The experimental studies of the effects of chemical warfare agents conducted on thousands of British military personnel over several decades at the Porton Down facility in the United Kingdom have been an ongoing source of controversy regarding the scientific, ethical, and moral environment in which they took place.1 Concerns about effects on health increased following a coroner’s finding in 2004 of unlawful killing regarding the death of a Porton Down subject in 1953 after cutaneous administration of a chemical warfare nerve agent in a non-therapeutic experiment. This finding understandably raised important questions about the longer term health of the 18 000 British veterans who took part in the Porton Down experiments.2 To investigate this, two linked studies have assessed whether the risks of cancer or mortality are higher in veterans who took part in tests compared with those who did not.3 4

Established in 1916 in response to the use of chemical warfare agents against British troops in the first world war, the Porton Down facility was later expanded because of the threat posed …