AGENT ORANGE AND BIRTH DEFECTS TO BE FOCUS OF A UT-HOUSTON STUDY
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HOUSTON -- (January 8, 1998) -- The Environmental Protection Agency has awarded The University of Texas-Houston School of Public Health a $874,195 grant to determine whether exposure to an ingredient found in Agent Orange during the Vietnam War can be associated with neural tube defects in the veterans' children.
The researchers will assess U.S. servicemen and women who served in Vietnam from 1962-75 for exposure to dioxin, an ingredient found in Agent Orange and other defoliants used in Vietnam. It is the first study of its kind to include women veterans. It is also the first to look at the possibility of an underlying genetic susceptibility to dioxin toxicity linked with an adverse health outcome.
The research team, led by Anne Sweeney, Ph.D., will focus its efforts on one neural tube defect--spina bifida--but hope to look at other congenital malformations. Spina bifida is a birth defect in which the spinal cord did not completely close during early fetal development. Many children with spina bifida may have permanent weakness and partial loss of sensation in the legs as well as other medical problems.
"We'll be looking at paternal and maternal genotype, their exposure to dioxin and birth defects in their offspring," said Sweeney, who is assistant professor of epidemiology.
Dubbed "Agent Orange" for the orange band used to mark the storage drums, this herbicide was used to defoliate trees and shrubbery in Vietnam from 1962-75. It was contaminated with dioxin, once hailed as "one of the most perplexing and potentially dangerous chemicals ever to pollute the environment" by a national Scientific Review Committee. It is an unwanted byproduct of many manufacturing and agricultural processes.
Sweeney explained that although the majority of aerial spraying involving Agent Orange took place between 1967-68, the highest concentration of dioxin was used between 1962-65. Called Agents Pink, Purple and Green, these chemicals had on average 16 times the average dioxin concentration than Agent Orange.
Although women were not directly involved in combat or spraying of herbicides, they did serve in areas where herbicides were routinely used. Most women served in medical units, and herbicides were routinely sprayed around the perimeters of the camps.
Debbie del Junco, Ph.D., a co-investigator on the project and developer of the National Registry of Women Veterans, explained the importance of including women veterans.
"Birth defects would more likely result from maternal than paternal dioxin exposure, and the length of time dioxin levels remain in the body depends on the amount of body fat," del Junco said, explaining that women typically have a higher percentage of body fat than men.
The research team hopes to include veterans who have been missed in previous dioxin exposure studies. Until last year, only those who served in the Vietnam War from 1965-75 were considered Vietnam veterans, although military operations were taking place as far back as 1962, when much of the heavier concentrations of dioxin were used.
"Misclassification has had a profound impact on the studies of dioxin and adverse reproductive events in Vietnam veterans," said del Junco, who is also assistant professor of epidemiology. She said that many veterans were missed not only because of the years served, but also because prior to 1971, the military used military identification numbers rather than social security numbers as identifiers.
Phase one of the project will involve looking at birth and death certificates to identify parents of children born with neural tube defects between the years of 1965-90 and cross matching with veteran service records. In phase two, the research team plans to enroll at least 100 veteran parents of children born with spina bifida and an equal number of veterans who parented children without birth defects. The next step is to obtain blood samples, which will be sent to a laboratory for genetic analysis at UT-Houston and dioxin screening at the University of California at Davis. Those participating in the study will be questioned through surveys as well.
Suppose two veterans were exposed to the same amount of dioxin. One had a normal baby. Another had a spina bifida baby. What's the explanation?
del Junco said that previous research has indicated that those who carry the genotype, Cytochrome P450, may be more susceptible to the effects of dioxin exposure. She said a particular allele of this gene initiates a multi-enzyme pathway that can activate the toxic action of dioxin. UT-Houston School of Public Health geneticist and co-investigator Xifeng Wu, M.D., Ph.D., assistant professor, will analyze blood samples for this genetic susceptibility.
The research team plan on involving veterans from throughout the U.S. They will use records from various governmental agencies, such as the Veterans Administration, to conduct the study. The research team is also interested in hearing from Vietnam veterans who have had an offspring with a neural tube defect.
Others involved in the study include Sharon Cooper, Ph.D., Chuan-Chuan Wun, M.D., Ph.D., and Elaine Symanksi, Ph.D., all from UT-Houston School of Public Health; Arnold Gorin, M.D., Veteran Affairs, Houston Medical Center; Mike Denison, Ph.D., University of California at Davis; Lowell Sever, P.D., Battelle Research Laboratory; and Major Kevin Grayson, Brooks Air Force Base.
*** Photos available upon request.
This news release is available on the World Wide Web at http://www.uth.tmc.edu/uth_orgs/pub_affairs/news.html
The University of Texas-Houston Health Science Center is dedicated to building a model health sciences center for the 21st century. It is a model built on education, research and patient care devoted to the maintenance of health and the prevention of disease. Located in the world-famous Texas Medical Center, the University is the state's most comprehensive institution of health sciences, comprising schools of medicine, dentistry, public health, nursing, allied health and biomedical sciences. In 1995, the Institute of Molecular Medicine for the Prevention of Human Diseases was created.
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