The Airport Air Quality and Asthma (AAA) indoor air intervention trial for children with asthma: Protocol for a community-based study in South King County, Washington State.

BACKGROUND: For children with asthma, exposure to indoor air pollution increases the risk of a serious asthma exacerbation, which can be life-threatening. Interventions aimed at improving indoor air quality, including the use of a portable air cleaner with a high-efficiency particle air (HEPA) filter, may reduce this risk; however, the effectiveness, feasibility, and acceptability of HEPA air cleaners vary, and more research in various settings is needed. METHODS: In collaboration with a community health worker (CHW) delivered asthma education program, we are conducting a randomized clinical trial to evaluate the effectiveness of HEPA air cleaners to improve indoor air quality and child asthma health in South King County of Washington State, a vulnerable community impacted by air pollution from airports and highway traffic. A key feature of the Airport Air Quality and Asthma (AAA) design is the extensive integration of CHWs, including CHWs recruited from community-based organizations, into multiple aspects of the trial protocol. We aim to recruit up to N = 60 children with asthma, randomized into intervention and less effective filtration (control) groups in a 1:1 ratio, conduct baseline assessments of indoor air quality and airway health, and collect repeated assessments of air quality and airway health during a 3-month intervention period as well as after the trial concludes. Primary effectiveness outcomes are the concentration of indoor air pollution during the intervention period and two measures of child airway health: change in asthma control score pre- and post-intervention and incidence of asthma symptoms during the intervention period. Several secondary outcomes related to air quality and child health will be explored as well. DISCUSSION: To our knowledge, this is the first trial of indoor air filtration and pediatric asthma health in a community highly impacted by airport-related air pollution. The close collaboration with a CHW-delivered asthma program is also unique and important for future translation of results to future public health programming. Study findings will inform future approaches to integrate HEPA air cleaners into existing CHW asthma education programs in this and similar communities. TRIAL REGISTRATION: The AAA research study was retrospectively registered at clinicaltrials.gov (identifier: NCT07047430; registration approved July 1, 2025).