Endocrine disruptors plants

Depending upon the circumstance and desired effects, endocrine-disrupting chemicals can be either good or bad. The endocrine system is a finely balanced system responsible for fertility and many of the feminine and masculine traits we are all familiar with. Endocrine disruptors are used by millions of women in the form of the pill to control fertility. Chemicals in birth control pills subtly manipulate the endocrine system to reduce fertility. Unfortunately, we now know that many chemicals are capable of influencing the endocrine systems. When these chemicals, such as DDT and TCDD, are released into the environment, they reduce the fertility of wildlife. Exposure to endocrine disruptors is linked to decreased fertility in shellfish, fish, birds, and mammals. Endocrine disruptors such as nonylphenol have been shown to feminize male fish, interfering with reproduction. Some studies have also linked exposure to endocrine disruptors to decreases in human male sperm count. Ironically, urinary metabolites of the birth control pill as well as the female hormone estrogen pass through waste treatment plants and are released into the aquatic environment, where even small concentrations cause feminization of male fish. 

Three chapters in this volume describe expensive and extensive research efforts devoted to images of risk. Stephen Safe assesses the research that fails to find any health from endocrine disruptors in the environment. Bruce Ames and Lois Swirsky Gold review the collapse of the scientific underpinnings for the assertion that environmental chemicals are a major cause of cancer. Bernard L. Cohen contrasts the absence of data to show that nuclear power plants have caused death and disease with the near-total demise of the nuclear power industry because of assertions about cancer risks from the plants. 

As we have seen, there are many other chemicals capable of causing these effects, although they are generally very much less potent that the natural oestrogens and the synthetic oestrogens used in the contraceptive piU. Mixtures of these chemicals, which includes natural substances from plants, pesticides, and industrial chemicals, may be more potent than the individual components. This phenomenon is called synergy (see p. 35) and is currently an area of intense scientific interest, as is the subject of endocrine disruptors. 

Fig. 1. Estrogen and estrogen mimics. Many natural plant compounds (e.g. coumestrol) and synthetic chemicals (e.g. ethynylestradiol, diethylstilbestrol, 4-nonylphenol, o,p DDT, and kepone) act as endocrine disruptors by mimicking or blocking normal estrogen function via estrogen receptor dependent or independent mechanisms.

Herbicidal 2,4-D selectively kills broadleaf weeds and is the most widely used of all herbicides worldwide on wheat, corn, rice, and other cereal grass crops. It is a synthetic auxin, or plant hormone that is absorbed through leaves, is transferred throughout the plant, and causes unsustainable growth that results in plant death. Fortunately, given its widespread use and human exposure, it has very low acute toxicity. It is possibly carcinogenic, a status shared with many other pesticides, and is a suspected endocrine disruptor (see Chapter 2, Section 2.16). 

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