Tony J. Ward

The 2003/2004 Libby, Montana PM2.5 Source Apportionment Research Study

Except for areas in California, Libby, Montana is the only designated EPA nonattainment area for fine particulate matter (PM 2.5 ) in the mid and western states. During the winter of 2003/2004, PM 2.5 speciated data (mass, elements, ions, organic/elemental carbon) were collected every six days from November 11, 2003 through February 27, 2004. Using a Chemical Mass Balance computer model (Version 8.0), these data were used to apportion the sources of PM 2.5 in the Libby valley. In support of the source apportionment program, a comprehensive evaluation of the particulate matter associated organic compounds (including polar organics, phenolics, polycyclic aromatic hydrocarbons, and 14 C) present in the airshed was also conducted. CMB modeling results revealed that emissions from residential wood combustion was the major source of PM 2.5 throughout the winter months in Libby, contributing an average of 82% of the measured PM 2.5 . Levoglucosan, a well-known chemical marker for wood smoke, had the highest measured concentrations of any of the 95 polar organic compounds quantified from the fine fraction, accounting for over 15.5% of the measured organic carbon fraction. Other semi-volatile organic compounds with high measured concentrations during the program were four phenolic compounds commonly found in wood smoke, including phenol, 2-methylphenol ( o -cresol), 4-methylphenol ( p -cresol), and 2,4-dimethylphenol. Results from 14 C analysis indicate that as much as 82% of the measured 14 C results from a wood smoke source. These indicators support modeling results that residential wood combustion was the major source of PM 2.5 in Libby, Montana throughout the winter months.

Results of a residential indoor PM2.5 sampling program before and after a woodstove changeout

UNLABELLED During 2005-2007, a woodstove changeout program was conducted in a Rocky Mountain valley community in an effort to reduce ambient levels of PM(2.5). In addition to changes in ambient PM(2.5), an opportunity was provided to evaluate the changes in indoor air quality when old stoves were replaced with US Environmental Protection Agency (EPA)-certified woodstoves. PM(2.5) samples were measured in 16 homes prior to and following the changeout. For each sampling event, PM(2.5) mass was continuously measured throughout the 24-h sampling periods, and organic/elemental carbon (OC/EC) and associated chemical markers of woodsmoke were measured from quartz filters. Results showed that average PM(2.5) concentrations and maximum PM(2.5) concentrations were reduced by 71% and 76%, respectively (as measured by TSI DustTraks). Levoglucosan was reduced by 45% following the introduction of the new woodstove. However, the concentrations of resin acids, natural chemicals found in the bark of wood, were increased following the introduction of the new woodstove. There were no discernible trends in methoxphenol levels, likely due to the semi-volatile nature of the species that were measured. Although there is some uncertainty in this study regarding the amount of ambient PM infiltration to the indoor environment, these findings demonstrated a large impact on indoor air quality following this intervention. PRACTICAL IMPLICATIONS Emissions from residential woodstoves are an important air quality issue (both indoors and ambient) in many regions throughout the US and the world. More specifically, woodstoves have been identified as a major source of PM(2.5) in valley locations throughout the Northern Rocky Mountains, where biomass combustion is the predominant source of home heating. In this study, we present results that demonstrate the dramatic reduction in PM(2.5) concentrations (as measured by TSI, Inc. DustTrak PM(2.5) air samplers) inside homes following the replacement of old, polluting woodstove with new EPA-certified woodstoves.

The impact of wood smoke on ambient PM2.5 in northern Rocky Mountain valley communities.

During the winters of 2006/2007 and 2007/2008, PM2.5 source apportionment programs were carried out within five western Montana valley communities. Filter samples were analyzed for mass and chemical composition. Information was utilized in a Chemical Mass Balance (CMB) computer model to apportion the sources of PM2.5. Results showed that wood smoke (likely residential woodstoves) was the major source of PM2.5 in each of the communities, contributing from 56% to 77% of the measured wintertime PM2.5. Results of 14C analyses showed that between 44% and 76% of the measured PM2.5 came from a new carbon (wood smoke) source, confirming the results of the CMB modeling. In summary, the CMB model results, coupled with the 14C results, support that wood smoke is the major contributor to the overall PM2.5 mass in these rural, northern Rocky Mountain airsheds throughout the winter months.

Urinary Levoglucosan as a Biomarker of Wood Smoke Exposure: Observations in a Mouse Model and in Children

Background Biomass smoke is an important source of particulate matter (PM), and much remains to be discovered with respect to the human health effects associated with this specific PM source. Exposure to biomass smoke can occur in one of two main categories: short-term exposures consist of periodic, seasonal exposures typified by communities near forest fires or intentional agricultural burning, and long-term exposures are chronic and typified by the use of biomass materials for cooking or heating. Levoglucosan (LG), a sugar anhydride released by combustion of cellulose-containing materials, is an attractive candidate as a biomarker of wood smoke exposure. Objectives In the present study, Balb/c mice and children were assessed for LG in urine to determine its feasibility as a biomarker. Methods We performed urinary detection of LG by gas chromatography/mass spectrometry after intranasal instillations of LG or concentrated PM (mice) or biomass exposure (mice or humans). Results After instillation, we recovered most of the LG within the first 4 hr. Experiments using glucose instillation proved the specificity of our system, and instillation of concentrated PM from wood smoke, ambient air, and diesel exhaust supported a connection between wood smoke and LG. In addition, LG was detected in the urine of mice exposed to wood smoke. Finally, a pilot human study proved our ability to detect LG in urine of children. Conclusions These results demonstrate that LG in the lungs is detectable in the urine of both mice and humans and that it is a good candidate as a biomarker of exposure to biomass smoke.

A rural community intervention targeting biomass combustion sources: effects on air quality and reporting of children's respiratory outcomes

Objective Improvements in urban air quality are largely driven by controls on industrial and mobile source emissions, but such factors may have limited influence on many rural environments where biomass combustion (eg, wood stoves) serves as the primary source of fine particulate matter (PM2.5). The authors tracked changes in childrens respiratory health during a wood stove intervention in a rural mountain valley community heavily impacted by wood smoke-derived PM2.5. Methods Community-wide impacts on childrens health were assessed by prospectively collecting surveys from parents of school children during four winter periods in Libby, Montana. Generalised estimating equations with a logit link were used to estimate the effect of reduction in ambient PM2.5 on wheeze prevalence and other reported symptoms and infections. Results Over 1100 wood stoves were replaced with new lower emission wood stoves or other heating sources. Ambient PM2.5 was 27.6% lower in the winters following the changeout programme compared with baseline winters. There was a 26.7% (95% CI 3.0% to 44.6%) reduced odds of reported wheeze for a 5 μg/m3 decrease in average winter PM2.5. Lower ambient PM2.5 was also associated with reduced odds for reported respiratory infections, including cold (25.4% (95% CI 7.6% to 39.7%)), bronchitis (54.6% (95% CI 24.2% to 72.8%)), influenza (52.3% (95% CI 42.5% to 60.5%)) and throat infection (45.1% (95% CI 29.0% to 57.6%)). Conclusion This wood stove intervention provided a unique opportunity to prospectively observe health benefits resulting from a targeted air pollution reduction strategy in a rural community.

Residential indoor PM2.5 in wood stove homes: follow-up of the Libby changeout program

UNLABELLED In 2005 through 2008, a small rural mountain valley community engaged in a woodstove changeout program to address concerns of poor ambient air quality. During this program, we assessed changes to indoor air quality before and after the introduction of a new, lower emission woodstove. We previously reported a >70% reduction in indoor PM(2.5) concentrations in homes following the installation of a new Environmental Protection Agencys-certified stove within the home. We report here on follow-up of the experiences in these and other homes over three winters of sample collection. In 21 homes, we compared pre-changeout PM(2.5) concentrations [mean (s.d.) = 45.0 (33.0) μg/m(3)] to multiple post-changeout measures of PM(2.5) concentrations using a DustTrak. The mean reduction (and 95% confidence interval) from pre-changeout to post-changeout was -18.5 μg/m(3) (-31.9, -5.2), adjusting for ambient PM(2.5) , ambient temperature, and other factors. Findings across homes and across years were highly variable, and a subset of homes did not experience a reduction in PM(2.5) following changeout. Reductions were also observed for organic carbon, elemental carbon, and levoglucosan, but increases were observed for dehydroabietic acid and abietic acid. Despite overall improvements in indoor air quality, the varied response across homes may be due to factors other than the introduction of a new woodstove. PRACTICAL IMPLICATIONS Biomass combustion is a common source of ambient PM(2.5) in many cold-climate communities. The replacement of older model woodstoves with newer technology woodstoves is a potential intervention strategy to improve air quality in these communities. In addition to ambient air, woodstove changeouts should improve residential indoor air quality. We present results from a multi-winter study to evaluate the efficacy of woodstove changeouts on improving indoor air quality. Reductions in indoor PM(2.5) were evident, but this observation was not consistent across all homes. These findings suggest that other factors beyond the introduction of an improved wood burning device are relevant to improving indoor air quality in wood burning homes.

Lessons learned from a woodstove changeout on the Nez Perce Reservation.

A woodstove changeout program was conducted within 16 homes on the Nez Perce Reservation in Idaho to evaluate the effectiveness of a woodstove changeout in improving indoor air quality. PM(2.5) samples were collected within the common area (rooms where the stoves were located) of the homes both before and after the installation of cleaner burning EPA-certified stoves. During the pre- and post-changeout sampling, indoor PM(2.5) mass, Organic Carbon (OC), Elemental Carbon (EC), and chemical markers of woodsmoke (including levoglucosan) were measured. Sampling results from this study showed that indoor air quality was improved in 10 of the 16 homes following the woodstove changeout and educational training program. Five homes had increased indoor PM(2.5) concentrations following the changeout, while one home did not have final PM(2.5) results for comparison. The median pre-changeout PM(2.5) mass (as measured by TSI DustTraks) was 39.2 μg/m³, with a median post-changeout concentration of 19.0 μg/m³. This resulted in an overall 52% reduction in median indoor PM(2.5), a 36% reduction in mean indoor PM(2.5) and a 60% reduction in PM(2.5) spikes when the old stoves were replaced with EPA-certified stoves. Another significant finding of the project was that targeted education and outreach is a critical component of the overall success of the program. Effective messaging to homeowners on proper use of their new stove is a necessary task of a woodstove changeout.

Environmental Tobacco Smoke, Woodstove Heating and Risk of Asthma Symptoms

The effect of common indoor combustion heating sources on childhood asthma is not well described. The objective was to determine if the use of woodstoves in the home or other factors such as environmental tobacco smoke exposure were associated with the frequency of asthma-related symptoms among children in a rural community. Having a person in the household who smoked was associated with a more than doubling in risk for wheezing and other asthma-related symptoms. The use of woodstoves or other types of heating in the homes of children was not associated with reported wheezing during the winter.

Determination and evaluation of selected organic chemical tracers for wood smoke in airborne particulate matter

PM2.5 is released during combustion reactions and industrial processes. The chemical composition of PM can be a strong indicator of its origin, or source. A method was developed for the determination of selected chemical tracers for wood smoke in particulate matter using solvent extraction and GCMS analysis. The chosen tracers were levoglucosan, dehydroabietic acid, abietic acid, vanillin, acetovanillone, guaiacol, and 4-ethylguaiacol. Deuterated compounds of similar structure to the chosen tracers were employed as standards in the procedure to eliminate the possible effects of incomplete extraction from the filters and other fluctuations throughout the analysis period. The method had recoveries of 105 ± 7.7% for levoglucosan, 64 ± 3.5% for dehydroabietic acid, 60±3.6% for abietic acid, 98±2.2% for vanillin, 102 ± 3.8% for acetovanillone, 104 ± 4.9% for guaiacol and 116 ± 4.7% for 4-ethylguaiacol. The developed analytical method was applied to ambient particulate matter samples collected in Libby, MT. Libby has been designated as a non-attainment area for current USEPA PM2.5 standards, and a recent study showed that 82% of the PM2.5 in Libby resulted from residential wood smoke. The concentrations of levoglucosan, dehydroabietic acid, and abietic acid were found to be strongly correlated with total PM2.5 levels in Libby, while the methoxyphenols did not show a correlation to PM2.5 levels. Levoglucosan, dehydroabietic acid, and abietic acid were found to be suitable tracers for wood smoke in particulate matter.

Urinary levoglucosan as a biomarker of wood smoke: results of human exposure studies.

Urinary levoglucosan was investigated as a potential biomarker of wood smoke exposure in two different controlled experimental settings. Nine subjects were exposed to smoke from a campfire in a controlled setting, and four were exposed to smoke from an older-model wood stove. All subjects were asked to provide urine samples before and after exposure, and to wear personal particulate matter with a diameter of ≤2.5 μm (PM2.5) monitors during exposure. Urinary levoglucosan measurements from both studies showed no consistent response to the smoke exposure. A third experiment was conducted to assess the contribution of dietary factors to urinary levoglucosan levels. Nine subjects were asked to consume caramel and provide urine samples before and after consumption. Urinary levoglucosan levels increased within 2 h of caramel consumption and returned to pre-exposure levels within 24 h. These studies suggest that diet is a major factor in determining urinary levoglucosan levels and that recent dietary history needs to be taken into account for future work involving levoglucosan as a biomarker of wood smoke exposure.