Exposure to Dioxins Influences Male Reproductive System

A dioxin toxin contained in the herbicide Agent Orange affects male reproductive health by limiting the growth of the prostate gland and lowering testosterone levels, researchers at UT Southwestern Medical Center have found in a cohort study of more than 2,000 Air Force veterans who served during the Vietnam War.

The study, published in the November issue of the journal Environmental Health Perspectives, indicates that exposure to TCDD, the most toxic dioxin 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 UT Southwestern 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."

The researchers found that veterans exposed to dioxin had lower incidence rates of benign prostate hyperplasia (BPH), better known as enlarged-prostate disease. BPH is a disease in humans that is caused by an enlargement of the prostate. Patients must strain to pass urine and they also must urinate frequently. BPH can lead to complications such as an inability to urinate and urinary tract infection. Surgery is sometimes needed.

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."

Regarding the decreased risk for BPH found in the veterans groups, 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. Moreover, several effective treatments are available for BPH and thus reduction of BPH by a toxic compound is not a desirable effect."

The study was based on data from the Air Force Health Study (AFHS). The AFHS is 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. Agent Orange was contaminated by a dioxin called 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD).

This study also involved a comparison group comprising veterans who served in Southeast Asia during the same time period, 1962-1971, but were not involved in the spraying program and thus 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.