Oak Ridge Reservation: Public Health Assessment Work Group
Public Health Assessment Work Group
October 6, 2003 - Meeting Minutes
ORRHES Members attending:
Bob Craig (Chair), LC Manley, Kowetha Davidson, James Lewis, Susan Kaplan, Tony Malinauskas, Don Box, George Gartseff, and David Johnson
Public Members attending:
Tim Joseph, John Merkle, Gordon Blaylock, Rebecca Gardner, and Danny Sanders
ATSDR Staff attending:
Bill Taylor, Melissa Fish, Jack Hanley (telephone), and Lorine Spencer (telephone)
There were four items on the agenda for discussion.
- Review of Draft PHAWG meeting minutes for 9-2-03 and 9-15-03
- ATSDR Announcements
- New ATSDR public health assessor-Dr. Jo Freedman
- Handout for Cancer Incidence Review
- Upcoming schedule (October and November)
- Past Mercury exposures
- Soil and sediment mercury concentration estimates
- Mercury in vegetables, milk, and meat
- Other business as needed
James Lewis made the motion to approve the Draft minutes for the September 2, 2003 and the September 15, 2003 PHAWG meeting. Don Box seconded the motion. The meeting minutes for September 2, 2003 and the meeting minutes for September 15, 2003 were approved unanimously.
New ATSDR public health assessor-Dr. Jo Freedman
Bill Taylor told the group that Dr. Jo Freedman, a toxicologist and health assessor in Atlanta will be working on the PCB Public Health Assessment.
Handout for Cancer Incidence Review
Bill Taylor gave the group a print out of the reference to the National Cancer Institute page that Jack Hanley had mentioned during the September 15, 2003 PHAWG meeting when the group was discussing the Cancer Incidence Review. The reference listed different type of cancers with data available for those specific cancers. It was previously discussed that fact sheets from this site could be included in the Cancer Incidence Review as an appendix. The reference that was printed and distributed to the group was the first page of http://cancernet.nci.nih.gov/cancerinfo/wyntk
Jack Hanley added that the National Cancer Institute site, including the fact sheets, provides information such as possible risk factors for different types of cancer.
Upcoming schedule (October and November)
Bill Taylor told the group that tonight’s mercury presentation would be the last presentation that he would be presenting for some time. Bill Taylor explained that he would begin writing and looking at the mercury issue in depth. Bill will present again when he is further along in writing the Public Health Assessment. In the meantime, during the October 20, 2003 PHAWG meeting, Jack Hanley and Paul Charp are scheduled to present the Y-12 Uranium Public Health Assessment comments and how ATSDR responded to those comments. In addition to Jack and Paul’s presentation, there is a possibility that Dr. Allan Susten might present on risk analysis and PHA dose. However, Dr. Allan Susten has not been confirmed. Paul Charp will also be presenting material relating to the iodine-131 PHA.
Jack Hanley told the group that he is trying to get the Y-12 Uranium responses out in advance of the October 20th meeting so that the PHAWG will be able to discuss the comments and the responses. Jack Hanley also told the group that the comments and responses are lengthy and to not be overwhelmed. Jack Hanley requested that the work group members read the comments so that the group can engage in a good dialogue on October 20th.
After some discussion it was decided that EPA could be included on the email distribution of the next PHAWG meeting announcement.
Bill Taylor also told the group that the PHAWG meetings during the month of November would include presentations about White Oak Creek as well as a presentation by Karl Markiewicz about the screening of biota.
Bill Taylor told the group about four key points that Dr. Owen Hoffman had sent in an email dated September 24, 2003 regarding the last PHAWG meeting.
First, Owen Hoffman recommended the detailed meeting minutes.
Secondly, Owen Hoffman emphasized that it was not the intent of Task 2 to overestimate mercury concentrations; the intent was to produce realistic assumptions and exposure estimates.
Thirdly, regarding the estimates of historic mercury air concentrations, there are atmospheric dispersion models that can take into account terrain (such as CALPUFF) and could be used to test the conclusions of Task 2. Bill Taylor told the group that Task 2 used a flat terrain model for estimating mercury concentrations in the Wolf Valley area; but uranium data was used for other terrain in other communities. However, now there are new models.
James Lewis asked for clarification regarding the availability of new models. Bill Taylor said that he is not a model expert but thinks that Owen Hoffman’s email is suggesting that now there are models available that could be used to test the assumptions and conclusions of Task 2.
After further discussion Bill Taylor told the group that the results need to be reviewed more closely to see if using a new model is worth the time and effort.
Fourthly, mercury analysis of tree rings can be used to estimate historic air concentrations around trees using mathematical models and quantitative uncertainty analyses, by including assumptions about the rate of mercury absorption into wood and the potential of mercury in wood to translocate with time.
Overhead Two and Three
Bill Taylor described the locations of the two Oak Ridge community populations that were included in the Task 2 report and were used for estimating the dose impact for inhalation of air and ingestion of homegrown fruits and vegetables.
Bill Taylor said that there were not many comments or complaints from the technical reviewers regarding the soil and sediment mercury concentrations.
Bill Taylor explained that the first EFPC sediment samples that were analyzed for mercury were collected in 1970 and the second in 1982 and the earliest EFPC soil samples that were analyzed for mercury were collected in 1983. In order to estimate historic soil and sediment mercury concentrations, Task 2 used soil samples from two studies. The two studies used were the SAIC EFPC Floodplain Remedial Investigation from 1991-1992 and the Oak Ridge Associated University Study (ORAU) in 1984. Bill Taylor explained that the SAIC study was an extensive study with lots of data, but that the SAIC study did not include soil samples in Scarboro. Thus, the ORAU study was used in the Scarboro community as a soil data source.
Bill Taylor explained that the ORAU study involved a total of 57 samples while the SAIC study used samples from 159 transects of East Fork Poplar Creek.
Bill Taylor provided a description of the 159 transects.
Gordon Blaylock asked if higher concentrations of mercury would be missed when homogenizing soil samples. Bill Taylor indicated that he planned to address Gordon’s concern. (See overhead 6.)
Bill Taylor pointed out that the origin of SAIC soil samples used in Task 2 were different for each of the three communities (EFPC Farm Family, Scarboro Community, and Robertsville School).
Susan Kaplan said that mercury sinks. Susan has talked to people who have told her that if they take a shovel and dig down into the ground, they can see that the ground is darker X inches down from the top.
Bill Taylor pointed out that Gordon Blaylock had raised an issue about what happens when 0 to 16 inches of soil is homogenized. There were studies available that suggested that most of the mercury was within the first 16 inches. Thus, they were fairly confident that they were capturing most of the mercury in the first third of their core sample.
Bill Taylor went on to explain that there was an additional study conducted called the Vertical Integration Study where they took 5 samples, 18 inch cores and they analyzed each of the 1-inche depths separately. Key findings included that the highest mercury concentrations were found deep in the core and the lowest concentrations were found high in the core. In addition, the mercury concentration of the top 16 inches of soil when homogenized was approximately equal to the average mercury concentrations from the individual 16 inches analyzed separately. Based on that information, Task 2 created a table of soil concentration adjustment factors for the years 1950 - 1990. The chart assumes that the deposition of soil was constant over time.
Bill Taylor pointed out that in his reading of the Task 2 Report he did not find out how Task 2 derived Scarboro historical soil concentrations. Bill Taylor explained that this overhead is for the other two populations. Bill Taylor will try to find out how the historical soil concentrations for the Scarboro community were derived.
LC Manley asked if the group would have been able to find out more information if they had sliced the soil sample rather than homogenizing it? LC said that if the soil samples had been sliced there would have been some indication as to where the mercury was in the soil. Bill Taylor said yes, but the data that the Task 2 team used came from samples that had already been collected and analyzed, and the data set used to estimate the soil concentrations was an extensive set.
Tony Malinauskas asked if the soil itself was stratified or homogenized and said that he was wondering about different levels of absorbability.
Gordon Blaylock said that most of the floodplain is varied and that there is usually not a real distinct layer in the floodplain. It is possible to identify distinct areas of disturbance, but a person is unlikely to find stratification in the normal floodplain soils.
James Lewis asked if any portion of Scarboro is in the 100-year floodplain. Bill Taylor responded that he did not believe so.
Bill Taylor discussed the vegetation, milk, and meat pathways. The transfer of mercury from air to vegetation is based on estimates of mercury deposition and absorption by plants. The transfer of mercury from soil to vegetation is based on measurements of mercury concentrations in both soil and plants collected in the EFPC floodplain. The transfer of mercury to milk and meat is based on estimates of transfer of mercury ingested or inhaled by cattle. It was assumed by Task 2 that the air pathway was the only significant pathway for fruits and vegetables above ground. Soil was the only significant pathway considered for underground vegetables like beets and carrots.
John Merkle asked how mercury gets into the soil. Bill Taylor responded that mercury could have got into the soil via precipitation from the air and EFPC flooding.
Don Box asked how Task 2 accounted for the transfer of mercury from the upper layers to the lower layers. Bill Taylor responded that he believes the assumption was that the mercury was bound to soil and did not move and that soil deposition was consistent at 0.25 inch per year.
Bill Taylor explained that for human consumption Task 2 was measuring absorption (mercury in the plants rather than mercury on the plants) because they were assuming that people would take the vegetables from the garden and wash them off. For cattle, the same assumption was not used.
Bill Taylor said that mercury in plants was a significant portion of the dose received for the EFPC farm family. Bill was surprised that the absorption of mercury from air deposition would actually be high enough for some doses to be close to or to exceed comparison values.
Kowetha Davidson asked how it was shown that mercury was taken up by the part of the plant above ground. Bill Taylor responded that it was assumed that mercury in plants was either entirely due to air deposition or entirely due to root absorption. The evidence, and the rate or quantity of leave uptake of mercury comes from various studies in the scientific literature.
Bill Taylor explained that the model of deposition of mercury to vegetation includes terms for both dry deposition of mercury from air and wet deposition of mercury from rain or snow. Both dry deposition and wet deposition include “deposition velocity” terms and “mass interception” factors. Bill stated that the dry deposition velocity comes from a study in a forest near Oak Ridge and from studies at other sites. Wet deposition velocity comes from the annual precipitation rate in Oak Ridge and the ratio of mercury concentration in rainwater to mercury concentration in air. Mass interception factors were taken from scientific literature.
Bill Taylor told the group that one technical commenter felt surface area would have been more appropriate than mass for heavy vegetables and fruit. Bill Taylor said that he is not sure the technical commenter is correct and that the use of mass or surface area would depend on which values that were taken from the scientific literature. There could be an appropriate relationship for the surface area as well as for the mass of a fruit or vegetable, and both equations could be appropriate to estimate mercury concentrations in fruits and vegetables.
Bill Taylor described the uptake of mercury from soil to vegetation. Measurements of mercury in below-ground vegetables were measured in ORAU and SAIC studies. Soil samples co-located with vegetation samples were analyzed for mercury concentrations. The ratio of mercury concentrations in soil and vegetables and the estimate of historic concentrations of mercury in soils was used to predict the historic concentrations of mercury in below-ground vegetables.
Bill Taylor explained the biotransfer of mercury ingested by cattle to milk or meat. Bill explained that for intake of mercury from air and pasture, transfer factors were used directly to estimate mercury concentrations in milk and meat. For intake of mercury from soil, the transfer factors were multiplied by a bioavailability factor to account for the limited solubility of mercury from soil during digestion. Bill Taylor explained that a cow could eat soil contaminated with mercury but not all of the mercury would get into the milk or the meat.
Bill Taylor said that one technical commenter was concerned that the bioavailability factor for humans is different than the bioavailability factor for cattle. Bill Taylor said that he was not sure how big of a problem the cattle bioavailability factor is—but it might be something to look at.
Bill Taylor said that when looking at mercury doses, exposure to mercury from people eating meat was not a problem for any of the populations. However, there was some indication of children being exposed to high levels of mercury from milk.
Danny Sanders said that he is waiting for information about Happy Valley. Danny Sanders would like to see a Master Schedule for all of the Public Health Assessments.
Jack Hanley said that according to the project plan, K-25 Uranium and Flourides should begin mid-September. ATSDR is just getting started on K-25. Paul Charp is also completing the work on White Oak Creek.
Bob Craig said that the Public Health Assessments that are currently being worked on include: mercury, White Oak Creek, PCBs, TSCA Incinerator, K-25, and Karl Markiewicz’s work. Bob asked if ATSDR would provide an update at the next ORRHES meeting. Jack Hanley said that he is sure that Jerry Pereira will be glad to provide an update.
James Lewis said that an updated project plan with specifics should be included on the website.
- Be sure to include an EPA representative on the next PHAWG email distribution.
- Bill Taylor will try to find out how the historical soil concentrations
for the Scarboro community were derived.
- Jerry Pereira will provide a PHA update at the October 21st ORRHES meeting.
The meeting was adjourned at 6:30 PM.