Introduction to Endocrine Disrupting Chemicals

fer, or in a breastfeeding infant (68). According to measurements conducted by the
United Nations Environmental Programme and the World Health Organization
from 2001- 2013, high DDT levels in human breast milk were found in Ethiopia
(2013), Tajikistan (2009), Solomon Islands (2011), India (2009), Haiti (2005), Pacific
States (2011), Hong Kong SAR (2002), Mauritius (2009), Mali (2009), Moldova
(2009), Togo (2010), Uganda (2009), Fiji (2002), Sudan (2006), Philippines
(2002), Ukraine (2001), Djibouti (2011), Côte d’Ivoire (2010), and others (listed
from highest level first) (Figure 2). However, breast feeding has very important
health benefits to children, including decreased risk of infections, Sudden Infant
Death Syndrome, and childhood obesity (69). The World Health Organization recommends
women breast-feed their children for at least the first two years of life.
Elderly people also tend to have higher levels of DDTs because the DDTs accumulate
throughout life and because exposures in the past tended to be much greater
than in the present in many countries. Indeed, age is often the most powerful predictor
of levels of DDTs (70). For instance, in a community living near an old DDT
manufacturing plant, average adults had 159 ng DDT/ml serum, while the average
DDT level in people over 70 years old was 350 ng/ml (66). This raises the possibility
that elderly persons, who also have a higher chronic disease burden, may have
a greater sensitivity to their DDT burden than younger adults, and this should be
kept in mind when working with populations exposed to DDTs.
The persistence of DDTs from prior use, coupled with global migration patterns of
humans, both contribute to high levels of DDTs in people even in countries with
long-time bans. It takes between four and 10 years for concentrations of DDTs in
people to decrease by half (the so-called “half-life” (71)). Hence, while monitoring
studies have established that banning DDT succeeds in lowering human exposure,
levels of DDTs can remain high in people years later (67). For instance, more than
30 years after DDT was banned in the United States and near the time of the
phase-out and ban of DDT in Mexico, agricultural workers who migrated from
Mexico had much higher levels of DDTs than typically seen in the US. Further,
people living in a US community 10 km from a manufacturing plant site that used
to produce DDT also had substantially higher levels of DDTs in their bodies than
the general population (66). Thus even countries that do not use DDT should
recognize the possibility of higher exposures to DDTs within their population, such
as in migrants and in people living in communities that are near sites of previous
DDT production.
There is elevated exposure to DDTs in circumpolar countries because these chemicals
are semi-volatile and undergo long-range transport, meaning they rise into
the air in temperate regions and deposit at the earth’s surface in colder regions.
Introduction to EDCs (December 2014) 37