What is the Endocrine System?

It is a system that contains the following (Source: www.epa.gov):

• Glands located throughout the body.
• Hormones that are made by the glands and released into the bloodstream or the fluid surrounding cells.
• Receptors in various organs and tissues that recognize and respond to the hormones.

What does the Endocrine System do?

“The endocrine system regulates all biological processes in the body from conception through adulthood and into old age, including the development of the brain and nervous system, the growth and function of the reproductive system, as well as the metabolism and blood sugar levels. The female ovaries, male testes, and pituitary, thyroid, and adrenal glands are major constituents of the endocrine system”. (Source: epa.gov)

Figure 1 below shows the Endocrine glands of a human.

Figure 1. The Human Endocrine Glands. Source: http://kidshealth.org/parent/general/body_basics/endocrine.html (April 5, 2004)

What is an Endocrine Disruptor?

EPA defines an Endocrine Disruptor as “an exogenous natural or anthropogenic agent that produces reversible or irreversible adverse effects at the level of the individual, population and/or community by interfering with the synthesis, storage-release, secretion, transport-clearance, binding, action, or elimination of endogenous hormones in the body”.

Why is Endocrine Disruption important?

There is evidence that the number of incidences of various cancers is increasing (Figure 2). Although there are no direct evidences, there may be some correlations between the cancers and endocrine disrupting chemicals.

Figure 2. Trends of Cancer rates within the past 30 years. Source: Lomborg, Bjorn. 2001. The Skeptical Environmentalist. Cambridge University Press.

Many studies show the physiological changes among animals exposed to endocrine disruptors. One example: Fish living downstream of wastewater treatment plant has high changes in sexual characteristics compared to fish living upstream (Figure 3).

Figure 3. Smaller graph (summary) shows that sexual characteristics of fish living downstream of wastewater treatment plants are changed. Source: Lomborg, Bjorn. 2001. The Skeptical Environmentalist. Cambridge University Press.

Where do Endocrine Disrupting Chemicals come from?

Some examples of EDCs are:

1. Natural Estrogens, Animal Hormones

2. Phytoestrogens, which are compounds naturally excreted by plants.

3. Synthetic hormones such as from birth control pills

4. Therapeutic compounds such as Tamoxifen

5. Detergents.

Their ability to degrade with time varies on the chemical nature of each compound. Most of these compounds are not removed in a conventional wastewater treatment plant, thus flowing right through the treatment system and into the environment.

What do some of these EDCs look like?

Figures 4 and 5 show some chemical structures of chemicals of hormones that will initiate an endocrine response. Compounds in Figure 4 are natural (except for dexamethasone). Too many 17β-estradiol may be a form of an endocrine disruption. When exposed to unnatural compounds such as those in Figure 5 may be a problem and might lead to an endocrine disruption.

17b-Estradiol		Cortisol
	Testosterone

Dexamethasone (man made)

Corticosterone

Figure 4. These compounds are called steroidal hormones. Each has a similar molecular structure, which contains four rings and all are hydroxylated.

Nonylphenol

Bisphenol A

Octylphenol

Figure 4. These are just some examples of endocrine disruptors. Although they do not look like the steroidal hormones in Figure 5, the body may mistake it as a hormone and cause a response. It may also suppress natural endocrine responses.

Why are EDCS not monitored at wastewater treatment plants?

• Tests to determine endocrine disruption potential are not yet determined to be reliable

• Information about health effects on humans exposed to contaminants not available.

• The interactions between man-made chemicals and how they interact in the body and the environment are also not available.

• Human studies on the impact of age, dose, length of exposure, timing of exposure, and genetics has on health effects do not exist.