Health effects of liquid and gaseous fuels for household energy use: systematic evidence mapping

Exposure to household air pollution results in a substantial global health burden. The World Health Organization (WHO) Guidelines for Indoor Air Quality: Household Fuel Combustion stipulate emission rates for household energy devices should meet air quality guidelines and protect health. Liquefied petroleum gas (LPG), biogas, natural gas (NG), and alcohol fuels are considered clean for health due to their low emissions at the point of use. In light of the ongoing energy transition and increasing emphasis on these fuels, it is imperative to provide an updated synthesis of the impacts of these fuels on health. A systematic review was completed on the health effects of liquid and gaseous fuels for household energy use for cooking, heating, and lighting across high-, middle- and low-income countries. Comprehensive searches were undertaken in 12 international databases and selected studies were compiled into a new publicly available WHO Health Effects of Household Liquid & Gaseous Fuels Database, containing key study characteristics including pollutants and/or health outcomes measured. This database was then mapped to understand the breadth of evidence and potential gaps. From 48 130 search results, 587 studies were extracted for inclusion in the database on completion of the full-text review. Studies represented low-, middle- and high-income countries (HICs) over several decades - there has been a substantial increase in evidence from low- and middle-income countries (LMICs) published in the last decade, particularly in Asia. Most evidence focused on LPG for cooking in LMICs or NG used in HICs for cooking and heating. Women were the most studied demographic, with self-reported health outcomes and symptoms being the most common assessment method. Particulate matter and nitrogen oxides were the most monitored pollutants. A wide array of health symptoms and disease and injury outcomes were assessed, and most concerned respiratory health. This is the first time that evidence on the health effects of liquid and gaseous fuels for household energy use has been systematically catalogued and mapped. Most evidence concerned cooking and heating, with a paucity of information on the health effects from lighting. Limited evidence was available on the health effects of liquid fuels (such as alcohol fuels), with most studies concerning gaseous fuels. The WHO Health Effects of Household Liquid & Gaseous Fuels Database represents a valuable resource to enable the examination of the positive and negative health effects from these fuels.