AGENT ORANGE LINKED TO PROSTATE PROBLEMS

(ENS) -- A toxic chemical contained in the herbicide Agent Orange affects male reproductive health by limiting the growth of the prostate gland and lowering testosterone levels, researchers have found in a study of more than 2,000 Vietnam War Air Force veterans.

Published in the November issue of the journal "Environmental Health Perspectives," the study indicates that exposure to TCDD, the most toxic of the dioxin family of chemicals contained in Agent Orange, may disturb the male endocrine and reproductive systems in several ways.

"Until now, we did not have very good evidence whether or not dioxins affect the human reproductive system," said Dr. Amit Gupta, a urologist at the University of Texas Southwestern Medical Center and the study's lead author.

"Now we know that there is a link between dioxins and the human prostate leading us to speculate that dioxins might be decreasing the growth of the prostate in humans like they do in animals," he said.

Agent Orange is an herbicide that was developed for military use in Vietnam to deny cover and concealment to enemies of the United States and its allies.

The researchers found that veterans exposed to dioxin had lower incidence rates of benign prostate hyperplasia, BPH, a disease that is caused by an enlargement of the prostate.

Patients must strain to pass urine and they urinate frequently. BPH can lead to complications such as an inability to urinate and urinary tract infection.

Although the study found fewer incidences of disease, Dr. Gupta cautioned that the finding should not be interpreted as a positive result.

"It may be construed that a decrease in the risk of BPH is not a harmful effect, but the larger picture is that dioxins are affecting the normal growth and development of the reproductive system," he said.

"Several effective treatments are available for BPH," Dr. Gupta said, "and thus reduction of BPH by a toxic compound is not a desirable effect."

Dr. Claus Roehrborn, professor and chairman of urology at UT Southwestern and a study author, said, "We know that dioxin causes many endocrine disturbances in the human body. The study indirectly proves that BPH is an endocrine disorder."

The study was based on data from the Air Force Health Study, an epidemiologic study of more than 2,000 Air Force veterans who were responsible for spraying herbicides, including Agent Orange, during the Vietnam War.

This group is called the Ranch Hand group because the spray program was called Operation Ranch Hand.

A comparison group was made up of veterans who served in Southeast Asia during the same time period, 1962-1971, but were not involved in the spraying program and so were exposed to dioxins at levels equivalent to the general population.

The veterans were interviewed and underwent physical examinations and lab tests during six examination cycles. The first cycle was conducted in 1982, so the veterans were followed for more than 20 years.

"We found that the risk of developing BPH decreased with increasing exposure to dioxins in the comparison group," said Dr. Arnold Schecter, professor of environmental sciences at the UT School of Public Health Regional Campus at Dallas and a study author.

"The risk of developing BPH was 24 percent lower in the group with the highest dioxin levels compared to the group with the lowest levels. In the Ranch Hand group, the risk of BPH tended to decrease with increased exposure to dioxins, but at extremely high exposure levels there was a tendency for the risk to increase."

The study shows that higher dioxin exposure is associated with decreased testosterone levels, Dr. Gupta said.

"It is known that lower testosterone levels are associated with decreased sexual function, decreased muscle mass and strength, infertility, increased fatigue, depression and reduced bone density," Dr. Gupta said. "However, we could not conclude from this study that dioxin exposure did lead to any of these adverse affects in the veterans in the study."

There has been a rise in disorders of the male reproductive tract over the past several decades, including a decrease in sperm production by almost 50 percent.

Scientists also have found a four-fold increase in testicular cancer, and increases in the incidence of undescended testes and abnormality of the urethra.

The reason for this increase is not known, but it is thought that these disorders might be caused by environmental chemicals that are estrogenic and have endocrine disrupting effects, Dr. Gupta said.

Dioxins are among the most toxic substances known and are thought to be partially responsible for this increase in male reproductive tract disorders. They are formed as byproducts of processes such as incineration, smelting, paper and pulp manufacturing and pesticide and herbicide production.

Humans are exposed to these chemicals primarily through consumption of animal fat and dairy products. Babies are exposed to the highest levels of dioxins through breast milk.

Dioxins are eliminated extremely slowly from the body and they tend to stay in the body for up to several decades after exposure.

Vietnam veterans exposed to Agent Orange have suffered serious and life-threatening conditions. The Department of Veterans Affairs recognizes prostate cancer, respiratory cancers, multiple myeloma, Type II diabetes, Hodgkins disease, non-Hodgkins lymphoma and spina bifida as among the diseases resulting from exposure to the herbicide.

The study points out the necessity to conduct additional environmental studies of the impact of dioxins and other toxins on the male reproductive system, the authors say. Previous research was largely based on animal models.