Urologists from the University of Texas Southwestern Medical Center say that a dioxin in the herbicide Agent Orange impacts male reproductive health by impeding the growth of the prostate gland and lowering testosterone levels. Their findings, published in the journal Environmental Health Perspectives, are based on a study of more than 2,000 Air Force veterans who served during the Vietnam War. UT Southwestern urologist, Dr. Amit Gupta, said the dioxin in question - 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) - appears to upset the male endocrine and reproductive systems in several different ways. "Until now, we did not have very good evidence whether or not dioxins affect the human reproductive system," said Gupta. "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."
Gupta's study found that vets exposed to the TCDD dioxin had lower incidence rates of benign prostate hyperplasia (BPH - an enlarged prostate).
But Gupta cautioned that the finding should not be interpreted the wrong way. "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."
"We found that the risk of developing BPH decreased with increasing exposure to dioxins," said co-researcher Dr. Arnold Schecter. "The risk of developing BPH was 24 percent lower in [men] with the highest dioxin levels compared to the group with the lowest levels. 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."
Dioxin exposure is also associated with decreased testosterone levels, although Gupta did not make that connection with the study subjects. "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," he explained. "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."
Gupta said that additional environmental studies of the impact of dioxins and other toxins on the male reproductive system were needed. Previous research was largely based on animal models, he said, noting that the urgency of further research is underlined by a rise in disorders of the male reproductive tract over the past several decades. These disorders include a decreases in sperm production, an increase in testicular cancer and cryptorchidism (undescended testes) and hypospadias (abnormality of the urethra).
It is thought that these disorders might be caused by environmental chemicals that are estrogenic and have endocrine-disrupting effects. Dioxins are some of 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. Worryingly, they are eliminated extremely slowly from the body and they tend to stay in the body for several years to several decades after exposure.
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