Environmental Engineering Reference
In-Depth Information
In this chapter, we describe the methods that are available
for assessing the levels and effects of contaminants on humans
and ecoreceptors, including both risk evaluations and formal
risk assessment, relate these methods to mercury pollution
and risk, provide examples of such evaluations, and discuss
future research and information needs. Information needs,
however, partly depend on changing stakeholder interests
and concerns (Rowe and Frewer, 2000; Greenberg et al., 2005;
Burger, 2007; USEPA, 2009a; Burger et al., 2010). Our intent
is to provide the information needed to understand how to
evaluate risk (or potential harm) from mercury to humans
and ecoreceptors, to provide the basis for understanding and
evaluating possible management options (including cleanup
levels), and for making public policy issues.
Risk evaluations are necessary to determine potential dam-
age to humans and ecosystems, and their associated species,
to provide early warning of potential harm, and to allow
managers, regulators, public policy makers, and the public to
respond quickly and decisively (Gochfeld and Burger, 2007).
Risk evaluation is the process that governmental agencies
use to gain understanding of the degree of injury or harm
that may result from human activities, particularly pollut-
ants (Ruckelshaus, 1985). In this chapter, we make a distinc-
tion between risk evaluation (all methods of evaluating any
potential risk from a hazard) and risk assessment (a struc-
tured, formal approach). Risk assessment is a formal, quan-
titative process that crosses many disciplines, from bridge
construction to toxicology and food safety. Thus, risk assess-
ment is a type of risk evaluation. Today, risk evaluations are
also being used to assess siting of new energy facilities and
the potential threat of genetically engineered products and
plants, as well as terrorist threats (Burger, 2007; Williams
and Magsumbol, 2007). Risk evaluations are intended to pro-
vide objective, at least semiquantitative information useful
for public-policy decisions (Burger et al., 2001a), and they
are often used to facilitate individual decisions as well (i.e.
whether or not to engage in a particular activity, such as sky-
diving, riding a motorcycle, or eating fi sh).
Although mercury enters the environment from both
natural and anthropogenic (human-generated sources;
this topic, chapter 3), it is the anthropogenic sources that
are of greatest concern because of both historic and recent
changes and the increasing demand for electric power
generation, which releases mercury to the atmosphere,
resulting in both local and regional pollution through
atmospheric transport and deposition. Anthropogenic
activities account for up to 80% of the annual emission
to the environment (Sunderland et al., 2008), varying by
time and place, as well as method. For many areas of the
world, atmospheric deposition, both regional and global,
is the primary source of mercury in terrestrial and aquatic
systems (Fitzgerald and Mason, 1996; Driscoll et al., 2006;
Selin et al., 2010). The global release of mercury to the
atmosphere is unevenly distributed, and largely related
to coal combustion. The Asian countries contribute about
54% of the mercury to total atmospheric sources. China
alone contributes 28% to the total emissions, followed by
Africa (18%), and Europe (11%) (Pacyna et al., 2006).
Mercury is a persistent toxicant that bio-accumulates
(Nichols, 2001), making it critical to understand the risk it
poses to humans and the environment. Armed with knowl-
edge, managers and regulators can lower mercury emis-
sions to a level that reduces adverse effects on individuals
and populations. For example, in the Everglades of south
Florida, knowledge of the high levels of mercury in preda-
tory fi sh led to enacting controls on emissions by local
power plants and other industries, which ultimately led to
a drastic reduction in the levels in the fi sh eaten by birds
and mammals, including people (Davis and Ogden, 1994;
Lange et al., 1994; SFWMD, 2007), although levels remain
high in some species (SFWMD, 2010).
Risk Evaluations Versus Formal
Risk Assessment
Risk Evaluation
Many disciplines have examined the risks of chemical,
physical, or biologic stressors to human and nonhuman
populations and the environment. These studies are done by
health professionals, ecologists, wildlife and land managers,
toxicologists, and, more recently, restoration ecologists and
ecologic engineers. Risk evaluations assess the potential risk
to target organisms (including humans) or systems from
chemical, physical or other environmental stressors (haz-
ards). Even before the formal risk assessment paradigm was
widely applied (National Research Council [NRC], 1983),
scientists, health professionals, and managers were exam-
ining the effects of chemicals and other stressors on indi-
viduals. The risk methods and assumptions varied among
and even within agencies and others examining harm to
humans and the environment. Therefore, it was diffi cult
to assess general health and well-being over time and space,
to evaluate competing risks (past, present, and future),
and to evaluate risks from different stressors (e.g. mercury
vs. lead, eating fi sh vs. eating red meat, pollutants vs. devel-
opment). The lack of consistency among methods led to
confusion not only on the part of managers and decision
makers, but also for the public. This lack of clarity created
a need for a formal risk-assessment paradigm that could be
applied uniformly, regardless of the nature of the stressor
or the target organisms. In a time of competing needs for
money, time, and other resources, formal risk-assessment
paradigms can provide agencies, managers, public policy
makers, and the public with a framework for evaluating
risks, and prioritizing them for funding and action.
Formal Risk Assessment
For decades, agencies and organizations conducted risk eval-
uations using different methods. Evaluating the effect of
chemicals on humans became particularly critical because
