The herbicide Agent Orange, blamed by Vietnam veterans for a host of health problems, apparently does not cause reproductive problems in males or birth defects among their offspring, a long-awaited study reported yesterday.
An analysis of 200 mice, done by a team of federal agencies called the National Toxicology Program (NTP), is the first scientific attempt to evaluate veterans' charges that Agent Orange affected their sex lives and caused them to father deformed children.
"We failed to get an indication of a significant increase in birth defects or decreased fertility," said Dr. James Lamb of the National Institute of Environmental Health Sciences, who directed the study.
A scientific panel of the White House's interagency work group on Agent Orange, meanwhile, recommended in its fourth regular report that further health effects studies should regard the mere face of service in Vietnam as a possible cause of problems. Research now tries to focus on the existence and degree of exposure to a particular chemical.
Because many chemicals may cause or aggravate health problems such as cancer, studies of the veteran population cannot link those problems to any one of the many chemcials to which there could have been exposure, the report said. Studies "should provide evidence . . . that the risk is service-connected," if such a link exists, the panel wrote.
"It is our opinion that a prudent approach is to deisgn and conduct studies that indicate service in Vietnam as the casual factor," the group said.
Adoption of such an approach by the Veterans Administration, one member of the interagency panel, could mean a major policy shift. It would have major repercussions for thousands of Vietnam veterans whose claims for medial compensation have foundered on inability to relate their health problems to specific chemcial exposures.
The military dumped an estimated 107 million pounds of the defoliant Agent Orange over Vietnam between 1967 and 1969. Use of the chemcial was ended when high rates of miscarriage and deformed children were reported among Vietnamese women exposed to it. Veterans' groups have charged that the herbicide was carelessly handled and that those handling it were not told of any possible danger.
The male mouse study exposed to 100 mice to varying strengths of the three components of Agent Orange: the two defoliants 2,4-D and 2,4,5-T and the contaminant TCDD, also called dioxin. A control group of 100 mice was not exposed.
As expected, the exposed mice lost weight and suffered changes in their thymus glands and livers, effects "primarily related to the TCDD content of the mixture," the study said.
However, they remained healthy, ate well and showed no effects in any other organ by the end of the 20-week study. After eight weeks of Agent Orange exposure, the mice were mated for another eight weeks to groups of females that were then checked for fertility, fetal condition and offspring.
"No significant increase in reproductive abnormalities in the exposed groups was observed," the report said. "Exposure . . . did not appear to influence the fetal or [infant] development or the viability of offspring sired by these mice."
The mice exposed to Agent Orange components did not differ from the control group in numbers of impregnations, in stillbirths or birth defects in offspring, or in the ratio of male to female offspring. The males' rate of mating was the same, the sperm counts and sperm activity level were the same, and testicle condition was the same in both groups.
Steve Champlin of the Vietnam Veterans of America acknowledged that the results "certainly weaken our case on this point," but noted that other variables from Vietnam exposure could be involved in veterans' alleged reproductive problems. "I don't think this is definitive," he said.
He said he approved of the intragency group recommendation that Vietnam service be regarded as the significant factor in future research. "The interaction has to be looked at," he said.
Veterans Administration head Max Cleland, a Vietnam veteran, called the study "another piece of the puzzle" and said he would refer it to his advisory committee on herbicides.
The VA already is compensating veterans for illnesses demonstrably linked to their military service, Cleland said. "It's when they show up 10 years later with a problem that it's a more difficult case," he said.
Phillip Schneider of Dow Chemical Corp.; which manufactures Agent Orange, called the report "very good news for the Vietnam era veterans." He added that the study "substantiates Dow studies that conclude that 2, 4,5-T cannot be the cause of birth defects cited by the servicemen."
The NTP study noted that other research has found that sperm formation is affected or testes are damaged by "high [lethal range] doses of TCDD" -- applications that were not used in this survey.
Pregnant animals exposed to the levels used only on males in this test gave birth to offspring with cleft palates or kidney malformations. Other studies have focused on the effects of dioxin alone, and many have shown that high doses cause birth defects and stillbirths.
The Environmental Protection Agency is trying to ban all uses of 2,4,5-T, which is still permitted for control of forest undergrowth in some areas, because of its allegedly unavoidable contamination with dioxin. Dow is fighting the proposed ban.