HEPA filters in inner-city schools: can they mitigate asthma?

Published Online: September 15, 2016

Asthma is one of the most common chronic diseases in childhood in the United States, accounting for over 10 million missed school days every year. School children typically spend 7 to 12 hours a day in school, and the school indoor environment can be host to a wide range of asthma-exacerbating agents, including particulate air pollutants (eg, fine particulate matter [PM2.5] and black carbon [BC]). Traffic emissions are an important source of pollutants in schools, because schools are often centrally located within a community and consequently are closer to heavy traffic routes. In addition, there are many idling cars and buses for pickup and drop-off. While school exposures are undoubtedly important for asthma morbidity, most environmental intervention studies have been conducted in individual homes, given the significant administrative challenges of intervening at a school-level. Consequently, little is known about the role of school environmental exposures and the efficacy of school-based environmental interventions.

A study by Jhun et al. published in The Journal of Allergy and Clinical Immunology: In Practice is the first to pilot high efficiency particulate air (HEPA) cleaners as a school-based intervention and assess asthma morbidity outcomes among inner-city children. The Jhun and colleagues recruited 25 children with asthma from three urban elementary schools in the United States, and randomized half of them to receive active HEPA cleaners and the other half to receive sham air cleaners. The air cleaners were run continuously for a full academic school year. Before and throughout the school year, asthma symptoms, lung function, and indoor particulate air pollutant concentrations were measured in regular intervals.

In the intervention group, the authors observed a significant reduction in indoor particulate pollutants—fine particulate matter was reduced by up to 49% and black carbon was reduced by up to 58%. The magnitude of reductions was within the range reported by previous studies to have clinically meaningful effects on asthma morbidity. While the pilot was not powered to evaluate health effects, the authors found modest improvement in asthma symptoms and lung function in the intervention group. Larger studies are needed to fully evaluate the effects of the air cleaner intervention on asthma outcomes.

This pilot study is the first to demonstrate that an air cleaner intervention in classrooms is feasible and can be effective in reducing particulate pollutants in inner-city schools. This study suggests that the school environment might be considered as an effective target for reduction of asthma morbidity, and larger studies are needed to comprehensively asses the role of classroom/school-based interventions in reducing exposures for children in a community.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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