1. NABU (then the BfV) starts a campaign against destruction of the countryside through land clearance.

  2. Hermann Joseph Müller (1890 - 1965) discovers X-rays to be agents of mutation.

  3. The first German Nature Conservation Day (Deutscher Naturschutztag DNT) took place in Munich from 26 July - 28 July 1925. Since 1957 the conference is held every two years.

  4. Accident insurance is extended, at first to cover 11 occupational illnesses.

  5. A Prussian act to protect trees is passed in 1922, with positive effects in conurbations, above all.

  6. The Oppau explosion occurred on September 21, 1921 when a tower silo storing 4,500 tonnes of a mixture of ammonium sulfate and ammonium nitrate fertilizer exploded at a BASF plant in Oppau, now part of Ludwigshafen, Germany, killing 561 people and injuring about 2,000 more. About 80 percent of all buildings in Oppau were destroyed.