Increased concentrations of DDE in breast milk has also been correlated to a decreased period of lactation. There have also been reports of declining sperm quality and increased testicular cancer over the last several decades. At this point there is considerable uncertainty regarding the causal relationship between the presence of specific environmental chemicals and subsequent adverse effects in humans. Because of the startling findings in wildlife studies, and suggestions in the scientific literature on cancer and reproductive effects in humans, it is important to move rapidly to understand the impact of exposure to these chemicals on human health. Indeed, residues of these compounds can be measured in people around the world.
Exposure currently is via eating contaminated fish.
Zoeller has shown that PCBs can exert permanent effects on the thyroid hormones and brain development. Developmental exposure to a commercial mixture of PCBs causes elevation of serum thyroid hormones and a decrease in thyroid hormone receptor levels in the hippocampus, the area responsible for specific kinds of learning. This combination of animal- mechanistic studies with human epidemiologic studies should provide the data needed to protect the public health from this type of endocrine disruptors. The public health significance of these data is that the enlarged prostates may lead to prostate cancer - a form of a cancer that has been increasing in the human population. The Bisphenol A exposure during development also significantly reduced daily sperm production per gram of adult testis, increased preputial gland weight, all of which could affect fertility.