UC Irvine

Emissions from solid fuel use play a role both in climate forcing of the atmosphere and in the health ofthe global population through exposures in homes and contributions of solid fuel use to ambient and regional air pollution. Assessments of the overall impacts from emissions from household solid fuels used in cookstoves at a population level have been hampered by large variations in reported emission factors measured using different approaches with inconsistent conclusions between fuel types. In this thesis, emissions from traditional Indian cookstoves are evaluated for animal dung and brushwood, two of the most commonly utilized fuels in India, using both uncontrolled in-home measurements and minimally-directed cooking tasks performed in rural Indian kitchens. Following the validation of a moisture probe for use with dung fuels, emissions measurements from both the minimally directed and uncontrolled cooking tests demonstrated a negative correlation between fine particulate (PM2.5) emission factors and global forcing using 100-year global warming potentials. While the United Nations Clean Development Mechanism and voluntary carbon markets have featured emissions from cookstoves with a value of approximately 10 million dollars per year in 2020, these measurements that for the first time also include formation of secondary organic aerosol imply cookstoves are climate neutral at ~10 grams of primary PM2.5 per kilogram of dry fuel, which falls squarely in the middle of the range of emissions typically reported in global inventories (5-12 g/kg dry fuel). Emissions from solid fuels in cookstoves also cause major health burdens in global populations. In 2016, emissions from solid fuels were estimated to cause 2.6 million deaths and 77 million DALYS on a global basis, greater than Malaria, HIV and TB combined. Current global burden of disease approaches, however, do not incorporate the approximately 500 million people who live in homes that primarily cook outdoors. To refine estimates of the health burdens caused by solid fuel use, models were developed to estimate personal exposure contributions from outdoor emissions to allow the incorporation of outdoor cooking into Global Burden of Disease models. Notably, emissions from outdoor cooking can be much higher than those of indoor cooking while still contributing to personal exposures at levels less than the World Health Organization Air Quality Guidelines (WHO AQG) and interim targets due to the greater dispersion of pollutants in outdoor environments. While particulate matter emissions from solid fuel use are comprised of a wide variety of compounds, many unique to different fuel types, polycyclic aromatic hydrocarbons (PAHs) have been recognized as some of the more toxic constituents of particulate matter emissions, and are associated with cancer endpoints. In these emissions measurements, the ratio of high- to low-temperature combustion was predictive of synthesis of 2-3 ring particulate bound PAHs. Increased elemental carbon (EC) emissions, however, were better predicted by increases in modified combustion efficiency (MCE), since EC emissions reflect the balance between increased PAH synthesis and soot formation which reduces PAH concentrations. To estimate overall health implications of emissions from these stoves a modified box-model was used to estimate personal exposures to mixed fuels used in the Chulha, which would result in an average of approximately 2.7 cancers per 100,000 individuals cooking with these fuels. To alleviate these health burdens a suite of interventions are necessary, however, the effectiveness of different interventions approaches has not been systematically evaluated. Meta-analysis of randomized control trials of interventions indicated that use of simple chimneys and hoods were often more effective than the installation of unvented advanced combustion cookstoves in homes.