Public Comment

ATSDR's Response

General Comments

1

The Agency for Toxic Substances and Disease Registry's (ATSDR) PHA supports the less detailed findings of previous studies, especially the Florida A&M University sampling and follow-on U.S. Environmental Protection Agency (EPA) Region 4 sampling in the Scarboro community both process that the [organization] has followed in detail.

In this PHA on Y-12 uranium releases, ATSDR evaluated and analyzed the information, data, and findings from previous studies and investigations to assess the public health implications of past and current off-site exposures to uranium. ATSDR concluded that there is no apparent public health hazard for people living near the Y-12 plant because the past and current off-site exposures are not at levels expected to cause either radiation or chemical health effects. The Y-12 uranium releases are not a public health hazard for people living near the Y-12 plant.

The Scarboro Community Environmental Study (Florida Agricultural and Mechanical University [FAMU] 1998) was conducted to address community concerns about environmental monitoring in the Scarboro neighborhood. It addresses these concerns by validating the measurements taken at the perimeter air monitoring station #46 (located in the Scarboro community) and external gamma data collected during past aerial radiation surveys. The FAMU report presented the results of the soil, surface water, and sediment sampling in Scarboro and compared these concentrations with those measured in the Oak Ridge region. The study found that the concentrations of mercury and radionuclides in Scarboro are generally within the range found in the Oak Ridge region.

As part of EPA's oversight responsibilities at the ORR, EPA Region IV re-sampled 20% of the 1998 FAMU sampling. Based on the concentrations detected in the soil, sediment, and surface water in Scarboro, the EPA report (EPA 2003) concluded that "there is not an elevation of chemical, metal, or radionuclides above a regulatory health level of concern...the Scarboro community is not currently being exposed to substances from the Y-12 facility in quantities that pose an unreasonable risk to health or the environment." To expand the information presented, ATSDR added summary briefs of the EPA and FAMU reports in Appendix I of the final PHA.

2

The [organization] provisionally accepts ATSDR's conclusions that there was and is no health risk to the Oak Ridge community due to uranium releases from Y-12. However, the detailed critique submitted by Lowell Ralston of the Office of Radiation and Indoor Air at EPA Headquarters seems to disagree with the ATSDR's conclusions on technical grounds. ATSDR must address this critique point-by-point in a manner that the public can comprehend, clearly explaining the points of disagreement and/or differences in approach so that no doubt remains regarding the conclusions of the PHA.

It is ATSDR's policy to address comments collected during the public comment period. EPA's comments are included in this table along with ATSDR's responses.

3

When the Environmental Protection Agency disagreed with the ATSDR's findings, it seemed that lines were immediately drawn for damage control. I have talked with several community members who have all reached the conclusion that the ATSDR reports are controlled and predetermined, and public participation and input will be of little use, if the ATSDR's report is contested. Oak Ridge's nickname change to the "Secret City" seems to be no accident. My vote of credibility is with the EPA.

In a March 27, 2003 cover letter to ATSDR, EPA Region IV stated the following:

"EPA concurs with the assessment's conclusion that the available data does not indicate the presence of uranium releases that constitute a past, current or future health threat for the Scarboro Community."

Additionally, in a December 1, 2003 letter to ATSDR, EPA Region IV stated the following;

"... EPA agrees with ATSDR that there are no apparent adverse health effects, as documented in the subject report..."

"For the comments originating from EPA Region 4, we conclude that ATSDR has provided adequate response."

Also, EPA's Office of Radiation and Indoor Air stated the following in their June 22, 2003 comments:

"... we agree with ATSDR's conclusion that the current uranium exposures at Scarboro are probably within acceptable limits."

ATSDR embraces the philosophy that community involvement is a key component of the public health assessment process. At the Department of Energy (DOE) ORR, ATSDR's community involvement activities promote collaboration between ATSDR scientists, community members, and other agencies. These activities also provide opportunities for community members to have a role in ATSDR's public health assessment process.

ATSDR and the Centers for Disease Control and Prevention (CDC) established ORRHES in 1999 to provide a forum for communication and collaboration between citizens and the agencies that are evaluating public health issues and conducting public health activities at the ORR. The ORRHES consists of individuals who represent diverse interests, expertise, backgrounds, and communities, as well as liaison members from state and federal agencies. The ORRHES created the Public Health Assessment Work Group (PHAWG) to conduct in-depth exploration of issues, concerns, and the ATSDR PHAs. PHAWG meetings are held twice a month and are open to all who wish to attend and participate.

Since ATSDR began developing (in the Fall of 2002) the PHA on the Y-12 uranium releases, ATSDR scientists have presented and discussed the PHA in detail at least 6 times with the PHAWG and twice with the ORRHES. In addition, the PHAWG developed technical and editorial comments on the initial release draft PHA for the ORRHES. In March 2002 the ORRHES reviewed, deliberated, and approved the comments on the initial release draft PHA. As noted in ATSDR's response to comment 102, the ORRHES comments (which also include comments from community members not on the ORRHES) were incorporated in the PHA and have been very helpful in improving the technical aspects and overall readability of the document.

Figures 4 and 5 depict the process whereby the ORRHES, the PHAWG, and the public participate and provide input into the ATSDR public health assessment process. For example, ORRHES provided input in the discussion of the margin of safety in the uranium levels, degree of conservatism, the U 235 enrichment issue, ATSDR screening levels and process, the use of ATSDR's radiogenic cancer comparison value, and the development of the Y-12 Uranium Releases Brief.

ATSDR also believes that collecting and addressing community health concerns is an essential part of ATSDR's overall mission and commitment to public health. ATSDR and the ORRHES developed the Community Health Concerns Comment Sheet for community members to provide written comments about specific health concerns or other issues. The comment sheets are available at the ATSDR Oak Ridge Field Office (197 South Tulane Avenue; Oak Ridge, TN; phone: 865-220-0295). To improve the documentation and organization of community health concerns at the ORR, ATSDR developed a Community Health Concerns Database specifically designed to compile and track community health concerns related to the site. Please see the Community Concerns section of the PHA (Section VI.) for ATSDR's responses to concerns related to issues associated with uranium releases from the Y-12 plant. Also, it is ATSDR's policy to address comments received during the public comment period.

Evaluation of Past Exposures

4

Please note also, that the second level of screening performed in the Task 6 Report of the Oak Ridge Dose Reconstruction is not a rigorous analysis of retrospective exposure to real persons nor is it a conservative over-estimate of true exposure. Much more additional work is required prior to making a conclusion that past exposures are not of concern.

As stated in the title, the Task 6 report was a "Screening Evaluation of Potential Off-Site Exposure" that routinely and appropriately used several layers of conservatism and protective assumptions and approaches (see list of conservative aspects of the screening evaluation on pages 48 and 92 of the PHA). In addition, the Task 6 report states on pages E-9 and 3-27 that "because of the scarcity of information regarding estimates of uranium concentrations in the environment over the period of interest, some conservatism was maintained in the uranium concentration estimates used in the Task 6 Level II screening to ensure that hazards to a significant portion of the potentially exposed population were not underestimated" (ChemRisk 1999).

The internationally recognized expert technical reviewers hired by ATSDR to review the Task 6 report pointed out that "the estimates made in the report tend to be on the conservative side–one expects, therefore, that (when in error) the report would tend to overestimate the extent to which exposure to uranium is a problem in the Oak Ridge area. Further refinements to the study are likely to reveal that uranium exposures are actually lower than those currently estimated" (see page G-7 of the PHA).

The expert technical reviewers also stated that the Task 6 uranium screening evaluation report was technically sound and applicable to public health decision-making (see page G-7 in the PHA). In addition, CDC's staff participated in the Oak Ridge Health Agreement Steering Panel (ORHASP) and agreed that the Task 6 report is appropriate for public health decision-making.

Since the screening evaluation, which contained conservative aspects, resulted in an overestimation of total past uranium dose that is well below levels expected to cause adverse health effects, ATSDR does not believe the evaluation of Y-12 uranium releases requires a further nonconservative screening, a refined evaluation with uncertainty and sensitivity analyses, or additional sampling.

5

The fact that ATSDR committed to using the Oak Ridge Health Agreement Steering Panel Tasks as the main factual basis for conducting its public health assessment lays bare the inadequacy of its approach. The ORHASP Task 6 was found by the panel of experts who reviewed the original document as an inadequate factual basis for making public health findings and rightly concluded that more investigation is needed before drawing PH conclusions. ATSDR reviewers also concluded the information in Task 6 was insufficient to draw definite conclusions on the impact of uranium to local public health.

ATSDR Technical Review Process

The Agency for Toxic Substances and Disease Registry (ATSDR) had each of the Phase II Oak Ridge Health Studies documents reviewed by a group of technical experts to evaluate the quality and completeness of the studies and to determine if the studies provide a foundation on which ATSDR can base follow-up public health actions or studies, and particularly, to support its congressionally mandated public health assessment of the ORR. ATSDR will use the information from the Oak Ridge Health Studies, as well as data from the technical reviews and other studies, to develop public health assessments for the ORR.

ATSDR recognizes the great amount of oversight, technical peer review, and overall work that went into the Oak Ridge dose reconstruction project. However, ATSDR wanted an additional round of expert review of the Task 6 uranium screening evaluation to consider its value for the public health assessment. There are two reasons for the additional round of review. First, ATSDR will not attempt to reproduce (ab initio) the work or results of the Task 6 uranium screening evaluation for its public health assessment. Such an attempt cannot be justified without substantial new information about past releases of uranium, or historic environmental sampling data or meteorological data, which ATSDR does not presently have. Secondly, Task 6 uranium screening evaluation is a technical investigation fraught with uncertainty. ATSDR believes that an independent expert review of the methods and assumptions in the Task 6 uranium screening evaluation offers the best insight into the validity and usefulness of the results for making public health decisions.

ATSDR contracted with Eastern Research Group, Inc. (ERG) of Lexington, Massachusetts, to select four expert reviewers to technically review the uranium screening evaluation Task 6 report: Melvin Carter, Nolan Hertel, Ronald Kathren, and Fritz Seiler. The reviewers were asked to comment on the study design, methods, and completeness of the uranium report, as well as the conclusions of the authors of the report.

ATSDR Note to Reader of Technical Reviewers Comments

ATSDR cautions the reader that some of the technical reviewers' comments are critical of the Task 6 uranium screening evaluation report. This does not mean that the uranium screening evaluation report is flawed or should not be used. The reviewers were not provided with a forum for group discussion or with formal access to the uranium Task 6 study authors to ask questions. Not all reviewers answered every question posed to them. Sometimes they acknowledged they were commenting outside their field of expertise and sometimes they acknowledged that they did not wish to comment outside their field of expertise. The reviewers brought their varied experience to the task, and not all reviewer comments are equally valid. Occasionally two opinions are conflicted. In such an instance (and other information being equal) ATSDR will tend to prefer comments from the reviewer who had the greater expertise in the subject area. Finally, the technical reviewers knew and acknowledged the Task 6 report was a screening evaluation of the uranium releases and not a complete dose reconstruction. ATSDR intends to evaluate each of the reviewer comments for its applicability and usefulness on its own merit and it encourages the reader to do the same.

Technical Reviewers Comments

The internationally recognized expert reviewers concluded that the uranium screening evaluation in the Task 6 report was "technically sound and applicable to decision-making," that it was "supported by and developed on the basis of information in the reports," that it "conformed with established and generally accepted techniques," and that it had "no major or significant problems with respect to the study design or the scientific approaches used." Overall, the reviewers agreed that the screening assessment is adequate for public health decision-making (see page G-7). The technical reviewers agreed that IF it is found necessary to evaluate beyond the screening stage, additional modifications would be required for a complete dose reconstruction. They noted that further refinements to the study are likely to reveal that uranium exposures are actually lower than those currently estimated (see page G-7).

Task 6 Teams Comment Regarding the Use of the Task 6 Screening Evaluation

Also, the Task 6 team noted that there are areas identified throughout the report that contribute to the overall uncertainty of the results of the screening evaluation. They state that "these areas should be examined IF the evaluation of Oak Ridge uranium releases is to proceed beyond the conservative screening stage, and on to nonconservative screening and possibly a stage of refined evaluations" (see pages 5-2 and 5-3).

ATSDR Conclusion

ATSDR concluded that since the Task 6 uranium screening evaluation routinely and appropriately used several layers of conservatism and protective assumptions and approaches that resulted in overestimated total past uranium doses that are well below (32 times less than) the ATSDR radiogenic comparison value and levels expected to cause adverse health effects, ATSDR categorizes the Y-12 plant as having no apparent public health hazard from uranium exposure and does not believe the evaluation of Y-12 uranium releases requires a further nonconservative screening, a refined evaluation with uncertainty and sensitivity analyses, or additional sampling.

6

[Organization] made it very clear from the beginning that use of the ORHASP tasks as a factual baseline was in and of itself highly inappropriate due to these aforementioned and other clear restrictions the results would have on the PHA.

The Task 6 report underwent the State of Tennessee's external peer review prior to release and ORHASP provided technical and community oversight throughout the project. In addition, ATSDR had the Oak Ridge Health Study reports technically reviewed by an expert panel of internationally recognized scientists. The purpose of the technical review was to determine if the uranium report provides a foundation on which ATSDR can base follow-up public health actions or studies.

The ATSDR's expert technical reviewers concluded that the Task 6 report was "technically sound and applicable to decision-making," that it was "supported by and developed on the basis of information in the reports," and that it had "no major or significant problems with respect to the study design or the scientific approaches used." Overall, the reviewers agreed that the screening assessment is adequate for public health decision-making (see page G-7). In addition, CDC's staff participated in ORHASP and agreed that the Task 6 report is appropriate for public health decision-making.

Furthermore, one of the expert technical reviewers of the Task 6 report also participated in ATSDR's external peer review of the PHA on Y-12 Uranium Releases. In his peer review of the PHA, he stated that "the assessment is very well done, clearly characterized and summarized. I could find no errors of fact or logic, nor were assumptions inappropriate or unrealistic."

7

These restrictions include the lack of combined effects from other known releases of fallout such as NTS, Russian and Pacific weapons testing.

The air monitoring stations and soil sampling in Oak Ridge do not differentiate Y-12 uranium fallout from other sources.

ATSDR's PHAs on the ORR focus on off-site exposure to contaminants released from the ORR and are not designed to evaluate exposure to radiation from other sources. As mentioned several times (e.g., pages 2 and 31), this PHA evaluates community health concerns and issues associated with the uranium releases from the Y-12 plant. The release and exposure to other contaminants of concern such as mercury, iodine 131, polychlorinated biphenyls (PCBs), uranium from the K-25 facility, and fluorides are not addressed in this document. These contaminants and other topics will be evaluated by ATSDR in separate PHAs.

8

The Task also did not consider direct inhalation as the most important exposure pathway of concern, which is evident from other detailed dose reconstructions on atmospheric releases of uranium, such as those performed by CDC at Fernald, OH.

Tables 7, 9, and 10 in the PHA identify the pathways considered by the Task 6 team. Not only was inhalation of airborne particulates considered, it was the largest contributor to total uranium exposure via the air pathway (30% for U 234/235 and 10% for U 238; see Table 7).

During the evaluation, the Task 6 team also considered other human exposure pathways that were specific to the exposure potential of the communities living near ORR. For the water and soil pathways, fish consumption and vegetable consumption, respectively, were calculated to contribute larger percents of the total uranium dose (see Tables 9 and 10).

9

By repeated dismissal of such particulars in the face of comment submitted verbally and in writing from members of the community requesting such considerations ATSDR effectively has lost all credibility as a technically competent and independent investigator representing public health concerns.

ATSDR captured, reviewed, and considered the previous comments that were made during ORRHES and PHAWG meetings or provided in writing to ATSDR (see ATSDR's responses to comments 6, 7, and 8).

As stated in ATSDR's response to comment 3, community involvement and responding to health concerns are key components of the public health assessment process. There are several ways in which the public can become involved and provide input into the ATSDR public health assessment process. It is ATSDR's policy to address health concerns and comments collected during the public comment period.

ATSDR had the Task 6 report technically reviewed and the PHA peer reviewed. The technical reviewers concluded that the Task 6 report was adequate for public health decision-making (see page G-7) and all three external peer reviewers agreed that ATSDR's conclusions are appropriate. In the words of one peer reviewer also familiar with the Task 6 report: "the assessment is very well done, clearly characterized and summarized. I could find no errors of fact of logic, nor were assumptions inappropriate or unrealistic." Furthermore, CDC's staff participated in ORHASP and agreed that the Task 6 report is appropriate for public health decision-making.

Additionally, in a March 27, 2003 cover letter to ATSDR, EPA Region IV stated the following:

"EPA concurs with the assessment's conclusion that the available data does not indicate the presence of uranium releases that constitute a past, current or future health threat for the Scarboro Community."

10

And how many of the studies used were based on information that was "incomplete, inconsistent, or in the shredder?

ATSDR's conclusions in the PHA are based primarily on data and information from the Task 6 report (ChemRisk 1999), the FAMU report (FAMU 1998), the EPA Region IV report (EPA 2003), and the Oak Ridge Environmental Information System (OREIS) database. The evaluation of past exposure is largely based on the evaluations in the Task 6 report. The references ("studies") used in the Task 6 report and all the other Oak Ridge Health Studies reports are available to the public.

Availability of References Used in Task 6 Uranium Screening Evaluation Report

During the Oak Ridge Health Studies, the State of Tennessee, through its contractor ChemRisk, contracted with the firm Shonka and Associates to conduct the most intensive search of documents ever performed for the ORR. Staff from ChemRisk and Shonka and Associates performed a systematic data and records search at all on-site document storage areas, national archives, libraries, individual offices, as well as at other areas where data of any form may have existed.

The references used to generate all of the Oak Ridge Health Studies and Dose Reconstruction Reports are available to the public and researchers through five different mechanisms:

1. Project-CD entitled, "The Oak Ridge Health Agreement Studies, Oak Ridge Dose Reconstruction."
   The project-CD contains the full abstracted bibliographic database of references collected, all project reports, and all of the interviews in their complete form. Every document ChemRisk collected was entered into the formal bibliographic database. This CD does not contain the full text of referenced documents.



2. DOE Information Center
   All references and final project reports generated during the study were sent to the Information Center. It should contain all the references identified on the Project-CD. It should be noted that some references may have been inadvertently removed as there is unrestricted access to the documents and staff were not expected to police document use. Also, this collection does not have the modeling and dose calculations that were done by ChemRisk to calculate dose and risk.



3. On-Line DOE Comprehensive Epidemiologic Data Resource (CEDR)
   The CEDR project has all references "utilized" in the dose reconstruction reports. Note that it does not have all references listed on the Project-CD, only those that were actually used and referenced in the dose reconstruction documents. CEDR is available on line (http://cedr.lbl.gov/ ).



4. CEDR on CD ROMs
   The references contained in CEDR are also available on 18 CDs at ATSDR offices including the Oak Ridge Field Office. The references on the CDs link directly to the bibliographic database on the Project-CD.



5. Tennessee State Library and Archive
   The only complete set of project files, references, documents, reports, and calculations is at the Tennessee State Library and Archive in Nashville. It is the largest single collection ever accepted for permanent retention by the State. The library is now in the process of microfilming, indexing, and organizing the entire reference collection. When complete, the microfilmed records will be available to the public and the original documents will be catalogued and shelved in the library. The shelved documents will be made available through monitored access. This collection of documents represents the only fully complete document data set for this State Project. It is the only one that has the complete ChemRisk project file.

See the February 2001 ORRHES meeting minutes for a presentation and paper on the document and data management process during the Tennessee Department of Health Oak Ridge Health Studies & Dose Reconstruction Project.

In addition, the Task 6 report underwent an external technical peer review, an independent expert technical review, and had ORHASP involvement throughout the project. The internationally recognized expert technical reviewers hired by ATSDR concluded that the Task 6 report was "technically sound and applicable to decision-making," "supported by and developed on the basis of information in the reports," and had "no major or significant problems with respect to the study design or the scientific approaches used." Overall, the reviewers agreed that the screening assessment is adequate for public health decision-making (see page G-7). In addition, CDC's staff participated in ORHASP and agreed that the Task 6 report is appropriate for public health decision-making.

Additional data from OREIS, FAMU, and EPA Region IV were used to evaluate current exposures. OREIS is a centralized, standardized, quality-assured, and configuration-controlled environmental data management system that is publicly available (for additional details about the OREIS Web site, see http://www-oreis.bechteljacobs.org/oreis/help/oreishome.html ).

The validated sampling results presented in the FAMU report (FAMU 1998) were verified by EPA Region IV. The EPA report states on page vi: "EPA's study results are in agreement with similar, more extensive, studies done in 1998 by FAMU. EPA's study analyzed for hazardous substances and radionuclides associated with the operations of the nearby Y-12 Plant, several of which had not been included in sample analysis from other studies. EPA's work gives a completed representation of any contamination that might have been encountered. These results confirm that existing soil and water quality pose no risk to human health within the Scarboro community" (EPA 2003).

11

ATSDR's adjustment factor assumes an incorrect exposure duration of 52 years for the Task 6 report Level II assessment. According to Oak Ridge Dose Reconstruction Project Summary Report (ChemRisk 2000, p.70): "For radionuclides and carcinogenic chemicals, exposure durations of 50 years and 10 years were used in the Level I and Level II screening, respectively." Based on this, ATSDR's adjustment factor should be 0.14 (i.e., 10 y/70 y = 0.14) and, along with the Task 6 Level II total uranium dose of 114 mrem, should yield a corresponding recalculated total uranium dose of ~ 816 mrem (i.e., 114 mrem ÷ 0.14).

ATSDR used the correct exposure duration of 52 years to calculate the adjustment factor and doses.

The Level II screening assessment described on page 70 in the Oak Ridge Dose Reconstruction Project Summary Report (ChemRisk 2000) pertains to the Task 7 screening of additional chemicals and radionuclides to identify materials as low, medium, or high priority for further study, not the Task 6 Level II uranium screening evaluation. The Task 6 Level II uranium screening evaluation is discussed on page 71 of the Oak Ridge Dose Reconstruction Project Summary Report (ChemRisk 2000).

As stated on page 4-14 of the Task 6 report, "the doses are summed over 52 years of exposure" (ChemRisk 1999).

In addition, ATSDR staff verified that the doses are summed over 52 years by consulting the Task 6 manager and the Task 6 spreadsheets (personal communication, August 2003).

Scarboro

12

In any event, the public health assessment for uranium rests upon the concentration of total uranium in the Scarboro environment and not on a departure of the isotopic ratio from its normal U235 value. Fortunately, the data which determines this is of sufficiently high quality to ascertain that Scarboro total uranium levels are within the expected background range for East Tennessee soils. In fact, the levels of uranium in Scarboro soils is so low that even a considerable increase in its U235 percentage would not change the conclusion that it is safe.

ATSDR agrees that the public health conclusions are based on the evaluation of exposure to total uranium in the environment through several pathways, not on the evaluation of uranium enrichment in the soil. The amount of uranium present in the community is below levels known to cause adverse health outcomes.

ATSDR also agrees that a slight increase in the U 235 percentage would not change the conclusion that it is safe. However, if the percentage enrichment is about 10 to 15%, the uranium becomes a radiation hazard to the kidneys.

13

Considering the prior public demands for core samples, expand the footnote to indicate that finding background levels of total uranium in Scarboro soils indicates one of two cases: 1) little or no deposition of insoluble, immobile forms of uranium or 2) deposition of very soluble, mobile forms of uranium which have been eluted. Given the chemistry of uranium the latter case is very improbable on the clay soils of East Tennessee and surface soil sample are indicative of past exposures. (P67)

The predominant form of uranium released to the air was highly insoluble uranium oxide (ChemRisk 1999). As stated in the Current Soil Exposure Pathway discussion under the Current Radiation Effects section (Section III.B.2.a.), the overall results indicate that the concentrations of uranium detected in the Scarboro community are indistinguishable from the background concentrations of uranium in the area around Oak Ridge. Furthermore, the percentages of uranium in the Scarboro community are essentially identical to the amount of uranium found in nature (see Figures 24 and 25).

In 2001, EPA Region IV collected uranium core samples from two locations in Scarboro. The report stated that "none of the analytical values for the uranium cores were elevated above the PRG [preliminary remediation goal] or background... There is no evidence that the substance is present at levels 12 inches below ground surface" (pages 7 and 17). From page 19 of their report, EPA Region IV "does not propose to conduct any further environmental sampling in the Scarboro community," and from page 26: "based on EPA's results, the Scarboro community is safe. Therefore, additional sampling to determine current exposure is not warranted" (EPA 2003). Page 29 in the PHA provides a short summary of the EPA sampling. To expand the information presented, ATSDR added a summary brief of the EPA report in Appendix I of the final PHA.

In addition, the Auxier report compared the results of the FAMU Scarboro sampling results with the deposition estimates based on the August 1998 Task 6 results (Prichard 1998). The Auxier report concluded that the Task 6 air pathway analysis is supported by the 1998 FAMU Scarboro soil data (Prichard 1998). The report stated that the agreement between deposition inferred from soil samples and deposition predicted on the basis of Task 6 air concentrations projections is well within the uncertainties of the parameters used in the calculations (Prichard 1998). The internationally recognized independent technical reviewers hired by ATSDR commented that the analysis and conclusions of the Auxier report are compelling.

14

The problem is the public perception that Scarboro has been contaminated by airborne enriched uranium. The real question is: Are there significant levels of U235 in Scarboro soils?

No. Based on the data supplied to ATSDR, the soils in Scarboro are indistinguishable from regional soils. The PHA addresses this question in the Current Soil Exposure Pathway discussion under the Current Radiation Effects section (Section III.B.2.a.). Even though the Oak Ridge area appears to contain more U 235 than typically found in nature, the overall results indicate that the concentrations of uranium detected in the Scarboro community are indistinguishable from the background concentrations of uranium in Oak Ridge area. Furthermore, the percentages of uranium in the Scarboro community are essentially identical to the amount of uranium found in nature (see Figures 24 and 25).

15

(pp. 3 & 5) On p.48, the statement is made that Scarboro was, "...likely to have received the highest uranium exposures from the Y-12 plant". But on p. 95, two current uranium concentrations are given, and the one for the city of Oak Ridge is almost 2.6 times the value for Scarboro. Therefore, is the statement on p. 48 still correct?

Yes, the statement on page 48 [ATSDR note: page 48 in the public comment version] is correct. As noted in the footnote of Figure 22, the average air concentration for Station 46 (Scarboro) is based on data from 1995 to present, whereas the average concentration for Station 41 (Oak Ridge) is based on data from 1986 to 1991. Since the Y-12 missions were curtailed in 1992, operations, and hence emissions, were higher from 1986 to 1991 than from 1995 to present (see Section IIB. Operational History). This is also the same reason why the total radiation doses from inhalation in Table 15 are higher in the city of Oak Ridge than in Scarboro.

ATSDR compared the concentrations detected at Station 46 (Scarboro) to those detected at Station 41 (located in the city of Oak Ridge near the intersection of South Illinois Avenue and the Oak Ridge Turnpike) for the years in which both air monitors were in operation (1986 to 1991). The uranium air concentrations at Station 46 were, on average, 2.7 times higher than those at Station 41.

16

Both the comments by EPA Headquarters and by EPA Region 4 state that Scarboro may not have been the most affected community from releases from the Y-12 plant. The [organization] has requested repeatedly that other neighborhoods in Oak Ridge be sampled for potential contamination. Although a couple years ago DOE, Tennessee Department of Environmental and Conservation, and EPA had initiated discussions for a joint sampling program to cover the other neighborhoods in Oak Ridge, no such sampling has been performed to date. Terrain-based air-transport models reportedly find that the Woodland community may have received more emissions from Y-12 than Scarboro. In the PHA, pages 30-31, recommendations 3 and 4 by the Oak Ridge Health Agreement Steering Panel would have dispelled much of the controversy had they been followed.

Scarboro is not a representative and reference offsite-impact community, owing in part to the prevailing direction of the wind.

ATSDR believes the city of Oak Ridge is the only established community adjacent to ORR that could have been impacted by Y-12 uranium releases and that Scarboro is a representative community for the city of Oak Ridge. Therefore, the conclusions are valid for the people living near the Y-12 plant, including the city of Oak Ridge.

As noted on page 43 of the PHA, the Task 6 team identified Scarboro as the reference location using the air dispersion modeling (USEPA 1995, as cited in ChemRisk 1999). The Task 6 team used the results of the flat terrain ISC dispersion model to identify the off-site housing area with the highest estimated uranium air concentrations. The Task 6 team understood the limitations of applying the flat terrain ISC dispersion model in the complex terrain surrounding the Y-12 facility and also understood that the flat terrain model overestimated the air concentrations in Scarboro and other locations outside Bear Creek Valley (ChemRisk 1999, ORHASP 1997). However, when estimated results of air dispersion models were compared to the actual uranium air concentrations measured in Scarboro, the flat terrain model was the best predictor of estimated uranium air concentrations in Scarboro. The Task 6 report stated that "while other potentially exposed communities were considered in the selection process, the reference locations [Scarboro] represent residents who lived closest to the ORR facilities and would have received the highest exposures from past uranium releases...Scarboro is the most suitable for screening both a maximally and typically exposed individual" (ChemRisk 1999).

ATSDR agrees with the commenters that the predominant wind direction at the Y-12 facility is southwest or northeast. According to the ORR meteorological monitoring, "prevailing winds are generally up-valley from the southwest and west-southwest or down-valley from the northeast and east-northeast... winds in the valleys tend to follow the ridge axes, with limited cross-ridge flow within local valley bottoms" (DOE 2002c). Therefore, most of the uranium would deposit up and down the valley in which the Y-12 plant is located. The Y-12 plant is located in Bear Creek valley, between Pine Ridge and Chestnut Ridge. These ridges extend to the northeast into Union valley. No one lives in Bear Creek valley or Union valley. The closest population living in the valley system between Pine Ridge and Chestnut Ridge is more than 3 miles away, across the Clinch River, in Wolf valley. The people living in Wolf valley would likely have been exposed to lower amounts of uranium than the people living in Scarboro because the majority of the uranium deposition would have been relatively close to the Y-12 plant.

Aerial surveys performed since 1959 are sufficiently sensitive to detect radiation sources. Those sources outside the confines of Y-12 have been verified by the state not to constitute a health hazard. By implication, the aerial surveys will readily detect sources that do constitute a hazard and (except for a known few locations due to past or present operations within Y-12) the off-site areas such as the Bear Creek and Union valleys, including the residential areas of Oak Ridge, do not show any elevation of radiation above background. Thus, there is direct empirical evidence that the Oak Ridge neighborhoods have not been contaminated by Y-12 uranium releases.

ATSDR acknowledges that it is possible that the Woodland community, also located within the city of Oak Ridge (near the gap in Pine Ridge), might have received higher uranium emissions than Scarboro. To evaluate this potential, ATSDR compared the ambient air monitoring data for Station 46 (Scarboro) to Station 40 (located on the Y-12 plant near the intersection of Bear Creek Road and Scarboro Road). While Station 40 is not located in Woodland, it is located in Bear Creek valley near the gap in Pine Ridge. ATSDR compared the average uranium air concentrations from 1986 to 2002 and found that the concentrations at Station 40 were, on average, 20% higher than those at Station 46. The average air concentrations at Station 40 ranged from being less than half those at Station 46 in 1997, to almost double those at Station 46 in 1990. For the years from 1986 to 1989, during higher production, the average uranium concentrations at Station 40 remained steady at 20% higher than those at Station 46.

Assuming, therefore, that the Woodland community was exposed to the uranium air concentration at Station 40 in Bear Creek valley, they could have potentially received up to twice the amount of uranium emissions as Scarboro. If ATSDR doubled the estimated exposure calculated for Scarboro, the Woodland community could have received a past uranium radiation dose of up to 310 mrem over 70 years (based on an air monitoring station located at the Y-12 plant), which is well below the radiogenic cancer comparison value of 5,000 mrem over 70 years. The current uranium radiation dose is estimated to be less than one mrem, also well below the radiogenic cancer comparison value. Therefore, even if the Woodland community were to have received double the emissions of Scarboro (which is unlikely), the exposures are still too low to be of health concern.

For perspective, ATSDR also compared the concentrations detected at Station 46 (Scarboro) to Station 41 (located in the city of Oak Ridge near the intersection of South Illinois Avenue and the Oak Ridge Turnpike) for the years in which both air monitors were in operation (1986 to 1991). The uranium air concentrations at Station 46 were, on average, 2.7 times higher than those at Station 41.

In addition, the past uranium radiation doses used in the public health assessment are from the Task 6 report, which was a screening evaluation that routinely and appropriately used several layers of conservatism and protective assumptions and approaches in estimating concentrations and doses (see the list of conservative aspects of the screening evaluation on pages 48 and 92 of the PHA). The Task 6 report states that "some level of conservatism was maintained in the uranium concentration estimates used in Level II screening to ensure that hazards to a significant portion of the potentially exposed population were not underestimated" (ChemRisk 1999).

Also, the internationally recognized expert technical reviewers hired by ATSDR to review the Task 6 report pointed out that "the estimates made in the report tend to be on the conservative side–one expects, therefore, that (when in error) the report would tend to overestimate the extent to which exposure to uranium is a problem in the Oak Ridge area. Further refinements to the study are likely to reveal that uranium exposures are actually lower than those currently estimated" (see page G-7 of the PHA).

ATSDR's Health Guidelines for Radiation Effects

17

The statement on p. D-1 that "the risk associated with a dose that approaches background, 0.36 rem/year...is essentially impossible to measure" is untrue as analytic epidemiology techniques have advanced substantially such as those being used to study U.S. nuclear workers and other occupationally-exposed cohorts.

The comment is noted. The risk is not being measured but is being calculated using a derived risk coefficient with the "quantitative" result having the appearance of precision and an associated true value. Further, the statement cannot be wrong, as the case of zero additional exposure is included.

18

The 5000 mrem cancer screening value is simply a fallacious recommendation for public health screening. This value is in direct conflict with ICRP, IAEA and EPA standards. These plus the disagreement between the ORHASP's criteria of 10^-4 health risk of cancer and ATSDR's cancer comparison value are in stark contrast. How did ATSDR selectively decide to use Task 6 results but not use the same endeavor's screening criteria?

ATSDR's radiogenic cancer comparison value of 5000 mrem over 70 years is in line with many of the recommendations of the organizations cited by the commenter. The following comparisons were made in ATSDR's response to comments 158 through 162.

• The first approximation of ATSDR's radiogenic cancer comparison value of 5,000 mrem over 70 years is less than 100 mrem/year (5,000 mrem ÷ 70 years = 71 mrem/year).



• The first approximation of the 100 mrem/year dose limit recommended by the International Commission on Radiological Protection (ICRP) and the National Council on Radiation Protection and Measurements (NCRP) roughly equates to a 7,000 mrem dose over 70 years (100 mrem/year × 70 years). This lifetime dose is higher than ATSDR's radiogenic cancer comparison value of 5,000 mrem over 70 years. The exposure doses calculated for Scarboro residents (155 mrem over 70 years for past exposures and <1 mrem over 70 years for current exposures) are more than 45 times lower than ICRP's and NCRP's guidance. Figure 12 of the PHA graphically displays NCRP's guidance and NRC's regulations for public exposure (100 mrem/year) in relation to the doses estimated for Scarboro.



• The first approximation of EPA's cleanup level into a lifetime dose is roughly 1,050 mrem over 70 years (15 mrem/year ×70 years). The exposure doses calculated for Scarboro residents (155 mrem over 70 years for past exposures and <1 mrem over 70 years for current exposures) are more than 6 times lower than EPA's guidance.

ATSDR uses the public health assessment process to evaluate the potential for public health effects by comparing an estimate of the amount of uranium exposure (i.e., dose) that people might frequently encounter to conservative screening values and health effects levels documented in the scientific literature. To evaluate past uranium exposure to residents living near the Y-12 plant, ATSDR compared the Task 6 screening results (estimated doses, not the screening indices) to ATSDR's health based comparison values. ATSDR used only the basic release data of the Task 6 report and applies its own exposure pathways, dose calculations, and accepted screening levels during our evaluation. See the response to comment 127 for additional information distinguishing an EPA baseline risk assessment from an ATSDR public health assessment.

The Task 6 screening indices are a risk-based screening, as evidenced by the total detriment value of 0.073 in the task calculations. Current ATSDR policy does not allow for the use of risk coefficients in determining the impact on public health. As stated in the ATSDR Cancer Framework Policy, ATSDR recognizes the need for calculating risk during the assessment process. However, the agency acknowledge that, at present, no single, generally applicable procedure for exposure assessment exists, and, therefore, exposures to carcinogens must be assessed on a case-by-case or context-specific basis. While the need for, and reliance on, models and default assumptions is acknowledged, ATSDR strongly encourages the use of applicable empirical data (including ranges) in exposure assessment. For additional information, please review the framework policy that can be found at http://www.atsdr.cdc.gov/cancer.html.

However, if the Task 6 Level II screening indices and ORHASP decision criteria were used, the Level II screening index (8.3 x 10^-5) is 1.2 times less than the ORHASP decision guide (1 x 10^-4) and–therefore–below the threshold for consideration of more extensive health effects studies. Based on the ORHASP decision guides, the estimated Level II screening risk from off-site exposure to Y-12 uranium is so low that further detailed study of exposures is not warranted. (See the Level II screening index on page 4-12 of the Task 6 report and the ORHASP Decision Guides on page 57 of the ORHASP report.)

19

For at least four reasons, ATSDR is flat-out wrong in alleging that its recommendation of a "radiogenic cancer comparison value" for public health assessment screening - of 5,000 mrem effective dose - is protective of public health. One reason is that there is evidence of genetic and chromosomal damage at levels of ionizing radiation lower than this level. Second, this 5,000 mrem level relies only on epidemiological data and ignores all the molecular-level evidence of increase risk from radiation below this level. Third, the ATSDR assumes that background radiation is harmless, and this fact is false, as evidenced by the fact that the UNSCEAR calculates that 40,000 annual cancers arise in the U.S., just from background radiation. Fourth, the 5,000 mrem level contradicts the explicit norms of the ICRP, the IAEA, and UNSCEAR, all of which accept the linear, no-threshold thesis, and all of which require that radiation does be kept ALARA (as low as reasonably achievable).

In its report "Y-12 Uranium Releases: Public Comment Release," ATSDR in Appendix D states that epidemiological evidence from studies on cohorts exposed to chronic low doses of radiation have been inconclusive.

We agree that there are studies showing damage at doses lower than these. However, we are applying our screening value as a long-term screen. Many of the studies you may be referring to involve acute or short-term exposures. There is much disagreement in the scientific community as to the methods used to adjust long-term exposures to short-term exposures. With respect to the recent molecular studies, ATSDR is aware of those studies, many of which are cell culture studies and microbeam studies that indicate the bystander interactions, as well as direct and indirect actions. It is important to realize that many cellular processes mediate these molecular events. Background radiation studies are interesting, as it is not possible to measure the effect on human populations in the absence of background. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) value, as you state, is a calculated number based on the current risk estimates. With respect to the ALARA concept, this is not applicable to a screening evaluation. The ALARA concept is used to minimize the dose potentially received. As pointed out it the PHA, the maximum doses we calculated for current exposure were less than 5 mrem, well within the ALARA concept and well below the standards and recommendations you cite.

ATSDR derived the radiogenic comparison value of 5,000 mrem over 70 years after reviewing the peer-reviewed literature and other documents developed to review the health effects of ionizing radiation. ATSDR publicly discussed this issue in at least four PHAWG meetings and three ORRHES meetings.

The Ionizing Radiation Toxicological Profile states: "the annual dose of 3.6 mSv per year has not been associated with adverse health effects or increases in the incidences of any type of cancers in humans or other animals" (ATSDR 1999b).

20

I would like to inform you that there are numerous examples of significant epidemiological findings where radiation doses have been received from chronic or fractionated exposures. Much of this is documented in NCRP Report No. 136 (2001) and the International Agency for Research on Cancer (IARC) Monographs on the Evaluation of Carcinogenic Risks to Humans (Vols. 75 and 78, of 2000 and 2001).

ATSDR agrees that there are numerous epidemiologic findings, however, many of these reports do not show uniform statistical significance in the dose range ATSDR is using for the assessment. Also, the NCRP report states that results vary, based on the end point being evaluated (please see page 210 in NCRP 136 as an example of their issues).

21

Additional information related to epidemiological findings due to occupational exposure was summarized by NIOSH at the recent May 19-20, 2003, meeting in Oak Ridge of the NIOSH Advisory Board on Radiation and Worker Health. An attachment containing these epidemiological summaries is included, which I hope you will find to be of interest.

Thank you for the additional information.

22

I believe that, upon reviewing these documents, you will find that there is substantial scientific evidence in support of the presence of radiogenic cancer risks at organ doses below an effective dose of 5,000 mrem. This ATSDR "cancer comparison value" of 5,000 mrem is too high to be used for screening for public health concerns regarding exposure to radioactive contamination released from historic operations within the Oak Ridge Reservation. The cancer comparison value selected by ATSDR lacks a sufficient margin of safety with respect to organ doses that are associated with epidemiologically significant findings, to serve as a public health screening limit that discriminates against false negative conclusions. The cancer comparison value essentially ignores substantial evidence supporting the extrapolation of radiogenic cancer risk below limits of epidemiological detection.

ATSDR agrees that there are cases where cancer may be evidenced at doses less than 5,000 mrem, usually delivered during a working lifetime at industrial sites. The radiogenic cancer comparison value, as has been discussed many times, is a dose over a 70-year period (an average of 71 mrem/year). Using the analogy of a 30-year work span, this is a dose of less than 2,500 mrem.

When appropriate, ATSDR did calculate an organ-specific dose. Please see Table 15 and Table 19 for estimated doses to the lung and bone. In the case of organ doses, the cancer induction resulting from radiological exposures is not as rigorous as the radiological induction of soft tissue cancers such as leukemia. In that case, ATSDR agrees that the 5,000 mrem comparison value would not be an appropriate screening value.

23

The final statement on D-5 that 5 rem over 70 years is protective of human health at Oak Ridge is not substantially supported by the information presented in the appendix. This lifetime exposure may not even be at a level corresponding to de minimus risk if NCRP organ-specific factors are used.

The comment is noted.

24

The statement that excess cancer risks have not been observed at exposures of 5-10 rems is being challenged by the latest scientific evidence. The most recent analysis of solid cancers among atomic bomb survivors suggests that cancer risk is significantly elevated in doses of 5 rem (50 mSv), and is most consistent with a linear or supra-linear dose-response relationship (Pierce DA, Preston DL Radiation-related cancer risks at low doses among atomic bomb survivors. Radiat. Res. 154:178-186, 2000). Of particular note is that the "epidemiologically-detectable" risk from radiation exposure has decreased with each passing decade since follow up of the atomic bomb survivor cohort began. (Appendix D)

The cancer risks from the atomic bomb survivors show a 2% increase in cancer deaths in those who received essentially an instantaneous dose of 500 to 20,000 mrem. But there is still the issue of how one converts an instantaneous dose to a dose delivered over 70 years. ATSDR's annualized dose of approximately 71 mrem/year is much less than the atomic bomb survivor lowest reported dose of 500 mrem. For more information, please see the Web site of the bomb survivor studies: http://www.rerf.or.jp/top/healthe.htm

25

The statement on p. D-1 that effects have not been observed below 5 rem but "assumed to occur" is not accurate. Effects have been observed in many studies but statistical significance has not always been achieved.

The comment is noted. In many epidemiological studies, if the statistical significance is not present then consideration must be given that there is no cause and effect relationship.

26

Statement that "No studies exist for exposures or doses below this [0.01 Sv] limit" is inaccurate. Nearly all occupational studies include populations with cumulative exposure estimates less than 1 rem. (Appendix D)

The comment is noted. The text was changed in the final PHA

27

The report relies heavily on 1994 and 2001 GAO reports which are not scientifically rigorous. More appropriate sources for radiation exposures would be reports available from the ICRP, UNSCEAR, NCRP and BEIR committees, some of which are mentioned later in the appendix. (Appendix D)

The GAO report was cited not as a scientific source, but as a reference to show that the scientific community has not reached a consensus on the effects of low level exposures and low dose levels.

28

Discussions of the literature surrounding the quest to detect risk from excess background exposure are selective. Most of these studies are ecologic, not analytic, and suffer from bias as a result. Properly conducted analytic epidemiology studies of household radon exposure (e.g., Field RW et al. Residential radon gas exposure and lung cancer- the Iowa Radon Lung Cancer Study. Am. J. Epidemiol. 151:1091-1102, 2000) have detected excess risk at low exposure levels.

ATSDR has sent the radon study out for further review to determine its applicability for uses in PHAs.

29

The summary of nuclear worker studies is very incomplete, and highly selective. For leukemia risk, suggest looking at Occupational Medicine: State of the Art review article published by Schubauer-Berigan and Wenzl. The British worker study reviewed is outdated. More recent studies of U.S. and Canadian nuclear workers are omitted entirely.

ATSDR has sent this study out for further review to determine its applicability for uses in PHAs. One issue that is evident in this review is that the dose response is expressed as excess relative risk (ERR) per 10 mSv (1,000 millirem) and the ERR varies considerably among the studies reported.

30

Reference to "initial wave of leukemia" should be changed to "some of the early deaths from leukemia."

The text has been changed in the final PHA, as recommended.

31

Last paragraph on D-3 states that ATSDR could not identify any studies with risks from background radiation yet residential radon studies have found effects, as stated above.

The text has been clarified in the final PHA.

32

On p. D-3, the fact that the assessment of leukemia risk was delayed by 5 years after exposure among atomic bomb survivors is evidence that risk may have been underestimated in this cohort. There is also ample evidence of the leukemia from alpha exposures as seen among workers at the Mayak facility and elsewhere.

Thank you for the information. The comment is noted. It is interesting, however, that several of these reports indicate that risks may be overstated. Please see the International Journal of Radiation Biology, January 2003, 79(1):1-13, and Radiation Research, June 2003, 159(6):787-98, for additional information.

33

It is also stated that SMR's less than one for all cancers or for specific cancers are evidence for no effect, which is true. However, SMR analysis is not the best and most sensitive measure of effect. Hence the finding by Cardis, et al that found an association between radiation exposure level and risk of leukemia mortality. (Appendix D)

ATSDR agrees that the standardized mortality Ratio (SMR) may not be the best measure of an effect because the SMR is an indirect method of comparison to evaluate causes of death within a given area against a common standard.

34

The purpose for estimating the average dose for the "English study" is not given. (Appendix D)

The text has been clarified in the final PHA.

35

The Task 6 Report and ATSDR incorrectly refer to estimated radiation doses for Scarboro as committed effective dose equivalents or CEDEs. The quantities dose equivalent, committed dose equivalent, and committed effective dose equivalent are based on the dosimetry system, radiation quality factors, and tissue weighting factors formerly recommended by the International Commission on Radiological Protection in Publication 26 (ICRP 1977) and Publication 30 (ICRP 1979, et seq.). For Level I and Level II assessments, the Task 6 team used the adult dose coefficients or dose conversion factors (DCFs) for U 234, U 235, and U 238 taken from Publication 71 (ICRP 1995) for inhalation exposures, from Publication 72 (ICRP 1996) for ingestion exposures, and from Federal Guidance Report No. 12 (EPA 1995) for external exposures (see pp. 4-8 and 4-9 of the Task 6 Report (ChemRisk 1999)). Inhalation and ingestion DCFs are based on ICRP's latest dosimetry system, defined in Publication 60 (1991), for calculating age-dependent doses to members of the public from intakes of radionuclides. This system incorporates revised biokinetic and dosimetric models, radiation weighting factors, and tissue weighting factors. ICRP's current dosimetric quantities are the equivalent dose, committed equivalent dose, and committed effective dose. Calculations using inhalation and ingestion DCFs from ICRP 26/30 vs. ICRP 71/72 results in different radiation dose estimates for internal exposures. Strictly speaking, the radiation doses calculated by the Task 6 team, and used by ATSDR, represent the summation of the committed effective doses from internal exposures and the effective doses from external exposures. The resultant total dose may, perhaps, be best referred to as the total effective dose.

The term total effective dose (TEDE) is defined in 10 CFR 20 as the sum of the deep-dose equivalent (for external exposures) and the committed effective dose equivalents (CEDE) (for internal exposures). The ATSDR calculations only included the dose to the internal tissues so the committed dose equivalent is the appropriate term for the current pathway evaluations. While the Task 6 team reported both internal and external exposures and doses for the past evaluation (for which the TEDEs would have been appropriate), ATSDR only calculated the dose resulting from internalization of the uranium isotopes. Thus, CEDEs are appropriate for the ATSDR current dose assessment.

Miscellaneous Radiation Comments

36

The first line on D-3 mentions "types of radiation" when the term has not been defined. Is the reference to photons, neutrons, alpha-emitters and similar types?

The text has been clarified in the final PHA.

37

The first paragraph indicates that the 70-year dose is assumed to be received all in the first year (committed effective dose equivalent). Yet the comparison value is assumed to apply over 70 years. Most public health standards and guidelines place the annual limit at 1 mSv with an intrinsic expectation that such exposures would be extremely rare, i.e. on the order once in a lifetime. (Appendix D)

The comment is noted. The CEDE makes the stipulation that the entire dose, although distributed over time, is assumed to be delivered in the first year. In the case of regulatory limits, these are expressed as annual limits, mostly for external exposures.

38

It is invalid to divide the total dose delivered over 70 years by 70 in order to determine the annual dose delivered. As evidenced by figures 11, 14 & 16, the uranium releases varied greatly from year to year. The dose delivered in each year should be calculated and compared to the MRL of 100 mrem/yr. (p. 5, lines 12 - 17)

ATSDR agrees that the commenter is technically correct. This issue was discussed at several PHAWG meetings and at the ORRHES meetings where the screening process was discussed. The reason for dividing the total dose by 70 years was to establish a first approximation of the dose, as this would allow for comparison to ATSDR's minimal risk level (MRL) (100 mrem/year).

The first approximation values of 2.2 mrem/year for past exposures and 0.003 mrem/year for current exposures are 45 and 33,000 times less than the MRL. Because these approximated values are so much lower than the MRL during the screening-level evaluation, no further actions were necessary. Had the approximation shown an annual dose close to the MRL, ATSDR would have re-assessed the evaluation and conducted a full dose reconstruction.

39

It appears that total dose from Y-12 in 70 years are being added to annual background. This needs to be explained.

The text was clarified in the final PHA.

40

Footnote 5 on p. 49 of the PHA report shows that the CEDE is a total dose, not a dose rate. On pp. 47 & 50 of the PHA, the value of the average annual background dose rate in the U.S. is given as 360 mrem/yr. The figure of 300 mrem/yr. for Scarboro, appearing in Fig. 9, appears to be either a misprint or a value from a different source. In any event, a CEDE for 70 years cannot simply be added to a one-year background dose rate, because it isn't. It's an upper bound to the maximum one-year dose. Assuming that the CEDE is all absorbed in one year, for purposes of conservatively estimating its effects, its an additional issue that apparently needs explaining here. To be correct, the upper right-hand label in Fig. 9 should be modified to read something like, "Typical, and Maximum Possible One-Year, Doses from Ionizing Radiation Sources". The labels for the past and current theoretical peak annual doses received in Scarboro need to be re-worded accordingly. The first numerical value given in these labels should be the value actually being plotted. (pp. 47 & 49-50)

ATSDR revised Figure 12 in the final PHA.

41

Is it true that background radiation is harmless? Is the scientific community in agreement on this matter? And if it isn't which criteria did ATSDR use to arrive at the conclusion that background radiation is harmless which includes exposure to indoor radon? None of these questions have been answered.

The scientific community is not in agreement on the effects of exposure to background radiation. There are locations on the planet where the background radiation is much higher than at Oak Ridge and these populations do not overtly exhibit any adverse health problems. The statements in the PHA are based on the ATSDR Toxicological Profile on Ionizing Radiation (ATSDR 1999b), which has been extensively reviewed. See the response to comment 156 for a discussion of ATSDR's MRL.

42

The conversion from mSv to mrem on p. D-4 is off by a factor of ten.

Thank you. The text has been corrected in the final PHA.

43

Reference to medical accidents in the 2nd paragraph on p. D-3 should be changed to medical treatments.

In some cases, there were miscalculations on the administration of medical radionuclides or radiotherapy. Nonetheless, ATSDR added medical treatments to the list in the final PHA.

Specific Activities and Isotopic Ratios

44

On pages 69 and 75 and perhaps others ATSDR fouled up the Specific Activities of uranium isotopes. You should correct this error.

ATSDR disagrees. The specific activities listed are for pure uranium, taking into account their abundances in nature. Specific activities are defined as the curies per gram for the pure isotopes.

45

The uranium isotopic ratios of the Scarboro samples were obtained by methods less precise than the preferred mass spectrometer method. This has imposed a rather large, unavoidable scatter in the data greatly reducing the significance of the isotopic ratios to a point that no conclusion can be drawn that the isotopic ratios of the Scarboro uranium samples is other than normal.

ATSDR agrees. Mass spectroscopy for uranium (more specifically, inductively coupled plasma-mass spectroscopy) is more sensitive than alpha spectroscopy, with the added benefit that it can detect other forms of uranium not possible with alpha spectroscopy. However, the process is more expensive than alpha spectroscopy and may not have been readily available to the laboratories analyzing the samples from Scarboro.

FAMU determined uranium isotopic content using alpha spectroscopy (FAMU 1998). EPA Region IV verified their results using gamma spectroscopy (EPA 2003). The EPA Region IV report on page vi states that "EPA's study results are in agreement with similar, more extensive, studies done in 1998 by FAMU." They further explain on pages 7 and 9 that "gamma spectroscopy was used as a screen. It was chosen to analyze gamma-emitting isotopes which indicate radioactive decay... The analysis of the information reveals that all results for gamma emitters were within their predicted background ranges for the United States and Oak Ridge-wide. None of the analytical values were elevated above background. Uranium is both naturally occurring and site related... none of the EPA values were above the PRG or background" (EPA 2003).

From page 19 of EPA Region IV's report: EPA "does not propose to conduct any further environmental sampling in the Scarboro community" and from page 26 "based on EPA's results, the Scarboro community is safe. Therefore, additional sampling to determine current exposure is not warranted" (EPA 2003).

46

P85 Table 17 It is not clear how this table was constructed or what it means. Certainly 0.047 (.972) is not the isotopic ratio of U235/238 (U234/U238) in nature. I believe you mean the ratio of isotopic activities.

The text has been corrected in the final PHA.

47

P{86, l8: These are not the concentrations of uranium isotopes found in nature but are the isotopic percentages of natural uranium.

ATSDR agrees. The text has been clarified in the final PHA.

48

P88, Table 18: I believe the table is isotopic composition. While this table does indicate a slight U235 enrichment for Scarboro, it also indicates a slight depletion for U234 which is not consistent with the U235 trend. Both are explained by the imprecision of the measurements.

ATSDR agrees. The issue of precision is addressed by the uncertainty of the measurements; that is, the detection limits could have been lower resulting in a more precise measurement.

49

P84, l9: States that "enrichment is typically stated by percent by weight of U 235 in the uranium samples...". This is ambiguous and enrichment is in fact stated as the weight percent of U 235 based on total uranium, i.e., the weight of U235 divided by the weight of Total Uranium converted to percent. Often this is called the isotopic composition.

The text has been clarified in the final PHA.

Enriched Uranium

50

While this section reaches the correct conclusion about U235 enrichment in Scarboro soils, it does not properly discuss the errors in the EPA and FAMU data; lay to rest alleged enrichment in the EPA and FAMU data and the spatial trends in the FAMU data. This section should emphasize the nature of the data errors as well as their impact on the significance of the marginal increases in U235 enrichment and total uranium levels. (p83-88)

The text has been modified in the final PHA.

51

P86, L23-24 appears to be contradictory to P88, L20.

The text has been clarified in the final PHA.

52

P87 Figures 21,22: Units of "Percent U per gram" is not clear and may be wrong; Need units on bottom sub-tables.; Error bars do not seem to reflect the large 2sigma values of EPA Tables 2A-J.

Modifications were made to clarify the Figures 24 and 25 in the final PHA. The use of the logarithmic scale masks the magnitude of the error.