GES memo (7/16/04) to the MDEQ indicates the results of the Dow/Entrix Wild Game study
in the Tittabawassee River Flood plain confirms findings of MDEQ/GES 2003 T.River Aquatic
Ecological Risk Assesement. Conclusions:
Review of the Entrix (2004) report has shown that the data contained therein support one
of the major conclusions of the Michigan DEQ terrestrial ecological risk assessment (GES,
2004), that is that biota and food chains on the Tittabawassee River downriver of Midland
are contaminated by PCDDs and PCDFs. A reasonable conclusion from this is that predators
and scavengers at the tops of these food chains are likely to be even more exposed to
these contaminants than the deer, squirrels, and turkeys sampled in the Entrix (2004)
However, the Entrix (2004) study was designed to generate data for an evaluation of risk
to human health, rather than to ecological receptors. Because of this, design elements in
the Entrix (2004) study, though perhaps appropriate for a human health risk analysis,
result in an underestimation of the contaminant concentrations to which wildlife would be
exposed and, hence, the magnitude of the risks incurred. These design elements comprise:
The sampling was confined to organisms which, because of their diets, are unlikely to
bioaccumulate PCDDs and PCDFs to the extent that other organisms would.
The carcass handling procedures resulted in a likely underestimation of the magnitudes
of the PCDD/PCDF whole-body burdens to which predators and scavengers may be exposed.
The sample spatial distribution almost certainly results in an underestimation of the
PCDD/PCDF body burdens of turkeys in the lower sections of the floodplain, and, hence, in
the potential exposures to their predators and scavengers.