Cindy Tumiel, Express-News, San Antonio, November 21, 2006
Dioxin, the toxin contained in the Vietnam-era herbicide Agent Orange, appears to limit the growth of the prostate gland, potentially suppressing male hormones and causing infertility and decreased bone and muscle mass, a long-term study of Air Force Vietnam War veterans finds.
The conclusions are the latest from the Air Force Health Study, which was directed by San Antonio and Dallas-area scientists and began in 1982. The study tracks the health of almost 1,000 veterans who were involved in spraying the defoliant and compares them with 1,300 other Air Force Vietnam personnel who did not directly have contact with the chemical.
More than 50 research papers have been published since the study began. The latest findings appear in this month’s issue of the journal Environmental Health Perspectives.
The military sprayed millions of gallons of Agent Orange from 1962 to 1971 to kill vegetation that could conceal enemy troops.
In the latest study, scientists analyzed the dioxin levels in blood samples drawn in 1987, said Dr. Amit Gupta, a urologist at the University of Texas Southwestern Medical Center in Dallas, the lead author.
In their analysis, scientists found that soldiers who had higher levels of dioxin in their blood had a lower incidence of benign prostatic hyperplasia, or BPH, an abnormal enlargement of the prostate gland. But even men in the comparison group that did not handle Agent Orange directly had lower rates of BPH, Gupta said.
This should not be interpreted as a positive finding, he cautioned.
“BPH is thought to be the disease, and anything decreasing it can be thought of as a positive thing.
“But dioxins are very toxic chemicals. If you look at the larger picture, what they actually are doing is inhibiting the growth of the prostate so it is affecting the reproductive system, and that is not a good thing.”
The study also found a correlation between higher levels of dioxin exposure and lower levels of testosterone, the male sex hormone that contributes to bone and muscle mass and sexual functions.
The study could not show, though, that Agent Orange directly caused any of these conditions in the veterans, but it did establish that dioxin exposure does influence male reproductive hormones, said Gupta and Joel Michalek, a professor of epidemiology at the University of Texas Health Science Center who was principal investigator of the overall study.
The Air Force study officially ended in September. Scientists now are trying to get permission from the veterans involved so they can continue to analyze blood and tissue samples collected during the years the study was funded.
More research is important if scientists are to understand the full impact of dioxin, said Michalek, who was at Brooks AFB, now Brooks City-Base, during most of the years of the study.
“There are many health conditions that are suspected to be related to exposure to Agent Orange,” he said. “Many of those had to do with endocrine disruption, having to do with hormones … reproduction, including testicular and prostate cancer.”

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