Oak Ridge Reservation: Public Health Assessment Work Group

Public Health Assessment Work Group

September 2, 2003 - Meeting Minutes

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.