New York City particulate air pollution. Illustration of a visualisation of New York City (NYC), showing the volume of air saturated each day by PM2.5 particles from boilers heating buildings. The colours show emissions from buildings that burn number 6 oil (red), buildings that burn number 4 oil (pink), and emissions from buildings before they were converted to less polluting fuels (green). The NYC Clean Heat program (launched in 2011) has improved air quality and saved lives by eliminating heavy oil use and promoting the adoption of cleaner fuels. The saturation here is the legal maximum of 15 micrograms per cubic metre averaged over a year.