A joint research study by scholars from Harvard, Tsinghua and Harbin Institute of Technology indicates that China may have overlooked one of the key culprits of Beijing’s winter smog: formaldehyde. It is claimed that Chinese environmental policymakers had predominately sought to tackle sulphur dioxide emissions, believing that sulphates were the main driver of air pollution in the capital city. However, the recent study argues that air monitoring devices actually “confused sulphate with hydroxymethane sulphonate (HMS) – a chemical which is formed when formaldehyde and sulphur dioxide react”. This finding may offer some insights into why Beijing continued to experience air pollution even though the government took stringent steps to cut sulphur dioxide emissions including shutting down factories and limiting the use of coal. It is hoped that this new information may support Beijing to develop an effective strategy to combat its air pollution. For instance, as formaldehyde emissions are linked to transportation, oil refineries and the chemical industry, we may see the city make moves to manage these sources of the pollutant.