Acute lower respiratory tract infections (LRTIs) account for more than 27% of all hospitalizations among US children under five years of age, with recurrent LRTIs in children a recognized risk factor for asthma. Residential biomass combustion leads to elevated indoor levels of fine particulate matter (PM2.5) that often exceed current health-based air quality standards. PM2.5 exposure is associated with many adverse health outcomes, including a greater than three-fold increased risk of LRTIs. 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. In this project, the investigators propose to test the efficacy of two intervention strategies for reducing indoor wood smoke PM2.5 exposures and children's risk of LRTI in three unique and underserved settings: (1) rural mountain valley communities in western Montana; (2) Navajo Nation communities; and (3) Alaska Native Villages. The investigators will conduct a three-arm randomized placebo-controlled post-only intervention trial in wood stove homes with children less than five years old. Education on best-burn practices and training on the use of simple instruments (i.e., stove thermometers and wood moisture meters) will be introduced as one intervention arm (Tx1). This intervention will be evaluated against an indoor air filtration unit arm (Tx2), as well as a placebo arm (Tx3, sham air filters). The primary outcome will be LRTI incidence among children under five years of age. To allow for detection of exposure and outcome differences within each of the three regions, a sample of 324 homes, or 108 within each study area will be equally assigned to each of the three intervention arms. The overall hypothesis is that a low-cost, educational intervention targeting indoor wood smoke PM2.5 exposures will be sustainable, and can reduce children's risk of LRTI in underserved Native and rural communities.

Rural and Native areas of the western United States (US) and Alaska experience substantial exposure and health disparities compared to more populated urban centers. One such source of disparity is the elevated inhalation exposures related to the use of wood stoves for home heating. Within rural areas of Montana, Alaska, and the Navajo Nation, research has shown that residential biomass combustion leads to indoor levels of fine particulate matter (PM2.5) that often exceed current health-based air quality standards. Parallel findings have been observed in several developing countries where biomass combustion is commonly used for cooking and/or heating. This is concerning, as PM2.5 exposure is associated with many adverse health outcomes, including a greater than three-fold increased risk of acute respiratory tract infections. Throughout the world, lower respiratory tract infections (LRTIs) are the most common cause of death in children under five years of age, and account for more than 27% of all hospitalizations among US children under five years. Importantly, untoward effects of recurrent LRTIs are cumulative in children and a recognized risk factor for asthma.

Currently, there is a global effort to reduce indoor biomass smoke exposures in developing countries. A recent intervention trial found that exposure reductions following the introduction of improved cookstoves was protective for severe infant pneumonia. Similar evidence-based efforts are warranted in rural and Native American communities in the US that suffer from elevated rates of childhood LRTI and commonly use wood for residential heating. The investigators have previously demonstrated that a community-wide wood stove changeout program (i.e., replacing old wood stoves with newer model wood stoves) resulted in reduced wintertime ambient PM2.5 and corresponding reductions in occurrence of childhood wheeze and respiratory infections. In this and other studies, however, inconsistent effects on indoor air quality following the introduction of newer technology wood stoves have been observed. The investigators have also shown that the introduction of air filtration units is a less costly and more efficacious strategy for reducing indoor wood smoke exposures. Nevertheless, the energy costs of operation and need for filter replacement (maintenance) remain barriers to widespread dissemination and continued compliance in rural and economically disadvantaged communities. Experience with these interventions and qualitative input from wood stove experts suggest that educational interventions related to wood stove operation can translate to low-cost and sustainable strategies that reduce indoor biomass combustion exposures and improve respiratory health.

In this project, the investigators propose to test the efficacy of an education-based intervention strategy for reducing indoor wood smoke exposures and children's risk of LRTI in three unique and underserved settings. This study is a three-arm randomized trial in wood stove homes with children less than five years old. Education on best-burn practices and training on the use of simple instruments (i.e., stove thermometers and wood moisture meters) will be introduced as one intervention arm (Tx1). This intervention will be evaluated against an indoor air filtration unit arm (Tx2), as well as a placebo arm (Tx3, sham air filters). The primary outcome will be LRTI incidence among children under five years of age. A sample of 324 homes, or 108 within each study area equally assigned to each of the three intervention arms, will allow for detection of exposure and outcome differences within each of the three regions. Through three Aims, the overall hypothesis is that a low-cost, educational intervention targeting indoor wood smoke (PM2.5) exposures will be an effective, sustainable strategy for reducing children's risk of LRTI in underserved Native and rural communities.

Aim 1: Compare LRTI incidence in each intervention arm (Tx1 and Tx2) to LRTI in the placebo arm (Tx3). Investigators hypothesize that children less than five years old in intervention homes will experience lower LRTI.

Aim 2: Compare indoor PM2.5 concentrations in each treatment arm relative to the placebo arm. Investigators hypothesize that the intervention homes will have lower indoor PM2.5 concentrations.

Aim 3: Compare effectiveness and sustainability of treatment strategies relative to placebo, both within and between regional sites. Investigators hypothesize that Tx1 will be more effective and sustainable than Tx2.

Impact. LRTI is an important cause of morbidity among children, and exposure to biomass smoke puts children at a greater risk of LRTI. By reducing in-home wood smoke exposures, this study will evaluate sustainable evidence-based and culturally appropriate strategies for decreasing occurrence of LRTI. In addition, comparing the effectiveness of these interventions across three unique rural and Native regions will inform translation of study findings into diverse settings that utilize biomass fuels for heating and cooking.

Inclusion Criteria:

• Eligible homes will be any home in the described communities that uses a wood stove as a primary heating source, and has one or more children under the age of five years. The home must include a parent who is capable and willing to record symptom data for the enrolled children and wood stove usage data.

Exclusion Criteria:

• None.

The participants will be followed for four months during each of two successive winter periods for a total of eight months of observation.