1. There are demonstrable effects outside of the laboratory in wild animal populations and in groups of people exposed by accident or through medicine.
2. Work at low exposure levels, very low exposures, show that the classic high dose experiments can completely miss important low dose effects. Moreover, these results are reproducible in the lab. This science does not rest on extrapolating high dose curves down to the low end of exposure.
3. It's not just estrogens. While the first two decades of this work focused largely on man-made chemicals capable of mimicking estrogen, within the last five years we've seen that expand to include estrogen blockers, androgen blockers, progesterone blockers and compounds that interfere with thyroid. This last one is especially important because thyroid hormone is key to proper brain development.
4. It's not just the disruption of the endocrine system. Natural chemical signals are important at all levels of organization of life--within cells, among cells, between organs, even between organisms, including from one species to another. Any of these chemical signals, in principle, are vulnerable to disruption. Scientists, for example, have just begun to look at the chemical signals that mediate communication between symbiotic organisms, such as nitrogen-fixing bacteria and the roots of the plants in which they live, and are examining how synthetic chemicals might interfere with these signals. Disrupting these 'signals of life' could have important ecosystem impacts.
5. The developing fetus is exquisitely sensitive to both the natural hormone signals used to guide its development, and the unexpected chemical signals that reach it from the environment. Both the natural signals and the chemicals that disrupt them act as "morphogens." They guide the fetus through forks in its developmental path and also help set its sensitivity to subsequent hormonal signals. This involvement of setting sensitivity can have life-long consequences. New science, for example, on the developing prostate, shows that natural and synthetic estrogens experienced in the womb can lead to enlarged and hypersensitive prostate in adulthood.
6. Work with the best known of the endocrine disrupters, particularly diethylstilbestrol, or DES, led to great scientific confidence about the predictive value of lab animal studies for anticipating human endocrine impacts.
7. The contamination is very widespread and it comes from many sources, some quite conspicuous and others completely unexpected.
8. Some of the synthetic chemical compounds are notorious because they accumulate in our fatty tissue. These chemicals can then bioaccumulate up the food chain, and can be passed on in the womb and through breast milk. Because, they are not flushed through our bodies chemical accumulation in the fat tissue and breast milk can reach very high concentrations over time, concentrations millions of times higher or more than plant estrogens.
9. Plant estrogens are widespread in our diets and when eaten in large volume they can cause serious problems. In fact they have been used as antifertility agents by many cultures for a long time. But normal diets usually don't create risks because our gut chemistry quickly flushes them through and because there are special proteins in our blood that are effective at ensuring many (but not all) of these natural compounds don't reach the fetus at levels sufficient to have an effect. For example, while the most common plant estrogen in soy has a half life in our body of about 6-8 hours, DDT's half life is 10-12 years.

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