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.

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.

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.

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.