industrial zones on tokyo bay were developed as early as the meiji era (1868–1912). the keihin industrial zone was built on reclaimed land in kanagawa prefecture to the west of tokyo. this was expanded to the keiyō industrial zone in chiba prefecture along the north and east coasts of tokyo bay after world war ii. the development of the two zones has resulted in the largest industrialized area in japan. the large-scale industrial zones of the coastal tokyo region have caused significant air and water pollution.