A large-scale study by the Boston-based Health Effects Institute has found that more than 95% of the world’s population is breathing in air with concentrations of PM2.5 (fine particulate matter less than 2.5 micrometres in diameter) above what the World Health Organisation considers safe (10 µg/m3). Moreover, 60% of people live in areas where the PM2.5 level is above even 35 µg/m3, the WHO’s least stringent guideline, in countries such as China, India, many countries in the Middle East and North and Central Africa. Over six million deaths were attributable to air pollution in 2016 (with over one million being in China alone, and a further million in India), making it the fourth-worst cause of death amongst all health risks, below only high blood pressure, diet, and smoking.  As the HEI report states, “major sources residential, commercial, and industrial combustion of coal and other fossil fuels for heating and power generation, agricultural practices, residential burning of biomass (wood, dung, and peat) for heating and cooking, and traffic, among others.” Coal burning has been found to be the source of around 155,000 of the deaths in China in 2013. The report is sobering reading for all in the combustion industry.