II.E. Demographics

The White Oak Creek study area (see Figure 11) consists of the area along the Clinch River, from the Melton Hill Dam to the Watts Bar Dam. Four main cities fall within this area. Three of the cities—Harriman, Kingston, and Rockwood—are located in Roane County and one of the cities—Spring City—is located in Rhea County. Meigs County is also within the study area. Figure 13 provides the current population distribution in the White Oak Creek Study area, and Figure 14 details current demographic information for areas within ½ mile, 1 mile, and 5 miles of the White Oak Creek study area. There are 13,362 people living within ½ mile, 20,573 people living within 1 mile, and 70,700 people living within 5 miles. For children aged 6 and younger, 983 live within ½ mile, 1,621 live within 1 mile, and 5,812 live within 5 miles.

II.E.1. Counties Within the White Oak Creek Study Area

Since 1940, the populations of Meigs County, Rhea County, and Roane County have all grown by over 50% (Bureau of the Census 1993, 2000). Table 4 presents the population over a 60-year time period for these counties and Figure 15 shows the population distribution over time.

Table 4. Populations of Meigs, Rhea, and Roane Counties From 1940 to 2000









Meigs County








Rhea County








Roane County








Source: Bureau of the Census 1993, 2000

Population Distribution in the White Oak Creek Study Area
Figure 13. Population Distribution in the White Oak Creek Study Area

Population Demographics in the White Oak Creek Study Area
Figure 14. Population Demographics in the White Oak Creek Study Area

Population Distribution of Meigs, Rhea, and Roane Counties From 1940 to 2000
Figure 15. Population Distribution of Meigs, Rhea, and Roane Counties From 1940 to 2000

Meigs County

Although between 1940 and 1960, the population of Meigs County decreased, the population has more than doubled since that time, increasing from 5,160 to 11,086 (114.8%) (see Table 4 and Figure 15). The largest percentage increase in population occurred between 1970 and 1980, when the number of residents grew from 5,219 to 7,431 (42.4%). Since 1940, the population of Meigs County has grown by almost 75% (Bureau of the Census 1993, 2000). As of 2000, the majority of residents worked in the manufacturing industry. The Meigs County population is comprised of 10,826 Caucasians, 138 African-Americans, and 122 persons of other races. Also, the largest percentage of residents is between the ages of 35 and 44, and the median age is 36.7 (Bureau of the Census 2000).

Rhea County

The population of Rhea County declined between 1940 and 1960, but has continued to increase since the 1960s (see Table 4 and Figure 15). The largest increase (40.9%) occurred between 1970 and 1980, when the number of residents increased from 17,202 to 24,235. Over the past 60 years, the population of Rhea County has increased by nearly 75% (Bureau of the Census 1993, 2000). As of 2000, the majority of residents worked in the manufacturing industry. The Rhea County population consists of 27,097 Caucasians, 580 African-Americans, and 723 persons of other races. In addition, the largest proportion of residents is between the ages of 35 and 44, with a median age of 37.2 (Bureau of the Census 2000).

Roane County

Over this 60-year period, the population of Roane County has grown by 86.8%, as shown in Table 4 (Bureau of the Census 1993, 2000). Slight declines in population occurred between 1960 and 1970, and between 1980 and 1990 (East Tennessee Development District 1995; Bureau of the Census 1993). Meanwhile, the county population increased during the remaining time periods to reach a population of 51,910 in 2000. Figure 15 shows the population distribution of the county over time (East Tennessee Development District 1995; Bureau of the Census 1993, 2000).

The majority of Roane County's 2000 population is Caucasian (49,440); the remaining portion of the population consists of African-American residents (1,409) and persons of other races (1,061) (Bureau of the Census 2000). Since the 1970s, the median age of Roane County residents has increased from 32.1 to 40.7, suggesting that the county has an aging population (East Tennessee Development District 1995; Bureau of the Census 2000). The X-10 site and the K-25 site are both located within Roane County (East Tennessee Development District 1995; Jacobs EM Team 1997a). Primarily because of these two facilities, between 1940 and 1990 manufacturing was the predominant occupation for Roane County residents (East Tennessee Development District 1995; Bureau of the Census 1993).

II.E.2. Cities Within the White Oak Creek Study Area

Three cities in the White Oak Creek study area—Kingston, Rockwood, and Harriman—are located in Roane County and Spring City is located in Rhea County. The population of these four cities between 1940 and 2000 (see Table 5), and the population distribution during that time period (see Figure 16) appear below.

Table 5. Populations of Spring City, Kingston, Rockwood, and Harriman From 1940 to 2000









Spring City
































Source: Bureau of the Census 1940, 1950, 1960, 1970, 1980, 1993, and 2000

Population Distribution of Spring City, Kingston, Rockwood, and Harriman From 1940 to 2000
Figure 16. Population Distribution of Spring City, Kingston, Rockwood, and Harriman From 1940 to 2000

Spring City

Spring City is approximately 49 miles southwest of the X-10 site (see Figure 11) (MapQuest 2003). Between 1940 and 2000, the population of Spring City continually fluctuated, as shown in Table 5. During this time period, the number of residents increased between 1940 and 1960 and between 1970 and 1990. The population declined from 1960 to 1970 and from 1990 to 2000. The largest percentage increase in population was seen between 1980 and 1990, followed by the largest decrease between 1990 and 2000 (Bureau of the Census 1940, 1950, 1960, 1970, 1980, 1993, 2000). As of 2000, the largest percentage (31.6%) of residents worked in the manufacturing industry. The population consists of 1,914 Caucasians, 91 African-Americans, and 20 persons of other races. The highest percentage of the population is between the ages of 35 and 44, and the city's median age is 44.0 (Bureau of the Census 2000).


The city of Kingston, which is the seat of Roane County, is located at the confluence of the Clinch River and the Tennessee River (see Figure 11), and it is about 22 miles southwest of the X-10 site (MapQuest 2003). The population of Kingston (see Table 5) has grown steadily from 1940 to 2000, except for a 0.2% decrease between 1980 and 1990 (East Tennessee Development District 1995; Bureau of the Census 1993, 2000). In 1969, the city of Kingston had one manufacturing plant; by 1990, 6 of the 35 manufacturing plants in Roane County were in Kingston (East Tennessee Development District 1995). Since 1990, the greatest portion of residents has been employed in the professional services field (East Tennessee Development District 1995; Bureau of the Census 2000). In 2000, the population consisted of 4,935 Caucasians, 187 African-Americans, and 142 persons of other races. The majority of Kingston residents are between the ages of 45 and 54; the median age is 41.6 (Bureau of the Census 2000).


The city of Rockwood is about 33 miles southwest of the X-10 site (see Figure 11) (MapQuest 2003). The population of Rockwood has fluctuated from 1940 to 2000 (see Table 5). The city experienced steady growth between 1940 and 2000, except for slight declines that occurred between 1960 and 1970 and between 1980 and 1990 (East Tennessee Development District 1995; Bureau of the Census 1993, 2000). In 1969, 10 out of 29 manufacturing plants in Roane County were in Rockwood; by 1990, Rockwood had 13 out of the 35 manufacturing plants in the county (East Tennessee Development District 1995). The largest percentage of residents is employed in the manufacturing field. As of 2000, the Rockwood population consisted of 5,362 Caucasians, 314 African-Americans, and 98 persons of other races. The median age is 42.0, and the greatest portion of individuals is between the ages of 45 and 54 (Bureau of the Census 2000).


The city of Harriman is about 24 miles west of the X-10 site (see Figure 11) (MapQuest 2003). As also seen in Table 5, the population of Harriman peaked between 1970 and 1980, and has continued to decline since that time (East Tennessee Development District 1995; Bureau of the Census 1993, 2000). In 1969, 18 of the 29 manufacturing plants in Roane County were located in the city of Harriman. By 1990, Roane County had 35 manufacturing plants, but the number within Harriman had fallen to 15 (East Tennessee Development District 1995). Still, as of 2000, manufacturing is the leading source of employment for Harriman residents. In 2000, the population consisted of 6,077 Caucasians, 501 African-Americans, and 166 persons of other races. The majority of residents are between the ages of 45 and 54, with the median age of 40.5 (Bureau of the Census 2000). As of 1990, Harriman had more minority residents than any other city in Roane County (East Tennessee Development District 1995).

II.F. Summary of Public Health Activities Pertaining to White Oak Creek Radionuclide Releases

This section describes the public health activities that pertain to radionuclide releases to White Oak Creek from the X-10 site. ATSDR, the TDOH, and other agencies have conducted additional public health activities at the ORR, which are described in Appendix C. Please see Figure 5 for a time line of public health activities related to radionuclide releases from X-10.


Since 1991, ATSDR has addressed the health concerns of community members, civic organizations, and other government agencies by working extensively to determine whether levels of environmental contamination at and near the ORR present a public health hazard. During this time, ATSDR has identified and evaluated several public health issues and has worked closely with many parties, including community members, civic organizations, physicians, and several federal, state, and local environmental and health agencies. While the TDOH conducted the Oak Ridge Health Studies to evaluate whether off-site populations have experienced exposures in the past, to prevent duplication of the state's efforts ATSDR's activities focused on current and future public health issues. The following paragraphs highlight major public health activities conducted by ATSDR that pertain to White Oak Creek radionuclide releases.

Health consultations, exposure investigations, and other scientific evaluations. ATSDR health scientists have addressed current public health issues related to the Watts Bar Reservoir area.

Community and physician education on PCBs in fish, September 1996. 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 TDEC's fish consumption advisories for the Watts Bar Reservoir (ATSDR et al. 2000).

Coordination with other parties. Since 1992 and continuing to the present, ATSDR has consulted regularly with representatives of other parties involved with the ORR. Specifically, ATSDR has coordinated its efforts with TDOH, TDEC, the National Center for Environmental Health (NCEH), the National Institute for Occupational Safety and Health (NIOSH), the Health Resources and Services Administration (HRSA), and DOE. These coordinated efforts led to the establishment of the Public Health Working Group in 1999, and then to the formation of the Oak Ridge Reservation Health Effects Subcommittee (ORRHES). In addition, ATSDR provided some assistance to TDOH in its study of past public health issues (ATSDR et al. 2000).

Oak Ridge Reservation Health Effects Subcommittee. The ORRHES was established in 1999 by ATSDR and the Centers for Disease Control and Prevention (CDC) under the authority of the Federal Advisory Committee Act (FACA), and as a subcommittee of the U.S. Department of Health and Human Services' Citizens Advisory Committee on Public Health Service Activities and Research at DOE sites. The subcommittee consisted of people who represented diverse interests, expertise, backgrounds, and communities, as well as liaison members from federal and state agencies. It was a forum for communication and collaboration between the citizens and the agencies that evaluate public health issues and conduct public health activities at the ORR. To help ensure citizen participation, the meetings of the subcommittee's work groups were open to the public, and everyone was invited to attend and present their ideas and opinions. The subcommittee performed the following functions:

The ORRHES created various work groups that conducted in-depth exploration of specific issues and presented findings to the subcommittee for deliberation. Work group meetings were open to all who wished to attend and participate. Figure 17 shows the organizational structure of the ORRHES, and Figure 18 is a chart that shows the process of providing input into public health assessments. For more information on the ORRHES, visit the ORRHES Web site at (ATSDR et al. 2000).

ATSDR field office. ATSDR maintained a field office in the city of Oak Ridge from 2001 to 2005. The office was opened to promote collaboration between ATSDR and the communities surrounding the ORR by providing community members with opportunities to become involved in ATSDR's public health activities at the ORR (ATSDR et al. 2000).

Where can one obtain more information on ATSDR's activities at Oak Ridge?

ATSDR has conducted several additional analyses that are not documented here or in Appendix C, as have other agencies that have been involved with this site. Community members can find more information on ATSDR's past activities by the following three ways:

  1. Visit one of the records repositories. Copies of ATSDR's publications on the ORR, along with publications from other agencies, can be viewed in records repositories at public libraries and the DOE Information Center in Oak Ridge. For directions to these repositories, please contact ATSDR at 1-888-42ATSDR (or 1-888-422-8737).
  2. Visit the ATSDR or ORRHES Web sites. These Web sites include our past publications, schedules of future events, and other information materials. ATSDR's Web site is at and the ORRHES Web site is at The most comprehensive summary of past activities can be found at
  3. Contact ATSDR directly. Residents can contact representatives from ATSDR directly by dialing the agency's toll-free number, 1-888-42ATSDR (or 1-888-422-8737).

Organizational Structure for the Oak Ridge Reservation Health Effects Subcommittee
Figure 17. Organizational Structure for the Oak Ridge Reservation Health Effects Subcommittee

Process Flow Sheet for Providing Input Into the Public Health Assessment Process
Figure 18. Process Flow Sheet for Providing Input Into the Public Health Assessment Process


Oak Ridge Health Studies. In 1991, DOE and the state of Tennessee entered into the Tennessee Oversight Agreement, which allowed the TDOH to undertake a two-phase independent state research project to determine whether past environmental releases from ORR operations harmed people who lived nearby (ORHASP 1999). All of the technical reports produced for the TDOH Oak Ridge Health Studies are accessible in portable document format (PDF) at Exiting ATSDR Website.

The Screening-Level Evaluation of Additional Potential Materials of Concern was conducted to determine if contaminants other than those identified in the Oak Ridge Dose Reconstruction Feasibility Study warranted further evaluation to assess their potential to cause health effects to off-site populations. Three methods—a qualitative screening, a quantitative screening, and a threshold quantity approach—were used to evaluate the potential for 25 materials or groups of materials to cause off-site health effects. Based on the screening results, 5 materials used at the K-25 plant and 14 materials used at the Y-12 plant warranted no further study. Three materials used at the K-25 plant (copper powder, nickel, and technetium 99), three materials used at the Y-12 plant (beryllium compounds, lithium compounds, and technetium 99), and one material used at the ORR (chromium VI) were determined to be potential candidates for further study. High priority candidates for further study included one material used at the K-25 plant (arsenic) and two materials used at the Y-12 plant (arsenic and lead). A brief summary of the Task 7 report is provided in Appendix D.

The Oak Ridge Health Agreement Steering Panel (ORHASP)—a panel of experts and local citizens—was appointed to direct and oversee the Oak Ridge Health Studies and provide liaison with the community. Given the findings of the Oak Ridge Health Studies and what is generally known about the health risks posed by exposures to various toxic chemicals and radioactive substances, ORHASP concluded that, "past releases from the Oak Ridge Reservation were likely to have harmed some people." Two groups most likely to have been harmed were 1) local children who drank milk produced by a "backyard" cow or goat in the early 1950s and 2) fetuses of women who routinely ate fish from contaminated creeks and rivers downstream of the ORR in the 1950s and early 1960s. ORHASP noted, however, the Task 4 report determined that following exposure to fish contaminated with X-10 radionuclides via White Oak Creek, less than one excess cancer case was expected. Studies also indicate that elevated PCB concentrations drove the health risks associated with eating fish from the Clinch River and Watts Bar Reservoir. For additional information on the ORHASP findings, please see the final report of the ORHASP titled Releases of Contaminants from Oak Ridge Facilities and Risks to Public Health at Exiting ATSDR Website.

II.F.3. Tennessee Department of Environment and Conservation (TDEC)

Sampling of Public Drinking Water Systems in Tennessee. For 30 years, under the Safe Drinking Water Act of 1974 (summary available at Exiting ATSDR Website), the EPA has set health-based standards and specified treatments for substances in public drinking water systems. In 1977, EPA gave the state of Tennessee authority to operate its own Public Water System Supervision Program under the Tennessee Safe Drinking Water Act. Through this program, TDEC's Division of Water Supply regulates drinking water at all public water systems. As a requirement of this program, all public water systems in Tennessee individually monitor their water supply for EPA-regulated contaminants and report their monitoring results to TDEC. The public water supplies for Kingston, Spring City, Rockwood, and other supplies in Tennessee are monitored for substances that include 15 inorganic contaminants, 51 synthetic and volatile organic contaminants, and 4 radionuclides (USEPA 2004a). According to EPA's Safe Drinking Water Information System (SDWIS), the Kingston, Spring City, and Rockwood public water supply systems have not had any significant violations (USEPA 2004b). For EPA's monitoring schedules for each contaminant, go to Exiting ATSDR Website. On a quarterly basis, TDEC submits the individual water supply data to EPA's SDWIS (TDEC 2003c). To look up information and sampling results for public water supplies in Tennessee, go to EPA's Local Drinking Water Information Web site at Exiting ATSDR Website.

EPA's ERAMS program was established to provide radiological monitoring for public water supplies located close to US nuclear facilities.

In addition, in 1996 TDEC's DOE Oversight Division began participation in EPA's Environmental Radiation Ambient Monitoring System (ERAMS). As part of the Oak Ridge ERAMS program, TDEC collects samples from five facilities on the ORR and in its vicinity. These public water suppliers include the Kingston Water Treatment Plant (TRM 568.4), DOE Water Treatment Plant at K-25 (CRM 14.5), West Knox Utility (CRM 36.6), DOE Water Treatment Plant at Y-12 (CRM 41.6), and Anderson County Utility District (CRM 52.5) (TDEC 2003b). Under the Oak Ridge ERAMS, TDEC collects finished drinking water samples from the Kingston Water Treatment Plant on a quarterly basis and then submits the samples to EPA for radiological analyses. The schedule and contaminants sampled at the Kingston Water Treatment Plant are available at Exiting ATSDR Website. Also see the TDEC–DOE Oversight Division's annual report to the public at Exiting ATSDR Website for a summary of radiological drinking water sampling results. TDEC has also conducted filter backwash sludge sampling at Spring City—radioactive contaminants from the reservation could potentially move downstream into community drinking water supplies. TDEC analyzed Spring City samples for gross alpha, gross beta, and gross gamma emissions (TDEC 2002, 2003a, 2003b). To ask specific questions related to your drinking water, contact TDEC's Environmental Assistance Center in Knoxville, Tennessee at 865-594-6035. To find additional information related to your water supply or other water supplies in the area, please call EPA's Safe Drinking Water Hotline at 800-426-4791 or visit EPA's Safe Drinking Water Web site at Exiting ATSDR Website.

Watts Bar Reservoir and Clinch River Turtle Sampling Survey, May 1997. TDEC conducted this survey to assess the body burdens of contaminants in snapping turtles in the Clinch River and in the Watts Bar Reservoir. Because of PCB contamination, fish advisories had been in effect for several years, and TDEC was concerned that people who consumed turtles from these water sources could also be exposed to PCBs. TDEC concluded that PCBs and additional contaminants accumulate in turtles from the Clinch River and the Watts Bar Reservoir. Data from the area fish advisories show that the PCB concentrations in turtle tissue were detected at levels of concern for human consumption. The majority of PCB contamination was detected in the fat tissue of the turtles, which is also seen in fish. Thus food preparation techniques, particularly tissue selection, can significantly influence the quantities of PCBs consumed with turtle meat (ATSDR et al. 2000). A brief summary of this survey is in Appendix D.


Watts Bar Interagency Agreement, February 1991. DOE, EPA, TVA, TDEC, and USACE comprise the Watts Bar Reservoir Interagency Working Group (WBRIWG), which works collaboratively through the Watts Bar Interagency Agreement—an agreement that established guidelines related to any dredging in Watts Bar Reservoir. Through this agreement, these agencies review permitting and all other activities that could possibly disturb the sediment of Watts Bar Reservoir, such as erecting a pier or building a dock (ATSDR 1996; Jacobs EM Team 1997b; USDOE 2003a). The agreement also establishes guidelines for reviewing potential sediment-disturbing activities in the Clinch River below Melton Hill Dam, including Poplar Creek (Jacobs EM Team 1997b). According to the interagency agreement, DOE is required to take action if an institutional control is ineffective or if a sediment-disturbing activity could cause harm (USDOE 2003a).

Permit coordination under the Watts Bar Interagency Agreement was established to allow TVA, USACE, and TDEC (the agencies with permit authority over actions taken in Watts Bar Reservoir) to discuss proposed sediment-disturbing activities with DOE and EPA before conducting the normal permit review process to determine if there are any DOE contaminants in the sediments. The coordination follows a series of defined processes as outlined in the agreement.

The basic process of obtaining a permit, which is detailed in Section III.B.3, is the same for any organization or individual. If dredging is necessary in an area with contaminated sediments, DOE will assume the financial and waste management responsibility that is over and above the costs that would normally be incurred (Jacobs EM Team 1997b). For more details, please see the Clinch River/Poplar Creek OU ROD at Exiting ATSDR Website and page 3–5 of the Lower Watts Bar Reservoir ROD at Exiting ATSDR Website (Jacobs EM Team 1997b; USDOE 1995a).

Oak Ridge Environmental Information System (OREIS), April 1999. Because an abundance of environmental data exists for the ORR, DOE created an electronic data management system to integrate all of the data into a single database. This database was developed to facilitate public and governmental access to environmental data related to ORR operations, while also maintaining data quality. DOE's objective was to ensure that the database had long-term retention of the environmental data and useful methods to access the information. OREIS contains data related to compliance, environmental restoration, and surveillance activities. Information from all key surveillance activities and environmental monitoring efforts is entered into OREIS. These include but are not limited to studies of the Clinch River embayment and the Lower Watts Bar Reservoir, as well as annual site summary reports. As new studies are completed, the environmental data are entered as well (ATSDR et al. 2000).

Comprehensive Epidemiologic Data Resource (CEDR). CEDR is a public-use database that contains information pertinent to health-related studies performed at the Oak Ridge Reservation and at other DOE sites. DOE provides this easily accessible, public-use repository of data (without personal identifiers) collected during occupational and environmental health studies of workers at DOE facilities and nearby community residents. This large resource organizes the electronic files of data and documentation collected during these studies and makes them accessible on the Internet at Exiting ATSDR Website. Most of CEDR's large data collection pertains to about 50 epidemiologic studies of workers at various DOE sites. Of particular interest to Tennessee residents is an additional feature of CEDR (at Exiting ATSDR Website) that provides searchable text for about 1,800 original government documents (now declassified) used by the TDOH scientists for the Oak Ridge Dose Reconstruction. Also available through CEDR at Exiting ATSDR Website are all of the technical and summary reports produced by this study. For the first time, this complex information is easily accessible in a concise, uncluttered, and easily comprehended manner. In addition, CEDR now provides images in slideshow format that give estimated concentrations, doses, and risk values for three contaminants (iodine, mercury, and uranium) in air at locations studied in TDOH's Dose Reconstruction.


III.A. Introduction

In 2001, ATSDR scientists conducted a review and analysis of the Phase I and Phase II screening evaluation of TDOH's Oak Ridge Health Studies to identify contaminants that require further public health evaluation. In the Phase I and Phase II screening evaluation, TDOH conducted extensive reviews of available information and conducted qualitative and quantitative analyses of past (1944–1990) releases and off-site exposures to hazardous substances from the entire ORR. Having reviewed and analyzed Phase I and Phase II screening evaluations, ATSDR scientists determined that past releases of uranium, mercury, iodine 131, fluorides, radionuclides from White Oak Creek, and PCBs require further public health evaluation. The public health assessment is the primary public health process ATSDR is using to evaluate these contaminants further.

ATSDR scientists previously prepared a public health assessment on uranium releases from Y-12 and addressed current public health issues related to the East Fork Poplar Creek and the Lower Watts Bar Reservoir (LWBR). ATSDR is conducting public health assessments on the following releases: Y-12 mercury releases, X-10 iodine 131 releases, K-25 uranium and fluoride releases, and PCB releases from X-10, Y-12, and K-25. Public health assessments will also be conducted on other issues of concern, such as the Toxic Substances Control Act (TSCA) incinerator and off-site groundwater. In addition, ATSDR is screening current (1990 to 2003) environmental data to identify any other chemicals that will require further evaluation.

This public health assessment focuses on exposures to X-10 radionuclide releases to the Clinch River and the Lower Watts Bar Reservoir via White Oak Creek. More specifically, it evaluates 1) the data and findings of previous studies and investigations of X-10 radionuclide releases to the LWBR and the Clinch River via White Oak Creek; 2) assesses whether people who previously used the river, people who continue to use the river, or neighboring residents have been or could be exposed to radionuclides or radiation; and 3) determines the health implications of past, current, and future radiation exposure.

III.A.1. Exposure Evaluation Process

The five elements of an exposure pathway are (1) source of contamination, (2) environmental media, (3) point of exposure, (4) route of human exposure, and (5) receptor population. The source of contamination is where the chemical or radioactive material was released. The environmental media (e.g., groundwater, soil, surface water, air) transport the contaminants. The point of exposure is where people come in contact with the contaminated media. The route of exposure (e.g., ingestion, inhalation, dermal contact) is how the contaminant enters the body. The people actually exposed are the receptor population.

A release of a contaminant from a site does not always mean that the substance will have a negative impact on a member of the off-site community. For a substance to pose a potential health problem, exposure must first occur. Human exposure to a substance depends on whether a person comes in contact with the contaminant, for example by breathing, eating, drinking, or touching a substance containing it. If no one comes into contact with a contaminant, then no exposure occurs—and thus no health effects can occur. Even if the site is inaccessible to the public, contaminants can move through the environment to locations where people could come into contact with them. In the case of radiological contamination, exposure can occur without direct contact because of the emission of radiation, which is a form of energy.

ATSDR evaluates site conditions to determine if people could have been or could be exposed to site-related contaminants. When evaluating exposure pathways, ATSDR identifies whether exposure to contaminated media (soil, water, air, waste, or biota) has occurred, is occurring, or will occur through ingestion, dermal (skin) contact, or inhalation. ATSDR also identifies an exposure pathway as completed or potential, or eliminates the pathway from further evaluation. Completed exposure pathways exist if all elements of a human exposure are present. (See "Exposure Pathway" in Appendix A for a description of the elements of a completed exposure pathway.) A potential pathway is one that ATSDR cannot rule out because one or more of the pathway elements cannot be definitely proved or disproved. A pathway is eliminated if one or more of the elements are definitely absent.

Identifying the Types of Radiation Exposure

Beta particles can penetrate human skin and tissues and deliver a dose both internally and externally.

Gamma rays can travel long distances and easily penetrate body tissues, and are therefore the primary type of radiation that results in external radiation exposures. Most radionuclides from X-10 were beta or gamma emitters.

Alpha particles cannot penetrate skin, so they pose a minimal external exposure concern. Alpha particles can inflict biological damage if the body takes them in, for example by breathing or swallowing radioactive material in air or food. However, alpha particles were not associated with the majority of radionuclides released to White Oak Creek.

Source: ATSDR 1999b

There are two broad classes of radiation exposure: internal radiation and external radiation. Internal exposures result from radioactive sources taken into the body through the inhalation of radioactive particles or the ingestion of contaminated food. External exposure results from radiation sources originating outside the body, such as radiation emitted from contaminated sediment. These external sources can sometimes penetrate the human skin. Whether an exposure contributed to an individual's internal or external exposure depends primarily on the type of radiation—that is, alpha and beta particles or gamma rays—to which a person was exposed. Most radionuclides associated with White Oak Creek releases are beta or gamma emitters. Through its scientific evaluation, ATSDR eliminated internal radiation exposure from alpha particles associated with X-10 releases as a concern (see the text box).

Deriving Radiation Doses

The radiation dose is the amount of energy from radiation that is actually absorbed by the body.

ATSDR scientists calculate the radiation dose by using the concentration of the radionuclide in the environment and, if available, site-specific exposure factors such as time spent outdoors and amount of water ingested. If these site-specific factors are unavailable, ATSDR either uses default values or derives region-specific values. Once these inputs are derived, the dose coefficient that converts the radiation concentration to the radiation dose is applied. ATSDR scientists might use worst-case exposure factors as the basis for determining whether adverse health effects are possible. Because of this approach, the estimated radiation doses are usually much higher—that is, more conservative—than the levels to which the majority of people are exposed. Note that the concept of radiation dose is not as simple as related here; a number of other factors (for example, how radionuclides decay, the critical organ concept, particle size distribution, and the chemical form) might affect "dose" and therefore need to be factored into the dose derivation.

ATSDR uses the term "conservative" to refer to values that are protective of public health in essentially all situations. Values that are overestimated are considered to be conservative.

Internal radiation exposure from a radionuclide continues after the initial radioactive material has been taken into the body, even if no additional radionuclides are ingested or inhaled. That is, internal exposure of radiation from radioactive material commits the exposed person to receiving a radiation dose for a period of time that typically depends on the radionuclide's half-life and rate of elimination from the body. (See III.A.2.a. for a discussion on half-life.) This dose is called the committed equivalent dose for an organ-specific dose and the committed effective dose for a whole-body dose. Exposure to external radiation sources, however, stops when the source is removed or when a person moves away from the source. A dose associated with external radiation is called an effective dose. The doses are further defined as follows:

Committed Equivalent Dose
The International Commission of Radiological Protection's (ICRP's) term (starting with ICRP Publication 60) for the dose to organs and tissues of reference that an individual will receive from an intake of radioactive material over a 50-year period following the intake for workers or adults and over a 70-year period following the intake for children.

Committed Effective Dose
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.

Effective Dose
ICRP's term (starting with ICRP Publication 60) for the sum of the products of 1) the weighting factors applicable to each body organ or tissue that is irradiated and 2) the mean equivalent dose in the tissue or organ following exposure to external radiation.

The organ dose (equivalent, HT) and the whole-body dose (effective, E) can be defined mathematically using the equations below. W and D are the weighting factor and dose, respectively. The subscripts R and T represent the type of radiation and the tissue of concern.

mathematical equation (organ, equivalent dose)

mathematical equation mathematical equation (whole body, effective dose)

The sum of the equivalent dose is theoretically equal to the effective dose (E). By rearranging the equations, one can solve for the equivalent dose from the whole-body (effective) dose:

mathematical equation

Weighting factors (WT) are 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 (ICRP 1991).

The tissue weighting factors are based on both cancer fatality risk and the relative effect of an exposure to a single organ or tissue.6 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. Table 6 gives the currently adopted tissue weighting factors.

Table 6. Tissue Weighting Factors



∑ wT

Bone marrow (red), colon, lung, and stomach



Bladder, breast, esophagus, liver, and thyroid



Bone surface and skin






Remainder tissues–adrenals, brain, intestinal tract, kidneys, muscle, pancreas, spleen, thymus, and uterus






Assessing Health Effects

In its public health assessments, ATSDR uses radiation doses instead of risk to evaluate potential human exposures and health effects. ATSDR defines dose as "The amount of a substance to which a person may be exposed, usually on a daily basis." Dose is often explained as the "amount of substances(s) per body weight per day" and is the basis for determining levels of exposure that might cause adverse health effects. The Society for Risk Analysis defines risk as

"The potential for realization of unwanted, adverse consequences to human life, health, property, or the environment; estimation of risk is usually based on the expected value of the conditional probability of the event occurring times the consequence of the event given that it has occurred" (SRA 2004).

EPA-conducted risk assessments are useful in determining safe regulatory limits and in 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. That said, however, these quantitative risk estimates are not intended to predict the incidence of disease or to measure the actual health effects in people resulting from site-related hazardous substances. 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, nor do they measure the actual health effects that hazardous substances have on people. Please see Appendix F for more information on risk.

ATSDR recognizes that every radiation dose, action, or activity may carry an associated risk. 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. A public health assessment provides conclusions about the actual existence and level of the health threat (if any) posed by a site, as well as recommendations to stop or reduce exposures. 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. A public health assessment can, however, provide a framework that puts site-specific exposures and the potential for harm in perspective. Thus, ATSDR recognizes that uncertainties exist with doses, but it addresses these uncertainties by using health-protective safety factors.

Exposure does not always result in harmful health effects. The type and severity of health effects a person can experience depend on the dose, which is based on age at exposure, the exposure rate (how much), the frequency or duration of exposure (how long), the route or pathway of exposure (breathing, eating, drinking, or skin contact), and the multiplicity of exposure (combination of contaminants). Once a person is exposed, characteristics such as age, gender, nutritional status, genetics, lifestyle, and health status influence how that person absorbs, distributes, metabolizes, and excretes the contaminant. The likelihood that adverse health outcomes will actually occur depends on site-specific conditions, individual lifestyle, and genetic factors that affect the route, magnitude, and duration of actual exposure—an environmental concentration alone will not cause an adverse health outcome.

ATSDR uses comparison values to identify hazardous substances that are not considered a health hazard at a site and hazardous substances that require an additional follow-up evaluation.

As a first step in evaluating radiation exposures, ATSDR health assessors screened the radiation doses against comparison values. ATSDR develops comparison values from available scientific literature concerning exposure, dose, and health effects. Comparison values represent radiation doses that are lower than levels at which no effects were observed in studies on experimental animals or in human epidemiologic studies. They are not thresholds for harmful health effects; instead, they reflect an estimated dose that is not expected to cause harmful health effects. Estimated doses below these comparison values are not considered a health hazard, so doses at or below the relevant comparison value can reasonably be considered safe. Doses above the comparison values, meanwhile, will not necessarily produce adverse health effects. This screening process enables ATSDR to safely eliminate contaminants that are not of health concern and to evaluate potentially harmful contaminants further.

If the estimated radiation doses at a site are above comparison values, ATSDR proceeds with a more in-depth health effects evaluation to determine if the doses are sufficient enough to trigger public health action to limit, eliminate, or further study any potential harmful exposures. ATSDR scientists conduct a health effects evaluation by carefully examining site-specific exposure conditions about actual or likely exposures; conducting a critical review of radiologic, medical, and epidemiologic information in the scientific literature to ascertain the levels of significant human exposure; and comparing an estimate of the radiation doses that people might frequently encounter at a site to situations that have been associated with disease and injury. This health ffects evaluation involves a balanced review and integration of site-related environmental data, site-specific exposure factors, and toxicologic, radiologic, 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 observed in the exposed population by weighing the scientific evidence and keeping site-specific doses in perspective. See Figure 19 for ATSDR's health-based determination of radiological doses.

More information about the ATSDR evaluation process can be found in ATSDR's Public Health Assessment Guidance Manual at or by contacting ATSDR at 1-888-42-ATSDR. An interactive program that provides an overview of the process ATSDR uses to evaluate whether people will be harmed by hazardous materials is available at

III.A.2. Radiation-Related Terms


The half-life of a radionuclide is the time that it takes for the activity of radioactive material (or radioactivity) to decrease by one-half. This is known as the physical half-life. Radionuclides that are taken into the body will also be eliminated by biological processes, such as excretion. The measure of time it takes to eliminate half of a material taken into the body by biological processes is called the biological half-life. The measure of the combined influences of these physical and biological half-lives is called the effective half-life. For example, as shown in Table 7, the physical half-life of strontium 90 is about 10,439 days and the biological half-life is about 18,000 days for bone. Therefore, the effective half-life of strontium 90 deposited in the bone is 6,400 days. That is, half the radioactivity of strontium 90 taken into the body will be gone after 6,400 days, another half of the remaining radioactivity will be depleted after an additional 6,400 days, and this process will continue as the radioactivity is depleted from the body. The effective half-life is always less than or equal to either its physical or biological half-life.

ATSDR Health-Based Determination of Radiological Doses
Figure 19. ATSDR Health-Based Determination of Radiological Doses

Table 7. Half-Lives (in days) of Selected Radionuclides in the WOC PHA


Physical Half-Life

Biological Half-Life

Effective Half-Life*



12 (whole body)

12 (whole body)

Cesium 137


70 (whole body)

70 (whole body)

Strontium 90


18,000 (bone)

6,400 (bone)

Cobalt 60


9.5 (whole body)

9.5 (whole body)

Yttrium 90


14,000 (bone)


*Effective half-life is the time required for the radioactivity of a radionuclide to be diminished 50 percent through the combined action of radioactive physical decay and biological elimination.

Radiological Measurements

This PHA uses two systems for radiological measurements and doses: the Conventional System and the Systeme International. The key in Table 8 describes these units and lists their abbreviations.

Table 8. Units for Radiological Measurements




Conventional System

picocurie, pCi

The curie (Ci) is the basic unit of radioactivity. The pCi is 1,000,000,000,000 (one trillion) times smaller than one Ci.

millirem, mrem

Dose is given in units "roentgen equivalent man" or rem. One mrem is 1,000 times smaller than one rem. This is the unit for both the equivalent dose and the effective dose.

Systeme International

becquerel, Bq

The basic unit of activity is the becquerel (Bq). The number of curies must be multiplied by 3.7 × 1010 to obtain an equivalent number of Bq.

millisievert, mSv

The sievert (Sv) is the unit of equivalent dose and the effective dose. One mSv is 1,000 times smaller than one Sv. The number of millisieverts (mSv) must be multiplied by 100 to convert to millirem.

III.B. Exposure Evaluation of the Clinch River and Lower Watts Bar Reservoir

ATSDR evaluated past (Clinch River) and current exposures (Clinch River and LWBR) to radioactive contamination (based on environmental samples) that was released from X-10 via White Oak Creek. ATSDR evaluated future exposures to the Clinch River and the LWBR based on the current estimated exposure doses and the institutional and engineering controls that are in place for both of these watersheds. The highest exposure doses were estimated for people who frequently ate fish (1 to 2.5 fish meals a week) caught from the Clinch River near the mouth of White Oak Creek from 1944 to 1953. Doses were much lower for people who ate fewer fish or fished further downstream and for the other past and current exposure pathways evaluated in this public health assessment.

This section presents an overview of past, current, and future exposures to radioactive contaminants released to the Clinch River, and current and future exposure to radioactive contaminants released to the LWBR. An evaluation of potential public health hazards from likely exposures to White Oak Creek releases is presented in Section IV. Public Health Implications. ATSDR used the time periods and information presented below in its evaluation. Please note that because some studies are conducted simultaneously, the past and current time periods overlap slightly. The doses obtained from these studies are, however, based on different data. Therefore, even though the time periods overlap, the estimated past doses do not overlap with the estimated doses for current and future exposures.

III.B.1. Possible Exposure Situations in the Clinch River and the Lower Watts Bar Reservoir Areas

People could come in contact with contaminants along the Clinch River and the Lower Watts Bar Reservoir via several different pathways. ATSDR analyzed radioactive contaminant data for surface water, sediment, and biota (aquatic and terrestrial) to determine whether the levels detected in these media might pose a past or current public health hazard. This evaluation looked at the level of contamination present, the extent to which individuals contact the contamination, and estimated doses to individuals coming in contact with the media under different exposure scenarios. ATSDR identified several exposure situations for the Clinch River and LWBR areas that required further evaluation. This PHA evaluates the following situations for exposures at the Clinch River, LWBR, or at both locations:

Exposure situations associated with radioactive contaminants released from White Oak Creek are evaluated in detail in the following discussion and depicted in Figure 20.

Possible Exposure Situations Along the Clinch River
Figure 20. Possible Exposure Situations Along the Clinch River

To acquaint the reader with terminology and methods used in this PHA, Appendix A provides a glossary of environmental and health terms presented in the discussion. Additional background information is provided in appendices as follows: Appendix B summarizes detailed remedial activities related to the study area; Appendix C summarizes other public health activities at the ORR; Appendix D contains summaries of ATSDR, TDEC, and TDOH studies or investigations; Appendix E provides a table of Task 4 conservative screening indices (i.e., the calculated probabilities of developing cancer) for radionuclides in the Clinch River; Appendix F includes a discussion on risk; Appendix G presents responses to public comments; and Appendix H provides responses to peer reviewer comments.

6 For 2005, the ICRP is proposing a new system, which still involves weighting factors, that uses cancer incidence and considers lethality rate, years of life lost, and weighted contribution from the nonfatal cancers and hereditary disorders.

Next Section     Table of Contents