London grows cleaner.
D000397:Air Pollution / Q000517:prevention & control*; D008131:London; D010100:Oxygen / Q000032:analysis; D012722:Sewage; D014867:Water / Q000032:analysis; D014876:Water Pollution / Q000517:prevention & control*
D012722:Sewage; D014867:Water; D010100:Oxygen