Evaluating the effectiveness of a commercial portable air purifier in homes with wood burning stoves: a preliminary study

Portable Air Cleaner Usage and Particulate Matter Exposure Reduction in an Environmental Justice Community: A Pilot Study

Particulate matter (PM) exposure is associated with adverse health outcomes, including respiratory illness. A large fraction of exposure to airborne contaminants occurs in the home. This study, conducted over 5 months in a community with high asthma rates (Chelsea, MA, USA), investigated the use of portable air cleaners (PACs) to reduce indoor PM. Seven asthma-affected households participated, receiving a PAC (Austin Air Health Mate HEPA filter), a QuantAQ sensor to measure PM1, PM2.5, PM10 (µg/m3), and a HOBO plug-load data logger to track PAC usage. Results describe hourly and daily PM concentrations and PAC usage for each household. Hourly average PM concentrations decreased when PACs were turned on (vs. when they were turned off) across households during the study period: PM1 decreased by 0.46 µg/m3, PM2.5 decreased by 0.69 µg/m3, and PM10 decreased by 3.22 µg/m3. PAC usage varied for each household, including constant usage in one household and only usage at certain times of day in others. Higher filtration settings led to lower PM, with significant reductions in some, but not all, homes. Our findings highlight some difficulties in implementing household PAC interventions, yet also provide evidence to support household-level interventions to reduce PM and other indoor sources of air pollution. We also highlight academic-community partnerships as contributing to evidence-based solutions.

A systematic review and meta-analysis of field studies of portable air cleaners: Performance, user behavior, and by-product emissions

Indoor air quality is important for the health of building occupants, and public interest in controlling indoor airborne pathogens increased dramatically with the COVID-19 pandemic. Pollutant concentrations can be controlled locally using portable air cleaners (sometimes called air purifiers), which allow occupants to apply air cleaning technology to meet their needs in the location and times that they find appropriate. This paper provides a systematic review of scientific literature that describes field studies of the effectiveness of portable air cleaners. Over 500 papers were considered, and 148 were reviewed in detail, to extract 35 specific research results (e.g., particulate removal performance) or characteristics (e.g., type of building). These were aggregated to provide an overview of results and approaches to this type of research, and to provide meta-analyses of the results. The review includes: descriptions of the geographical location of the research; rate of publications over time; types of buildings and occupants in the field study; types of air cleaner technology being tested; pollutants being measured; resulting pollutant removal effectiveness; patterns of usage and potential barriers to usage by occupants; and the potential for by-product emissions in some air cleaner technologies. An example result is that 83 of the 148 papers measured reductions in fine particulates (PM2.5) and found a mean reduction of 49 % with standard deviation of 20 %. The aggregated results were approximately normally distributed, ranging from finding no significant reduction up to a maximum above 90 % reduction. Sixteen of the 148 papers considered gaseous pollutants, such as volatile organic compounds, nitrogen dioxide, and ozone; 36 papers considered biological pollutants, such as bacteria, viruses, pollen, fungi, etc. An important challenge, common to several studies, is that occupants run the air cleaners for shorter periods and on low airflow rate settings, because of concerns about noise, drafts, and electricity cost, which significantly reduces air cleaning effectiveness.

Effects of portable air cleaners and A/C unit fans on classroom concentrations of particulate matter in a non-urban elementary school

Given the increased use of air cleaners as a prevention measure in classrooms during the COVID-19 pandemic, this study aimed to investigate the effects of portable air cleaners with HEPA filters and window A/C fans on real-time (1 minute) concentrations of PM less than 2.5 microns (PM2.5) or less than 1 microns (PM1.0) in two classrooms in a non-urban elementary school in Rhode Island. For half of each school day, settings were randomized to "high" or "low" for the air cleaner and "on" or "off" for the fan. Descriptive statistics and linear mixed models were used to evaluate the impacts of each set of conditions on PM2.5 and PM1.0 concentrations. The mean half-day concentrations ranged from 3.4-4.1 μg/m3 for PM2.5 and 3.4-3.9 μg/m3 for PM1.0. On average, use of the fan when the air cleaner was on the low setting decreased PM2.5 by 0.53 μg/m3 [95% CI: -0.64, -0.42] and use of the filter on high (compared to low) when the fan was off decreased PM2.5 by 0.10 μg/m3 [95% CI: -0.20, 0.005]. For PM1.0, use of the fan when the air cleaner was on low decreased concentrations by 0.18 μg/m3 [95% CI: -0.36, -0.01] and use of the filter on high (compared to low) when the fan was off decreased concentrations by 0.38 μg/m3 [95% CI: -0.55, -0.21]. In general, simultaneous use of the fan and filter on high did not result in additional decreases in PM concentrations compared to the simple addition of each appliance's individual effect estimates. Our study suggests that concurrent or separate use of an A/C fan and air cleaner in non-urban classrooms with low background PM may reduce classroom PM concentrations.

Exposure to fine particulate matter (PM2.5) from non-tobacco sources in homes within high-income countries: a systematic review

The health impacts associated with exposure to elevated concentrations of fine particulate matter (PM_2.5) are well recognised. There is a substantial number of studies characterising PM_2.5 concentrations outdoors, as well as in homes within low- and middle-income countries. In high-income countries (HICs), there is a sizeable literature on indoor PM_2.5 relating to smoking, but the evidence on exposure to PM_2.5 generated from non-tobacco sources in homes is sparse. This is especially relevant as people living in HICs spend the majority of their time at home, and in the northern hemisphere households often have low air exchange rates for energy efficiency. This review identified 49 studies that described indoor PM_2.5 concentrations generated from a variety of common household sources in real-life home settings in HICs. These included wood/solid fuel burning appliances, cooking, candles, incense, cleaning and humidifiers. The reported concentrations varied widely, both between sources and within groups of the same source. The burning of solid fuels was found to generate the highest indoor PM_2.5 concentrations. On occasion, other sources were also reported to be responsible for high PM_2.5 concentrations; however, this was only in a few select examples. This review also highlights the many inconsistencies in the ways data are collected and reported. The variable methods of measurement and reporting make comparison and interpretation of data difficult. There is a need for standardisation of methods and agreed contextual data to make household PM_2.5 data more useful in epidemiological studies and aid comparison of the impact of different interventions and policies.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11869-022-01288-8.

Efficacy of air filtration and education interventions on fine particulate matter among rural Native American homes heated with wood stoves: Results from the EldersAIR randomized trial

BACKGROUND

Native Americans living in rural areas often rely upon wood stoves for home heating that can lead to elevated indoor concentrations of fine particulate matter (PM2.5). Wood stove use is associated with adverse health outcomes, which can be a particular risk in vulnerable populations including older adults.

OBJECTIVES

We assessed the impact of portable air filtration units and educational approaches that incorporated elements of traditional knowledge on indoor and personal PM2.5 concentrations among rural, Native American elder households with wood stoves.

METHODS

EldersAIR was a three-arm, pre-post randomized trial among rural households from the Navajo Nation and Nez Perce Tribe in the United States. We measured personal and indoor PM2.5 concentrations over 2-day sampling periods on up to four occasions across two consecutive winter seasons in elder participant homes. We assessed education and air filtration intervention efficacy using linear mixed models.

RESULTS

Geometric mean indoor PM2.5 concentrations were 50.5 % lower (95 % confidence interval: -66.1, -27.8) in the air filtration arm versus placebo, with similar results for personal PM2.5. Indoor PM2.5 concentrations among education arm households were similar to placebo, although personal PM2.5 concentrations were 33.3 % lower for the education arm versus placebo (95 % confidence interval: -63.2, 21.1).

SIGNIFICANCE

The strong partnership between academic and community partners helped facilitate a culturally acceptable approach to a clinical trial intervention within the study communities. Portable air filtration units can reduce indoor PM2.5 that originates from indoor wood stoves, and this finding was supported in this study. The educational intervention component was meaningful to the communities, but did not substantially impact indoor PM2.5 relative to placebo. However, there is evidence that the educational interventions reduced indoor PM2.5 in some subsets of the study households. More study is required to determine ways to optimize educational interventions within Native American communities.

Efficacy of Air Filtration and Education Interventions on Indoor Fine Particulate Matter and Child Lower Respiratory Tract Infections among Rural U.S. Homes Heated with Wood Stoves: Results from the KidsAIR Randomized Trial

BACKGROUND

Millions of rural U.S. households are heated with wood stoves. Wood stove use can lead to high indoor concentrations of fine particulate matter [airborne particles ≤2.5μm in aerodynamic diameter (PM2.5)] and is associated with lower respiratory tract infection (LRTI) in children.

OBJECTIVES

We assessed the impact of low-cost educational and air filtration interventions on childhood LRTI and indoor PM2.5 in rural U.S. homes with wood stoves.

METHODS

The Kids Air Quality Interventions for Reducing Respiratory Infections (KidsAIR) study was a parallel three-arm (education, portable air filtration unit, control), post-only randomized trial in households from Alaska, Montana, and Navajo Nation (Arizona and New Mexico) with a wood stove and one or more children <5 years of age. We tracked LRTI cases for two consecutive winter seasons and measured indoor PM2.5 over a 6-d period during the first winter. We assessed results using two analytical frameworks: a) intervention efficacy on LRTI and PM2.5 (intent-to-treat), and b) association between PM2.5 and LRTI (exposure-response).

RESULTS

There were 61 LRTI cases from 14,636 child-weeks of follow-up among 461 children. In the intent-to-treat analysis, children in the education arm [odds ratio (OR)=0.98; 95% confidence interval (CI): 0.35, 2.72] and the filtration arm (OR=1.23; 95% CI: 0.46, 3.32) had similar odds of LRTI vs. control. Geometric mean PM2.5 concentrations were similar to control in the education arm (11.77% higher; 95% CI: -16.57, 49.72) and air filtration arm (6.96% lower; 95% CI: -30.50, 24.55). In the exposure-response analysis, odds of LRTI were 1.45 times higher (95% CI: 1.02, 2.05) per interquartile range (25 μg/m3) increase in mean indoor PM2.5.

DISCUSSION

We did not observe meaningful differences in LRTI or indoor PM2.5 in the air filtration or education arms compared with the control arm. Results from the exposure-response analysis provide further evidence that biomass air pollution adversely impacts childhood LRTI. Our results highlight the need for novel, effective intervention strategies in households heated with wood stoves. https://doi.org/10.1289/EHP9932.

Improving the Indoor Air Quality in Nursery Buildings in United Arab Emirates

Children inhale indoor air at 400 mL/min∙kg per body weight, 2.76 times more than adults. They have weaker immunity than adults and are more exposed to asthma, allergies, and atopic diseases. The objective of this paper is to suggest effective management and improvement measures for indoor air quality for nurseries. As a methodology, 16 nurseries (total of 35 classrooms) were selected to measure the indoor air quality compared with WHO IAQ Standard, and identify the daily concentration change of the pollutants. Based on the measurements, IAQ improvements for selected facilities are carried out to compare the results before and after improvement. The result has shown that the concentration of Carbon Dioxide (CO₂), Total Volatile Organic Compounds (TVOC), Total Suspended Particles (TSP) and formaldehyde (CH₂O) exceeds WHO IAQ standards. The concentration of CO₂ and TSP is changed mainly by physical activity of children and that of CH₂O and TVOC is changed mainly by ventilation after school start. TVOC decreased by 46.4% and the TSP decreased by 21.7% after air purifier, but CH₂O and TVOC increased 1.8–3.8 times after interior renovation with low-emission finishing materials. After new ventilation installation, the CH₂O and TVOC reduced half and the TSP reduced one third. It is proven that the most effective way to reduce the concentration of air pollutants in nurseries is the installation of a new ventilation system, followed by an air purifier. The renovation with low-emission finishing materials cannot improve IAQ in a short period of time.

A review on reducing indoor particulate matter concentrations from personal-level air filtration intervention under real-world exposure situations

Improving air quality in indoor environments where people live is of importance to protect human health. In this systematic review, we assessed the effectiveness of personal-level use of air filtration units in reducing indoor particulate matters (PM) concentrations under real-world situations following systematic review guidelines. A total of 54 articles were included in the review, in which 20 randomized controlled/crossover trials that reported the changes in indoor fine PM (PM_2.5 ) concentrations were quantitatively assessed in meta-analysis. Standardized mean differences (SMDs) were calculated for changes in indoor PM concentrations following air filtration interventions. Moderate-to-large reductions of 11%-82% in indoor PM_2.5  concentrations were observed with SMD of -1.19 (95% CI: -1.50, -0.88). The reductions in indoor PM concentrations varied by geographical locations, filtration technology employed, indoor environmental characteristics, and air pollution sources. Most studies were graded with low-to-moderate risk of bias; however, the overall certainty of evidence for indoor PM concentration reductions was graded at very low level. Considering the effectiveness of indoor air filtration under practical uses, socio-economic disparities across study populations, and costs of air filter replacement over time, our results highlight the importance of reducing air pollution exposure at the sources.

Assessing effectiveness of air purifiers (HEPA) for controlling indoor particulate pollution

The present study deals with an evaluation of the air purifier's effectiveness in reducing the concentration of different sized particulate matter (PM) and ions in the real-world indoor environment. Two types of air purifiers (API and APII) mainly equipped with High-Efficiency Particulate Air (HEPA) filters that differed in other specifications were employed in general indoor air and the presence of an external source (candles and incense). The gravimetric sampling of PM was carried out by SKC Cascade Impactor and further samples were analyzed for determining ions' concentration while real-time monitoring of different sized PM was done through Grimm Aerosol Spectrometer (1.109). The result showed that API reduced PM levels of different sizes ranged from 12-52% and 29–53% in general indoor air and presence of external source respectively. Concerning the APII, a higher decrease percent in PM level was explored in presence of an external source (52–68%) as compared to scenarios of general indoor air (37–64%). The concentrations of the ions were noticed to be decreased in all three size fractions but surprisingly some ions' (not specific) concentrations increased on the operation of both types of air purifiers. Overall, the study recommends the use of air purifiers with mechanical filters (HEPA) instead of those which release ions for air purification.

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Efficiency of air purifier (AP) in removing indoor air pollutants was observed.

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AP was more effective on small-sized particles than large ones.

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AP of large Clean Air Delivery Rate removed particulate and ions more effectively.

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APs with mechanical filters must be employed instead of ions generators.

Can Public Spaces Effectively Be Used as Cleaner Indoor Air Shelters during Extreme Smoke Events?

During extreme air pollution events, such as bushfires, public health agencies often recommend that vulnerable individuals visit a nearby public building with central air conditioning to reduce their exposure to smoke. However, there is limited evidence that these "cleaner indoor air shelters" reduce exposure or health risks. We quantified the impact of a "cleaner indoor air shelter" in a public library in Port Macquarie, NSW, Australia when concentrations of fine particulate matter (PM_2.5) were elevated during a local peat fire and nearby bushfires. Specifically, we evaluated the air quality improvements with central air conditioning only and with the use of portable high efficiency particulate air (HEPA) filter air cleaners. We measured PM_2.5 from August 2019 until February 2020 by deploying pairs of low-cost PM_2.5 sensors (i) inside the main library, (ii) in a smaller media room inside the library, (iii) outside the library, and (iv) co-located with regulatory monitors located in the town. We operated two HEPA cleaners in the media room from August until October 2019. We quantified the infiltration efficiency of outdoor PM_2.5 concentrations, defined as the fraction of the outdoor PM_2.5 concentration that penetrates indoors and remains suspended, as well as the additional effect of HEPA cleaners on PM_2.5 concentrations. The infiltration efficiency of outdoor PM_2.5 into the air-conditioned main library was 30%, meaning that compared to the PM_2.5 concentration outdoors, the concentrations of outdoor-generated PM_2.5 indoors were reduced by 70%. In the media room, when the HEPA cleaners were operating, PM_2.5 concentrations were reduced further with a PM_2.5 infiltration efficiency of 17%. A carefully selected air-conditioned public building could be used as a cleaner indoor air shelter during episodes of elevated smoke emissions. Further improvements in indoor air quality within the building can be achieved by operating appropriately sized HEPA cleaners.

Air Pollution and Asthma: Critical Targets for Effective Action

Evidence to advocate for cleaner air for people with asthma is not in short supply. We know that air pollution is associated with the development and worsening of the condition and that mitigating interventions can improve respiratory outcomes. We have clear targets, particularly traffic emissions, especially in urban areas, and plenty of potentially effective actions. Road traffic must be reduced, and what remains should be cleaner and greener. Urban green spaces, safe cycle networks and wider pavements will promote active travel and leisure time exercise. Healthcare professionals must ensure people are aware of their air quality, its impact on asthma and the appropriate behaviour to safeguard health. What remains are realistic policies and effective measures, based on the correct scientific evidence, to be taken forth with political courage and investment so that air pollution no longer contributes to the development or worsening of respiratory ill health.

Electrostatic Precipitators as an Indoor Air Cleaner—A Literature Review

Many people spend most of their time in an indoor environment. A positive relationship exists between indoor environmental quality and the health, wellbeing, and productivity of occupants in buildings. The indoor environment is affected by pollutants, such as gases and particles. Pollutants can be removed from the indoor environment in various ways. Air-cleaning devices are commonly marketed as benefiting the removal of air pollutants and, consequently, improving indoor air quality. Depending on the type of cleaning technology, air cleaners may generate undesired and toxic byproducts. Different air filtration technologies, such as electrostatic precipitators (ESPs) have been introduced to the market. The ESP has been used in buildings because it can remove particles while only causing low pressure drops. Moreover, ESPs can be either in-duct or standalone units. This review aims to provide an overview of ESP use, methods for testing this product, the performance of existing ESPs concerning removing pollutants and their byproducts, and the existing market for ESPs.

Control of wildfire-sourced PM2.5 in an office setting using a commercially available portable air cleaner

A steady increase in wildfire event severity and season length has led to greater potential for exposure to fine particulate matter associated with wildfire smoke. Research has found fine particulate matter to be correlated with a myriad of health ailments and thus effective strategies for controlling exposures are needed. In this study, a correction factor associated with wildfire-sourced fine particulate matter was established for a TSI SidePak AM520 by conducting sampling with a co-located MetOne BAM 1020. Portable air cleaner efficacy was assessed by simultaneously measuring PM_2.5 mass concentrations in two identical offices with the inclusion of a portable air cleaner in one. The relationship between indoor and outdoor PM_2.5 mass concentrations was assessed by comparing concentrations recorded in an office to those recorded at the nearest National Ambient Air Quality Standards monitoring station. Results revealed that a portable air cleaner reduced indoor fine particulate matter within an office by 73% and 92% during working and non-working hours, respectively, and that a strong significant correlation (ρ = .91, p = 0.00) existed between indoor and outdoor fine particulate matter mass concentration measurements. A direct relationship between indoor and outdoor PM_2.5 mass concentrations was observed during this study, suggesting that elevated fine particulate matter concentrations due to wildfire smoke could be a concern in the indoor work environment; however the current study determined that the use of a portable air cleaner can substantially decrease fine particulate matter concentrations even in an active office setting.

Wood stove interventions and child respiratory infections in rural communities: KidsAir rationale and methods

BACKGROUND

Acute lower respiratory tract infections (LRTIs) account for >27% of all hospitalizations among US children under five years of age. Residential burning of biomass for heat leads to elevated indoor levels of fine particulate matter (PM2.5) that often exceed current health based air quality standards. This is concerning as PM2.5 exposure is associated with many adverse health outcomes, including a greater than three-fold increased risk of LRTIs. Evidence-based efforts are warranted in rural and American Indian/Alaska Native (AI/AN) communities in the US that suffer from elevated rates of childhood LRTI and commonly use wood for residential heating.

DESIGN

In three rural and underserved settings, we conducted a three-arm randomized controlled, post-only intervention trial in wood stove homes with children less than five years old. Education and household training on best-burn practices were introduced as one intervention arm (Tx1). This intervention was evaluated against an indoor air filtration unit arm (Tx2), as well as a control arm (Tx3). The primary outcome was LRTI incidence among children under five years of age.

DISCUSSION

To date, exposure reduction strategies in wood stove homes have been either inconsistently effective or include factors that limit widespread dissemination and continued compliance in rural and economically disadvantaged populations. As part of the "KidsAIR" study described herein, the overall hypothesis was that a low-cost, educational intervention targeting indoor wood smoke PM2.5 exposures would be a sustainable approach for reducing children's risk of LRTI in rural and AI/AN communities.

Reducing indoor air pollutants with air filtration units in wood stove homes

BACKGROUND

Biomass burning has been shown to be a major source of poor indoor air quality (IAQ) in developing and higher income countries across the world. Specifically, wood burning for cooking and heating contributes to high indoor concentrations of fine (particles with aerodynamic diameters<2.5μm; PM_2.5) and coarse (particles with aerodynamic diameters <10μm and >2.5μm; PMc) particulate matter. Endotoxin, predominantly found within the coarse fraction of airborne particulate matter, is associated with proinflammatory effects and adverse outcomes among susceptible populations. The aim of this study was to assess the efficacy of air filter interventions in reducing indoor PM_2.5, PMc, and PMc-associated endotoxin concentrations in homes using a wood stove for primary heating.

RESULTS

Homes (n=48) were randomized to receive in-room air filtration units with either a high efficiency filter (i.e. active) or a lower efficiency fiberglass filter (i.e., placebo). The active filter intervention showed a 66% reduction in indoor PM_2.5 concentrations (95% CI: 42.2% to 79.7% reduction) relative to the placebo intervention. Both the active and the placebo filters were effective in substantially reducing indoor concentrations of PMc (63.3% and 40.6% average reduction for active and placebo filters, respectively) and PMc-associated endotoxin concentrations (91.8% and 80.4% average reductions, respectively).

CONCLUSIONS

These findings support the use of high efficiency air filtration units for reducing indoor PM_2.5 in homes using a wood stove for primary heating. We also discovered that using lower efficiency, lower cost filter alternatives can be effective for reducing PMc and airborne endotoxin in homes burning biomass fuel.

Efficacy of interventions targeting household air pollution from residential wood stoves

Wood is commonly used for residential heating, but there are limited evidence-based interventions for reducing wood smoke exposures in the indoor environment. The Asthma Randomized Trial of Indoor Wood Smoke (ARTIS) study was designed to assess the efficacy of residential interventions to reduce indoor PM exposure from wood stoves. As part of a three-arm randomized placebo-controlled trial, two household-level interventions were evaluated: wood stove changeouts and air filtration units. Exposure outcomes included indoor measures such as continuous PM_2.5, particle counts, and carbon monoxide. Median indoor PM_2.5 concentration was 17.5 μg/m³ in wood-burning homes prior to interventions. No significant reductions in PM_2.5 concentrations were observed in the 40 homes receiving the placebo filter intervention. Sixteen homes received the wood stove changeout and showed no significant changes in PM_2.5 or particle counts. PM_2.5 concentrations were reduced by 68% in the filter intervention homes. Relative to placebo, air filtration unit homes had an overall PM_2.5 reduction of 63% (95% CI: 47-75%). Relative to the wood stove changeout, the filtration unit intervention was more efficacious and less expensive, yet compliance issues indicated a need for the evaluation of additional strategies for improving indoor air quality in homes using wood stoves.

Impacts of air cleaners on indoor air quality in residences impacted by wood smoke

Residential wood combustion is an important source of ambient air pollution, accounting for over 25% of fine particulate matter (PM2.5) emissions in Canada. In addition to these ambient contributions, wood smoke pollutants can enter the indoor environment directly when loading or stoking stoves, resulting in a high potential for human exposure. A study of the effectiveness of air cleaners at reducing wood smoke-associated PM2.5 of indoor and outdoor origin was conducted in 31 homes during winter 2009-10. Day 1, the residents' wood burning appliance operated as usual with no air cleaner. Days 2 and 3, the wood burning appliance was not operational and the air cleaner was randomly chosen to operate in "filtration" or "placebo filtration" mode. When the air cleaner was operating, total indoor PM2.5 levels were significantly lower than on placebo filtration days (p = 0.0001) resulting in a median reduction of 52%. There was also a reduction in the median PM2.5 infiltration factor from 0.56 to 0.26 between these 2 days, suggesting the air cleaner was responsible for increased PM2.5 deposition on filtration days. Our findings suggest that the use of an air cleaner reduces exposure to indoor PM2.5 resulting from both indoor and ambient wood smoke sources.

Asthma randomized trial of indoor wood smoke (ARTIS): rationale and methods

BACKGROUND

Particulate matter (PM) exposures have been linked with poor respiratory health outcomes, especially among susceptible populations such as asthmatic children. Smoke from biomass combustion for residential home heating is an important source of PM in many rural or peri-urban areas in the United States.

AIM

To assess the efficacy of residential interventions that reduce indoor PM exposure from wood stoves and to quantify the corresponding improvements in quality of life and health outcomes for asthmatic children.

DESIGN

The asthma randomized trial of indoor wood smoke (ARTIS) study is an in-home intervention study of susceptible children exposed to biomass combustion smoke. Children, ages 7 to 17, with persistent asthma and living in homes that heat with wood stoves were recruited for this three arm randomized placebo-controlled trial. Two household-level intervention strategies, wood stove replacement and air filters, were compared to a sham air filter placebo. Improvement in quality of life of asthmatic children was the primary outcome. Secondary asthma-related health outcomes included peak expiratory flow (PEF) and forced expiratory volume in first second (FEV(1)), biomarkers in exhaled breath condensate, and frequency of asthma symptoms, medication usage, and healthcare utilization. Exposure outcomes included indoor and outdoor PM(2.5) mass, particle counts of several size fractions, and carbon monoxide.

DISCUSSION

To our knowledge, this was the first randomized trial in the US to utilize interventions targeting residential wood stoves to assess the impact on indoor PM and health outcomes in a susceptible population.