The Future of Sensors for Detecting Air Pollution in Cities Image Credit: Shyjo/Shutterstock.com Air pollution threatens the lives of millions each year. It is now considered to be the largest threat to human health globally. Exposure to air pollution exacerbates a wide range of diseases, including asthma, different types of cancers, heart disease, acute respiratory infections, and pulmonary illnesses. The World Health Organization (WHO) estimates that 91% of the world’s population breathe air that exceeds WHO guideline limits, demonstrating the urgent need to reduce air pollution to limit the vast number of unnecessary deaths (4.2 million annually) caused by exposure to high levels of pollutants.