Controlling Power Plant Emissions
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The five Guiding Principles outlined below provide a context for additional
inquiry and help to focus the Agency’s deliberations as we move
toward a final rule in March, 2005. The Agency will continue to study
the mercury health impacts, control technologies, economic consequences
of regulation and domestic and international emission sources throughout
the next several months. Guiding Principle 1 has been expanded to include
further explanation and areas where the Agency seeks additional information.
Guiding Principles 2-5 will be expanded to provide similar information
as the decision process continues.
Guiding Principle 1:
The final rule will concentrate on the need to protect children and
pregnant women.
Critical Questions:
Speciation – How
do different forms of mercury behave?
Explanation: When coal is
burned, the mercury contained within the coal
is released in the combustion system and can
be found in three main chemical forms: elemental
mercury, oxidized mercury and particulate-bound
mercury. Understanding the chemistry associated
with the three forms of mercury is fundamental
in designing appropriate air pollution control
programs to remove mercury from the environment.
Additional Information: We
seek the following information:
- Information on the effectiveness of existing, commercially-available
air pollution control systems to reduce the emissions of mercury.
- Information on the ability of models to accurately predict the transport,
chemistry and deposition of mercury once it is released into the atmosphere.
Deposition and Transport – How
and where does mercury enter our waterways?
Explanation: Mercury in the
atmosphere is eventually deposited to the earth’s
surface, either through dry or wet deposition
onto either land or water. We measure deposition
through a network of monitors across the US
and study the relationships between different
sources and changes in deposition with a variety
of computer models. The rate at which mercury
moves through the terrestrial and aquatic environment
is not well understood.
Additional Information: We seek
the following information:
- Information on terrestrial and aquatic transport, particularly on
how such transport should be modeled.
Bioaccumulation – How
does mercury move through the food chain?
Explanation: Only a small
component of the mercury released by power
plants and present in the atmosphere is converted
into the form of most concern: methyl mercury.
Methyl mercury is formed by microbes in the
environment and accumulates in organisms at
many thousand times the concentrations found
in most water and sediments. The amount of
mercury in fish in different waterbodies is
determined by a number of factors, including
the amount of mercury deposited from the atmosphere
and the biology and chemistry of different
ecosystems. This explains why some lakes with
similar sources of mercury can have dramatically
different concentrations in fish. As fish eat
other fish, methyl mercury accumulates. Thus,
concentrations of mercury will be highest in
older, larger fish.
Additional Information: We
seek the following information:
- Approaches for modeling methylation rates in freshwater and saltwater
ecosystems.
- Information on the pathway of methyl mercury entry into the base
of both freshwater and marine food chains.
- Site-specific data documenting the bioaccumulation of mercury in
different types of freshwater and marine food chains.
Consumption patterns – What
are the types, sources and amounts of fish consumed?
Explanation: Almost all exposure
to mercury comes from eating fish. Americans
get their fish from a variety of sources from
all over the world. Understanding fish consumption
patterns is crucial to a more complete picture
of the health benefits of reducing emissions
from U.S. power plants.
Additional Information: We seek
the following information:
- The types of fish Americans eat and the concentrations of mercury
found in these fish.
- Location where these fish are caught.
- Source of the mercury contained in the fish.
- Types, amounts, location and mercury levels in fish consumed by
highly exposed populations.
Dose response –What are
the health impacts from different exposure levels?
Explanation: An important
part of evaluating and communicating the benefits
of EPA's rules is to estimate how the health
of people in the United States is improved
when exposure to an environmental contaminant
is reduced. A numerical relationship, known
as a "dose-response function," shows
the change in a health effect (e.g. lung cancer)
in an animal, organism, or human caused by
differing levels of exposure to some contaminant
(e.g. tobacco smoke).
Additional Information: We seek
information on the following:
- The relationship between levels of exposure and associated health
impacts.
Local health impacts – Is
there a relationship between emissions and local health impacts?
Explanation: Americans eating
fish from a variety of sources are exposed to
mercury from regional and global emissions. Some
people, however, may be at risk from eating a
large amount of fish from a single watershed,
raising concerns about the possibility of elevated
mercury deposition nearby emission sources. The
possibility that mercury emissions from power
plants could have significant local impacts for
some people depends on a number of factors, including
the height of the stack from which it is emitted,
the form in which it is emitted, local and regional
meteorology and atmospheric chemistry, a variety
of watershed characteristics including methylation
and bioaccumulation rates, fishing habits, and
consumption patterns of people that eat substantial
amounts of fish.
Additional Information: We seek
information on the following:
- Understanding of the exposure pathway so that the final rule will
appropriately address potential local health impacts.
Guiding Principle 2:
The final rule will stimulate and encourage early adopters of new technology
that can be adequately tested and widely distributed across the full
fleet of U.S. power plants and coal types.
Critical Questions:
- When will mercury-specific technologies be adequately tested and
broadly distributable on all coal types?
- How long will it take to install and begin operating technologies
on the fleet of power plants?
- What is the cost of installing and operating such technologies?
- What incentives can be used to accelerate the adoption of new technology?
- What disincentives hinder early adopters of new technology?
Guiding Principle 3:
The final rule will significantly reduce total emissions by leveraging
the $50 billion investment that the Clean Air Interstate Rule will
require.
Critical Question:
- What is the level of mercury co-benefit that comes from a comprehensive,
multi-pollutant approach?
Guiding Principle 4:
The final rule will consider the need to maintain America ’s
competitiveness.
Critical Questions:
- How can we keep electricity prices stable for consumers and businesses
and still protect public health?
- What approach best keeps America’s abundant reserves of all
types of coal as a vital part of our energy mix?
- How do we make certain that the rule ensures a level playing field?
- How do we make certain that the rule does not contribute to unacceptable
increases in natural gas prices, causing hardship during the winter
heating season or adversely affecting the manufacturing sector?
- How do we make certain we do not contribute to electricity reliability
concerns?
- How can we provide the right incentives to burn coal more cleanly
with the best new technologies over the long term?
Guiding Principle 5:
The final rule will be one component of our overall effort to reduce
mercury emissions.
Critical Questions:
- What appropriate options are available to decrease mercury exposure
from other domestic sources such as mercury switches in automobiles?
- Recognizing that mercury is a global issue, what opportunities are
there to reduce mercury emissions worldwide?
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