Do improved biomass cookstove interventions improve indoor air quality and blood pressure? A systematic review and meta-analysis

Background Household air pollution (HAP) kills 4 million annually, with access to clean cooking being a challenge for 37% of the world’s population. Whilst there have been advancements in improved biomass cookstove (ICS) technologies, reviews on the impact of these ICS on HAP are now more than three years old. Objectives This review and meta-analysis examines the most recent evidence on the impact of ICS on HAP and blood pressure (BP). Methods A literature search was conducted using scientific literature databases and grey literature. Studies were included if they were published between January 2012 and June 2020, reported impact of ICS interventions in non-pregnant adults in low/middle-income countries, and reported post-intervention results along with baseline of traditional cookstoves. Outcomes included 24- or 48-hour averages of kitchen area fine particulate matter (PM 2.5 ), carbon monoxide (CO), mean systolic BP (SBP) and mean diastolic BP (DBP). Meta-analyses estimated weighted mean differences between baseline and post-intervention values for all outcome measures. Results Nine studies were included; eight contributed estimates for HAP and three for BP. Interventions lead to significant reductions in PM 2.5 (−0.28 mg/m 3 , 95% CI: -0.46, -0.10), CO (−6.59ppm, 95%CI: - 10.73, -2.46) and SBP (−2.82mmHg, 95% CI: -5.53, -0.11); and a non-significant reduction in DBP (−0.80 mmHg, 95%CI: -2.33, 0.73), when compared to baseline of traditional cookstoves. Except for DBP, greatest reductions in all outcomes came from standard combustion ICS with a chimney, compared to ICS without a chimney and advanced combustion ICS. WHO air quality targets were met by post-intervention values for CO but not for PM 2.5. Conclusion Our review suggests that ICS with a chimney results in the greatest reductions in HAP and BP. Further research on qualitative impact of such ICS on end-users is required to understand feasibility of adoption at scale.