Endocrine disrupting chemicals in the environment

In recent years, a growing body of scientific research indicates that certain substances in the environment, natural or synthetic, may interfere with the normal functioning of the endocrine system (which is made up of glands that produce and secrete hormones such as estrogen) in wildlife and even humans. Generally, these substances are called “endocrine disruptors”. Those that mimic estrogen and anti-estrogens are receiving more attention because they have been shown to produce effects such as neurologic, immunologic, and developmental disorders in vertebrates [1, 2].

Natural estrogens are secreted by the adrenal cortex (the outer portion of the adrenal gland located on top of each kidney), testis, ovary and placenta in humans and animals. Other estrogens are commonly used as contraceptives or in estrogen substitution hormonal therapies. Steroid estrogens are among the most potent endocrine disrupting chemicals (EDCs), causing effects in aquatic organisms even at trace-level concentrations [3].

Water is, without a doubt, one of the biggest transporters of these compounds. Runoff from farmlands carries pesticides and natural and synthetic livestock hormones into the rivers and groundwater. Effluents from industrial and sewage treatment plants are full of chemical residues that are constantly being released in minute amounts into surface waters, ubiquitously contaminating them and harming the wild life living near the effluents. It is to be expected that drinking water can also get contaminated since water treatment plants are not designed to remove all of these compounds. It is also worth mentioning that a wide range of natural compounds and synthetic chemicals dominate the long list of EDCs.

Some scientists have hypothesized that little amounts of these chemicals are able to disrupt the endocrine system and harm both male and female reproductive systems and even cause cancer in humans[4]. In both animals and humans, exposure to endocrine-disrupting substances in the egg or in the womb can alter the normal process of development. Adult organisms can also be affected, but it is the developing organism that is especially vulnerable. Experts suggest that endocrine disruptors could be a great risk during fetal development [5-8], which is regulated by hormones at specific levels. In humans, hormonal alterations due to maternal exposure during pregnancy could lead to harmful effects on learning ability, behavior, reproduction, and increased susceptibility to cancer and other diseases.

These effects may not be evident until later in life, yet the standard tests used by the U. S. Environmental Protection Agency (EPA) to evaluate reproductive and developmental disruption often fail to consider the impact of doses lower than those producing no evident adverse effects [4, 9]. All of this raises concern about the extent to which EPA protocols are able to accurately evaluate endocrine-disrupting effects. More research is needed to develop new methods for assessing reproductive and environmental disruption and to determine which changes in the policies are in serious need of evaluation to protect the wellbeing of all ecosystems.

References

1. Cheshenko, K., et al., Interference of endocrine disrupting chemicals with aromatase CYP19 expression or activity, and consequences for reproduction of teleost fish. General and Comparative Endocrinology, 2008. 155(1): p. 31-62.
2. Mahmoud, A. and F. Comhaire, Endocrine Disorders and the Role of Hormone Disrupters, in Andrology for the Clinician. 2006. p. 313-322.
3. Peng, X., et al., Simultaneous determination of endocrine-disrupting phenols and steroid estrogens in sediment by gas chromatography-mass spectrometry. Journal of Chromatography A, 2006. 1116(1-2): p. 51-56.
4. Gasnier, C., et al., Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines. Toxicology, 2009. 262(3): p. 184-191.
5. Contardo-Jara, V., E. Klingelmann, and C. Wiegand, Bioaccumulation of glyphosate and its formulation Roundup Ultra in Lumbriculus variegatus and its effects on biotransformation and antioxidant enzymes. Environmental Pollution, 2009. 157(1): p. 57-63.
6. Ostrach, D.J., et al., Maternal transfer of xenobiotics and effects on larval striped bass in the San Francisco Estuary. Proceedings of the National Academy of Sciences, 2008. 105(49): p. 19354-19359.
7. She, J., et al., PBDEs in the San Francisco Bay Area: measurements in harbor seal blubber and human breast adipose tissue. Chemosphere, 2002. 46(5): p. 697-707.
8. McDonald, T.A., A perspective on the potential health risks of PBDEs. Chemosphere, 2002. 46(5): p. 745-755.
9. U.S. Environment Protection Agency, Washington., Endocrine disruptor screening and testing advisory committee (ECSTAC) final report. 1998: Washington.