Bombs containing B. anthracis spores were detonated on Gruinard island in 1942 and 1943 as a part of a British research programme set up in response to fears that the Germans were developing biological weapons. In 1986 island was decontaminated by spraying with 5% formaldehyde. As a demonstration of confidence in the success of the decontamination operation a flock of 40 sheep was allowed to graze for several months with no ill effects.