Environmental Engineering Reference
In-Depth Information
Conditions linked to exposure to EDCs, such as reproductive problems,
incidence of certain cancers, asthma, obesity, diabetes, behavioral or
learning disorders, and ADHD, are on the increase worldwide. Of this
disease burden, 24-33% has been attributed to environmental
contributions (Smith et al., 1999).
But EDCs were never regulated until recently. This lack of scientific and
regulatory recognition of the hazard posed by EDCs was mainly a result of
theconventionalapproachesusedtoevaluatethetoxicityofthesechemicals.
With EDCs, it is the developmental (
in utero
and first years of life) stages
that are particularly sensitive to health effects. While a significant fraction
of human diseases are attributed to environmental factors (Prüss-Üstün
and Corvalán, 2006), quantifying this fraction accurately is complicated.
However, a clear trend in increase in human reproductive health problems,
with rising production of EDCs, has been reported. Human studies show a
strong association between exposure to EDCs and the incidence of adverse
health conditions (Baillie-Hamilton, 2002; Bergman et al., 2012).
Conclusive etiology or cause-effect relationships are deduced mainly from
animal exposure studies.
The need for precautionary action to restrict their use as a class of chemicals
was agreed to at the Prague Declaration on Endocrine Disruption (June,
Europe and the United States have also urged a similar stance. Research
focus is finally shifting (US Environmental Protection Agency, 2012) from
investigating effects of adult exposure to examining developmental
exposure and related disease outcomes.
Studying the health effects of EDCs is complicated by several factors. Like
hormones, the EDCs also act at very low concentrations but have a marked
effect in perturbing physiological responses. These perturbations are not
always immediately apparent but can still be long term (in some instances,
generational), and the long latent periods involved often confound research
studies. As the exposure in nature is generally to multiple EDCs, their
synergistic effects (Focazio et al., 2008; Hayes et al., 2006) need to be also
taken into account. Some EDCs are in fact active only in combination, not
individually (Hass et al., 2007). To complicate studies even further, subjects
are not uniform in their response; particularly susceptible or resistant
subgroups (e.g., children, subjects with genetic polymorphisms) may exist.
