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) 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 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 (separately) as the dependent variable, adjusting for time. We also compared PM 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 exposures were 81 μg/m (25th-75th percentile: 50-141 μg/m) for the traditional stove condition (n=622) and 43 μg/m (25th-75th percentile: 27-73 μg/m) for the Justa stove condition (n=585). Median 24-hour average kitchen concentrations were 178 μg/m (25th-75th percentile: 69-440 μg/m; n=629) and 53 μg/m (25th-75th percentile: 29-103 μg/m; n=578) for the traditional and Justa stove conditions, respectively. The Justa intervention resulted in a 32% reduction in geometric mean personal PM (95% confidence interval [CI]: 20-43%) and a 56% reduction (95% CI: 46-65%) in geometric mean kitchen PM. During rainy and dry seasons, 53% and 41% of participants with the Justa intervention had 24-hour average personal PM exposures below the WHO interim target-3 guideline (37.5 μg/m), respectively.

Conclusion: The Justa stove intervention substantially lowered personal and kitchen PM 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.