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

Recent Insights into the Environmental Determinants of Childhood Asthma

PURPOSE OF REVIEW

Ubiquitous environmental exposures, including ambient air pollutants, are linked to the development and severity of childhood asthma. Advances in our understanding of these links have increasingly led to clinical interventions to reduce asthma morbidity.

RECENT FINDINGS

We review recent work untangling the complex relationship between air pollutants, including particulate matter, nitrogen dioxide, and ozone and asthma, such as vulnerable windows of pediatric exposure and their interaction with other factors influencing asthma development and severity. These have led to interventions to reduce air pollutant levels in children's homes and schools. We also highlight emerging environmental exposures increasingly associated with childhood asthma. Growing evidence supports the present threat of climate change to children with asthma. Environmental factors play a large role in the pathogenesis and persistence of pediatric asthma; in turn, this poses an opportunity to intervene to change the course of disease early in life.

Feasibility of residential air quality monitoring to address asthma outcomes

Improving asthma outcomes for underserved populations can be addressed through interventions to improve indoor air quality (IAQ). New protocol for measuring IAQ and health outcomes are imperative given advances in IAQ monitoring technology and challenges in conducting intervention research in homes. In this pilot study HEPA air purifiers and HEPA vacuum cleaners were provided to five homes with children with asthma. For 6 weeks, eight common components of air quality were measured using a low-cost multi-channel air quality monitoring device, with data conveyed directly from participant homes via Wi-Fi connection. In conjunction with periodic surveys on asthma control, impact of asthma on quality of life and intervention compliance, outcomes compared IAQ, home characteristics, and asthma-related measures. This pilot study demonstrates the feasibility of a protocol to evaluate a dual component intervention to improve IAQ in homes, as measured with a low-cost air quality monitoring device.

Effectiveness of filtering or decontaminating air to reduce or prevent respiratory infections: A systematic review

Installation of technologies to remove or deactivate respiratory pathogens from indoor air is a plausible non-pharmaceutical infectious disease control strategy.

OBJECTIVE

We undertook a systematic review of worldwide observational and experimental studies, published 1970-2022, to synthesise evidence about the effectiveness of suitable indoor air treatment technologies to prevent respiratory or gastrointestinal infections.

METHODS

We searched for data about infection and symptom outcomes for persons who spent minimum 20 h/week in shared indoor spaces subjected to air treatment strategies hypothesised to change risk of respiratory or gastrointestinal infections or symptoms.

RESULTS

Pooled data from 32 included studies suggested no net benefits of air treatment technologies for symptom severity or symptom presence, in absence of confirmed infection. Infection incidence was lower in three cohort studies for persons exposed to high efficiency particulate air filtration (RR 0.4, 95%CI 0.28-0.58, p < 0.001) and in one cohort study that combined ionisers with electrostatic nano filtration (RR 0.08, 95%CI 0.01-0.60, p = 0.01); other types of air treatment technologies and air treatment in other study designs were not strongly linked to fewer infections. The infection outcome data exhibited strong publication bias.

CONCLUSIONS

Although environmental and surface samples are reduced after air treatment by several air treatment strategies, especially germicidal lights and high efficiency particulate air filtration, robust evidence has yet to emerge that these technologies are effective at reducing respiratory or gastrointestinal infections in real world settings. Data from several randomised trials have yet to report and will be welcome to the evidence base.

Childhood asthma and household exposures to nitrogen dioxide and fine particles: a triple-crossover randomized intervention trial

OBJECTIVE

Triple-crossover randomized controlled intervention trial to test whether reduced exposure to household NO₂ or fine particles results in reduced symptoms among children with persistent asthma.

METHODS

Children (n = 126) aged 5-11 years with persistent asthma living in homes with gas stoves and levels of NO₂ 15 ppb or greater recruited in Connecticut and Massachusetts (2015-2019) participated in an intervention involving three air cleaners configured for: (1) NO₂ reduction: sham particle filtration and real NO₂ scrubbing; (2) particle filtration: HEPA filter and sham NO₂ scrubbing; (3) control: sham particle filtration and sham NO₂ scrubbing. Air cleaners were randomly assigned for 5-week treatment periods using a three-arm crossover design. Outcome was number of asthma symptom-days during final 14 days of treatment. Treatment effects were assessed using repeated measures, linear mixed models.

RESULTS

Measured NO₂ was lower (by 4 ppb, p < .0001) for NO₂-reducing compared to control or particle-reducing treatments. NO₂-reducing treatment did not reduce asthma morbidity compared to control. In analysis controlling for measured NO₂, there were 1.8 (95% CI -0.3 to 3.9, p = .10) fewer symptom days out of 14 in the particle-reducing treatment compared to control.

CONCLUSIONS

It remains unknown if using an air cleaner alone can achieve levels of NO₂ reduction large enough to observe reductions in asthma symptoms. We observed that in small, urban homes with gas stoves, modest reductions in asthma symptoms occurred using air cleaners that remove fine particles. An intervention targeting exposures to both NO₂ and fine particles is complicated and further research is warranted.

REGISTRATION NUMBER

NCT02258893.

Can individual protective measures safeguard cardiopulmonary health from air pollution? A systematic review and meta-analysis

Evidence supporting the effect of individual protective measures (IPMs) on air pollution is relatively scarce. In this study, we performed a systematic review and meta-analysis to investigate the effects of air purifiers, air-purifying respirators, and cookstove changes on cardiopulmonary health outcomes. We searched PubMed, Scopus, and Web of Science until December 31, 2022, 90 articles and 39,760 participants were included. Two authors independently searched and selected the studies, extracted information, and assessed each study's quality and risk of bias. We performed meta-analyses when three or more studies were available for each IPMs, with comparable intervention and health outcome. Systematic review showed that IPMs were beneficial in children and elderly with asthma along with healthy individuals. Meta-analysis results showed a reduction in cardiopulmonary inflammation using air purifiers than in control groups (with sham/no filter) with a decrease in interleukin 6 by -0.247 μg/mL (95% confidence intervals [CI] = -0.413, -0.082). A sub-group analysis for air purifier as an IPMs in developing counties reduced fractional exhaled nitric oxide by -0.208 ppb (95% confidence intervals [CI] = -0.394, -0.022). However, evidence describing the effects of air purifying respirator and cook stove changes on cardiopulmonary outcomes remained insufficient. Therefore, air purifiers can serve as efficient IPMs against air pollution. The beneficial effect of air purifiers is likely to have a greater effect in developing countries than in developed countries.

Testing of a novel questionnaire of Household Exposure to Wood Smoke

Household air pollution from wood smoke (WS), contributes to adverse health effects in both low- and high-income countries. However, measurement of WS exposure has been limited to expensive in-home monitoring and lengthy face-to-face interviews. This paper reports on the development and testing of a novel, self-report nine-item measure of WS exposure, called the Household Exposure to Wood Smoke (HEWS). A sample of 149 individuals using household wood stoves for heating from western states in the U.S., completed the HEWS during the winter months (November to March) of 2013 through 2016 with 30 subjects having in-home particle monitoring. Hard copy or online surveys were completed. Cronbach's alpha (α), intraclass correlations (ICC), exploratory factor analysis (EFA) and tests of associations were done to evaluate reliability and validity of the HEWS. Based on initial analysis, only 9 of the 12 items were retained and entered in the EFA. The EFA did not support a unitary scale as the 9 items demonstrated a 3-factor solution (WS exposure duration, proximity, and intensity) with Cronbach's α of 0.79, 0.91, and 0.62, respectively. ICC was 0.86 of the combined items with single items ranging from 0.46 to 0.95. WS intensity was associated with symptoms and levoglucosan levels, while WS duration was associated with stove and flume maintenance. The three-dimensional HEWS demonstrated internal consistency and test-retest reliability, structural validity, and initial criterion and construct validity.

Exposure of children to smoke in clay figures craft in Caruaru, state of Pernambuco, Brazil

Introduction

Alto do Moura, a neighborhood located in the city of Caruaru, state of Pernambuco, Brazil, is known by the production of figurative art in clay, which uses wood as the main fuel in its finishing process. Chronic exposure to toxic gases released in combustion can trigger respiratory atopies.

Objectives

To identify children with respiratory atopies accompanied by the Alto do Moura Family Health Unit and the spatial distribution of furnaces used in the burning of figurative art in clay.

Methods

This was an exploratory, observational, descriptive, cross-sectional study analyzing 596 medical records of children with respiratory atopies living in the aforementioned neighborhood from July 2018 to October 2020. Fifty-two children aged 2 to 10 years were identified. A sociodemographic questionnaire was applied, and the location of furnaces, source of smoke, was mapped. Data were collected using the HC Maps^® application, which stores and generates an electronic spreadsheet for analysis. The prevalence of respiratory atopies and the average distance between children's homes and furnaces were calculated.

Results

A prevalence of respiratory atopies of 8.6% was found in the population studied. Allergic rhinitis was the most common diagnosis, followed by asthma. School-age children were the most affected group, and the average distance between children's homes and furnaces was 76.8 meters.

Conclusions

The presence of environmental pollution resulting from burning wood for making figurative art in clay may be contributing to the occurrence of respiratory atopies in children. Preventive measures, such as using exhaust fans, opening windows, and increasing ventilation, should be encouraged.

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 a portable HEPA air cleaner intervention to reduce asthma morbidity among Latino children in an agricultural community

BACKGROUND

Data on pediatric asthma morbidity and effective environmental interventions in U.S. agricultural settings are few. We evaluated the effectiveness of HEPA air cleaners on asthma morbidity among a cohort of rural Latino children.

METHODS

Seventy-five children with poorly controlled asthma and living in non-smoking homes were randomly assigned to asthma education alone or along with HEPA air cleaners placed in their sleeping area and home living room. The Asthma Control Test (ACT) score, asthma symptoms in prior 2 weeks, unplanned clinical utilization, creatinine-adjusted urinary leukotriene E4 (uLTE4 [ng/mg]), and additional secondary outcomes were evaluated at baseline, six, and 12 months. Group differences were assessed using multivariable-adjusted generalized estimating equations. Incident rate ratios of ever experiencing the metrics of poorer asthma health during follow-up (suboptimal asthma management) were estimated using Poisson regression models in secondary analysis.

RESULTS

Mean child age was 9.2 and 8.6 years in intervention and control groups, respectively, and two-thirds of participants were male. Primary analysis of repeated measures of ACT score did not differ between groups (HEPA group mean change compared to controls 10% [95% CI: - 12-39%]). A suggestion of greater decrease in uLTE4 (ng/mg creatinine) was observed (- 10% [95% CI: - 20 -1%]). Secondary analysis showed children with HEPAs were less likely to have an ACT score meeting a clinically defined cutoff for poorly controlled asthma using repeated measures (IRR: 0.45 [95% CI: 0.21-0.97]). In Poisson models, intervention participants had reduced risk of ever meeting this cutoff (IRR: 0.43 [95% CI: 0.21-0.89]), ever having symptoms in the past 2 weeks (IRR: 0.71 [95% CI: 0.52-0.98]), and lower risk of any unplanned clinical utilization (IRR: 0.35 [95% CI: 0.13-0.94]) compared to control participants.

DISCUSSION

The HAPI study showed generally improved outcomes among children in the HEPA air cleaner group. However, primary analyses did not meet statistical significance and many outcomes were subjective (self-report) in this unblinded study, so findings must be interpreted cautiously. HEPA air cleaners may provide additional benefit for child asthma health where traditional asthmagens (traffic, tobacco smoke) are not prominent factors, but larger studies with more statistical power and blinded designs are needed.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04919915 . Date of retrospective registration: May 19, 2021.

Children's Particulate Matter Exposure Characterization as Part of the New Hampshire Birth Cohort Study

As part of the New Hampshire Birth Cohort Study, children 3 to 5 years of age participated in a personal PM_2.5 exposure study. This paper characterizes the personal PM_2.5 exposure and protocol compliance measured with a wearable sensor. The MicroPEM™ collected personal continuous and integrated measures of PM_2.5 exposure and compliance data on 272 children. PM_2.5, black carbon (BC), and brown carbon tobacco smoke (BrC-ETS) exposure was measured from the filters. We performed a multivariate analysis of woodstove presence and other factors that influenced PM_2.5, BC, and BrC exposures. We collected valid exposure data from 258 of the 272 participants (95%). Children wore the MicroPEM for an average of 46% of the 72-h period, and over 80% for a 2-day, 1-night period (with sleep hours counted as non-compliance for this study). Elevated PM_2.5 exposures occurred in the morning, evening, and overnight. Median PM_2.5, BC, and BrC-ETS concentrations were 8.1 μg/m³, 3.6 μg/m³, and 2.4 μg/m³. The combined BC and BrC-ETS mass comprised 72% of the PM_2.5. Woodstove presence, hours used per day, and the primary heating source were associated with the children’s PM_2.5 exposure and air filters were associated with reduced PM_2.5 concentrations. Our findings suggest that woodstove smoke contributed significantly to this cohort’s PM_2.5 exposure. The high sample validity and compliance rate demonstrated that the MicroPEM can be worn by young children in epidemiologic studies to measure their PM_2.5 exposure, inform interventions to reduce the exposures, and improve children’s health.

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.

The Effect of Particulate Matter Reduction by Indoor Air Filter Use on Respiratory Symptoms and Lung Function: A Systematic Review and Meta-analysis

PURPOSE

Exposure to particulate matter (PM) is a key public health issue, but effective intervention has not yet been established. A systematic literature review and meta-analysis has been conducted to assess the relationship between the use of air filters, one of the most commonly studied interventions, and respiratory outcomes in patients with chronic respiratory diseases.

METHODS

We systematically reviewed intervention studies on PM using PubMed, EMBASE, and Cochrane databases up to September 2019. Studies that included data on PM concentration changes and respiratory symptoms or lung function in patients with respiratory diseases were eligible for inclusion. Effect estimates were quantified separately using the random-effects model.

RESULTS

Six studies were included in the quantitative analysis. Air filter use reduced indoor PM2.5 by 11.45 µg/m³ (95% confidence interval [CI], 6.88, 16.01 µg/m³). Air filter use was not associated with improvements in respiratory symptoms in 5 of the 6 studies or significant changes in the predicted forced expiratory volume in one second (FEV1) (mean change, -1.77%; 95% CI, -8.25%, 4.71%). Air filter use was associated with improved peak expiratory flow rate by 5.86 (95% CI, 3.5, 8.19 of standardized difference).

CONCLUSIONS

The findings of this systematic review suggest that air filters may reduce indoor PM and increase peak expiratory rate in asthmatic patients. However, most studies showed no significant effects of air filters on respiratory symptoms or FEV1. Further studies in regions with high-density PM may provide additional information on this issue.

TRIAL REGISTRATION

PROSPERO Identifier: CRD42020156258.

Portable air purification: Review of impacts on indoor air quality and health

A systematic literature review was carried out to examine the impact of portable air purifiers (PAPs) on indoor air quality (PM_2.5) and health, focussing on adults and children in indoor environments (homes, schools and offices). Analysed studies all showed reductions in PM_2.5 of between 22.6 and 92.0% with the use of PAPs when compared to the control. Associations with health impacts found included those on blood pressure, respiratory parameters and pregnancy outcomes. Changes in clinical biochemical markers were also identified. However, evidence for such associations was limited and inconsistent. Health benefits from a reduction in PM_2.5 would be expected as the cumulative body of scientific evidence from various cohort studies shows positive impacts of long-term reduction in PM_2.5 concentrations. The current evidence demonstrates that using a PAP results in short-term reductions in PM_2.5 in the indoor environment, which has the potential to offer health benefits.

Creating Clean Air Spaces During Wildland Fire Smoke Episodes: Web Summit Summary

Effective strategies to reduce indoor air pollutant concentrations during wildfire smoke events are critically needed. Worldwide, communities in areas prone to wildfires may suffer from annual smoke exposure events lasting from days to weeks. In addition, there are many areas of the world where high pollution events are common and where methods employed to reduce exposure to pollution may have relevance to wildfire smoke pollution episodes and vice versa. This article summarizes a recent virtual meeting held by the United States Environmental Protection Agency (EPA) to share research, experiences, and other information that can inform best practices for creating clean air spaces during wildland fire smoke events. The meeting included presentations on the public health impacts of wildland fire smoke; public health agencies' experiences and resilience efforts; and methods to improve indoor air quality, including the effectiveness of air filtration methods [e.g., building heating ventilation and air conditioning (HVAC) systems and portable, free-standing air filtration systems]. These presentations and related research indicate that filtration has been demonstrated to effectively improve indoor air quality during high ambient air pollution events; however, several research questions remain regarding the longevity and maintenance of filtration equipment during and after smoke events, effects on the pollution mixture, and degree to which adverse health effects are reduced.

Exposure to indoor and outdoor air pollution from solid fuel combustion and respiratory outcomes in children in developed countries: a systematic review and meta-analysis

Epidemiological studies have shown a positive association between exposure to outdoor and indoor solid fuel combustion and adverse health effects. We reviewed the epidemiological evidence from Europe, North America, Australia and New Zealand on the association between outdoor and indoor exposure to solid fuel combustion and respiratory outcomes in children. We performed a systematic review and meta-analysis. Pooled relative risks (RRs) and 95% confidence intervals (CI) were calculated using random-effects models. We identified 74 articles. Due to limited evidence on other exposures and outcomes, we performed meta-analyses on the association between indoor wood burning exposure and respiratory outcomes. The RR for the highest vs the lowest category of indoor wood exposure was 0.90 (95% CI 0.77-1.05) considering asthma as an outcome. The corresponding pooled RRs for lower respiratory infection (LRI) and upper respiratory infection (URI) were 1.11 (95% CI 0.88, 1.41) and 1.11 (95% CI 0.85, 1.44) respectively. No association was found between indoor wood burning exposure and risk of wheeze and cough. Inconsistent and limited results were found considering the relationship between indoor wood burning exposure and other respiratory outcomes (rhinitis and hay fever, influenza) as well as indoor coal burning exposure and respiratory outcomes in children. Results from epidemiological studies that evaluated the relationship between the exposure to outdoor emissions derived from indoor combustion of solid fuels are too limited to allow firm conclusions. We found no association between indoor wood burning exposure and risk of asthma. A slight, but not significant, increased risk of LRI and URI was identified, although the available evidence is limited. Epidemiological studies evaluating the relationship between indoor coal burning exposure and respiratory outcomes, as well as, studies considering exposure to outdoor solid fuels, are too limited to draw any firm conclusions.

The nonparametric Behrens-Fisher problem in partially complete clustered data

In randomized trials or observational studies involving clustered units, the assumption of independence within clusters is not practical. Existing parametric or semiparametric methods assume specific dependence structures within a cluster. Furthermore, parametric model assumptions may not even be realistic when data are measured in a nonmetric scale as commonly happens, for example, in quality-of-life outcomes. In this paper, nonparametric effect-size measures for clustered data that allow meaningful and interpretable probabilistic comparisons of treatments or intervention programs will be introduced. The dependence among observations within a cluster can be arbitrary. Point estimators along with their asymptotic properties for computing confidence intervals and performing hypothesis test will be discussed. Small sample approximations that retain some of the optimal asymptotic behaviors will be presented. In our setup, some clusters may involve observations coming from both intervention groups (referred to as complete clusters), while others may contain observations from one group only (referred to as incomplete clusters). In deriving the asymptotic theories, we do not impose any relation in the rate of divergence of the numbers of complete and incomplete clusters. Simulations show favorable performance of the methods for arbitrary combinations of complete and incomplete clusters. The developed nonparametric methods are illustrated using data from a randomized trial of indoor wood smoke reduction to improve asthma symptoms and a cluster-randomized trial for smoking cessation.

Health Benefits of Air Pollution Reduction

Air pollution is a grave risk to human health that affects nearly everyone in the world and nearly every organ in the body. Fortunately, it is largely a preventable risk. Reducing pollution at its source can have a rapid and substantial impact on health. Within a few weeks, respiratory and irritation symptoms, such as shortness of breath, cough, phlegm, and sore throat, disappear; school absenteeism, clinic visits, hospitalizations, premature births, cardiovascular illness and death, and all-cause mortality decrease significantly. The interventions are cost-effective. Reducing factors causing air pollution and climate change have strong cobenefits. Although regions with high air pollution have the greatest potential for health benefits, health improvements continue to be associated with pollution decreases even below international standards. The large response to and short time needed for benefits of these interventions emphasize the urgency of improving global air quality and the importance of increasing efforts to reduce pollution at local levels.

The home air in agriculture pediatric intervention (HAPI) trial: Rationale and methods

BACKGROUND

Data addressing air quality effects on children with asthma in rural U.S. communities are rare. Our community engaged research partnership previously demonstrated associations between neighborhood NH3 and ambient PM2.5 and asthma in the agricultural lower Yakima Valley of Washington. As a next step, the partnership desired an intervention approach to address concerns about pediatric asthma in this largely Latino immigrant, farm worker community.

OBJECTIVE

The Home Air in Agriculture Pediatric Intervention (HAPI) sought to examine the effectiveness of enrichment of an existing asthma education program with portable high-efficiency particulate air (HEPA) cleaners designed to reduce PM2.5 and NH3. We investigated the effect of this enriched approach on these exposures and asthma health measures.

DESIGN

We randomized children with poorly controlled asthma to a control arm (current asthma education program) or an intervention arm (current asthma education program + placement of two indoor air cleaners in the family's home). Outcomes included (1) 14-day integrated samples of indoor air contaminants (PM2.5 and NH3) at baseline and one-year follow-up and (2) child asthma health metrics at baseline, midpoint (4-6 months) and one-year follow-up. These included the Asthma Control Test, symptoms days, clinical utilization, oral corticosteroid use, pulmonary function, fractional exhaled nitric oxide, and urinary leukotriene E4 concentration.

DISCUSSION

To our knowledge, this is the first randomized HEPA cleaner intervention designed to assess NH3 as well as PM2.5 and to evaluate health outcomes of children with asthma in an agricultural region.

Impact of Air Pollution on Asthma Outcomes

Asthma is a chronic respiratory disease characterized by variable airflow obstruction, bronchial hyperresponsiveness, and airway inflammation. Evidence suggests that air pollution has a negative impact on asthma outcomes in both adult and pediatric populations. The aim of this review is to summarize the current knowledge on the effect of various outdoor and indoor pollutants on asthma outcomes, their burden on its management, as well as to highlight the measures that could result in improved asthma outcomes. Traffic-related air pollution, nitrogen dioxide and second-hand smoking (SHS) exposures represent significant risk factors for asthma development in children. Nevertheless, a causal relation between air pollution and development of adult asthma is not clearly established. Exposure to outdoor pollutants can induce asthma symptoms, exacerbations and decreases in lung function. Active tobacco smoking is associated with poorer asthma control, while exposure to SHS increases the risk of asthma exacerbations, respiratory symptoms and healthcare utilization. Other indoor pollutants such as heating sources and molds can also negatively impact the course of asthma. Global measures, that aim to reduce exposure to air pollutants, are highly needed in order to improve the outcomes and management of adult and pediatric asthma in addition to the existing guidelines.

Assessing Impact of Household Intervention on Indoor Air Quality and Health of Children with Asthma in the US-Mexico Border: A Pilot Study

Few studies have investigated household interventions to enhance indoor air quality (IAQ) and health outcomes in relatively low-income communities. This study aims to examine the impact of the combined intervention with asthma education and air purifier on IAQ and health outcomes in the US-Mexico border area. An intervention study conducted in McAllen, Texas, between June and November 2019 included 16 households having children with asthma. The particulate matter (PM2.5) levels were monitored in the bedroom, kitchen, and living room to measure the IAQ for 7 days before and after the intervention, respectively. Multiple surveys were applied to evaluate changes in children's health outcomes. The mean PM2.5 levels in each place were significantly improved. Overall, they significantly decreased by 1.91 μg/m3 on average (p < 0.05). All surveys showed better health outcomes; particularly, quality of life for children was significantly improved (p < 0.05). This pilot study suggests that the combined household intervention might improve IAQ in households and health outcomes for children with asthma and reduce health disparities in low-income communities. Future large-scale studies are needed to verify the effectiveness of this household intervention to improve IAQ and asthma management.

Personal strategies to minimise effects of air pollution on respiratory health: advice for providers, patients and the public

As global awareness of air pollution rises, so does the imperative to provide evidence-based recommendations for strategies to mitigate its impact. While public policy has a central role in reducing air pollution, exposure can also be reduced by personal choices. Qualified evidence supports limiting physical exertion outdoors on high air pollution days and near air pollution sources, reducing near-roadway exposure while commuting, utilising air quality alert systems to plan activities, and wearing facemasks in prescribed circumstances. Other strategies include avoiding cooking with solid fuels, ventilating and isolating cooking areas, and using portable air cleaners fitted with high-efficiency particulate air filters. We detail recommendations to assist providers and public health officials when advising patients and the public regarding personal-level strategies to mitigate risk imposed by air pollution, while recognising that well-designed prospective studies are urgently needed to better establish and validate interventions that benefit respiratory health in this context.

Household Air Pollution from Cooking Fires Is a Global Problem

Over the past several decades, important advances have been made in the United States to ensure that our residents breathe clean air. Still, nearly 12 million homes in this country burn wood for heating. Globally, 3 billion people, or close to half of the world's population, depend on polluting solid fuels such as wood for daily cooking and heating. Unlike in the United States where stoves used for heating are vented, many homes in low-income countries use simple stoves that often lack chimneys, leading to toxic amounts of smoke inside and outside the home. Household air pollution from these fires is the 16th leading risk factor for death and disability worldwide. Childhood pneumonia, chronic obstructive pulmonary disease, and cardiovascular disease have all been associated with household air pollution globally, yet many nurses are not aware of this burden when caring for immigrants and refugees residing in the United States. Global organizations are working to provide access to clean cookstoves (those that run on electricity, solar power, or liquid fuel), and nurses can get involved. This is one step toward improving the lives of vulnerable populations in the United States and worldwide. This series is in collaboration with the Alliance of Nurses for Healthy Environments (https://envirn.org).

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.

Modeling the Impact of an Indoor Air Filter on Air Pollution Exposure Reduction and Associated Mortality in Urban Delhi Household

Indoor exposure to fine particulate matter (PM_2.5) is a prominent health concern. However, few studies have examined the effectiveness of long-term use of indoor air filters for reduction of PM_2.5 exposure and associated decrease in adverse health impacts in urban India. We conducted 20 simulations of yearlong personal exposure to PM_2.5 in urban Delhi using the National Institute of Standards and Technology's CONTAM program (NIST, Gaithersburg, MD, USA). Simulation scenarios were developed to examine different air filter efficiencies, use schedules, and the influence of a smoker at home. We quantified associated mortality reductions with Household Air Pollution Intervention Tool (HAPIT, University of California, Berkeley, CA, USA). Without an air filter, we estimated an annual mean PM_2.5 personal exposure of 103 µg/m³ (95% Confidence Interval (CI): 93, 112) and 137 µg/m³ (95% CI: 125, 149) for households without and with a smoker, respectively. All day use of a high-efficiency particle air (HEPA) filter would reduce personal PM_2.5 exposure to 29 µg/m³ and 30 µg/m³, respectively. The reduced personal PM_2.5 exposure from air filter use is associated with 8-37% reduction in mortality attributable to PM_2.5 pollution in Delhi. The findings of this study indicate that air filter may provide significant improvements in indoor air quality and result in health benefits.

Assessing the impact of air pollution on childhood asthma morbidity: how, when, and what to do

PURPOSE OF REVIEW

Exposure to air pollutants is linked with poor asthma control in children and represents a potentially modifiable risk factor for impaired lung function, rescue medication use, and increased asthma-related healthcare utilization. Identification of the most relevant pollutants to asthma as well as susceptibility factors and strategies to reduce exposure are needed to improve child health.

RECENT FINDINGS

The current available literature supports the association between pollutants and negative asthma outcomes. Ethnicity, socioeconomic status, and presence of certain gene polymorphisms may impact susceptibility to the negative health effects of air pollution. Improved air quality standards were associated with better asthma outcomes.

SUMMARY

The link between air pollution and pediatric asthma morbidity is supported by the recent relevant literature. Continued efforts are needed to identify the most vulnerable populations and develop strategies to reduce exposures and improve air quality.