Introduction to Endocrine Disrupting Chemicals

5. EXPOSURE OF HUMANS
TO EDCs
EDCs are a global and ubiquitous problem. Exposure occurs at home, in the office,
on the farm, in the air we breathe, the food we eat, and the water we drink. Of the
hundreds of thousands of manufactured chemicals, it is estimated that about 1000
may have endocrine-acting properties. Biomonitoring (measurement of chemicals
in body fluids and tissues) show nearly 100% of humans have a chemical body
burden. 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 and up the food chain.
Top predators, including humans, have amongst the highest concentrations of
such environmental chemicals in their tissues. Of great concern is evidence that
some chemicals are transported by air and water currents to other parts of the
world that are quite distant from their original source. In fact, there are regions
that never had any chemical industry, such as the polar regions, yet humans and
animals who live in those regions have detectable levels of some EDCs. Moreover,
the persistence of some chemicals, especially those chemicals that are persistent
organic pollutants (POPs), means that even some banned chemicals will persist in
the environment for years if not decades. Some of these POPs such as polychlorinated
biphenyls (PCBs), dioxins, and DDT, are known endocrine disruptors.
Exposure to EDCs may indeed be in the form of pesticides, algicides, and other
chemicals designed to kill unwanted organisms. Spraying of homes, agricultural
crops, and ponds releases airborne and sedimented chemicals that are inhaled, get
on skin, and are ingested from sprayed food. It is not surprising that some of these
chemicals are EDCs. Many, especially those used for pest control (e.g. for extermination
of insects or rodents), were specifically designed to be neurotoxicants
or reproductive toxicants. The high sensitivity of reproductive and neural systems
to natural hormones, and the similarity of these physiological processes in both
invertebrates and vertebrates, means that chemicals designed to perturb these
functions in one species will affect another – including humans. Herbicides in
widespread use such as atrazine, 2,4-D, and glyphosate, are considered EDCs, and
the fungicide vinclozolin is a known EDC. Further discussion of two pesticides,
32