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.

Randomized Trial of Interventions to Improve Childhood Asthma in Homes with Wood-burning Stoves.

BACKGROUND: Household air pollution due to biomass combustion for residential heating adversely affects vulnerable populations. Randomized controlled trials to improve indoor air quality in homes of children with asthma are limited, and no such studies have been conducted in homes using wood for heating. OBJECTIVES: Our aims were to test the hypothesis that household-level interventions, specifically improved-technology wood-burning appliances or air-filtration devices, would improve health measures, in particular Pediatric Asthma Quality of Life Questionnaire (PAQLQ) scores, relative to placebo, among children living with asthma in homes with wood-burning stoves. METHODS: A three-arm placebo-controlled randomized trial was conducted in homes with wood-burning stoves among children with asthma. Multiple preintervention and postintervention data included PAQLQ (primary outcome), peak expiratory flow (PEF) monitoring, diurnal peak flow variability (dPFV, an indicator of airway hyperreactivity) and indoor particulate matter (PM) PM2.5. RESULTS: Relative to placebo, neither the air filter nor the woodstove intervention showed improvement in quality-of-life measures. Among the secondary outcomes, dPFV showed a 4.1 percentage point decrease in variability [95% confidence interval (CI)=-7.8 to -0.4] for air-filtration use in comparison with placebo. The air-filter intervention showed a 67% (95% CI: 50% to 77%) reduction in indoor PM2.5, but no change was observed with the improved-technology woodstove intervention. CONCLUSIONS: Among children with asthma and chronic exposure to woodsmoke, an air-filter intervention that improved indoor air quality did not affect quality-of-life measures. Intent-to-treat analysis did show an improvement in the secondary measure of dPFV. TRIAL REGISTRATION: ClincialTrials.gov NCT00807183. https://doi.org/10.1289/EHP849.

Lung function measures following simulated wildland firefighter exposures.

Across the world, biomass smoke is a major source of air pollution and is linked with a variety of adverse health effects. This is particularly true in the western U.S. where wood smoke from wildland forest fires are a significant source of PM2.5. Wildland firefighters are impacted as they experience elevated PM2.5 concentrations over extended periods of time, often occurring during physical exertion. Various epidemiological studies have investigated wood smoke impacts on human health, including occupational field exposures experienced by wildland firefighters. As there are numerous challenges in carrying out these field studies, having the ability to research the potential health impacts to this occupational cohort in a controlled setting would provide important information that could be translated to the field setting. To this end, we have carried out a simulated wildland firefighter exposure study in a wood smoke inhalation facility. Utilizing a randomized crossover trial design, we exposed 10 participants once to clean filtered-air, 250 µg/m3, and 500 µg/m3 wood stove-generated wood smoke PM2.5. Participants exercised on a treadmill at an absolute intensity designed to simulate wildland firefighting for 1.5 hr. In addition to measured PM2.5 smoke concentrations, mean levels of CO2, CO, and % relative humidity were continuously monitored and recorded and were representative of occupational "real-world" exposures. Pulmonary function was measured at three time points: before, immediately after, and 1-hr post-exposure. Although there were some reductions in FVC, FEV1, and FVC:FEV1 measures, results of the spirometry testing did not show significant changes in lung function. The development of this wood smoke inhalational facility provides a platform to further address unique research questions related to wood smoke exposures and associated adverse health effects.

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 PM2.5, particle counts, and carbon monoxide. Median indoor PM2.5 concentration was 17.5 µg/m3 in wood-burning homes prior to interventions. No significant reductions in PM2.5 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 PM2.5 or particle counts. PM2.5 concentrations were reduced by 68% in the filter intervention homes. Relative to placebo, air filtration unit homes had an overall PM2.5 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.

Dust Allergens within Rural Northern Rocky Mountain Residences.

To date, few studies have characterized allergens within residences located in rural areas of the northern Rocky Mountain region. In this study, we collected dust samples from 57 homes located throughout western Montana and northern Idaho. Dust samples were collected and later analyzed for dust mite allergens Der f 1 and Der p 1, Group 2 mite allergens (Der p 2 and Der f 2), domestic feline (Fel d 1), and canine (Can f 1). Indoor temperature and humidity levels were also measured during the sampling program, as were basic characteristics of each home. Dog (96%) and cat (82%) allergens were the most prevalent allergens found in these homes (even when a feline or canine did not reside in the home). Results also revealed the presence of dust mites. Seven percent (7%) of homes tested positive for Der p 1, 19% of homes were positive for Der f 1, and 5% of homes were positive for the Group 2 mite allergens. Indoor relative humidity averaged 27.0 ± 7.6% within the homes. Overall, humidity was not significantly associated with dust mite presence, nor was any of the other measured home characteristics. This study provides a descriptive assessment of indoor allergen presence (including dust mites) in rural areas of the northern Rocky Mountains, and provides new information to assist regional patients with reducing allergen exposure using in-home intervention strategies.

Indoor particulate matter in rural, wood stove heated homes.

Ambient particulate matter (PM) exposures have adverse impacts on public health, but research evaluating indoor PM concentrations in rural homes in the United States using wood as fuel for heating is limited. Our objectives were to characterize indoor PM mass and particle number concentrations (PNCs), quantify infiltration of outdoor PM into the indoor environment, and investigate potential predictors of concentrations and infiltration in 96 homes in the northwestern US and Alaska using wood stoves as the primary source of heating. During two forty-eight hour sampling periods during the pre-intervention winter of a randomized trial, we assessed PM mass (<2.5µm) and PNCs (particles/cm(3)) in six size fractions (0.30-0.49, 0.50-0.99, 1.00-2.49, 2.5-5.0, 5.0-10.0, 10.0+µm). Daily mean (sd) PM2.5 concentrations were 28.8 (28.5)µg/m(3) during the first sampling period and 29.1 (30.1)µg/m(3) during the second period. In repeated measures analyses, household income was inversely associated with PM2.5 and smaller size fraction PNCs, in particular. Time of day was a significant predictor of indoor and outdoor PM2.5 concentrations, and infiltration efficiency was relatively low (Finf (sd)=0.27 (0.20)). Our findings demonstrate relatively high mean PM concentrations in these wood burning homes and suggest potential targets for interventions for improving indoor air quality and health in rural settings.

A comparison of 1978 and 2006 peak pollen seasons and sampling methods in Missoula, Montana.

A study was conducted in Missoula, Montana to compare local pollen counts from 1978 with those measured nearly 30 years later in 2006 using two different measurement techniques (Durham gravimetric sampler and a Burkard volumetric sampler). Trends in peak pollen times measured during the spring, summer and autumn, respectively, were compared between the two years by Pearson's correlation and frequency of occurrence of plant genus. Meteorological conditions were also examined during each of the two study periods.In comparing the two years, there was a statistically significant linear association between the different counts for the months of April through August, with similar levels of pollen types for any given month. The five predominant pollen types (based on counts) identified in each study were Pinus, Poaceae, Populus, Alnus, and Betula for 2006 and Pinus, Poaceae, Populus, Acer and Artemisia for 1978. In summary most of the genera displayed similar peak pollination timing between the two years, suggesting that results from the Durham (gravimetric) and Burkard (volumetric) sampling methods are comparable when reporting relative frequency of occurrence.