Porton Down veterans exposed to chemical warfare agents died slightly earlier than others who did not take part in the tests, an Oxford University study revealed today.

Two papers published in the British Medical Journal reported results from an independent scientific study of death and cancer rates in veterans who took part in the Ministry of Defence’s Human Volunteer Programme at Porton Down, near Salisbury, between 1941 and 1989.

The research team for the study was led by Oxford University academics Dr Katherine Venables and Dr Lucy Carpenter, with co-investigators from the University of London.

The programme tested the effects of exposure to chemical warfare agents on people, and the protective potential of respirators or clothing against them.

Over the course of study, 18,276 men were identified as having taken part in experimental tests at Porton Down and followed up for an average of 40 years between 1941 and 2004.

Porton Down veterans were found to have a slightly higher death rate than a similar group of 17,600 veterans who did not participate.

Speaking about the results, Dr Venables said: "This is the first time that the long-term effect of participation by members of the armed forces in experimental tests at Porton Down has been studied.

"We aimed to include every veteran who participated in tests at Porton Down between the 1940s and the 1980s.

"This has enabled us to build as clear a picture as possible of the overall impact that taking part in tests at Porton Down has had on their long-term health."

Six per cent more men died over the course of the average 40-year follow-up period in the PDV group than in the group of veterans who did not participate in the volunteer programme.

The MoD provided funding for the study.

The research team used cancer registration records and entries for cancer on death certificates to determine rates of cancer in each group of veterans. Overall, the cancer rate was the same in Porton Down veterans and non-Porton Down veterans.

However, cancers that could not be easily defined were more common in the Porton Down Veterans group.

Co-investigator Dr Carpenter said: "What we have found is a small increase in overall death rates in the Porton Down veterans when compared with other veterans but no increase in overall cancer rates.

"Many of the Porton Down veterans have concerns about the effect that taking part in experimental tests will have had on their health.

"We hope the results of this independent study may help to answer some of their questions."