Impact of the wood-burning Justa cookstove on fine particulate matter exposure: A stepped-wedge randomized trial in rural Honduras

Trial design: We evaluated the impact of a biomass stove intervention on fine particulate matter (PM_2.5) concentrations using an individual-level, stepped-wedge randomized trial. Methods: We enrolled 230 women in rural Honduran households using traditional biomass stoves and randomly allocated them to one of two study arms. The Justa stove, the study intervention, was locally-sourced, wood-burning, and included an engineered combustion chamber and chimney. At each of 6 visits over 3 years, we measured 24-hour gravimetric personal and kitchen PM_2.5 concentrations. Half of the households received the intervention after Visit 2 and half after Visit 4. We conducted intent-to-treat analyses to evaluate the intervention effect using linear mixed models with log-transformed kitchen or personal PM_2.5 (separately) as the dependent variable, adjusting for time. We also compared PM_2.5 concentrations to World Health Organization (WHO) guidelines. Results: Arms 1 and 2 each had 115 participants with 664 and 632 completed visits, respectively. Median 24-hour average personal PM_2.5 exposures were 81 μg/m³ (25th–75th percentile: 50–141 μg/m³) for the traditional stove condition (n=622) and 43 μg/m³ (25th–75th percentile: 27–73 μg/m³) for the Justa stove condition (n=585). Median 24-hour average kitchen concentrations were 178 μg/m³ (25th–75th percentile: 69–440 μg/m³; n=629) and 53 μg/m³ (25th–75th percentile: 29–103 μg/m³; n=578) for the traditional and Justa stove conditions, respectively. The Justa intervention resulted in a 32% reduction in geometric mean personal PM_2.5 (95% confidence interval [CI]: 20–43%) and a 56% reduction (95% CI: 46–65%) in geometric mean kitchen PM_2.5. During rainy and dry seasons, 53% and 41% of participants with the Justa intervention had 24-hour average personal PM_2.5 exposures below the WHO interim target-3 guideline (37.5 μg/m³), respectively. Conclusion: The Justa stove intervention substantially lowered personal and kitchen PM_2.5 and may be a provisional solution that is feasible for Latin American communities where cleaner fuels may not be available, affordable, or acceptable for some time. Clinicaltrials.gov: NCT02658383.