We hear a lot about particulate matter these days, mostly in the context of air pollution in inner cities. But what about particulate matter in the Amazon rainforest? Well, the short answer is that particulate matter is present in the air above the Amazon, too. And although its concentrations are lower than those in large cities, urbanization and deforestation fires have a significant impact. To find out what that impact exactly is, was the aim of a new study by Suzane de Sá and co-authors.