Endocrine System

aragraph are, for the most part on the macro level, compared to the items listed here, which are more on the micro level.

To re-cap briefly, chemical agents that bind in the specified hormone sites produce effects on a larger scale than chemicals that only block the function of the natural hormones. Depending on which chemical is involved in the exposure, the effects can vary somewhat. These effects can also vary from individual to individual since they may also be muti-factorial.

Endocrine disrupters can produce several effects within the body. These effects can include, but are not limited to androgenic, estrogenic, thyroid problems, and neurological problems. Androgenic problems would involve those related to the male reproductive system, while the female reproductive system is associated with estrogenic effects. The last two problems listed could possibly be grouped together. The thyroid problems associated with endocrine disruption are also closely related to thyroid function. In a later part of the paper I will give some research examples of all four of these effects. Next I would like to discuss the different chemicals that are either known as endocrine disrupters, or highly suspected.

There are approximately 15,000 chemicals that are used commercially today. To test this many substances for endocrine disruption activity would take billions of dollars and an extremely large amount of time. However, even as early as 1938 we have known that certain chemicals were able to exert estrogenic effects on organisms. We by no means have a complete list, but the one we possess is becoming more complete as additional research is conducted. The majority of endocrine disrupting chemicals (EDC) fall into two broad categories of pesticides (including herbicides, insecticides, and fungicides) and industrial chemicals. In the following paragraphs a description of several of these chemicals will be given in addition to their chemicals structures.

Industrial chemicals are widely used throughout the world. They constitute a majority of the 15,000 substances used for commercial use. In addition to the high number of substances used, there are also exists high diversity in the methods the chemicals are disposed of. This is a major contributing factor in why we are examining these chemicals to begin with.

The first chemicals I will describe are dioxins and furans. Their chemical structures are as follows:

Dioxin Furan

These two substances are chemically different from one another, but are both produced in similar ways. The are left as unwanted byproducts from industrial activity such as medical and municipal waste incineration, pulp and paper bleaching, fuel combustion, and PVC manufacturing. Both of these chemicals are considered very dangerous by the EPA not only due to damage they may cause themselves, but also do to reactions they undergo with other substances.

An example of dioxins and furans reacting with other chemicals would be their reaction with polychlorinated biphenyls. Both dioxins and furans are fairly reactive to begin with, but adding heat and PCB's can produce some fairly nasty mixtures. The substances formed in these reactions are polychlorinated dibenzofurans (PCDF) and polychlorinated dibenzodioxins (PCDD) respectively. The PCDF's and PCDD's that were formed in the reactions have been linked to a few very large disease outbreaks. One of the incidents occurred in Japan, while the other occurred in Taiwan. The people who were exposed to these chemicals experienced severe side effects that were also passed on to their young.

Continuing from the previous group of chemicals, I will now briefly look at PCB's (polychlorinated biphenyls). One of the chemical structures is as follows:

This picture represents one of over 206 possible congeners, which

are similar to isomers. These chemicals were first used

commercially around 1930. At first glance, they were almost considered a miracle substance. They were used in electrical capacitors, adhesives, oils, and paints, among several other things due to their flame-retardant capabilities. This was all found irrelevant in the 1960's when the U.S. began testing the substance. It was shown to have carcinogenic effects in mice, so its production was eventually banned in the United States in the late 70's. We have now discovered it has estrogenic effects and impairs neurological development as well. In a later section, I will discuss how PCB's inhibit thyroid function in the developing fetus thereby causing neurological problems.

The next chemical I will describe is bisphenol-A with its chemical structure:

Looking at all the structures I have discussed

thus far, there is commonality between them.

All of them up to this point have exhibited some sort of ring structure, and bisphenol-A continues with that trend. This substance is a major component in polycarbonate plastics, epoxy resins, and flame retardants. There are over one billion pounds of this chemical produced annually in the United States, Europe, Japan, Taiwan, and Korea. The epoxy resins that contain bisphenol-A are used to coat the inside of food cans and also as dental sealants. This chemical is one I mentioned on page five, that we have known that it exhibits estrogenic effects since 1938. Why is this a large concern? This is important because lab test show that the bisphenol-A leaches out of the epoxy coatings and sealants into our food and saliva. We do not know exactly how detrimental this is to us, but we have known that it is estrogenic for over 60 years now.

The final substances I will discuss under the industrial chemical category are phthalates. Their chemical structure is as follows:

This is the most abundant manmade chemical in our environment and found virtually everywhere in the world. Phthalates have been shown to produce weak

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