Air pollution is a major problem around the world that is harming human health and ecosystems. The document discusses high levels of air pollution in several countries and cities such as the USA, China, Mexico, and Asia. It notes that air pollution is estimated to cause 200,000 to 570,000 deaths globally each year and that cars are responsible for 40-90% of the world's air pollution. It calls for action to clean up air pollution to protect the world.