Abstract

This study evaluates how long-term use (i.e., at least one year) of three types of residential ventilation interventions, some of which are coupled with improved central filtration, affects asthma outcomes in adults by reducing exposure to indoor air pollutants. We conducted a quasi-randomized, parallel-group intervention trial involving 51 adults with physician-diagnosed asthma across 40 homes. Each home received one of three interventions: continuous energy recovery ventilators (ERVs), intermittent central-fan-integrated supply (CFIS) systems, or continuous bathroom exhaust fan(s). Homes with ERV or CFIS systems also received central air filtration upgrades to MERV 10 filters, replaced quarterly. Indoor and outdoor air pollutants were measured quarterly. Asthma Control Test (ACT) scores were collected monthly and health-related quality of life and stress were assessed at baseline and endline. Overall, the interventions led to a 6.3 % increase in ACT scores (p < 0.001) over a > 12-month duration, while the increase was 5.4 % when comparing ACT scores within the initial 12-month window following interventions (p < 0.001). The ERV group experienced the greatest improvement, with an 8.4 % increase in ACT scores (p < 0.001) and an increase in the proportion of participants with well-controlled asthma from 50 % to 86 % (p = 0.030). Additionally, the association between reduced indoor pollutant concentrations and asthma outcomes showed that a one standard deviation decrease in indoor NO₂ (IQR: 9.3 ppb) was associated with a 7.1 % increase in ACT scores (p = 0.034). Subgroup analysis indicates that asthma improvements were greater among participants aged ≥45, Black/African American individuals, and those with incomes below $75,000, compared to their respective comparison groups, driven in part by having lower baseline ACT scores.