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Intervention Strategies for Woodstove Homes. Tony Ward, Ph.D. The University of Montana Center for Environmental Health Sciences June 16, 2011. Mexico City, Mexico. Beijing, China. Los Angeles, California.

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Intervention Strategies for Woodstove Homes

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Intervention strategies for woodstove homes

Intervention Strategies for Woodstove Homes

Tony Ward, Ph.D.

The University of Montana

Center for Environmental Health Sciences

June 16, 2011

Mexico city mexico

Mexico City, Mexico

Beijing china

Beijing, China

Los angeles california

Los Angeles, California

Intervention strategies for woodstove homes


Ambient pm

Ambient PM

Epa 24 hour pm 2 5 nonattainment areas

EPA 24-Hour PM2.5Nonattainment Areas

*As of Aug 2010

National Ambient Air Quality Standard (NAAQS): Annual, 15 μg/m3; 24-hr, 35 μg/m3.



Chemical mass balance cmb pm 2 5 source apportionment

Chemical Mass Balance (CMB) PM2.5 Source Apportionment

  • Computer modeling to determine what the sources of PM2.5 are in the airsheds.

    1) Collect PM2.5 air samples.

    2) Analyze the air samples for chemical species.

    3) Use an EPA computer model (CMB) to apportion the sources.

Air samplers

Air Samplers

Sources of hamilton pm 2 5 winter 2007 2008

Sources of Hamilton PM2.5Winter 2007/2008

Average PM2.5:

11.0 μg/m3

11/2/07 – 3/1/08

Sources of butte pm 2 5 winter 2007 2008

Sources of Butte PM2.5Winter 2007/2008

Average PM2.5:

13.5 μg/m3

11/8/07 – 3/1/08

Sources of helena pm 2 5 winter 2007 2008

Sources of Helena PM2.5Winter 2007/2008

Average PM2.5:

9.0 μg/m3

11/2/07 – 3/1/08

Sources of kalispell pm 2 5 winter 2008 2009

Sources of Kalispell PM2.5Winter 2008/2009

Average PM2.5:

9.0 μg/m3

11/2/07 – 3/1/08

Average PM2.5:

10.1 μg/m3

11/2/08 – 2/24/09

Fairbanks state building cmb results november 11 2008 april 7 2009

Fairbanks State Building CMB Results(November 11, 2008 – April 7, 2009)

Fairbanks north pole cmb results january 25 2009 april 7 2009

Fairbanks - North Pole CMB Results(January 25, 2009 – April 7, 2009)



  • 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 woodstoves (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.

Woodstove changeouts

Woodstove Changeouts

  • Woodstove changeouts are becoming a common tool targeting ambient woodsmoke PM2.5.

  • A good example is Libby, Montana.

Woodstove changeout

Woodstove Changeout

Old stove

40-60 g smoke/hr

EPA-certified stove

2-5 g smoke/hr

Pm 2 5 nonattainment areas 2003

PM2.5 Nonattainment Areas (2003)

NAAQS: Annual, 15 μg/m3; 24-hr was 65 μg/m3.

Pm 2 5 seasonal trends

PM2.5 Seasonal Trends

Winter 2003 2004 libby montana sources of pm 2 5

Winter 2003/2004 Libby, Montana Sources of PM2.5

Ward, T.J., Rinehart, L.R., and Lange, T., 2006. The 2003/2004 Libby, Montana PM2.5 source apportionment

research study, Aerosol Science and Technology, 40: 166-177.

Temperature inversions

Temperature Inversions



Libby woodstove changeout program

Libby Woodstove Changeout Program

Funding provided by Montana DEQ, EPA, and HPBA.

Libby woodstove changeout program1

Libby Woodstove Changeout Program

  • Nearly 1,200 old woodstoves were changed out, modified, or surrendered between 2005 and 2008.

Wood stove change out program a natural experiment

Wood Stove Change-out Program: A Natural Experiment

Conduct prospective multi-year study to assess changes in woodsmoke PM2.5 and impact on health of school children following the intervention.

  • Monitor changes in ambient PM2.5.

  • Monitor changes in school indoor PM2.5.

  • Evaluate the change in residential indoor PM2.5 following a changeout.

  • Track changes in reporting of symptoms and illness-related absences among students.

Intervention strategies for woodstove homes

PM2.5 in Libby and NAAQS

Intervention strategies for woodstove homes

PM2.5 in Libby and NAAQS

Key finding libby

Key Finding - Libby

  • A large woodstove changeout can be effective in reducing ambient levels of PM2.5.

Bergauff, M.A., Ward, T.J., Noonan, C.W., and Palmer C.P. 2009. The effect of a woodstove changeout on ambient levels of PM2.5 and chemical tracers for woodsmoke in Libby, Montana. Atmospheric Environment, 43, 2938-2943.

Ward, T.J., Palmer, C.P., Houck, J.E., Navidi, W.C., Geinitz, S., and Noonan, C.W., 2009. A community woodstove changeout and impact on ambient concentrations of polycyclic aromatic hydrocarbons. Environmental Science & Technology, 43(14), 5345–5350.

Ward, T. J., Palmer, C. P., and Noonan, C. W., 2010, PM2.5 source apportionment following a large woodstove changeout program in Libby, Montana. Journal of the Air and Waste Management Association, 60: 688-693.

Intervention strategies for woodstove homes

What about the impact of a woodstove changeout on indoor levels of PM2.5?

1) Libby, Montana.

2) Nez Perce Woodstove Changeout Program.

Exposure assessment within homes

Exposure Assessment Within Homes

Intervention strategies for woodstove homes

Before Changeout




Start Sampling:

10/25/06 @ 14:00

End Sampling:

10/26/06 @ 14:00

Avg = 131.8 μg/m3

2006 2007 libby residential pm 2 5 sampling program

2006/2007 Libby Residential PM2.5 Sampling Program

Sampling focused on 20 homes containing woodstoves.

24-hour PM2.5 sampling

Pre-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 pm 2 5 mass results pre and post stove changeout

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

Pm 2 5 maximum spikes pre and post stove changeout

PM2.5 Maximum Spikes – Pre and Post Stove Changeout

Pre-changeout spike avg: 434 μg/m3

Post-changeout spike avg: 103 μg/m3

Libby residential program cont

Libby Residential Program, cont.

Did the stove changeout work over time?

Ward, T.J., Palmer, C., Bergauff, M., Hooper, K., and Noonan, C., 2008. Results of a residential indoor PM2.5 sampling program before and after a woodstove changeout, Indoor Air, 18: 408–415.

Followup pm 2 5 indoor study

Followup PM2.5 Indoor Study

Air sampling was conducted in a total of 26 woodstove homes.

Five phases:

Phase 1 = pre stove change, 2006/2007 winter.

Phase 2 = post change, same winter.

Phase 3 = post change, 2nd 2007/2008 winter.

Phase 4 = post change, 3rd 2007/2008 winter.

Phase 5 = post change, 4th 2008/2009 winter.

Intervention strategies for woodstove homes

Libby Residential Study (winters of 2006/2007 - 2008/2009 (3 winters)

Pre-changeout avg PM2.5: 63.2 µg/m3

Post-changeout avg PM2.5: 28.9 µg/m3

Results of multi winter residential study

Results of Multi-Winter Residential Study

  • Overall reductions following the wood stove changeout were observed in 16 of 21 homes.

  • High variability was observed for post-changeout sampling within some homes, but 14 of the 21 homes still had lower PM2.5 concentrations for all post-changeout sampling compared to pre-changeout PM2.5 concentrations.

Nez perce woodstove changeout program

Nez Perce Woodstove Changeout Program

Nez perce woodstove changeout

Nez Perce Woodstove 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 woodstove changeout pm 2 5 mass results

Nez Perce Woodstove Changeout PM2.5 Mass Results

~278% PM2.5


Pre-changeout avg PM2.5: 43.1 μg/m3

Post-changeout avg PM2.5: 126.0 μg/m3

Importance of training

Importance of Training

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.

Woodstove changeouts1

Woodstove Changeouts

  • Effective in reducing ambient PM2.5.

  • Expensive (~$1500 - $4500).

  • Learning curve.

  • Results can be variable for indoor air.

Another indoor intervention filtration units

Another Indoor Intervention- Filtration Units -

Intervention strategies for woodstove homes

Avg ~50% PM2.5 Reduction in Woodstove Homes

A randomized trial for indoor smoke artis

A Randomized Trial for Indoor 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 woodsmoke PM exposures.

Study design randomized trial

Study Design: Randomized Trial



Group 1 (n=36)

Group 2 (n=36)

Group 3 (n=36)

Winter #1: Baselines Exposure and Health Outcomes Measures


Tx1: EPA-Certified Woodstove

Tx2: Active Air Filter Units In two rooms

Tx3: Inactive Air Filter Units (Placebo)

Winter #2: Post-intervention Exposure

and Health Outcomes Measures

Health outcome measures

Health Outcome Measures

  • PAQoL

  • Peak flow

  • Symptoms

  • eNO

  • Biol. samples

    • EBC

    • Urine

      Dr. Curtis Noonan

Intervention strategies for woodstove homes

Indoor Air Sampling

Artis preliminary results

ARTIS Preliminary Results



  • Woodstoves are a significant source of PM2.5 in both ambient and indoor environments.

  • Woodstove changeouts can be effective in reducing ambient wintertime PM2.5 – results are more variable indoors.

  • Filtration units are consistently effective in improving indoor air in homes with woodstoves.




  • NIH Centers of Biomedical Research Excellence (p20-RR017670).

  • Health Effects Institute (#4743-RFA04-4/06-4).

  • NIEHS (1R01ES016336-01; 3R01ES016336-02S1)

  • Montana Department of Environmental Quality (DEQ).

  • Alaska Department of Environmental Conservation (DEC, Barbara Trost and Jim Connor).

  • EPA Region 10 (Mary Manous).

  • Nez Perce ERWM (Johna Boulafentis and Julie Simpson).

  • The 3M Corporation.

  • Toyota USA Foundation.

Thank you

Thank you.

Tony Ward

(406) 243-4092

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