Endocrine Disrupting Compounds; Bisphenol-A, Phthalate Esters, Dioxins, and lots of others

One hot topic you may hear about in Environmental Science and Toxicology are Endocrine Disrupting Compounds. They have been all over the news in the last 10 to 15 years. You might have heard about fish and guppies spontaneously changing sex or baby bottles releasing chemicals after being heated in the microwave. These are two examples of Endocrine Disrupting Compounds (EDCs).

Endocrine systems of animals and humans are very complex, and rely on the ability to send and receive ‘messages’ in the form of hormones inside cells. When part of a cell sends a message in the form of a hormone to another part of the cell it is called the messenger. The portion that receives the information is called the receptor. This message tells the cell to perform a specific biological task such as growth or reproduction or embryonic development⁴.

An Endocrine Disrupting Compound is therefore a compound that interferes with the communication. Some compounds can mimic hormones and therefore produce normal but untimely responses. Others are antagonistic and disrupt the normal functions by binding to the receptor thus blocking other messages or by interfering with the way hormones are made and controlled.

EDCs are very controversial within the scientific community. It is not controversial that certain organic compounds can disrupt the endocrine messaging process, but there is great controversy as to whether the dose/response relationship of tests accurately models real life. Let me explain. In the lab scientists often spike samples with high doses to see the results. In the environment animals are almost never subjected to very high concentrations^7.8. This leads to the question of whether EDCs can be additive with time (i.e. low dose long time=high dose short time) or whether different EDCs can be synergistic (i.e. work together).

There are many different types of EDCs around. Here is a table of some of the most well known.

Some Endocrine Disrupting Compounds
Category	Name	Some Sources
Alkylphenols (Surfactants)	Nonylphenol, Pentylphenol, octylphenol, nonylphenol mono and diethoxylates	Industrial and municipal effluents
Bisphenolic Compounds	Bisphenol A	Used in the synthesis of polycarbonate plastic and epoxy resins
Natural Hormones/ Synthetic Steroids	17-b-estradiol, estrone, Testosterone; ethynyl estradiol	Municipal effluent and agricultural runoff
Organochlorine Pesticides	DDT, dieldrin , lindane	Agricultural runoff, Atmospheric transport
Organotins	Tributyltin	Shipping Harbors; Used in: Wood Preservative, Antibiofouling Agents
Pesticides	Atrazine, trifluralin, permethrin	Agricultural runoff
Phthalates	Dibutyl phthalate, butylbenzyl phthalate, phthalate esters	Industrial effluent
Phytoestrogens	Isoflavones, ligans, coumestans	Pulp mill effluents
Polybrominated Compounds	Polybrominated diphenyl ethers	Flame retardants
Polychlorinated Compounds	Polychlorinated dioxins, polychlorinated biphenyls	Landfills Used in: Coolants, Insulating Fluids, PVC Pipes, Flame Retardents, etc.

Source 4,6

That is all I will write about Endocrine Disrupting Compounds in this post. I will try to write descriptions of each of these soon. Look for links.

1. Bisphenol-A: an estrogenic substance is released from polycarbonate flasks during autoclaving; AV Krishnan, P Stathis, SF Permuth, L Tokes and D Feldman; Endocrinology, Vol 132, 2279-2286, Copyright © 1993 by Endocrine Society

2. Relative binding affinity-serum modified access (RBA-SMA) assay predicts the relative in vivo bioactivity of the xenoestrogens bisphenol A and octylphenol; S C Nagel, F S vom Saal, K A Thayer, M G Dhar, M Boechler, and W V Welshons; Environ Health Perspect. 1997 January; 105(1): 70-76.

3. A physiologically based approach to the study of bisphenol A and other estrogenic chemicals on the size of reproductive organs, daily sperm production, and behavior; vom Saal FS, Cooke PS, Buchanan DL, Palanza P, Thayer KA, Nagel SC, Parmigiani S, Welshons WV.; Toxicol Ind Health. 1998 Jan-Apr;14(1-2):239-60

4. Endocrine Disrupting Substances in the Environment; Environment Canada; http://www.ec.gc.ca/eds/fact/broch_e.htm

5. Phthalates, Alkylphenols, Pesticides, Polybrominated Diphenyl Ethers, and Other Endocrine Disrupting Compounds in Indoor Air and Dust; Ruthann A. Rudel, David E. Camann, John D. Spengler, Leo R. Korn, Julia G. Brody; Environmental Science & Technology

6. Analysis and environmental levels of endocrine-disrupting compounds in freshwater sediments; Mira Petrovi , Ethel Eljarrat, Maria J. López de Alda and Damià Barceló; Copyright © 2001 Elsevier Science B.V.

7. Endocrine disruptors and reproductive development: a weight-of-evidence overview; RL Cooper and RJ Kavlock; Journal of Endocrinology, Vol 152, Issue 2, 159-166

8. Endocrine Disruptors and Human Health-is there a problem? An update.; Stephen H Safe; Environmental Health Perspectives, Vol. 108, Number 6, June 2000