A TOXIC LEGACY
UPI’s Christine Dell’amore profiles new research on Dioxin’s reproductive dangers
New evidence on the effects of dioxin in the Vietnam-era herbicide Agent Orange suggests the chemical interferes with the reproductive systems of men. The research, led by Dr. Amit Gupta, is one of the first studies to find that men exposed to a type of dioxin called TCDD experience smaller prostate glands and lower testosterone levels — even at minimal exposure to dioxin.
“Now we now know dioxins have an effect on the prostate, and it’s somehow affecting normal development,” says Gupta, a urologist at UT Southwestern Medical School in Dallas.
The study, published in the November issue of Environmental Health Perspectives, also offers new insight into whether lower doses of dioxin are dangerous to human health. Previous studies have observed dioxin’s effects only in highly exposed populations; some research has found a link between these populations and development of cancer.
However, because the study was not a true experiment, it’s not known whether it was really dioxin that led to the effects.
Gupta and colleagues followed participants of the Air Force Health Study for more than 20 years, beginning in 1987. The study had two groups: About 1,200 ranch hands, or veterans who sprayed Agent Orange in Asia between 1962 and 1971, and a comparison group of about 2,400 Air Force veterans not involved in herbicide spraying during the war, says co-author Dr. Arnold Schecter, a professor of environmental sciences at the University of Texas School of Public Health in Dallas. The two groups were matched on age, race and military occupation.
The researchers examined the men in 1982, 1985, 1987, 1992, 1997 and 2002, recording their prostate and reproductive health. In 1987 the research team measured the level of TCDD dioxin in their blood.
As expected, the levels of TCDD — the most toxic form of dioxin — were higher in the ranch hand group than the comparison group, although both groups in the study experienced changes in their reproductive function. These higher levels were associated with a lower risk of diagnosis of a prostate condition called BPH, in which the prostate grows in size. TCDD somehow inhibits the prostate from growing, although scientists are unsure of the mechanism of how it happens, Gupta said.
Of course, most men would want to avoid BPH, since a larger prostate can create several uncomfortable side effects, such as frequent urination.
Yet dioxin’s ability to thwart prostate growth isn’t exactly cause to celebrate, says Gupta — rather, it’s a worrisome indication that dioxins are altering the reproductive system’s natural course.
A reduction in testosterone due to dioxin can also cause several health problems, such as loss of muscle strength, infertility, drop in sexual function and depression.
Since the comparison group had exposures consistent with the exposures of the general American population in 1987, even lesser amounts of dioxin present in the United States may impact Americans who never stepped foot in Vietnam.
“Most of the 30 types of dioxin produced in the United States come from industrial processes such as waste incineration, chlorine bleaching of pulp and paper and other chemical processes. It’s also a component of pesticides and herbicides, which move up the food chain from contaminated crops, to poultry and beef, to humans. Once inside the body, the chemical settles into the fat. That’s why, sadly, human babies get dioxin from their mother’s dioxin-laden milkfat,” says Gupta.
In the United States, the Environmental Protection Agency — which is close to issuing a new scientific reassessment of the health risks of dioxin and dioxin-like compounds exposure — has successfully cut down on much of the dioxin pollution since the 1970s. In fact, quantifiable industrial emissions of dioxin in the United States have fallen more than 90 percent from 1987 levels, according to the EPA.
Since Gupta and colleagues used a 1987 marker of TCDD in their research, the risk could have gone down for the U.S. population exposed to dioxin.
In addition, it may be difficult to compare one type of dioxin — TCDD — to the effects of other types of the chemical. “In the case of Vietnam, where people were exposed almost exclusively to TCDD through Agent Orange, it’s reasonable to attribute any irregularities in the reproductive system to that chemical,” says Dr. John Constable, a former surgeon at Harvard Medical School and one of the first Americans to study the effects of herbicides in Vietnam in the 1960s.
“But if someone has a ragbag of chemicals in their bodies, as Americans likely do, it’s harder to parse out which dioxins really caused the abnormalities.”
Indeed, the number of male reproductive tract disorders, such as testicular cancer, has risen sharply over past decades. “Some scientists have suggested dioxins might be partially responsible for the spike,” the authors wrote. But there could be other endocrine disruptors at play, substances that have already been shown to alter reproductive processes in rat models.
“Although more research could help in nailing down some of the causes of dioxin, the government has decided to discontinue the Air Force Health Study,” Schecter says.
The next 20 years will answer the question as to how much damage Agent Orange did to our Vietnam vets, says Schecter. “With the program now out of existence, that’s really most unfortunate for the health of our vets, and for anyone exposed to dioxins — which is anyone in the industrial world.”