The study, conducted by a group of U.S. Air Force and other researchers, analysed cancer rates among nearly 1,500 Air Force veterans who served in Southeast Asia during the Vietnam War, but did not actually spray Agent Orange or other herbicides.
Even though they did not work with Agent Orange, veterans in the comparison group had significant blood levels of TCDD, the highly toxic dioxin contaminant of Agent Orange. For veterans with blood TCDD levels above the median, cancer risk was 60 percent higher than for veterans with lower levels.
The increased risk was not limited to any specific type of cancer, although much of it was related to digestive and respiratory cancers and of the skin cancer melanoma. Veterans whose time in Southeast Asia was above the median were more than twice as likely to develop prostate cancer, compared to those with shorter tours of duty. Prostate cancer risk was unrelated to TCDD level.
There was also a significant interaction between duration of service and dioxin contamination - veterans who served longer in Southeast Asia tended to have higher blood levels of TCDD. Cancer risk was highest for vets who spent more than two years in Southeast Asia and had TCDD levels above the median.
A recent study found increased rates of cancer - specifically prostate cancer and melanoma - in Air Force veterans who sprayed Agent Orange during the Vietnam War. That study also suggested possible increases in cancer risk in the comparison group of Air Force veterans who served in Southeast Asia but did not spray Agent Orange.
The new results support the finding of increased cancer rates for veterans with higher TCDD levels, even though they were not directly exposed to Agent Orange. TCDD may promote the development of cancer even at very low levels of exposure. Another possible explanation is that blood TCDD levels reflect some other, unknown risk factor.
MEDICA.de; Source: Lippincott Williams & Wilkins