid speed of global warming (relating

to BC in ne particles and VOCs thatpromote ozone formation) and reducethe great burden of disease causedby wood combustion-derived particles(especially organic compounds carriedby BC). Such regulations should includetight – but technically achievable – limitsin particular for the primary emissions ofparticulate mass, gaseous hydrocarbonsand CO from new boilers and heaters.

Education on energy efciency is

needed . Improved efciency of woodcombustion in small-scale heatingappliances greatly reduces emissions ofmajor greenhouse gases, such as CO 2 and methane (CH 4 ), per unit of energyrequired for heating purposes. There is

Residential solid fuel combustion for

heating is likely to persist in many parts ofthe world in the near future. The following isa summary of the policy needs regardingbiomass and other solid fuel use forheating and energy production.

Any renewable energy or climate change-related policies that support combustionof wood for residential heating need toconsider the local and global ambientair pollution impacts and immediatelypromote the use of only the lowest

emission or best available combustiontechnologies.

Legal regulations for wood combustionefciency in new heating appliances areurgently needed throughout the world.These will both slow down the current

Better alignment is needed between climate and air pollution policies in many countries.Information campaigns – especially those that increase knowledge about the energyefciency of heating options – are encouraged.

Policy needs regardingfuture use of biomassfor heating and energyproduction

7.


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more generally in valleys of mountainousareas. This can be introduced rapidly bothto alleviate local air pollution episodesin vulnerable areas with prevalent woodburning and to reduce the risk of acuteadverse health outcomes among thefast-growing susceptible population

group of people aged over 65 years withchronic respiratory or cardiovasculardisease. This would also be favourablein health terms for newborn babies andpre-schoolchildren, who also spendmuch time in the home and are moresusceptible than older children and adultsto respiratory symptoms and infections.

Local and regional authorities, with patientorganizations, need to create community-wide information campaigns to informresidents about the climate and healthbenets of local emission-free alternativesfor house heating. These may includedistrict heating by controlled combinedheat and power plants, geothermalenergy for single houses or as a largerlocal installation and heat pumps forsingle houses or apartments. Authoritiescould arrange distribution of leaets andpersonal information to residents on howto arrange proper drying and storage of

wood logs and how to use current small-scale heaters properly during annualchimney sweeps. An example of this isthe information campaign implementedby chimney sweeps in Finland (Levander& Bodin, 2014). The most challenging taskis to change the attitudes of people whoare attached to the tradition of burningwood for house heating and comfort,and who often get their wood cheaply orwithout charge from their own or relatives’

and friends’ forests by harvesting smalltrees and making the wood logs in theirspare time.

an urgent need for education around thisissue, including active outreach by airpollution, energy and health ministries.

As new wood-burning devices becomemore energy efcient and emit lesspollution (especially PM), nationalgovernments need to prepare heaterexchange regulations or voluntaryprogrammes. Municipalities, countiesand states should consider requiringheater exchanges at the time of homeremodels or sales. In many cases, theseregulations will be most successful ifnancial compensation is offered to assistwith the cost of replacing old heaters withthose meeting tight energy efciency oremission limits regulations.

“No burn” areas are needed . Especiallywith current combustion technologies, itis important to dene urban areas withdense populations and/or geographicalfeatures (such as valleys betweenmountains) where residential heatingor cooking with small-scale appliancesburning solid fuels (wood and coal) is notpermitted at all or is at least limited toregistered models of low-emission woodcombustion devices. Residential heatingwith coal in small-scale appliances shouldalso be permanently prohibited, at leastin communities of developed countries,as should the use of wood log burnersfor central heating without a sufcientlylarge water tank (which otherwise leadsto badly incomplete combustion and verylarge emissions).

Regulatory use of “no wood burning”days or morning and evening hoursduring unfavourable meteorologicalconditions (low wind speed, temperatureinversion) needs to be introduced invulnerable, densely populated areas, and


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heating should be discontinued for bothhealth and climate reasons.Coal is an extremely greenhouse gas-intensive energy source. Coal produces 1.5times the CO 2 emissions of oil combustionand twice the CO 2 of burning natural gas(for an equal amount of energy produced)(Epstein et al., 2011). When burned inhomes rather than power plants, coal isalso a major source of BC and other PM 2.5 (see Box 2). Wood and other forms ofbiomass are often considered renewableand climate-friendly fuels because treestake up CO 2 as they grow and store it inthe form of carbon. As wood is burned,however, this carbon is released back tothe the atmosphere, not only as CO 2 butin most household combustion also in theform of short-lived greenhouse pollutantssuch as BC, CO and VOCs includingCH4. Thus, to be perfectly “carbonneutral”, wood fuel has to be not onlyharvested renewably but also combusted

completely to CO 2.For both climate and health purposes, theform these fuels’ carbon takes when it isreleased matters greatly, since BC andCH4 are both strongly climate-warming.BC is a climate-relevant component ofne particles, whether they are derivedfrom tailpipe emissions of cars orresidential heaters burning wood or otherbiomass. It is also harmful to health (seesection 3). Note that although the toxicitybehind the health impacts is indirect,

Co-benets include health benets thatarise from actions that are primarilymotivated by an interest in mitigatingclimate change and climate mitigationbenets produced by actions that areprimarily motivated by an interest inimproving public health. Reducingemissions of health-relevant air pollutants– especially those that are also climate-active pollutants (such as CH 4 and BC)– can have short- and medium-term co-benets for health; it can also immediately

reduce exposure to associated particulateair pollution. Accounting for thesehealth co-benets can produce a morecomplete economic picture of the costsand benets associated with efforts toreduce heating-related emissions, suchas wood stove change-out programmes.

Increasing efciency and tighteningrestrictions on emissions from wood andcoal heating throughout the world wouldboth slow down the current rapid speed

of global warming (relating to BC in neparticles and VOCs and CH 4 that promoteozone formation) and reduce the burdenof disease caused by combustion-derivedparticles (especially organic compoundscarried by BC and contaminants in coal).The public needs to be better educatedabout the facts that improved efciency ofwood combustion in small-scale heatingappliances greatly reduces emissions ofmajor long-lived greenhouse gases (such

as CO 2 ) and short-lived climate forcers(such as BC and CH 4 ); and that coal

Co-benets forhealth and climate of

reducing residentialheating emissions

8.Co-benets are win–win outcomes for sectors other than the one from which a policyoriginates. Reducing emissions from residential heating can have signicant benetsfor both climate and health, especially in the short term.


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mitigation could improve health, sincethese interventions lead to reductionsin PM2.5 . Major reductions in annualpremature deaths expected as a resultof these interventions include about 22000 fewer deaths in North America andEurope, 86 000 fewer deaths in east

and southeast Asia and the Pacic, and22 000 fewer deaths in south, west andcentral Asia (UNEP & WMO, 2011).

If Arctic climate change becomes a focusof targeted mitigation action (becauseof threats from rising sea levels, forexample), widespread dissemination ofpellet stoves and coal briquettes maywarrant deeper consideration because oftheir disproportional benet to mitigatingwarming from BC deposition in the Arctic(UNEP & WMO, 2011). The World Bankfound that replacement of wood logs withpellets in European stoves could lead to a15% greater cooling in the Arctic (about0.1 °C). For Arctic nations the modellingstrongly indicates that the most effectiveBC reduction measures would targetregional heating

WHO ResidentialHeatingWoodCoalHealthImpacts

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