Leukemia Threat to Vietnam Vets

The Otago study will shortly appear in the international journal BMJ Open and was funded by the War Pensions Medical Research Trust Fund.

(AUCKLAND) - New Zealand Vietnam veterans deployed in a "toxic war environment" were exposed to a significantly higher risk of leukaemia, a newly released Otago University study finds.

The study found veterans who served between 1962 and 1971 have double the rate of chronic lymphatic leukaemia compared to the general population, lead author David McBride said.

McBride is an associate professor in the university's department of preventive and social medicine.

Most veterans deployed in the Nui Dat area of Phuoc Tuy province, experienced a "toxic environment" because of the widespread use of 2,4,5-T and 2,4-D as defoliant herbicides, the study found.

This mixture - more commonly known as Agent Orange - was contaminated with the carcinogen 2,3,7,8,TCDD, or dioxin.

However the study does not have specific data on herbicide exposure of individual soldiers, McBride said.

"The US Institute of Medicine, in its report Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam first classified chronic lymphatic leukaemia on its sufficient evidence for cancer list in 2002, based on dioxin toxicity and studies of farm workers exposed to herbicides.

"The cohorts of Australian and New Zealand soldiers are the only group of Vietnam veterans to show an actual excess of the disease."

The Otago study will shortly appear in the international journal BMJ Open and was funded by the War Pensions Medical Research Trust Fund.

McBride and colleagues examined from 1998 to 2008 the health records of 2752 out of nearly 3400 New Zealand military personnel who served in Vietnam.

It was the first cohort study of New Zealand Vietnam veterans to assess long-term health effects of serving in a combat zone, he said.

However, the results also showed that although 407 veterans died over the study period, the overall rate of death from all causes was 15 per cent lower than the general population, suggesting lower incidence of mortality and morbidity. Mortality from cancer was not significantly lower or higher, however, than the general population, and there was no decrease in "all cancer" incidence.

"The pattern of lower overall mortality is known as the 'healthy soldier effect' which is related to the fact that this cohort would have been selected for its health and fitness," McBride said.

"However the study shows a doubling of the risk of mortality from cancers of the head and neck, as well as an increase in oral cancers of the pharynx and larynx. Lung cancer contributed the greatest burden of deaths in both New Zealand and Australian veterans."

McBride said further work was still needed, including the selection of a non-deployed comparison group to reduce the 'healthy soldier effect'.

"As some of the cancers are also associated with smoking and alcohol consumption there is a need to collect further information on confounding factors such as ethnicity, smoking and alcohol use."

The study will be one of those discussed at the annual University of Otago two-day research colloquium in Dunedin this week, under the theme Health of Veterans, Serving Personnel and their Families.