Introduction to Endocrine Disrupting Chemicals

II. EDC EXPOSURES TO THE INDIVIDUAL, AND TO FUTURE
GENERATIONS
Exposure to environmental chemicals is life-long. Animals and humans living
in contaminated environments carry personal body burdens – the amount of
chemicals contained in an individual’s tissues – from direct exposure accumulated
throughout their lives. Some of these EDCs are persistent and bioaccumulative
(i.e., build up over time in body tissues). When humans are tested for the presence
of EDCs in their blood, fat, urine, and other tissues, the results consistently
demonstrate a variety of EDCs in all individuals worldwide. These measurements
reflect contact with EDCs through food, water, skin absorption, and from the
atmosphere. Fat is a particularly important reservoir for EDCs, as these chemicals’
compositions tend to make them fat-soluble. In addition, measures of EDC
body burdens reflect not only contemporary contact with EDCs; they also include
past exposures, sometimes decades ago, to persistent chemicals such as PCBs
and others. Beyond an individual’s own lifetime of exposures is the inheritance of
exposures to EDCs from his/her ancestors. For example, during pregnancy, some
of the chemicals stored in a woman’s body fat may cross the placenta and affect her
developing embryo. Some EDCs are detectable in breast milk and can be passed to
the suckling infant. In addition, there is now evidence that EDCs induce changes
to germ cells – precursors to sperm and egg cells – making their effects heritable
not just to one’s own children, but also to grandchildren, great-grandchildren, and
beyond. In other words, children can inherit the negative consequences induced
by the exposures of their ancestors. This is very important, because it underscores
the point that the introduction of a chemical into the environment, if it affects the
germ cells, will be inherited long after the chemical is cleaned up or breaks down.
III. EDCs AND ENDOCRINE DISEASE
It has been estimated that, globally, upwards of 24% of human diseases and
disorders are attributable to environmental factors (10) and that the environment
plays a role in 80% of the most deadly diseases, including cancer and respiratory
and cardiovascular diseases (11). Because perturbation of the endocrine system
is fundamental to the most prevalent of these diseases, EDCs may be primary
contributors. The incidence of endocrine-associated pediatric disorders, including
male reproductive problems (cryptorchidism, hypospadias, testicular cancer),
early female puberty, leukemia, brain cancer, and neurobehavioral disorders, have
all risen rapidly over the past 20 years. The prevalence of developmental disability
in US children increased from 12.84% to 15.04% between 1997-2008 (12).
The preterm birth rate in the US, UK and Scandinavia has increased by more
than 30% since 1981, an outcome associated with increased rates of neurological
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