Coal burning produces an array of chemicals and particulates that, when released into the atmosphere, contribute to pollution, poor air quality and threats to public health. Measurements of particulate air pollution typically focus on particles called PM2.5, which have diameters of 2.5 micrometers or less. This group includes nano-sized particles, although these bits of minerals, dust and organics often go undetected because of their tiny size. In a new study, researchers sampling a coal ash spill have unearthed a type of nanoparticle not previously known to be produced by burning coal. While the particles might be useful in detecting pollution problems, they may also have consequences for human and environmental health.