Improved cookstoves enhance household air quality and respiratory health in rural Rwanda.

Household air pollution (HAP) from biomass combustion in traditional cooking methods poses significant health risks, particularly in rural communities of low- and middle-income countries. Improved cookstoves (ICS), designed to enhance combustion efficiency and reduce emissions, have been promoted as a transitional alternative towards cleaner cooking. However, evidence of their benefits remains mixed and context-specific. A randomized controlled trial was conducted to evaluate the impact of introducing the Save80 ICS on the respiratory health of adults in rural settlements in Rwanda. The study comprised two assessment rounds, and participants (n = 1001) were divided into two groups: one using traditional cooking methods and one using improved cookstoves. Baseline and follow-up data were collected through structured questionnaires and lung function tests. Furthermore, HAP was measured in a field campaign at households cooking with the ICS or traditional methods. The primary outcomes included respiratory symptoms, spirometry (FVC, FEV, and PEF), and exposure to particulate matter (PM) and its components (EC, OC, BC, BrC, and PAH). We found that households using the ICS spent, on average, 34% less time cooking and had 77% lower indoor PM levels. BC and BrC exposure decreased by 50% and 78%, respectively; OC and TC concentrations were 58% and 45% lower. PAH concentrations showed inconsistent patterns, with most species presenting non-statistically significant changes, constraining objective conclusions. Over the study period (3 years), ICS users reported lower prevalence of cough (-11%) and mucus production (-9%), and showed better forced vital capacity than users of traditional methods. A comparison of lung function decline over time showed that the ICS users had lower deterioration of FVC over three years. This study documents the effects and benefits of introducing ICS. While limitations such as the lack of baseline HAP data during the first health assessment and inconclusive PAH concentrations constrain interpretations and quantified causality, the results contribute to the evidence on the health and indoor air pollution impacts of ICS adoption in rural East African areas.