TATE  OF  THE GREAT LAKES 2003
     CAN WE EAT THE FISH?
       Atmospheric Deposition
The Issue: Chemical pollution that may result in fish
consumption advisories can enter the Great Lakes from
sources close to, as well as very distant from the Great
Lakes.

•  Contaminants such as PCBs, DDT, and PAHs
   can enter the Great Lakes from the atmosphere
   as a result of rain or other atmospheric
   processes.

•  A  significant portion of the contaminants
   found in the Great Lakes may have been used
   in other parts of the world and then transferred
   to the Lakes via the atmosphere. However,
   nearby sources in the Great Lakes basin can
   also contribute greatly.

•  Contaminants transferred to the Lakes through
   atmospheric deposition contribute to elevated
   contaminant levels in fish tissue, and
   consequently, determine whether or not we can
   eat the fish.
     system, they are ingested by fish and stored in
     their tissue. As these fish are ingested by other
     fish, the contaminants accumulate at increasingly
     higher concentrations.  Large fish, the types most
     often desired for human consumption, are often
     those carrying the largest amount of contaminants.

     The Assessment
     IADN measures many toxic substances in air and
     precipitation. Most of the chemicals measured in
     the IADN program fall under three main groups:
     poly chlorinated biphenyls (PCBs), chlorinated
     pesticides (DDT, lindane), and poly cyclic aromatic
     hydrocarbons (PAHs).

     Poly chlorinated Biphenyls (PCBs)
     PCBs are a man-made mixture of chemicals most
     commonly used as coolants and lubricants, and in
     electrical equipment. PCB levels and loadings to
     the Great Lakes have generally decreased since
     production was banned in 1979. PCB
     concentrations are still relatively high in urban
     areas such as Chicago, Illinois (Figure 1).
The Indicator - SOGL 2003
Contaminant transfer from     "
the air to the earth's surface is
known as atmospheric
deposition. The United States and Canada are
working together to measure the levels of toxic
chemicals in the air and precipitation in the
Great Lakes basin through the Integrated
Atmospheric Deposition Network (IADN).
IADN consists of five major sampling sites, one
near each of the Great Lakes, and several
smaller stations.

Air monitoring helps us better estimate
atmospheric loadings—the amount of a
pollutant entering any of the Great Lakes from
the air. Once particular contaminants are in the
100000
 10000
J& 1000 H
I
3
           Lk. Superior (Eagle Harbor)
           Lk. Superior (Brule River)
           Chicago
           Lk. Michigan (SI. Bear Dunes)
Lk. Erie (Sturgeon Point)
Lk. Huron (Burnt Island)
Lk. Ontario (Ft. Petre)
                  &
       Figure 1. PCB levels measured at IADN stations.

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     CAN WE EAT THE FISH?
Chlorinated Pesticides
Many extensively used chlorinated pesticides
were banned in the late 1970s and early 1980s
over concerns for human and ecological health.
DDT, one of the most commonly applied
pesticides, was linked to severe reproductive and
physiological abnormalities such as the crossed-
bill syndrome seen in many bird populations.
Overall, the atmospheric levels and loadings of
chlorinated pesticides have decreased over time
as a result of banning their use decades ago.

PAHs
Certain types of PAHs, such as benzo(a)pyrene
(BaP), are linked to an increased incidence of
cancer in exposed individuals. These
contaminants escape into the atmosphere after the
incomplete burning of almost any fuel.  The BaP
concentrations measured in
the atmosphere today have
remained consistent over
the last decade and are
relatively high near major
population centers.
The Outlook
Atmospheric deposition of contaminants will
affect the Great Lakes for decades to come. Over
the last 30 years, we have made significant
progress by banning the most toxic and persistent
chemicals, but residual sources are still found in
the environment and some chemicals are still used
in other parts of the world. For example, PCBs are
still found in many urban areas, but Canada and
the United States are currently investigating the
significance of the remaining source areas and are
also working to encourage the decommissioning of
remaining PCB-containing electrical equipment.

The effects of some currently used chemicals are
not yet fully understood and require continued
research. Focused monitoring programs are
crucial to track changes in the system and better
understand how these changes may affect the
Great Lakes ecosystem.


For More Information...
Visit the web site, www.binational.net, to access
the State of the Great Lakes 2003 and other
references reporting on the state of the Great
Lakes.
                                                                                          12/03

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