Environmental Engineering Reference
In-Depth Information
amination of chemicals before they reach the market and for ongoing monitoring vigilance
when such products come into general use.
The epidemiological evidence for low-dose chronic exposure effects for certain POPs
is not restricted to prenatal exposure or to neurological effects. For quite some time, a link
has been suspected between a particular form of breast cancer and exposure to some POPs,
such as DDT and its metabolite DDE (which can mimic the hormone estrogen). This is
probably an example of endocrine disruption. Human fertility has also been suspected for
some time to be susceptible to disruption through chronic low-dose exposure to certain
POPs. For example, the prospective studies of Buck Louis and colleagues have implicated
exposure to several PCBs, PFOS and DDE to reduced fecundity in couples that were fol-
lowed for 12 months after they ended the use of contraception.
Another recurrent suspicion has been whether chronic exposure to POPs increases the
risk of developing a particular form of diabetes, known as type 2 diabetes. Type 2 diabetes
(also known as adult-onset or noninsulin-dependent diabetes) is a chronic condition. It af-
fectsthewayourbodymetabolizes glucosebyeitherimpairingtheregulatoryactionsofin-
sulin that normally control the movement of sugar into our cells or by preventing the body
from producing enough insulin to maintain a normal glucose level. I include this work here
to give an example of a purported effect for which different epidemiological studies have
been unable to reach entirely consistent conclusions. These types of confusing results prob-
ably occur when several different factors, such as genetics and environmental exposure to
chemicals, are responsible for the susceptibility to certain medical disorders, such as type
2 diabetes. Nevertheless, a report published by Wu and colleagues in 2013 is a large and
robust study that gives a clear result. Using a database of more than 1,000 female nurses
whose blood was collected in 1989-1990 and who were diabetes free at that time, the re-
searchers found that the incidence of type 2 diabetes by 2008 was associated with HCB and
total PCB serum concentration.
Thiswillconclude(forthemoment)ourshortandveryrestricted reviewofthepresent
understanding of the chronic toxicity of POPs. If you go back to Table 8.3 , you will see just
how selective I have been and how I have ignored many types of purported effects attrib-
Search WWH ::




Custom Search