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Estimating the health benefit of reducing indoor air pollution in a randomized environmental intervention.

ABSTRACT: Recent intervention studies targeted at reducing indoor air pollution have demonstrated both the ability to improve respiratory health outcomes and to reduce particulate matter (PM) levels in the home. However, these studies generally do not address whether it is the reduction of PM levels specifically that improves respiratory health. In this paper we apply the method of principal stratification to data from a randomized air cleaner intervention designed to reduce indoor PM in homes of children with asthma. We estimate the health benefit of the intervention amongst study subjects who would experience a substantial reduction in PM in response to the intervention. For those subjects we find an increase in symptom-free days that is almost three times as large as the overall intention-to-treat effect. We also explore the presence of treatment effects amongst those subjects whose PM levels would not respond to the air cleaner. This analysis demonstrates the usefulness of principal stratification for environmental intervention trials and its potential for much broader application in this area.

SUBMITTER: Peng RD

PROVIDER: S-EPMC5042208 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature

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Estimating the health benefit of reducing indoor air pollution in a randomized environmental intervention.

Peng Roger D RD Butz Arlene M AM Hackstadt Amber J AJ Williams D'Ann L DL Diette Gregory B GB Breysse Patrick N PN Matsui Elizabeth C EC

Journal of the Royal Statistical Society. Series A, (Statistics in Society) 20140715 2

Recent intervention studies targeted at reducing indoor air pollution have demonstrated both the ability to improve respiratory health outcomes and to reduce particulate matter (PM) levels in the home. However, these studies generally do not address whether it is the reduction of PM levels specifically that improves respiratory health. In this paper we apply the method of principal stratification to data from a randomized air cleaner intervention designed to reduce indoor PM in homes of children ...[more]

PMID: 27695203

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Project description:BackgroundIndoor air quality represents a modifiable exposure to Chronic Obstructive Pulmonary Disease (COPD) health. In a randomized controlled trial (CLEAN AIR study), air cleaner assignment had causal effect in improving COPD outcomes. It is unclear, however, what is the treatment effect among those for whom intervention reduced air pollution and whether it was reduction in fine particulate matter (PM2.5) or nitrogen dioxide (NO2) that contributed to such improvement. Because pollution is a posttreatment variable, treatment effect cannot be assessed while controlling for pollution using intention-to-treat (ITT) analysis.ObjectiveUsing principal stratification method, we assess indoor pollutants as the intermediate variable, and determine the causal effect of reducing indoor air pollution on COPD health.MethodIn randomized controlled trial, former smokers with COPD received either active or placebo HEPA air cleaners and were followed for 6 months. Saint George's Respiratory Questionnaire (SGRQ) was the primary outcome and secondary measures included SGRQ subscales, COPD assessment test (CAT), dyspnea (mMRC), and breathlessness, cough, and sputum scale (BCSS). Indoor PM2.5 and NO2 were measured. Principal stratification analysis was performed to assess the treatment effect while controlling for pollution reduction.ResultsAmong those showing at least 40 % PM2.5 reduction through air cleaners, the intervention showed improvement in respiratory symptoms for the active (vs. placebo), and the size of treatment effect shown for this subgroup was larger than that for the overall sample. In this subgroup, those with active air cleaners (vs. placebo) showed 7.7 points better SGRQ (95%CI: -14.3, -1.1), better CAT (β = -5.5; 95%CI: -9.8, -1.2), mMRC (β = -0.6; 95%CI: -1.1, -0.1), and BCSS (β = -1.8; 95%CI: -3.0, -0.5). Among those showing at least 40 % NO2 reduction through air cleaners, there was no intervention difference in outcomes.ConclusionAir cleaners caused clinically significant improvement in respiratory health for individuals with COPD through reduction in indoor PM2.5.Trial registrationClinicalTrials.gov: NCT02236858.

Project description:Because most people spend the majority of their time in microenvironments, indoor air pollution (IAP) has gained more attention than outdoor air pollution recently. It is indeed crucial to understand IAP sources and the factors that influence human exposure. We synthesized evidence on IAP levels and contributing factors in Ethiopia from available literature, utilizing findings from 19 studies to retrieve 66 relevant values. Particulate matters (PM2.5, PM4, PM10, and TSP), as well as gaseous pollutants such as carbon monoxide (CO), nitrogen dioxide (NO2), polyaromatic hydrocarbons (PAHs), and total volatile organic compounds (TVOCs), were analyzed. The calculated mean concentrations for PM2.5, PM10, NO2, TVOCs, and CO were 477.47 μg/m3, 228.38 μg/m3, 63.84 μg/m3, 1361.79 μg/m3, and 18.82 ppm, respectively, all of which exceeded the annual WHO exposure guidelines. Geographical location, stove type, and household activities showed a variation in pollutants concentration. The higher levels of pollutants were attributed to emissions from biomass fuel used for baking injera, wot preparation, and conducting a coffee ceremony, as well as poor ventilation, season, cooking time, and tobacco smoke. The health risk assessments for exposure to various domestic activities were found to be acceptable, except for PM10, with the highest correlation with an acute respiratory infection. Although improved cookstove technology has been proposed as a sustainable energy source, investigations in Ethiopia have revealed that there is still room for public health protection. There is a paucity of research on the relationship between indoor and outdoor air pollution. Future research should prioritize these issues, with a focus on the link between IAP exposure and health effects. In conclusion, there is a higher IAP concentration in Ethiopia so the community should be made aware of it as well as related health effects, and immediate mitigation measures are needed to achieve a reduction in exposure.

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Estimating the health benefit of reducing indoor air pollution in a randomized environmental intervention.

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Estimating the health benefit of reducing indoor air pollution in a randomized environmental intervention.

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