The Spanish cooking oil scandal is thought to have started on 1 May 1981. Poisoned cooking oil was thought to have eventually caused the deaths of around 300 people of the 20,000 or so affected by the problem.
For the scientific review of causes of the outbreak I refer you to:
The Spanish Toxic Oil Syndrome 20 Years after Its Onset: A Multidisciplinary Review of Scientific Knowledge, Emilio Gelpí,1 Manuel Posada de la Paz,2 Benedetto Terracini,3 Ignacio Abaitua,2 Agustín Gómez de la Cámara,4 Edwin M. Kilbourne,5 Carlos Lahoz,6 Bénoit Nemery,7 Rossanne M. Philen,8 Luis Soldevilla,2 and Stanislaw Tarkowski9 (WHO/CISAT Scientific Committee for the Toxic Oil Syndrome) Environmental Health Perspectives Volume 110, Number 5, May 2002, url given here.
