Male fish are becoming hermaphroditic due to environmental insults (such as chemicals in the water), says participants in a new study from North Carolina State University not yet published. Where they once had the usual testes containing abundant sperm that made them suitable for reproduction, male fish now may have testes that contain eggs, and their ability to reproduce has become questionable. 
What is causing such an unnatural occurrence? Powerful endocrine disrupters known as xenoestrogens are the culprit, according to the study authors. These are estrogens similar in structure to the estrogens made in the body of the female of the species, but in males as well as females, they function as hormone disruptors. Xenoestrogens have become ubiquitous in the environment. They come from things man-made, including pollution, pesticides, and plastics.
Black bass and sunfish, commonly found in the fresh waters of North Carolina, were studied by the researchers, who had tested 20 streams and rivers containing xenoestrogens during the 2012 spawning season and detected 135 types of them. They found that 60% of the black bass tested had eggs in their testes, as did 10% of the sunfish they evaluated. Forty-three of the xenoestrogen types the team documented in 2012 were found in these fish. 
“Males guard the nest, create spawning nests for young, and guard fertilized eggs, said Crystal Lee Pow, a PhD student at North Carolina State who was one of the investigators. “Males are crucial for hatching success, and their behavior could be altered by exposure to contaminants and the presence of the intersex condition.”
Why were so many of the black bass affected? Dana Kolpin, from the U.S. Geological Survey, noted that not all species are impacted in the same manner.
Are Xenoestrogens a Threat to Humans?
In both men and women, the role of hormones in the body is communication. Their release sends a chemical message to body components telling them what to do to maintain health and homeostasis. Chemicals from the environment can mimic our natural hormones, dock into the receptors the body has for them, and alter this communication. Organs involved with reproduction are especially vulnerable to receiving altered messages, and so are the immune and neurological systems.
Estrogen has many roles in the bodies of both men and women, such as building healthy bone, powering cognition, and enabling reproduction, but men need only a fraction of the estrogen that women do. Getting too much can tip the scales toward femininity, and such things as the development of man-breasts.
If high estrogen goes on long enough, prostate and testicular cancer can develop. As you can probably see, xenoestrogens are particularly hard on men because they increase estrogen exponentially, and can lead to the development of more estrogen receptors.
Women don’t get a free pass either. Xenoestrogens do not biodegrade, and they are stored in fat cells. This means that when a body is being assaulted by xenoestrogens docking in its estrogen receptors, the message is sent to to make more fat so it has a place to put them.
Another outcome of xenoestrogens may be breast cancer, because they have no balancing hormones as the estrogen naturally produced in the body does. This allows it to stimulate breast cells unabated. Women exhibiting xenoestrogens have breasts that are more dense in nature, a marker of breast cancer risk.
Prolonged exposure to xenoestrogens has also been indicated in other conditions, such as infertility, endometriosis, early onset of puberty, miscarriages, and diabetes.
The Women in Balance Institute, a part of National College of Natural Medicine has compiled a list of the most potent xenoestrogens and guidelines to use for reducing exposure. Be sure to check it out here.