Humans are exposed to thousands of chemicals during their lifetime, through the air they breathe, the food they eat, and the water they drink. A significant number of these chemicals are toxic due to the fact that they can disrupt the endocrine system. Over the past decade, the list of chemicals with endocrine disrupting activity has dramatically increased [142
]. Evidence has shown that EDCs compromise the reproductive system, thyroid signaling mechanisms, as well as tissues and organs associated with energy metabolism, glucose control, fat cell development and satiety. Indeed, it is plausible that all endocrine systems are to some degree affected by environmental chemical exposures. Since EDCs activate the same receptors and signaling pathways as hormones and act at low concentrations, they are subject to the same biological regulatory systems as hormones. And since hormones control all aspects of physiology across the lifespan, the same can be expected from chemicals with endocrine disrupting activity.
Hormones play a critical role in tissue development and the programming of stem cells and tissues during the developmental process. The same can be said for EDCs. The DOHaD paradigm illustrates that many, if not all, diseases have their origin during development. EDCs pose the most risk during the development period as they alter programming, which leads to increased susceptibility to disease later in life. Testing for chemicals with endocrine disrupting activity can be challenging as the effects are often subtle (functional changes such as alterations in epigenetic marks, and changes in gene expression), and they can manifest effects later in life, long after the EDC is eliminated from the body. Over the past 40 years, there has been a significant increase in a variety of endocrine-associated diseases including, infertility, premature puberty, ADHD, obesity and diabetes, and endocrine cancers such as prostate, ovarian and breast. It is biologically plausible that EDCs are playing a significant role in these and other diseases.
The notion that EDCs are significantly impacting human health is of great concern. More data is needed to expand the list of tissues affected by EDCs, and more effort is needed to identify and classify the diseases and dysfunctions they are causing in humans and animal models. Nevertheless, current data is sufficient to identify a public health problem that must be addressed. There must be concerted efforts to reduce exposures to EDCs across the lifespan, with particular emphasis in pregnant women and infants. In addition, it is important for scientists to develop biomarkers to measure exposure to EDCs during development periods. These biomarkers could be used to identify windows of susceptibility to EDCs and to develop early therapeutic interventions.