Public Health Assessment Work Group
Meeting Minutes
September 2, 2003
Attendance
ORRHES Members attending:
Bob Craig (Chair), Charles Washington,Don Box, LC Manley, Kowetha Davidson,
James Lewis, and David Johnson Public Members attending:
Roger Macklin, Tim Joseph, Casey Johnson, and J.D. Hutchins
ATSDR Staff attending:
Bill Taylor, Melissa Fish, Jack Hanley-telephone, and Lorine Spencer-telephone
Purpose
The purpose of the meeting was to continue the discussion of past mercury
exposures. Bill Taylor discussed mercury concentrations in fish and the
population-pathway pairs, which the Oak Ridge Dose Reconstruction Task
2 team selected.
Meeting Minutes
LC Manley noted a correction to be made to the August 18, 2003 draft
minutes. On page 7 of the Draft August 18, 2003 meeting minutes the text
reads LC Manley asked where the data comes from that indicates that a
resident of Scarboro was exposed to all three species of mercury and
exposed to more mercury than a resident of another community. LC Manley
indicated that the text should read LC Manley asked where the data comes
from that indicates that the residents of Scarboro were exposed to all
three species of mercury and exposed to more mercury than a resident
of another community.
The meeting minutes were approved with the correction to page 7 of the
draft minutes.
Bob Craig stated that he would like to see the documentation regarding
alternative ways to manage the meeting minutes that was discussed at
the previous PHAWG meeting. Bill Taylor said that he would get that information
to Bob Craig.
Mercury Presentation
Bill Taylor addressed a question raised by Don Box after the previous
PHAWG meeting concerning mercury uses at the X-10 and K-25 plants. Bill
said that the Dose Reconstruction Task 2 team did not include releases
from X-10, K-25 or some minor uses of mercury at Y-12 in the dose reconstruction
because they considered them insignificant compared with those from the
Y-12 lithium separation operations.
Bill Taylor used 13 different overheads and passed out a copy of the
Technical Reviewer Comments document critiquing the Dose Reconstruction
Task 2 (mercury) reports.
Bill Taylor presented the problem that there are no fish sample data
describing mercury concentrations in fish downstream of Y-12 before 1970.
However, the largest water releases of mercury to the East Fork Poplar
Creek were in the 1950s and early 1960s.
To estimate fish concentrations in fish before 1970, the Dose Reconstruction
Task 2 team first studied the relationship between surface sediment mercury
concentrations and fish mercury concentrations in fish that were captured
near those same sediment samples during the 1970s and 1980s. The sediment
and fish data were mathematically well correlated (r2 = 0.66, from linear
regression analysis) for both bluegill and largemouth bass, and the correlation
(numerical relationship between mercury in fish and mercury in sediment)
for those fish is described mathematically by one linear (“regression”)
equation for each species. Historic mercury concentrations in surface
sediment were estimated by analyzing both mercury and Cs-137 in sediment
core samples. Those estimated historic surface sediment mercury concentrations
were used in the regression equations developed for bluegill and largemouth
bass from the 1970s and 1980s data to estimate bluegill and largemouth
bass mercury concentrations for the years before 1970. This method was
used for three expanses of surface water: the Tennessee River (from the
mouth of the Clinch River to Watts Bar Reservoir), Poplar Creek and the
Clinch River (from the mouth of East Fork Poplar Creek to the mouth of
the Clinch River), and East Fork Poplar Creek (EFPC). Core sediment samples
were taken from each end of each surface water segment to estimate the
historic concentrations of mercury in fish, except that there was no
core sample for the lower end of EFPC where EFPC feeds into Poplar Creek.
The core sample for the upper end of EFPC was taken from New Hope Pond,
immediately downstream of Y-12. For the lower end of EFPC, it was noted
that the surface sediment mercury concentration was approximately 20%
of the surface sediment mercury concentration at New Hope Pond. Therefore,
it was assumed that the historic concentrations of sediment at the lower
end of EFPC were all 20% of those at New Hope Pond.
Bill discussed two specific limitations to this method of estimating
historic fish mercury concentrations. First, for some years and some
locations, core sediment mercury concentrations exceeded the surface
sediment mercury concentrations used to generate the regression or correlation
equations. The Task 2 authors did not think it was appropriate to generate
fish mercury concentrations outside the range of the regression equations.
For those years, the mean and maximum fish mercury concentrations (for
both species) were based on a fish study in 1971 from the St. Clair River
and Lake St. Clair in the Great Lakes region. A second limitation to
the method was that the New Hope Pond sediment core (analyzed in 1982)
was only as old as 1973 because the pond was dredged in 1973 and preexisting
sediment was removed at that time. Since all the New Hope Pond sediment
mercury concentrations exceeded the regression sediment mercury concentration
range, all of the fish concentrations at New Hope Pond, including those
before 1973 were the default values from the Lake St. Clair study. Bill
Taylor does not yet know how mercury concentrations for the lower end
of EFPC were estimated before 1973, or how fish mercury concentrations
at all locations were estimated in the late 1980s to 1990 (after the
date of the top of the core samples).
In the final analysis, the estimated fish concentrations were averaged
for both ends of the three water expanses (EFPC, Poplar Creek/Clinch
River, and Watts Bar Reservoir downstream from the Clinch River to the
dam). Also, the estimated fish mercury concentrations for bluegill and
largemouth bass were averaged together. And finally, minimum, mean, and
maximum mercury fish concentrations were generated from all of these
data for all the years, 1950 – 1990.
In the second part of Bill Taylor’s presentation, he presented
a detailed look at the populations eating fish downstream from Y-12.
In the chart of population-pathways pairs that Bill presented at previous
PHAWG meetings (Table ES-1, from the Dose Reconstruction Task 2 report),
the only residential fish-eating populations were the Scarboro Community
and the East Fork Poplar Creek Floodplain Farm Family. These were specified
in the chart in this way because they were considered to be the only
residential populations that would have fished from East Fork Poplar
Creek. The chart also included fish consumers who ate fish from Clinch
River/Poplar Creek or Watts Bar Reservoir, but in this case, the residential
population is not specified. The Task 2 team estimated mercury doses
for fish consumers from Clinch River/Poplar Creek and Watts Bar Reservoir
based on several different consumption patterns.
Finally, Bill Taylor distributed Table 6-4 from the Task 2 report and
asked for feedback concerning the population estimates which the Task
2 team generated for its report. Bill wondered if the PHAWG considered
these population numbers reasonable.
Major Concerns and Comments Raised
Charles Washington would like to see the new study that is out which
says that mercury is less harmful than previously thought.
Charles Washington said that there have been so many sediment disturbances
that mercury levels could be raising instead of decreasing further downstream.
Charles Washington wanted to know what other types of fish besides largemouth
bass the Dose Reconstruction analyzed and wanted to know where largemouth
bass feed. The group responded that largemouth bass are top predators.
Bill Taylor said that there were not enough data available for other
fish species to obtain good correlation coefficients between sediment
mercury concentrations and other fish mercury concentrations apart from
bluegill and largemouth bass.
Don Box asked if the core sediment samples were homogenized or cross-sectioned.
Bill Taylor said that it would depend on the core sample and that he
does not believe that the samples were all handled the same way. Bill
Taylor does not believe that any samples were completely homogenized.
However, that type of data was not provided in the Dose Reconstruction
narrative.
Al Brooks said that there are two types of sediments—deep channel
and shallow. Most mercury is in deep channel sediments. If samples are
taken in a deep channel, the samples barely go through the clean sediment
layer. The issue of the structure of the sediments in the river raises
questions about the choice of values that were used in the Dose Reconstruction.
Bill Taylor responded that with regard to the choice of location, a certain
type of consistency is assumed when making these calculations. Bill Taylor
added that the total depth of core samples analyzed for the regression
analysis were not over 100 cm so the samples were not real deep.
Referring to overhead eight, Al Brooks stated that the maximum mercury
concentration of Poplar Creek Mile 5 is 20 to 40 times higher than any
other number. What is the explanation for this number? Where could the
number (460 mg/kg dry weight) have come from? Al said that if this were
his data he would be looking for a decimal point because the number is
very suspect looking. Bill Taylor responded that the 460 mg/kg dry weight
number was not used because it was outside of the range of the sediment
mercury concentrations used to construct the regression analysis.
Al Brooks felt that it was important that the group remembers that no
person ever lived in the floodplains; they may have lived near the floodplains.
Al Brooks told the group that in all of the years that he has lived
near East Fork Poplar Creek he has seen very few children fishing in
the Creek and has never seen a child with a fish. Al pointed out that
the thirteenth overhead has a fishing population that exceeds the housing
population.
Bob Craig pointed out that Jim Loar is a resource that is still in Oak
Ridge and could be contacted.
James Lewis was concerned that key work group members were not present
at the PHAWG meeting.
James Lewis clarified that the PHAWG Ad Hoc work group is working on
a Cancer Incidence Review and not a Health Statistics Review.
The meeting was adjourned at 7:15 P.M.
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