Environmental Engineering Reference
In-Depth Information
the population will not be affected by a five-point reduction of intelligence. However, if the
entire curve is shifted a little to the left, the “tails” of the curve have also moved. The pro-
portion of the population we once considered as gifted has decreased and the proportion we
may call challenged and that will require assistance during their entire lives has increased.
This can be the huge financial (not to mention moral) legacy left by our continued use of
such substances. Will this financial argument influence our politicians? One might think
so, but the Arctic Messenger finds it difficult to understand why the new understanding of
low-dose relationships has still not entered the procedures used to evaluate the chemical
safety of “new” substances. Rather than embrace the precautionary principle, our society
prefers to wait for health problems to emerge.
I should say a few more words about endocrine-disrupting substances. The endocrine
(hormonal) system modulates many biological processes in vertebrates, such as develop-
ment, reproduction, behaviour and metabolic processes. Over the last 20 years, scientists
have identified about 800 chemicals that are able (or suspected of being able) to disrupt
hormonal systems and have linked them to disease outcomes in laboratory animal studies.
At the same time, epidemiologists have been tracking increasing trends of endocrine-re-
lated diseases in human and wildlife populations that roughly correspond to the prevalen-
ce of these substances in the environment. Many of these substances are also POPs. This
is why you have been encountering intermittent references to endocrine disruption in the
preceding paragraphs and will continue to do so later in this chapter. One important char-
acteristic of endocrine disruption is that it is often most effective during a short window of
vulnerability. This is frequently located during embryonic development, but the effect may
not be apparent until a later stage in the life cycle. It is probably one of the main reasons
why disorders related to endocrine disruption do not follow the classic dose-response rela-
tionships. That should sound familiar to you from the work noted earlier on POPs and mer-
cury by Eric Dewailly, Joseph and Sandra Jacobson, Olivier Boucher, Gina Muckle, Philip
Landrigan and L. N. Vandenberg. If you have found the whole topic of low-dose relation-
ships to environmental exposure to toxic substances interesting, have a look at some of the
references given in the bibliography by these authors.
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