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Wood StovesWood Stoves
AcknowledgementsAcknowledgementsJohna Boulafentis, Nez PerceJohna Boulafentis, Nez PerceTony Ward, University of MontanaTony Ward, University of Montana
Wood Stove InterventionsWood Stove Interventions
• Wood stove changeouts (ambient and indoor).
• Filtration units (indoor).
• Best-burn practices (ambient and indoor).
• Wood banks (ambient).
Case Study - Libby Montana
PM2.5 Nonattainment Areas (2003)
NAAQS: Annual, 15 μg/m3; 24-hr was 65 μg/m3.
http://www.epa.gov/oar/particlepollution/pdfs/20061025_graphsmaps.pdf
PMPM2.52.5 Nonattainment Areas – 2006 Nonattainment Areas – 2006
Temperature InversionsTemperature Inversions
Valley Locations
Wood stovesWood stoves
Winter 2003/2004 Libby, Montana Winter 2003/2004 Libby, Montana Sources of PMSources of PM2.52.5
Residential Wood
Combustion82%
Diesel4%
Autos7%
NH4NO35%
SO42%
Street Sand0%
Avg PM2.5: 28.2 ug/m3
Missoula Belgrade Butte Hamilton Helena Kalispell
PM2.5 Mass 13.7 ± 13.1 9.9 ± 6.9 13.5 ± 7.7 11.0 ± 10.6 9.0 ± 9.5 10.1 ± 4.8
Sample Days 26 18 19 17 2119
Street Sand 0.12 (0.8%) 0.4 (3.8%) 0.4 (2.6%) 0.1 (1.0%) 0.3 (2.9%) 0.21 (1.8%)
NH4NO32.9 (18.7%) 2.0 (19.7%) 1.4 (10.2%) 2.0 (17.4%) 1.8 (18.9%) 1.8 (15.5%)
Sulfate ND 0.3 (3.4%) 0.4 (3.2%) 0.5 (4.4%) 0.5 (4.9%) 0.43 (3.8%)
Diesel 0.71 (4.6%) 0.04 (0.4%) 0.03 (0.2%) ND 0.03 (0.3%) 0.79 (6.9%)
Autos 0.1 (0.7%) 0.2 (1.9%) 0.5 (3.6%) ND 0.2 (2.4%) 0.09 (0.8%)
Wood Smoke 8.6 (55.5%) 7.0 (70.2%) 10.9 (77.0%) 8.6 (75.8%) 6.3 (66.4%) 7.8 (68.8%)
Industry 2.9 (18.7%) ND ND ND 0.05 (0.5%) ND
Unexplained 0.2 (1.0%) 0.1 (0.7%) 0.5 (3.2%) 0.2 (1.5%) 0.4 (3.7%) 0.2 (2.3%)
CMB Source Estimates (μg/m3, and % of Total Measured PM2.5 )
Wood stovesWood stoves
• In the rural Northern Rocky Mountains of western Montana, PM2.5 is the major ambient air pollution issue (especially during the winter months).
• The majority of the wintertime PM2.5 comes from wood stoves (56 – 77%).
Ward T, Lange T. The impact of wood smoke on ambient PM2.5 in northern Rocky Mountain valley communities. Environ Pollut. 2010 Mar;158(3):723-9.
So what can be done?So what can be done?
• Wood stove changeouts have become a common tool targeting ambient wood smoke PM2.5.
• A good example is Libby, Montana.
Wood Stove ChangeoutWood Stove Changeout
Old stove40-60 g smoke/hr
EPA-certified stove2-5 g smoke/hr
Wood Stove Changeout Program: Wood Stove Changeout Program: A Natural ExperimentA Natural Experiment
Conduct prospective multi-year study to assess changes in wood smoke PM2.5 and impact on health of school children following the intervention.
1. Monitor changes in ambient PM2.5.
2. Monitor changes in school indoor PM2.5.
3. Evaluate the change in residential indoor PM2.5 following a changeout.
4. Track changes in reporting of symptoms and illness-related absences among students.
PM2.5 in Libby and NAAQS
Key Finding - LibbyKey Finding - Libby
• A large woodstove changeout can be effective in reducing ambient levels of PM2.5.
What about indoors?What about indoors?
Exposure assessment within homesExposure assessment within homes
Wood stovesWood stoves
Libby 2006/2007 Residential PM2.5 Program
PM2.5 Mass - Home 4A
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15:22
19:53
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Start Sampling:10/25/06 @ 14:00
End Sampling:10/26/06 @ 14:00
Avg = 131.8 μg/m3
Before Changeout
How does a wood stove changeout How does a wood stove changeout impact indoor air quality?impact indoor air quality?
Old stove40-60 g smoke/hr
EPA-certified stove2-5 g smoke/hr
2006/2007 Libby Residential 2006/2007 Libby Residential PMPM2.52.5 Sampling Program Sampling Program
Sampling focused on 20 homes containing wood stoves.
24-hour PM2.5 samplingPre-changeout period (Oct/Nov 2006).
Post-changeout (Dec 2006 – Feb 2007).
The goal of the program was to evaluate the impact of this “intervention” on indoor air quality within the home.
Libby PM2.5 Mass Results – Pre and Post Stove Changeout
Pre-changeout avg PM2.5: 53.4 μg/m3 Post-changeout avg PM2.5: 15.0 μg/m3
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Home 1
Home 3
Home 5
Home 6
Home 7
Home 8
Home 9
Home 1
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Home 1
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Home 1
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Home 1
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Home 1
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Home 1
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Home 1
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Home 2
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Pre Avg PM2.5
Post Avg PM2.5
Results of Multi-Winter Results of Multi-Winter Residential StudyResidential Study
• Overall reductions following the wood stove changeout were observed in 16 of 21 homes.
Case Study - Nez Perce Case Study - Nez Perce
Nez Perce Wood Stove ChangeoutNez Perce Wood Stove Changeout
• Conducted during the winters of 2006/2007, 2007/2008, and 2008/2009.
• Kamiah and Lapwai, Idaho on the Nez Perce Reservation.
• 16 homes.
Nez Perce Wood Stove Changeout Nez Perce Wood Stove Changeout PMPM2.52.5 Mass Results Mass Results
0.0
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Home
PM
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Con
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ug/m
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Avg PM2.5 Pre (ug/m3)
Avg PM2.5 Post (ug/m3)
Pre-changeout avg PM2.5: 43.1 μg/m3 Post-changeout avg PM2.5: 126.0 μg/m3
~278% PM2.5
increase
Nez Perce Wood Stove Changeout Nez Perce Wood Stove Changeout PMPM2.52.5 Mass Results Mass Results
0.0
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Avg PM2.5 Pre (ug/m3)
Avg PM2.5 Post (ug/m3)
Pre-changeout avg PM2.5: 43.1 μg/m3 Post-changeout avg PM2.5: 126.0 μg/m3
~278% PM2.5
increase
Importance of TrainingImportance of Training
0.0
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Pre Post 1 Post 2
Sampling Event
PM
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/m3 )
Home 2
Home 6
Home 11
Home 13
PM2.5 Mass (µg/m3) Measured in Homes Following Outreach/Education.
Ward, T.J., Boulafentis, J., Simpson, J., Hester, C., Moliga, T., Warden, K., and Noonan, C.W., 2011. Results of the Nez Perce woodstove changeout program, Science of the Total Environment, 409, 664-670.
Wood Stove ChangeoutsWood Stove Changeouts
• Effective in reducing ambient PM2.5.
• Expensive (~$1500 - $4500).
• Learning curve.
• Results can be variable for indoor air.
Filtration UnitsFiltration Units
A Randomized Trial for Indoor A Randomized Trial for Indoor Smoke (ARTIS)Smoke (ARTIS)
• 5-year, NIEHS funded study.
• The Primary Aim of this study is to assess the impact on quality of life among asthmatic children following interventions that reduce in-home wood smoke PM exposures.
Health Outcome MeasuresHealth Outcome Measures
• PAQoL• Peak flow• Symptoms• eNO• Biol. samples
– EBC– Urine
Dr. Curtis Noonan
Indoor Air Sampling
Preliminary results of Preliminary results of ARTIS interventionsARTIS interventions
59% Reduction
Use of best-burn practicesUse of best-burn practices
Education coupled with the use of inexpensive tools.
•Burn at proper temperatures (thermometer).
270-460 °F is optimal.
Use of best-burn practices, Use of best-burn practices, cont.cont.
• Burn dry, seasoned wood (moisture meter).
<20% moisture is optimal.
Use of best-burn practices, Use of best-burn practices, cont.cont.
• Don’t burn trash, etc.• Stove maintenance (ash cleaning, clean out
chimneys, etc).
EPA Burn Wise Programhttp://www.epa.gov/burnwise/
Summary – Change OutsSummary – Change Outs
• Wood stoves are a significant source of PM2.5 in both ambient and indoor environments.
• Wood stove changeouts can be effective in reducing ambient wintertime PM2.5 – results are more variable indoors.
• Changeouts are expensive• Training and Education on new stoves essential
Summary – Filtration UnitsSummary – Filtration Units
• Filtration units are consistently effective in improving indoor air in homes with wood stoves.
• Improves indoor air quality by ~60%, but does nothing for outdoors.
• Electricity costs are a concern and units can be noisy.
Summary – Burning PracticesSummary – Burning Practices
• Best-burn practices are inexpensive and sustainable strategies.
• Education, outreach, and training are critical.
Summary – Other ConsiderationsSummary – Other Considerations
• Each intervention should be culturally and regionally appropriate.
• Interventions need to be sustainable.• Can we replace wood stoves• Passive solar heating
