A new study appears to back concerns Vietnam War veterans have about Agent Orange.
The research by the University of Otago's Department of Preventive and Social Medicine shows Vietnam veterans who served from 1962-1971 have double the rate of chronic lymphatic lukemia compared to the general population.
Many of the veterans deployed experienced a "toxic environment" and were exposed to Agent Orange.
"The study also 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," lead author Dr David McBride said.
"Lung cancer contributed the greatest burden of deaths in both New Zealand and Australian veterans."
Out of the 3,400 people who served in Vietnam, the study examined the health records of 2752 men from 1988 to 2008.
This is the first cohort study of New Zealand Vietnam War veterans which assesses the long-term health effects of serving in a combat zone.