Singapore has some of the worst air quality in the world. Air pollution levels are high year-round, and they often exceed the safe limit set by the World Health Organization (WHO). The main sources of air pollution in Singapore are cars and trucks, factories, and coal-fired power plants. Singapore has taken steps to improve air quality, such as introducing a congestion charge and expanding its public transportation system, but more needs to be done. Air quality in Singapore is rated as “very unhealthy” on the Air Quality Index (AQI).