Introduction to Endocrine Disrupting Chemicals

umbilical cord blood, and body tissues such as adipose tissue (fat). Some common
examples of EDCs include DDT and other pesticides; bisphenol A (BPA) and
phthalates used in children’s products, personal care products and food containers;
and flame retardants used in furniture and floor coverings. In addition to the
known EDCs, there are countless suspected EDCs or chemicals that have never
been tested.
Exposures to known EDCs are relatively high in contaminated environments in
which industrial chemicals leach into soil and water; are taken up by microorganisms,
algae, and plants; and move into the animal kingdom as animals eat the
plants, and bigger animals eat the smaller animals. Animals at the top of the food
chain, including humans, have the highest concentrations of such environmental
chemicals in their tissues.
There is good reason to suspect that increasing chemical production and use
is related to the growing incidence of endocrine-associated pediatric disorders
over the past 20 years, including male reproductive problems (cryptorchidism,
hypospadias, testicular cancer), early female puberty, leukemia, brain cancer, and
neurobehavioral disorders. At the same time, the global production of plastics
grew from 50 million tons in the mid-1970s to nearly 300 million today, and sales
for the global chemical industry have sharply increased from USD$171 billion in
1970 to over USD$4 trillion in 2013. Chemicals such as polychlorinated biphenyls
(PCBs), BPA, and phthalates, are now detectable in serum, fat, and umbilical cord
blood in humans around the globe. In fact, the concept of “better living through
chemistry” was introduced by the chemical industry in the 1930s. This pervasive
notion underlies the global escalation in chemicals production.
Over the last two decades there has been burgeoning scientific evidence based on
field research in wildlife species, epidemiological data on humans, and laboratory
research with cell cultures and animal models that provides insights into
how EDCs cause biological changes, and how that may lead to disease. However,
endocrinologists now believe that a shift away from traditional toxicity
testing is needed. The prevailing dogma applied to chemical risk assessment is
that “the dose makes the poison.” These testing protocols are based on the idea
that there is always a simple, linear relationship between dose and toxicity, with
higher doses being more toxic, and lower doses less toxic. This strategy is used
to establish a dose below which a chemical is considered “safe,” and experiments
are conducted to determine that threshold for safety. Traditional testing involves
chemicals being tested one at a time on adult animals, and they are presumed
safe if they did not result in cancer or death.
A paradigm shift away from this dogma is required in order to assess fully the
impact of EDCs and to protect human health. Like natural hormones, EDCs
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