Peer Reviewer Comment
ATSDR's Response
Does the public health assessment adequately describe the nature and extent of contamination?
1
It does quite a good job at this. The radionuclides were the appropriate ones to examine, as were the environmental media in which they were determined. The authors have chosen the appropriate locations to characterize the contamination, given the use of the region by the surrounding population.
Thank you for your comment.
2
Yes, it appears that the study carefully considers the local and disseminated levels of contamination of both radionuclide and chemical contaminants. The study further addresses local concerns raised by the residents of the area even when it is doubtful that there is any validity to the concern raised.
Thank you for your comment.
3
To the careful reader it is clear that ATSDR does not generate any contamination level information by direct measurement but rather relies on the information published by others for the ATSDR analysis. This feature of the report should be directly stated in the introductory aspect of the report as the conclusions reached in the report are based on the accuracy of this information.
ATSDR does explain the sources of information used to evaluate past, current, and future exposures in Section I. Summary and Section III. Evaluation of Environmental Contamination and Potential Exposure Pathways of the public health assessment.
For past exposures, we state that ATSDR primarily relied on data generated during Task 4 of the TDOH's Reports of the Oak Ridge Dose Reconstruction: Radionuclide Releases to the Clinch River from White Oak Creek on the Oak Ridge Reservation—an Assessment of Historical Quantities Released, Off-Site Radiation Doses, and Health Risks (referred to as the "Task 4 report"). For current exposures to the Clinch River and Lower Watts Bar Reservoir, the summary section details how ATSDR uses data collected from 1988 to 1994 as presented in ATSDR's 1996 Lower Watts Bar Reservoir Health Consultation. It has been added to the summary section of the PHA that these data include environmental sampling data from the 1980s and 1990s collected and assembled by the U.S. Department of Energy (DOE), the Tennessee Valley Authority (TVA), and various consultants, as well as data from TVA's 1993 and 1994 annual radiological environmental reports for the Watts Bar Nuclear Plant. In addition, the PHA states that ATSDR used data collected from 1989 to the present (2003) in the Oak Ridge Environmental Information System (OREIS). The PHA explains that OREIS falls under DOE ownership, and that OREIS contains data related to compliance, to environmental restoration, and to surveillance activities (including but not limited to studies of the Clinch River embayment and the Lower Watts Bar, as well as annual site summary reports).
For future exposures, the PHA states that ATSDR based its evaluation on current exposures and doses related to releases from White Oak Creek, data on current contaminant levels in the Clinch River and Lower Watts Bar Reservoir, institutional controls in place to monitor contaminants in these water bodies, and consideration of the possibility that remedial activities could release radionuclides to White Oak Creek. Further, the data show that because of remedial actions and preventive measures at X-10, because of physical movement of sediments from the area, and because of radiological decay, the radionuclide releases from White Oak Creek have decreased over time, and the concentrations of radionuclides in the water and along the shoreline have decreased as well.
4
Yes! Most emphatically! So many different agencies and very interested and competent individuals have been involved in this process that it would be difficult if not impossible to not perform a complete assessment of the nature and extent of contamination.
Thank you for your comment.
Does the public health assessment adequately describe the existence of potential pathways of human exposure?
5
Yes, these are the appropriate pathways given the nature of the contamination and the environmental media affected. However, I am not fully comfortable with the way in which selected exposure pathways were dropped from the analysis. The approach taken by the authors (in which the relative contribution from each exposure pathway is determined by a screening assessment, and the pathway is retained only if it is in some upper percentile of the contributions by all pathways) is often taken in risk assessment, and so is valid from that perspective. But the description in the text did not convince me that the SUM of the doses from the rejected pathways was significantly smaller than the SUM of the doses from the retained pathways. I suspect their assumption is valid, and the authors have the results to show that this is the case, and so they should make that point more forcefully. Otherwise, there can be a stream of public complaints that pathways X, Y and Z aren't reflected in the summary dose tables at the end.
Page 76 is where the issue of dropping radionuclides, and then dropping pathways, becomes important. I am not suggesting any specific changes here, but the process used seems to me to run the danger of leaving most of the risk within the pool of dropped radionuclides and pathways. If you subdivide the total exposure enough, you eventually find that no one cell is contributing much. If I were a new reader, I might worry that the contribution of the dropped radionuclides and pathways may in the end be greater than that of the retained pathways.
Similar to the comments made on an expansion of the summation of the organ dose hazards previously mentioned, the hazards for 16 radioisotopes are each individually discussed and found to be below the CV for the isotope and thus not subject to further study (page 75). A brief treatment of the fact that the sum of the effects of the 16 are also below any CV would be appropriate.
The authors of the Task 4 of the Tennessee Department of Health's Reports of the Oak Ridge Dose Reconstruction (Task 4 report) used a screening assessment to identify the most important radionuclides and pathways associated with past exposures to X-10 radionuclides released off site to the Clinch River via White Oak Creek. Because the Task 4 team evaluated each radionuclide individually by pathway for its screening analysis, the team compared conservative screening estimates to a minimal screening level of 1 x 10-5—a factor of ten below the Oak Ridge Heath Agreement Steering Panel's (ORHASP) decision guide value of 1 x 10-4.
Because the screening risk estimates for the swimming and irrigation pathways were below the Task 4 report's minimal risk level for all 24 radionuclides, the Task 4 team was able to eliminate these two exposure pathways (and therefore, consumption of locally grown crops) from further analysis. It is important to note that no swimming is allowed in White Oak Creek and no irrigation water comes from the creek, which is located on site at the reservation where public access is restricted. The Task 4 team determined that swimming in the past primarily occurred in creeks emptying into the Clinch River—not in the river itself—and the screening analysis did not identify this as a significant pathway. Also, the Task 4 team found that irrigation was not a relevant exposure pathway for additional analysis because the only documented incidence of river water use was to irrigate a small acreage of peaches. The irrigation scenario produced a screening value below 1 x 10-5. Therefore, any potential exposure occurring via these pathways was determined to be so low that it would not yield doses or risks capable of producing adverse health effects.
According to page 3-8 of the Task 4 report, "A value of 10-5 was used because each radionuclide was compared to the decision guide independently for each exposure pathway. Using the more conservative decision guide for the screening analysis results in high confidence that the radionuclides assigned low priority for a pathway do not in fact contribute significantly to the overall dose or risk for that pathway." Further, the Task 4 team stated: "If the maximally exposed target individual has a low screening index for a contaminant (i.e., the screening estimate of risk for that contaminant is below the decision guide), then the true but unknown risk to members of the general population is expected to be even lower." In other words, as presented on page 3-1 of the Task 4 report, "Detailed study for contaminants whose presence is clearly below a minimum level of concern is not warranted, as further investigation is expected to show that the risk to any actual individual would have been much less than that calculated during the conservative screening analysis (Thiessen et al. 1996)."
In addition, ORHASP—a panel of experts and local citizens—provided technical guidance and community oversight of the Task 4 report. The state of Tennessee also had the Task 4 report externally peer-reviewed prior to its release, and ATSDR had the report evaluated by independent technical reviewers. ATSDR's reviewers agreed that the overall design and the scientific approach of the Task 4 report were appropriate, the results generally quite valid and consistent with earlier studies, and the findings applicable to public health decision-making. Furthermore, ATSDR reviewed the radionuclides and exposure pathways excluded in the Task 4 report and concurred that further evaluation was not necessary. Thus, ATSDR agrees with the findings of the Task 4 report and believes that even if these excluded pathways and radionuclides were summed with those that were retained, the estimated doses and risks would be minimal and still below levels expected to cause adverse health effects.
6
Yes, the potential pathways are carefully addressed and such minor ones as the geese feeding in the river habitat, migrating to another area, and subsequently being shot by a hunter and eaten are shown to be of negligible consequence.
Thank you for your comment.
7
The treatment of the variation of the pathways importance with time such as the pumping of the corehole #8 plume and the benefit of radioactive decay is not directly treated. A resident of the area who is a casual reader might draw some solace from a conservative discussion of these ameliorating factors even though they are in the predicted doses for future exposures.
In this public health assessment, ATSDR evaluated radioactive contaminant data for White Oak Creek releases that enter the Clinch River and travel downstream to the Lower Watts Bar Reservoir. To be clear, this public health assessment only evaluated X-10 radionuclides in White Oak Creek after the surface water was released off site. We recognize that oftentimes contaminants released into surface water may originate from contaminated groundwater, including on-site seeps and other sources of groundwater contamination such as the corehole 8 plume. These potential exposures to off-site groundwater associated with the Oak Ridge Reservation were, however, addressed in another public health assessment entitled Evaluation of Potential Exposures to Contaminated Off-site Groundwater From the Oak Ridge Reservation (USDOE). This groundwater PHA addresses issues including plumes, contaminants flowing from groundwater, underlying aquifers, and other topics as well. Copies of this and other ATSDR documents are available from the ATSDR Information Center. You may call the center toll-free at 1-888-422-8737 or view the document online at http://www.atsdr.cdc.gov/HAC/PHA/region_4.html#groundwater.
In Section III. Evaluation of Environmental Contamination and Potential Exposure Pathways of the PHA, ATSDR states that because of remedial actions and preventive measures at X-10, physical movement of sediments from the area, and radiological decay, the radionuclide releases from White Oak Creek have decreased over time and the concentrations of radionuclides in the water and along the shoreline have decreased as well. Similar text has also been added to the I. Summary and IV. Public Health Implications sections of the document, and the term radioactive decay has been added to the glossary in Appendix A of the final PHA.
8
The non-disturbance of the sediment is a critical factor in the calculations of future exposures to both chemical and radioactive materials. This is recognized by the agencies involved and stated in the report but it might be emphasized more strongly. It appears to be the most significant factor in the assumptions made on future exposures to the carcinogens.
ATSDR agrees that the nondisturbance of sediment is a critical factor in considering potential future exposures to radionuclides in the Lower Watts Bar Reservoir and the Clinch River. For this reason, nondisturbance of sediment is discussed throughout the document in Sections II.C. Remedial and Regulatory History, II.F. Summary of Public Health Activities Pertaining to White Oak Creek Radionuclide Releases, III.B.3. Current and Future Exposure, and VIII. Conclusions. These sections provide information on the institutional controls in place to prevent disruption of sediment, ATSDR's evaluation of DOE's remedial measures to keep contaminated deep channel sediment in place, and ATSDR's current and future evaluation of potential exposures to sediment in the Lower Watts Bar Reservoir and the Clinch River. Also, please refer to the brief in Appendix D of the final PHA on ATSDR's Lower Watts Bar Reservoir Health Consultation, which evaluated DOE's remedial decisions for the reservoir including leaving contaminated deep channel sediment in place. In the health consultation, ATSDR concluded: "Current levels of chemical and radioactive contaminants in the reservoir sediment do not and will not pose a public health problem. For the sake of caution and to prevent unnecessary exposure to workers and the public, sediment should not be disturbed without thorough review of sediment sampling data in the specific area where sediment-disturbing activities will take place."
9
From the radiological viewpoint or my area of competence, it does a very good job of describing the existence of potential pathways of human exposure. I would call this one of the strong points of the report. I believe that it has also done a good job on chemicals but I am not competent to judge that.
Thank you for your comment.
Are all relevant environmental and toxicological data (i.e., hazard identification, exposure assessment) being appropriately used?
10
Very few data make an appearance in the document. Most results appear to be from modeling. This is in part surprising for the exposure assessment, as there is a strong dataset for at least some of the geographic locations considered. There is an attempt to at least display some of the data in Figure 21, but no mention is made of the degree of fit between data and models, and whether this supports confidence in the models.
I do think the authors could have done a better job of showing how well model results on contamination agree with available monitoring data, as there are quite a few datasets available.
For evaluating past exposures to X-10 radionuclides released off site to the Clinch River via White Oak Creek, ATSDR primarily relied on data generated during Task 4 of the TDOH's Reports of the Oak Ridge Dose Reconstruction: Radionuclide Releases to the Clinch River from White Oak Creek on the Oak Ridge Reservation—an Assessment of Historical Quantities Released, Off-Site Radiation Doses, and Health Risks (referred to as the "Task 4 report"). Because historical records were not maintained to today's standards, the Task 4 team performed independent reviews of environmental monitoring reports and existing data on releases and also used mathematical models to estimate the radiation doses and the associated risks.
According to the Task 4 report, accurate environmental monitoring and sampling data were not available to evaluate thoroughly past exposures for X-10 radionuclides released to the Clinch River. Therefore, the Task 4 team performed an in-depth evaluation to estimate the amount of radionuclides that flowed from X-10, over White Oak Dam, and into the Clinch River. Through this evaluation the team derived annual estimates for the eight radionuclides of interest: Co 60, Sr 90, Nb 95, Ru 106, Zr 95, I 131, Cs 137, and Ce 144. Using this information, the team then performed mathematical modeling to estimate the annual average concentrations of the eight radionuclides in water and sediment at specified locations downstream of White Oak Creek.
According to the Task 4 report and one of its authors, when available, the Task 4 team used actual measurements in Clinch River water collected at CRM 14.5 (K-25/Grassy Creek) and 4.5 (Kingston Steam Plant) from 1960–1990 to calculate doses for Cs 137, Sr 90, Ru 106, and Co 60. The Task 4 team used modeling to estimate the historical radionuclide concentrations in Clinch River water for the remaining radionuclides and for time periods when data were unavailable. Limited available monitoring data were used to calibrate the results of the team's modeling efforts.
Limited information on the Task 4 team's efforts to estimate annual average
radionuclide concentrations in Clinch River water and shoreline sediments with the
HEC-6-R model is presented in Section 6 of the Task 4 report (available at
http://www2.state.tn.us/health/CEDS/OakRidge/WOak1.pdf 
). The HEC-6-R model,
developed by the Hydrologic Engineering Center at the U.S. Army Corps of
Engineers, can be used for: a) water surface and energy profile simulation, b) sediment scour and deposition modeling, c) sediment transport modeling, and d)
river geometry simulation. For more information on the model, a fact sheet is
available at http://www.epa.gov/ORD/NRMRL/pubs/600r05149/600r05149hec6.pdf and the model program files are available for free downloading at
http://www.hec.usace.army.mil/software/legacysoftware/hec6/hec6-documentation.htm .
Similar concerns were also mentioned by ATSDR's technical peer reviewers regarding the Task 4 report. One reviewer stated, "The report does not present any statistically sound comparisons for the measured and modeled concentrations." Another reviewer stated, "The report does not provide sufficient details to allow calculations and model estimates to be duplicated and verified. In my opinion, this is the primary weakness of the report."
In response, one of the authors of the Task 4 report stated, "We agree, more documentation of the models and coefficients used for sediment and water transport are needed and presently missing from the Task 4 report. This section of the Task 4 report could be improved. The detailed documentation of the HEC-6-R sediment and water transport code resides with ChemRisk." The Task 4 report states that the modeled and measured values were comparable in many cases, but that the concentrations based on measurements generally reflected a higher degree of confidence (lower uncertainty) than the modeled concentrations.
ATSDR understands and recognizes that insufficient details are provided on the modeling efforts used in the Task 4 report. Nonetheless, a panel of technical experts convened to evaluate the study design, the scientific approaches, the methodologies, and the conclusions of the Task 4 report commented that the results were generally quite valid, consistent with earlier studies, and applicable to public health decision-making as long as careful attention was given to the assumptions behind the estimates. The reviewers agreed that the overall design and scientific approach were appropriate. Therefore, ATSDR believes that the findings of the Task 4 report are appropriate for evaluating past exposures to X-10 radionuclide releases to the Clinch River via White Oak Creek and for making public health decisions regarding these past exposures.
11
On page 95, bone samples appear to be included as part of the Sr90 concentrations in catfish. Why is this done? Sr90 accumulates in bone, but do people really eat the bones? This does not seem to have been assumed for other fish.
According to DOE officials and the Task 4 of the Tennessee Department of Health's Reports of the Oak Ridge Dose Reconstruction (Task 4 report), research and anecdotal information suggest that people living in the Oak Ridge area have consumed fish patties comprised of ground fish, consisting of fish bones and fish flesh.
When preparing the health consultation in 1995, limited data describing radionuclide concentrations in fish from the Lower Watts Bar Reservoir were available for ATSDR's review. The available data came from three sites along or downstream of the reservoir: Mid Watts Bar Reservoir (Tennessee River Mile 557.0), the Lower Watts Bar Reservoir north of the Watts Bar Dam (Tennessee River Mile 530.5), and the Upper Chickamaugua Reservoir (Tennessee River Mile 518.0 and below Watts Bar Dam). A combined total of 42 fish specimens were collected, coming from three different species—channel catfish, bluegill sunfish, and largemouth bass. All of the fish fillet samples were analyzed for cesium 137 and cobalt 60.
Channel catfish samples were also sampled and analyzed for strontium 90. Because strontium is a bone-seeking radionuclide, higher concentrations of strontium 90 appear in whole fish rather than in fish flesh alone (see Section 8 of the Task 4 report). Thus, ATSDR evaluated consumption of channel catfish with bones since these strontium 90 data were available. ATSDR used a worst-case scenario using the maximum concentration and assuming that adults and children consumed two 8-ounce fish meals a week and that the meal could include some bone. ATSDR concluded that the level of potential radiological exposure from these radioactive contaminants in reservoir fish posed no public health hazard.
12
On page 105, it is mentioned that some geese had high measured concentrations, but then it seems these higher concentrations were not used in calculations because the authors believe it is unlikely a hunter would catch one of them. This may be the opinion of Blaylock (2004), but I don't see why this opinion is valid. How "likely" is "unlikely"?
ATSDR included information from this source (Blaylock 2004) in the text of the PHA only to provide background information on goose consumption for the reader. These comments neither affected nor influenced how ATSDR selected the radionuclide concentrations for estimating exposure doses via goose consumption. To evaluate the current exposures and doses for goose ingestion, ATSDR used data from the Oak Ridge Environmental Information System (OREIS), detailed in Section II.F.4 of the final PHA. The data received and analyzed for geese covered the time period from 1989 to the present (2003). To estimate the radiation doses from ingestion of geese, ATSDR used the average radionuclide concentrations from OREIS to obtain realistic doses to the bone surface, lower large intestine, and whole body (the estimated radiation doses are presented in Table 20 of the final PHA). The highest committed effective dose to the whole body from goose consumption was 14 mrem to a 10-year-old child based on a 60-year exposure—over 355 times less than ATSDR's radiogenic cancer comparison value of 5,000 mrem over 70 years.
13
The reader is dependent on the author to present all of the existing toxicological environmental data for the area. It appears that this is the case as data from both state, federal regulatory, and laboratory sources are quoted and used in the report.
The authors are to be complimented on presenting the information in a clear format that is both readable by the non-scientific resident of the area and the radiation protection community. The methods of radiological hazard estimation used in the report appear to follow the "best practice" calculational techniques in existence at this time.
Thank you for your comments.
14
The relative weighting of the radiological vs. chemical hazards has not been made and this is probably prudent as the risk levels associated with each are open to much interpretation.
This public health assessment evaluates off-site exposure to radionuclide releases from X-10 via the Clinch River and Lower Watts Bar Reservoir. Because no chemical exposures are evaluated in this public health assessment, weighing radiological versus chemical hazards is not applicable. The radioactive materials released from White Oak Creek are chemical in nature, and in most cases, heavy metals. The potential health effects resulting from their intake are driven by their radiological properties, however, not their chemical properties. Hypothetically, if an individual had an intake sufficient to result in heavy metal toxicity, the radiation levels would be sufficient to result in adverse health effects. Adverse effects from radiation could occur following exposure to levels well below those required to result in heavy metal poisoning; natural uranium, however, is the only radioactive material where this does not apply. Therefore, as a conservative (protective) measure, ATSDR sets its minimal risk level (MRL) values for radioactive elements (other than uranium) on their radiological properties, not on their chemical properties.
15
As I understand the situation, I believe that all relevant environmental and toxicological data have been appropriately used.
Thank you for your comment.
Does the public health assessment accurately and clearly communicate the health threat posed by the site?
16
Yes, it does a very good job of this, conditional on the analysis in the report. There is a good summary of the doses received, and a comparison of these against dose limits selected by the authors. Further, the dose limits selected are appropriate.
Thank you for your comments.
17
I do disagree with the claim by the authors throughout that staying below such limits precludes adverse health effects. They seem to be assuming a threshold model as is typical in non-cancer effects. Such a model has not been recommended by the ICRP or the NCRP, and so is inappropriate here. The wording needs to be changed to refer to a risk that is below unacceptable levels. This will pose a bit of a challenge because the dose limit proposed is on the order of 5,000 mrem over a lifetime. Using the ICRP risk coefficient, which is now close to 5 E-4 per rem, 5,000 mrem (or 5 rem) would produce a lifetime excess probability of cancer of 2.5 E-3. This is well above what is normally considered an acceptable lifetime risk for chemicals. It is inherent in the dose limits, and I don't expect ATSDR to change the regulations, but it does point to a potential public health controversy, and the authors might need to find some wording to convey this.
ATSDR uses the public health assessment process to evaluate the public health implications of exposure to environmental contamination and to identify the appropriate public health actions for particular communities. ATSDR health physicists conduct a health effects evaluation by carefully examining site-specific exposure conditions about actual or likely exposures; conducting a critical review of available radiological, medical, and epidemiologic information to ascertain the substance-specific toxicity characteristics (levels of significant human exposure); and comparing an estimate of radiological dose people might frequently encounter at a site to situations associated with disease and injury. This health effects evaluation involves a balanced review and integration of site-related environmental data, site-specific exposure factors, and toxicological, radiological, epidemiologic, medical, and health outcome data to help determine whether exposure to contaminant levels might result in harmful effects. The goal of the health effects evaluation is to decide whether harmful effects might be possible in the exposed population by weighing the scientific evidence and by keeping site-specific doses in perspective. The output is a qualitative description of whether doses are of sufficient nature and magnitude to trigger a public health action to limit, eliminate, or study further any potential harmful exposures. The PHA report presents conclusions about the actual existence and level of the health threat (if any) posed by a site. It also recommends ways to stop or reduce exposures. For detailed information on risk, please see Appendix F in the final PHA. This appendix, which is not normally included in ATSDR's public health assessments, was added to this PHA because of public requests for risk information. It is important to note that ATSDR does not base its public health conclusions on these risk numbers; they are included in this PHA to provide detailed information on risk for the community.
Risk assessments conducted by the U.S. Environmental Protection Agency (EPA) are useful in determining safe regulatory limits and prioritizing sites for cleanup. These risk assessments provide estimates of theoretical risk from possible current or future exposures and consider all contaminated media regardless of whether exposures are occurring or are likely to occur. These quantitative risk estimates are not intended, however, to predict the incidence of disease or measure the actual health effects in people resulting from hazardous substances at a site. By design, these risk estimates are conservative predictions that generally overestimate risk. Risk assessments do not provide a perspective on what the risk estimates mean in the context of the site community and do not measure the actual health effects that hazardous substances have on people.
There are subtle differences in ATSDR's process of evaluating chemicals and radiation such as dose to individual organs, age-specific dose coefficients, and other metabolic differences as discussed in several publications from the International Commission on Radiological Protection (ICRP). It is of interest to note that the National Council on Radiation Protection and Measurements (NCRP) in 1989 released a report titled: Comparative Carcinogenicity of Ionizing Radiation and Chemicals, NCRP Report 96. In its conclusion, the NCRP stated that fewer than 30 chemicals were known to be cancer-inducing in humans and of those, in most it was not possible to define a dose-incidence relationship except generally. Also, there is much uncertainty in chemical metabolism, in the possibility of additive or synergistic effects between or among chemicals, in the potency of chemicals, and in the dosimetry of chemicals than there is in radiation evaluations. The NCRP stated that risk assessment for chemicals is "generally more uncertain than risk assessments for radiation." Because of these statements by the NCRP, ATSDR does not, in the true sense of the comment, evaluate radiation in the similar manner as the agency evaluates chemicals.
ATSDR recognizes that every radiation dose, action, or activity may have an associated risk. In this public health assessment, ATSDR compares annual doses to the 100 mrem/year dose limit of the ICRP, NCRP, and U.S. Nuclear Regulatory Commission (NRC), as well as ATSDR's MRL. ATSDR compares lifetime doses to the agency's radiogenic cancer comparison value of 5,000 mrem over 70 years, which is based on peer-reviewed literature and other documents developed to review the health effects of ionizing radiation. These values, used as screening tools during the public health assessment process, are levels below which adverse health effects are not expected to occur. If the screening indicates that past or current doses exceed our comparison values, then we would conduct further in-depth health evaluation.
When ATSDR developed its screening values for radiation exposures, safety margins were incorporated. The approach ATSDR uses to derive MRLs, such as those in the Toxicological Profile for Ionizing Radiation, was developed with the EPA. MRLs for radiation are estimates of daily human exposure to an amount of radiation that is likely to be without appreciable risk of adverse noncancer health effects. MRLs are screening tools used by public health professionals to determine which exposure situations require further evaluation. The chronic MRL for ionizing radiation is 100 mrem/year, which is consistent with the dose limits recommended for the public by the ICRP, NCRP, and NRC.
The ATSDR MRL for ionizing radiation is based on numerous evaluations of health effects from exposures to background and occupational levels of radiation. The Ionizing Radiation Toxicological Profile states: "The annual dose of 3.6 mSv [360 mrem] 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). The MRL was derived by reducing the 360 mrem/year by a factor of three to account for human variability (and conservatively rounded down from 120 mrem/year to 100 mrem/year) to be protective of human health. Although the MRL is for noncancerous health effects, when deriving the MRL, no studies were identified that did not result in cancer as the specific end point. Furthermore, the ATSDR legislative authority, as discussed many times, limits ATSDR to evaluating exposures based on observable and tolerable adverse health effects. If adverse health effects are not observed in an epidemiological study, then the doses used in the study should be considered tolerable.
Contrary to this reviewer's comment, ATSDR's radiogenic comparison value of 5,000 millirem over 70 years incorporates the linear no-threshold (LNT) model for evaluating public health hazards associated with exposure to radiation. It assumes a total lifetime dose (70 years of exposure) above background that is considered safe in terms of cancer induction. In addition to the LNT model, ATSDR also incorporates a margin-of-dose (MOD) approach into this comparison value. During an evaluation, if ATSDR determines that further investigation is needed, we review scientific literature associated with radiological doses and dose estimates particularly related to adverse health effects. ATSDR then compares the dose estimates from scientific literature to site-specific dose estimates. Thus, ATSDR uses the LNT model to determine when a more detailed site-specific evaluation is necessary and uses the MOD approach to develop realistic information for communities regarding what is known and unknown about radiation levels at a particular site.
An independent expert panel convened to review ATSDR's site-specific approaches used to evaluate past, current, and future radiation risks to communities surrounding the Oak Ridge Reservation concluded that this combination of approaches (LNT and MOD) is appropriate for ATSDR to use to determine radiation levels at which health effects actually occur. The panel found that ATSDR's use of the MRL of 100 millirem per year and radiogenic cancer comparison value of 5,000 millirem over 70 years were appropriate screening values. If extrapolated over 70 years assuming constant exposure, the radiogenic cancer comparison value dose estimate would be about 71 millirem per year—a level the panel determined to be very protective of public health in terms of cancer and noncancer risks. The panel also concluded that ATSDR's approach considers evidence for both individual organs and whole-body doses (effective doses), noting that a whole-body dose could not be developed without accounting for doses to single organs. Further, the panel determined that ATSDR's method of distinguishing dose levels from risk levels was acceptable; when calculating doses, ATSDR incorporated risk and LNT explicitly and implicitly.
Given our evaluation in this public health assessment, ATSDR concludes that exposures to X-10 radionuclides released from White Oak Creek to the Clinch River and to the Lower Watts Bar Reservoir are not a health hazard. Past and current exposures are below levels associated with adverse health effects and regulatory limits. Adults or children who have used, or might continue to use, the waterways for recreation, food, or drinking water are not expected to have adverse health impacts due to exposure. ATSDR has categorized these exposure situations as posing no apparent public health hazard. ATSDR uses this category in situations in which human exposure to contaminated media might be occurring, might have occurred in the past, or might occur in the future, but where the exposure is not expected to cause any harmful health effects. Therefore, we are conveying to the public that radiation exposure is possible, but that this exposure is not expected to result in observable and tolerable health effects.
18
The report is well written and well referenced so the reader can go to the source document for any studies concerning the measurement of the levels of contamination reported.
Thank you for your comment.
19
With the exception of the committed effective whole body doses, the hazard level of each isotope/toxic compound is calculated separately and compared to the ATSDR CV. The casual reader might appreciate some expansion of the CEDE discussion which emphasizes that it is indeed the summation of the individual dose hazards which are listed below it in the tables.
Thank you for your comment. On page 67 of the final PHA the committed effective dose is defined as ICRP's term for the sum of the products of 1) the weighting factors applicable to each body organ or tissue that is irradiated and 2) the committed equivalent dose to the appropriate organ or tissue integrated over time (in years) following the intake, with the assumption that the entire dose is delivered in the first year following the intake. The integrated time for an adult is 50 years; for children, it is from the time of intake to 70 years. The committed effective dose is used in radiation safety because it implicitly includes the relative carcinogenic sensitivity of the various tissues.
20
Yes. This has been described in detail by comparison with known hazards and the doses causing these known hazards.
Thank you for your comment.
Are the conclusions and recommendations appropriate in view of the site's condition as described in the public health assessment?
21
The authors have done a nice job of summarizing and justifying their conclusion.
Thank you for your comment.
22
Based on the information presented, the conclusions and recommendations appear to be fully warranted.
Thank you for your comment.
23
The continued need for public information/education could be stressed more.
Throughout our involvement in public health activities associated with the Oak Ridge
Reservation, ATSDR has promoted and been involved in outreach efforts to educate
the community on various topics. In its 1996 health consultation of the Lower Watts
Bar Reservoir, ATSDR recommended working with the state of Tennessee to
implement a community health education program on the Lower Watts Bar fish
advisory and on the health effects of PCB exposure. As a follow-up to the
recommendations in the Lower Watts Bar Reservoir Health Consultation, ATSDR
created a program to educate the community and physicians on PCBs in the Watts
Bar Reservoir. On September 11, 1996, Daniel Hryhorczuk, MD, MPH, ABMT, from
the Great Lakes Center at the University of Illinois at Chicago, presented information
on the health risks related to the consumption of PCBs in fish. Dr. Hryhorczuk made
his presentation to about 40 area residents at the community health education
meeting in Spring City, Tennessee. In addition, on September 12, 1996, an
educational meeting for health care providers in the Watts Bar Reservoir area was
held at the Methodist Medical Center in Oak Ridge, Tennessee. Furthermore, ATSDR
collaborated with local residents, associations, and state officials to create a brochure
informing the public about the Tennessee Department of Environment and
Conservation's (TDEC) fish consumption advisories for the Watts Bar Reservoir. The
Tennessee Wildlife Resources Agency (TWRA) also has an information and
education department (see http://www.state.tn.us/twra/infoed.html ) that distributes
information to the public.
In addition, ATSDR has held many educational workshops and presentations in the community on topics such as iodine and radiation. ATSDR has also created numerous fact sheets for the community to convey the findings of our public health assessments and other studies. Further, particular to this public health assessment on White Oak Creek Radionuclide Releases, ATSDR is presenting the document and its findings to the public and to health officials, creating a video to communicate the findings of this public health assessment to the public, and distributing fact sheets to communicate the PHA's conclusions. In addition, ATSDR has a Web site solely dedicated to public health activities associated with the Oak Ridge Reservation (available at http://www.atsdr.cdc.gov/HAC/oakridge/).
24
Information such as the results of the quarterly water testing should be publicized and historical results shown so the general population can see the trends in the measurements.
TDEC–DOE Oversight Division publishes its environmental monitoring results in an
annual report to the public, including the results of radiological water monitoring. For
example, the Annual Report to the Public for 2004 provides findings of radiological
water testing dating from 1996 to 2004. These reports are available on line at
http://www.state.tn.us/environment/doeo/active.shtml and this link has been
added to the public health assessment where appropriate. Copies of the report are
also available from the TDEC–DOE Oversight office at 865-481-0995 and the Local
Oversight Committee (LOC) office at 865-483-1333. In addition, copies of the reports
are available for review at the DOE Reading Room (PD-01816), Information
Resource Center, and public libraries located in Kingston, Oak Ridge, Clinton,
Knoxville, Meigs County, Loudon County, Dayton, and Wartburg, Tennessee.
25
This reviewer was not impressed with the PCB warning being placed on the Tennessee fishing license material. It appears to be an ineffective way to get the message across. Bolder and more pointed methods should be used to get this message across.
ATSDR developed a brochure on the Tennessee Department of Environment and Conservation (TDEC) fish consumption advisories for the Watts Bar Reservoir. The brochure was the result of the collaborative effort of local citizens, organizations, and state officials. See Appendix D for a brief of the exposure investigation and Section II.F.1. for ATSDR's public health activities related to White Oak Creek radionuclide releases.
TDEC's Division of Water Control is responsible for issuing and posting fish
advisories. Evaluating fish tissue problems in the state of Tennessee involves a multi-agency effort, comprised of DOE, EPA, TDEC, the Tennessee Wildlife Resources
Agency (TWRA), and the Tennessee Valley Authority (TVA). The state fish advisories
are available at http://www.state.tn.us/twra/fish/contaminants.html and the current
fishing regulations are available at http://www.state.tn.us/twra/fish/fishmain.html .
Though PCBs are not within the scope of this public health assessment that focuses
solely on radionuclide releases to the Clinch River and Lower Watts Bar Reservoir,
ATSDR is preparing a public health assessment that will evaluate PCB releases from
the three main ORR facilities: X-10, Y-12, and K-25. When available, copies of
ATSDR's public health assessment on PCBs can be obtained by contacting ATSDR's
Information Center toll-free at 1-888-422-8737.
26
Yes. I believe they have arrived at a well thought out position supported by a lot of measurements and considerable epidemiological data.
Thank you for your comment.
Are there any other comments about the public health assessment that you would like to make?
27
Nowhere in the document does the assessment consider a subsistence fisher, which the EPA often considers. I am not suggesting one, but it may be a point of contention. I assume the upper bound consumption rate considered is to be an approximation to this susceptible subpopulation.
To evaluate past, current, and future exposures to radionuclides in Clinch River and
Lower Watts Bar Reservoir fish, higher than average fish consumers were evaluated
(detailed below). In its Exposure Factors Handbook (available at
http://www.epa.gov/ncea/pdfs/efh/front.pdf ) that outlines factors commonly used in
exposure assessments, EPA recommends for fish consumption using an assumed
average intake rate for the general population of 20.1 grams/day (140.7 grams/week)
of total fish. Of this fish intake rate, however, only 6.0 grams/day (42 grams/week) is
considered as an average intake rate for the general population consuming
freshwater and estuarine fish. All of the exposure assumptions used by ATSDR for
past, current, and future exposures to radionuclides in Clinch River and Lower Watts
Bar Reservoir fish were at least five times more than this average intake for the
general population eating freshwater and estuarine fish. As detailed below, even
when evaluating fish consumption by using assumed intake rates significantly above
these recommended assumptions, ATSDR's estimated doses for past, current, and
future exposures were below health-based comparison values.
In the Task 4 of the Tennessee Department of Health's Reports of the Oak Ridge Dose Reconstruction (Task 4 report), past exposures to radionuclides in Clinch River fish were evaluated for high fish consumers. Reportedly, a maximum fish consumer in the east south central region of the country would eat about 2.4 fish meals per week (based on a 200 gram per meal fish portion) (Rupp et al. 1980. Age dependent values of dietary intake for assessing human exposures to environmental pollutants. Health Physics 39:151-163. Cited in the Task 4 report). The Task 4 report evaluated high fish consumers, who were referred to as "Category I fish consumers" and were described as individuals who frequently ate fish (between 1 and 2.5 fish meals per week).
ATSDR summarized the Task 4 organ doses for the bone, lower large intestine, red bone marrow, breast, and skin locations using the 50th percentile value of the 95% confidence interval. The 50th percentile (central) values represent the medians of organ doses. The highest radiation doses were associated with eating fish taken from the Clinch River near Jones Island between 1944 and 1991. Doses were much lower for all other pathways (see Table 11 and Table 12 in the final PHA). The Task 4 report's estimated organ doses to the bone, lower large intestine, red bone marrow, breast, and skin from eating fish were at least six times greater than the radiation doses to these organs from ingesting meat and milk, drinking water, and via external radiation (see Table 12 in the final PHA). Likewise, ATSDR's derived annual whole-body and committed equivalent doses from eating fish were at least 10 times more than any of the other exposure pathways (see Table 11 in the final PHA). As mentioned and shown in Table 11, radiation doses from eating fish were highest near Jones Island—these annual whole-body and lifetime (70-year) doses were more than eight times greater than for people consuming fish from the Clinch River farther downstream near Kingston. The annual whole-body dose was 3.4 mrem/year for an individual ingesting fish near Jones Island—more than 29 times less than the 100 mrem/year recommended dose limit for the public by the NCRP, ICRP, and NRC. The whole-body lifetime dose for an individual ingesting fish caught near Jones Island was 238.6 mrem over 70 years, which is more than 20 times less than ATSDR's radiogenic cancer comparison value of 5,000 mrem over 70 years.
To evaluate current and future exposures to radionuclides in Lower Watts Bar Reservoir fish, this public health assessment used data from ATSDR's Lower Watts Bar Reservoir Health Consultation. The health consultation used worst-case scenarios to evaluate radiological exposure to fish, assuming adults and children consumed two 8-ounce fish meals per week (454 grams/week). Even using these conservative assumptions, the estimated dose was 6 mrem per year or less than 420 mrem over 70 years for the committed effective dose. The annual whole-body dose of 6 mrem per year is more than 16 times less than the dose of 100 mrem/year recommended for the public by the NCRP, ICRP, and NRC. The committed effective dose of 420 mrem over 70 years is more than 11 times less than ATSDR's radiogenic cancer comparison value of 5,000 mrem over 70 years.
To evaluate current and future exposures to radionuclides in Clinch River fish, ATSDR assumed a child ate 4 ounces of fish per week (113.4 grams/week) and an adult ate 8 ounces of fish per week (227 grams/week). The highest estimated whole-body dose of 89.3 mrem was calculated for an adult based on a 50-year intake to age 70—less than 55 times below ATSDR's radiogenic cancer comparison value of 5,000 mrem over 70 years.
28
Around page 45, there is information provided on populations. However, this information is never used, or even relevant, given the later focus on exposure scenarios and individual risk. It is not clear why the information is provided.
The White Oak Creek study area evaluated in this public health assessment consists of the area along the Clinch River from the Melton Hill Dam to the Watts Bar Dam. All ATSDR public health assessments regularly include demographic information. Such information helps to identify and define the size, characteristics, locations (distance and direction), and possible susceptibility of known populations related to the site and study area. Demographic data provide information on potentially exposed populations and can provide important information for determining site-specific exposure pathways. The information presented in this section is for the largest communities located within the study area (Harriman, Kingston, Rockwood, and Spring City) that could potentially be exposed to radiological contamination in the Clinch River and Lower Watts Bar Reservoir. For more information on ATSDR's public health assessments, please see our Public Health Assessment Guidance Manual online at http://www.atsdr.cdc.gov/HAC/PHAManual/toc.html.
29
On page 64, line 22, the statement is made that the doses are higher than the levels to which people are really exposed. I think you should say "the levels to which the majority of people are exposed." The point of using an upper-bound, conservative, procedure is that it captures a plausible upper bound, not that it creates a fictitious dose. If the latter is implied, that will cause controversy.
Thank you for your comment. The change was incorporated into the final public health assessment.
30
On page 66, the description of weighting factors is poor. It needs to be re-written. I am not convinced the authors understand this concept, given the description they provide.
Thank you for your comment. On page 68 of the final PHA, ATSDR not only defines weighting factors but presents a user-friendly table detailing the currently adopted weighting factors by tissue. The term weighting factors (WT) is defined as modifying factors selected for the type of radiation and its energy as it impacts matter to convert organ or tissue dose equivalents to committed effective dose equivalents for the whole body. They are used because the same radiation exposure to different parts of the body can have very different results. That is, if the entire body were irradiated, some parts of the body would react more dramatically than other parts. To take this effect into account, the ICRP developed weighting factors for a number of organs and tissues that most significantly contribute to the overall biological damage to the body. The tissue weighting factors are based on both cancer fatality risk and the relative effect of an exposure to a single organ or tissue. The grouping of tissues is complex, and substantial rounding of the values takes place. When summed for the entire body, the values of WT are normalized to give a total of one.
31
The figure on page 74 caused me to wonder whether exposures to aerosolized radionuclides hitting a skier might be important. I doubt they are, but the figure does raise the issue.
Thank you for your comment. This possible exposure was implicitly evaluated in the intake of Lower Watts Bar Reservoir and Clinch River surface water by recreational users.
32
Page 81 seems to raise an issue of variability and uncertainty analysis, but I cannot follow how these analyses were done. Distributions are mentioned, and said to be related to "individual sets of measured data," but no detail is provided on this. The EPA has a good Exposure Factors Handbook, and perhaps this is what the authors mean by data? But I could not determine the distributions used. And I am uncomfortable in assessing whether the authors have properly disentangled uncertainty and intersubject variability. This becomes particularly troubling to me on page 82, lines 8-10, where the authors speak of the 50th percentile of the 95% confidence interval. That is strange wording. Is this 95% interval variability or uncertainty. And a confidence interval does not have a 50th percentile, the underlying distribution from which the confidence interval is constructed has this 50th percentile. The authors need to better describe how variability and uncertainty are being reflected, and how these relate to specific confidence intervals mentioned.
The uncertainty analysis was performed by the Tennessee Department of Health's (TDOH) contractors, not by ATSDR. For ATSDR's analysis, we used the EPA's Exposure Factors Handbook to select values reflective of lifestyle patterns for people living in the area of study—the southeastern United States.
The wording "50th percentile of the 95% confidence interval" has been clarified in the text and represented as the "50th percentile of the uncertainty distribution" as reported in the Task 4 report.
33
I see no description of the pharmacokinetic and dosimetric models used. Are they the ICRP ones? Are they buried inside ChemRisk? EPA has created RadRisk for radionuclides. Why was that system not used?
Please see Section 11. Internal Dosimetry of the Task 4 of the TDOH's Reports of the Oak Ridge Dose Reconstruction: Radionuclide Releases to the Clinch River from White Oak Creek on the Oak Ridge Reservation—an Assessment of Historical Quantities Released, Off-Site Radiation Doses, and Health Risks (referred to as the "Task 4 report"). As noted in this section, to calculate doses to people ingesting contaminated drinking water or food, the Task 4 team used the internal dosimetry methodology of the International Commission on Radiological Protection (ICRP) that is based on the ICRP models for bioaccumulation and transfer of radionuclides in the body. This methodology was used to estimate ingestion dose factors and their uncertainty for adults ingesting cesium 137, strontium 90, cobalt 60, and ruthenium 106; for iodine 131, estimates were made for a child up to age 15. Please refer to Section 11 in the Task 4 report for specific details on the internal dosimetry methodology used by the Task 4 team.
34
On page 87 and elsewhere, ingestion doses for water are mentioned. Is treatment of the water assumed? Many water treatment systems will remove radionuclides such as Cs and Sr to some extent.
For past exposures, the Task 4 team evaluated the ingestion of filtered, treated Clinch River water as drinking water. For current exposures to Lower Watts Bar Reservoir surface water, ATSDR evaluated potential exposures to unfiltered surface water via recreational activities and exposure to treated water via municipal waters from household taps. For current exposures to Clinch River surface water, ATSDR evaluated potential exposures to unfiltered surface water via recreational activities. This information has been clarified in the text in the final public health assessment.
35
On page 88, there must be some mention of the exposure duration assumed for external exposures on the shore.
Table 10 in the final public health assessment provides the years of exposure considered for each exposure scenario. As shown in the table, the time period varied by location for external exposures to shoreline sediment. For Jones Island, the years of exposure evaluated were 1963 to 1991. The years of exposure evaluated for external exposures to shoreline sediment at K-25/Grassy Creek, the Kingston Steam Plant, and the City of Kingston were 1944 to 1991. The years of exposure, along with a reference to Table 10, have been added to this section of the final public health assessment.
36
On page 88, the authors mention (on line 27) an uncertainty analysis. But I can find no details on that, and whether it was a nested variability-uncertainty analysis (which would be appropriate and state-of-the-art).
This refers to a comment made by a technical peer reviewer who was part of a panel
of experts ATSDR convened to evaluate the Task 4 report. More details on this
uncertainty analysis are not provided in the public health assessment itself, but
additional information can be found by accessing the Task 4 report online at
http://www2.state.tn.us/health/CEDS/OakRidge/WOak1.pdf .
37
On page 94, tritium is called a "very weak emitter" of radiation. This is not a relevant characterization, since the betas it emits have sufficient range and energy to strike and break DNA bonds. In fact, the RBE of tritium is above 1.
Thank you for your comment. The text was removed from the referenced sentence, which now reads as the following: "The likelihood of adverse health effects from H 3 is extremely low; the concentrations were well below the EPA's current maximum contaminant level (MCL) of 20,000 pCi/L of H 3, an amount that would produce a radiation dose of 4 mrem/year if ingested at 2 liters of water per day for a year."
38
Some ingestion rates are used throughout, but no mention is made of the percentile of the intersubject variability distribution represented by these assumed rates of ingestion. Are these upper percentiles (to be protective)?
To evaluate past, current, and future exposures to radionuclides in Clinch River and
Lower Watts Bar Reservoir fish, higher than average fish consumers were evaluated
(detailed below). In its Exposure Factors Handbook (available at
http://www.epa.gov/ncea/pdfs/efh/front.pdf ) that outlines factors commonly used in
exposure assessments, EPA recommends for fish consumption using an assumed
average intake rate for the general population of 20.1 grams/day (140.7 grams/week)
of total fish. Of this fish intake rate, however, only 6.0 grams/day (42 grams/week) is
considered as an average intake rate for the general population consuming
freshwater and estuarine fish. All of the exposure assumptions used by ATSDR for
past, current, and future exposures to radionuclides in Clinch River and Lower Watts
Bar Reservoir fish were at least five times more than this average intake for the
general population eating freshwater and estuarine fish. As detailed below, even
when evaluating fish consumption by using assumed intake rates significantly above
these recommended assumptions, ATSDR's estimated doses for past, present, and
future exposures were below health-based comparison values.
In the Task 4 of the Tennessee Department of Health's Reports of the Oak Ridge Dose Reconstruction (Task 4 report), past exposures to radionuclides in Clinch River fish were evaluated for high fish consumers. Reportedly, a maximum fish consumer in the east south central region of the country would eat about 2.4 fish meals per week (based on a 200 gram per meal fish portion) (Rupp et al. 1980. Age dependent values of dietary intake for assessing human exposures to environmental pollutants. Health Physics 39:151-163. Cited in the Task 4 report). The Task 4 report evaluated high fish consumers, who were referred to as "Category I fish consumers" and were described as individuals who frequently ate fish (between 1 and 2.5 fish meals per week). See Table 7.3 in the Task 4 report for more information on the parameters used for fish ingestion rates. Also, the Task 4 report used different ingestion rates to evaluate the water and milk/meat ingestion pathways. See Table 7.2 and Table 7.4 in the Task 4 report for the rates used to evaluate the water and milk/meat ingestion pathways, respectively. ATSDR summarized the Task 4 organ doses for the bone, lower large intestine, red bone marrow, breast, and skin locations using the 50th percentile value of the uncertainty distribution. The 50th percentile (central) values represent the medians of organ doses.
To evaluate current and future exposures to radionuclides in Lower Watts Bar Reservoir fish, this public health assessment used data from ATSDR's Lower Watts Bar Reservoir Health Consultation. The health consultation used worst-case scenarios to evaluate radiological exposure to fish, assuming adults and children consumed two 8-ounce fish meals per week (454 grams/week). To evaluate exposures via water ingestion at the Lower Watts Bar Reservoir, ATSDR used data from the health consultation that conservatively assumed a worst-case scenario using the maximum concentrations for each radionuclide. ATSDR evaluated exposure to children aged about 10-years-old and assumed they drank and showered with unfiltered reservoir water and swam in the reservoir daily.
To evaluate current and future exposures to radionuclides in Clinch River fish, ATSDR assumed a child ate 4 ounces of fish per week (113.4 grams/week) and an adult ate 8 ounces of fish per week (227 grams/week). For evaluating potential exposures for the Clinch River via water ingestion, ATSDR used exposure values from the EPA's Federal Guidance Report 13. These values assumed that a swimmer might incidentally ingest surface water at a rate of 0.1 liters per hour while swimming. ATSDR used a swimming frequency of 1 hour per day for 150 days per year as noted in the EPA's Exposure Factors Handbook. These values are conservative, and therefore typically overestimate true exposure. Also, to evaluate potential exposures related to current and future goose and turtle consumption, ATSDR used consumption values based on the findings of ATSDR's Watts Bar Exposure Investigation of 500 grams of goose liver per year (about 1 pound) and 10 kilograms (about 22 pounds) of goose muscle per year. For turtle consumption, ATSDR estimated doses based on ingesting 100 grams (about 3.5 ounces) of turtle each year.
ATSDR conservatively assumed hunters might consume as much as 10 kilograms (about 22 pounds) of goose muscle per year. This amount averages to about one 6 to 8 ounce serving per week or 27 grams/day. Based on fish consumers surveyed during the exposure investigation, the high, average, and low consumption groups consumed about 108, 66.5, and 1.9 grams of fish per day, respectively. Assuming that similar consumption ratios apply to goose consumption, ATSDR calculated that the amount and ratios for a 70-kilogram adult goose consumer would be 27, 17, and 0.5 grams/day, respectively, for high, average, and low consumption groups. If, as assumed for the fish, 10-kilogram children eat one-third the portion sizes that adults eat, their consumption levels would be in the ratios of 9, 5.6, and 0.16 grams/day of goose muscle for high, moderate, and low consumers, respectively. From the exposure investigation, ATSDR learned that average consumers eat about 100 grams of turtle meat a year (0.27 grams/day). High consumers eat turtle meals twice as often as moderate consumers (0.55 g/day), and low consumers eat one-sixth the amount that moderate consumers do (0.05 g/day).
39
On page 107, Table 21, it seems odd to me that the bone and skin ratios for Clinch River (external) divided by background are around 10, and then the ratio for whole body is 60. Bone is representative of the deep dose and skin of the shallow dose, so usually these bracket the ratio for the whole body. But in this case, the whole body ratio is a factor of 6 higher than for either the shallow or deep doses. It may be correct, but it does seem odd to me. The authors should check this.
The variation of ratios is a result of the time weighted averages, the time spent on the shoreline and in the water, and the ingestion and uptake coefficients—each calculated for a specific radionuclide.
40
As a non-regulatory agency, ATSDR keeps a low profile in the public press. Those that are impacted by the Superfund clean up efforts learn of the agency, but the typical citizen has no idea ATSDR exists. Strongly recommend that the introduction be enhanced to give a brief overview to what ATSDR is and how it relates to DHS, CDC, NIOSH, and other similar agencies. I mentioned the CDC and NIOSH only because both make the popular press on a frequent basis and are known to the public.
Additional text describing ATSDR's relationship to the U.S. Department of Health and Human Services (HHS), the Centers for Disease Control and Prevention (CDC), and the National Center for Environmental Health (NCEH) has been added to Section I. Summary on page 1 of the final PHA. Also, Internet links for ATSDR (http://www.atsdr.cdc.gov/) and CDC (http://www.cdc.gov/) have been added as resources for more information about these and affiliated agencies.
41
Reference page 71: One time scope is the period 1988 to present but given the time to publish such a report, present might be defined. Then the past exposure period is 1944 to 1991. The reader gets the impression that the doses for the 3-year period overlap are being double counted. If this overlap is accounted for in any manner, this reader missed it.
The time periods for ATSDR's evaluation of past exposures (1944–1991) and current and future exposures (1988–present and future for Lower Watts Bar Reservoir; 1989–present and future for Clinch River) overlap slightly due to some studies being conducted simultaneously. The doses obtained from these studies are, however, based on different data. Therefore, the estimated past doses do not overlap with the estimated doses for current and future even though the time periods overlap. Text has been added to the final PHA to explain the overlapping time periods. Further, ATSDR's evaluation of future exposures includes exposures occurring after the present time period (2003) evaluated in the PHA.
42
It would be prudent to add statistical uncertainty information to the tabulated dose/hazard data. One result is within a factor of 3 of a CV. What range is this expected to be within: 2.5 or 3.5? Such information would be beneficial to the non-scientific reader.
Because of uncertainties regarding exposure conditions and adverse effects related to environmental levels of exposure, definitive answers on whether health effects actually will or will not occur are not possible. That said, it is possible for a public health assessment to provide a framework that puts site-specific exposures and the potential for harm in perspective. ATSDR recognizes that uncertainties exist with its dose-based assessments, but using health protective safety factors addresses these uncertainties.
ATSDR evaluated the need for an uncertainty analysis as outlined in NCRP Commentary 14 entitled A Guide for Uncertainty Analysis in Dose and Risk Assessments Related to Environmental Contamination. In essence, the use of conservative and biased screening calculations indicated the possible resulting dose would be clearly below a regulatory limit. "Conservative screening calculations are designed to provide a risk estimate that is highly unlikely to underestimate the true dose or risk. Therefore, a more detailed analysis will likely demonstrate that the true risk is even less."
The document states that screening can be considered among the first steps in conducting an uncertainty analysis as this roughly defines the upper and lower bounds of a distribution of exposed populations or individuals. To use these screening calculations successfully, a decision point has to be determined to establish the boundary at which no further analyses are necessary. According to NCRP Commentary 14, "For example, for dose reconstruction, the National Academy of Sciences has suggested that an individual lifetime dose of 0.07 Sv be used as a decision criterion for establishing the need for more detailed investigation (NAS/NRC 1995)." A value of 0.07 Sv is equivalent to 7 rem or 7,000 mrem—a value that is 40% higher than ATSDR's radiogenic cancer comparison value of 5,000 mrem over 70 years. Thus, ATSDR's screening value is more conservative than the criteria suggested by the National Academy of Sciences as reported by the NCRP. Furthermore, the calculations of other comparison values used by ATSDR in this public health assessment incorporate health-protective safety factors to account for uncertainty, such as human variability and sensitivity of populations.
43
Page 114, line 11: I would replace the word "derived" with "arrived at" or similar wording as the NRC limit was accepted rather than derived.
For clarification, the line being referenced by the peer reviewer does not refer to a U.S. Nuclear Regulatory Commission (NRC) limit. Instead, this line refers to ATSDR's radiogenic comparison value of 5,000 millirem over 70 years that was derived after a review of peer-reviewed literature and other documents developed to review the health effects of ionizing radiation.
44
Page 123: Of the 2,500 community health concerns logged, what is the basis for the listing of the sample on pages 124–140?
As detailed in the introductory text of Section VI. Community Health Concerns, the community health concerns addressed in this public health assessment are those concerns in ATSDR's Community Health Concerns Database related to issues associated with radionuclide releases from White Oak Creek. These include X-10 facility processes and exposure pathway concerns, concerns about radionuclides associated with X-10's releases to White Oak Creek, concerns about contaminants released from the Oak Ridge Reservation, and general concerns related to the Oak Ridge Reservation.
45
Appendix B, page B-6: The bar graph is clear and informative only if the sentence on line 4, page B-4 is noted. As the initial schedule is no longer being used, recommend that the initial schedule be eliminated and the revised schedule only be shown.
The following sentence was added as a note to the bottom of Figure B-2: "The current Melton Valley closure schedule was accelerated by 9 years to have all closure activities completed by fiscal year 2006." The figure presents both the initial and revised schedule in order to show which closure activities in Melton Valley have been accelerated from the current schedule.
46
I would not change the public health assessment which has been made. This is a group effort from a lot of very competent and interested professionals who have a lot riding on the outcome and who I believe have done a very good job under difficult circumstances.
Thank you for your comment.
47
This document presents ATSDR in a pretty favorable manner. You have done a good job under very difficult circumstances with a lot of unwanted publicity and carping. The science under the report is very good and the report is written in a very good manner that is suitable for both an informed and interested public and the scientific community.
Thank you for your comment.