Impact of residential cooking and heating on temporal changes of black carbon in rural India

Rural households in India and other low- and middle-income countries (LMICs) commonly use solid biomass fuels (SBF) for cooking and winter heating. SBF combustion emits pollutants like black carbon (BC), which contributes to local warming and poses health risks. This study examines how traditional SBF use affects hourly indoor and outdoor BC concentrations in two northern Indian villages during early winter. Indoor BC concentrations ranged from 4.2-37.6 μg m^-3 in outdoor enclosed kitchens and 5.7-33.3 μg m^-3 in indoor kitchens. Integrating BC measurements with community survey data indicated that usual cooking times corresponded with peak BC concentration levels. Concentrations declined more rapidly during the day after morning cooking, due to improved atmospheric ventilation. Afternoon reductions (30-34% indoors, 49-53% outdoors) were linked to increased boundary layer height and wind speed, while stable late-night conditions limited dispersion. Higher evening and nighttime concentrations during colder days were likely driven by increased outdoor burning for space heating. Despite 81% of households subscribing to LPG, SBF use persists, highlighting fuel stacking and barriers to cleaner fuel adoption. In resource-limited settings where mixed fuel use is common, prioritizing LPG for evening cooking could meaningfully reduce daily BC exposure and serve as a practical step toward cleaner energy transitions.