Outdoor Pollution Sources Modify the Impact of Improved Cookstoves on Indoor Particulate Matter Levels: Findings from Rural India

Abstract

Background/Aim: Improved cookstoves that decrease biomass fuel pollutants have had mixed results in rural areas of developing countries. Ambient air pollution is usually not taken into consideration when measuring the impact of improved cookstoves. Our aim was to determine the impact of improved cookstoves on particulate matter (PM) levels in two different areas in rural India with different ambient PM levels (PM10, PM2.5 and PM1) and their impact on indoor exposure. Methods: The sample of 105 households from an intervention that provided clean cooking and lighting energy options (Integrated Domestic Energy System (IDES)) and 75 control groups of houses that used traditional mud cookstove (TM). Mean outdoor and indoor air quality (IAQ) of each household was measured for concentrations of PM10, PM2.5, and PM1. Results: Regression analyses of the association between IDES and indoor PM10, PM2.5 and PM1 reduction was only significant in the village with high ambient PM and there was no effect of IDES in the low ambient PM village. After adjusting for level of ambient PM in a multivariate model, IDES was associated with a statistically significant reduction ranging between 14-31% in all indoor PM levels during cooking time and 24-hr average levels. Conclusions: Ambient PM is an effect modifier of the impact of improved cookstoves on reduction of indoor PM. Future analyses of indoor air pollution reduction from cookstoves must take into consideration the effect modification of ambient PM to provide better estimates of the risk reduction from using such cookstoves.