Fuel switching and energy stacking in low-income households in South Africa: A review with recommendations for household air pollution exposure research

Households stack and switch the fuels they use to meet their energy needs for cooking, heating and lighting. The type of fuel used and how fuels are stacked and switched affects household air pollution concentrations and consequently impacts human health. Fuel use patterns are often incorporated into household air pollution studies as an exposure proxy, but this is not always done in a comprehensive manner, especially as the fuel stacking and switching phenomena are excluded from the research methodology. Many low-income households in South Africa do and are likely to continue to stack and switch the fuels they use, including a range of polluting energy sources such as coal or wood, substantially contributing to the country's disease burden. This review paper sought to identify how studies have assessed fuel stacking and switching in the context of household air pollution studies to help guide researchers to develop improved surveys and questionnaires which incorporate household fuel stacking and switching practices in a more detailed manner for exposure studies. While quantitative data remains the gold standard, obtaining detailed information on fuel use practices can significantly improve our understanding of associated air pollution exposure. We demonstrate that more comprehensive and localized studies are necessary when we seek to fully understand fuel stacking and switching practices for household air pollution exposure studies in epidemiological research. This is also important for effective policy development and implementation.