PUBLIC HEALTH ASSESSMENT

WHITE OAK CREEK RADIONUCLIDE RELEASES
OAK RIDGE RESERVATION (US DOE)
OAK RIDGE, ROANE COUNTY, TENNESSEE

VII. CHILD HEALTH CONSIDERATIONS

ATSDR recognizes that infants and children can be more sensitive to environmental exposure than adults in communities faced with contamination of their water, soil, air, or food. This sensitivity is a result of the following factors: 1) children are more likely to be exposed to certain media (for example, soil or surface water) because they play and eat outdoors; 2) children are shorter than adults, which means that they can breathe dust, soil, and vapors close to the ground; and 3) children are smaller; therefore, childhood exposure results in higher doses of chemical exposure per body weight. Children can sustain permanent damage if these factors lead to toxic exposure during critical growth stages. ATSDR is committed to evaluating the special interests of children at sites such as the ORR.

Children playing in and living along the Clinch River and Watts Bar Reservoir could have been exposed to radiation when they used these waterways for food, water, or recreation. In addition, in utero and infant exposures could have resulted from exposure of pregnant or lactating women (or both) to radiation in and near the Clinch River and Watts Bar Reservoir. Radionuclide levels in water, sediment, and biota are, however, below levels shown to cause adverse health effects in these populations. For past exposures, the Task 4 team concluded that its estimated radiological doses and excess lifetime cancer risks were "incremental increases above those resulting from exposure to natural and other anthropogenic sources of radiation." Still, they were "not large enough for a commensurate increase in health effects in the population to be detectable, even by the most thorough of epidemiological investigations." The Task 4 team noted that "in most cases, the estimated organ-specific doses are clearly below the limits of epidemiological detection (1 to 30 cSv [1,000 to 30,000 mrem]) for radiation-induced health outcomes that have been observed following irradiation of large cohorts of individuals exposed either in utero (Doll and Wakeford 1997), as children, or as adults (NRC [National Research Council] 1990; Thompson et al. 1994; Pierce et al. 1996) (ChemRisk 1999a)."

Further, dose and risk factors for most radionuclides in the Task 4 analysis do not differ greatly between children and adults (ChemRisk 1999a). Exposure to iodine 131 has been shown to increase the likelihood of thyroid disorders in children—that is, exposed children could have an increased likelihood of developing a disease (e.g., thyroid cancer) in their lifetimes (Vykhovanets et al. 1997; Astakhova et al. 1998; Heidenreich et al. 1999; Hahn et al. 2001). Nevertheless, based on the Task 4 analysis, the levels of iodine 131 in the surface water of the Clinch River and in the locally produced milk are too low to cause such health effects in children living near the Clinch River.

Therefore, even past radiation exposures—when doses were the highest—were not expected to cause harmful health effects in utero, in infants, and in children. Accordingly, because estimated doses for exposures to the Clinch River and Lower Watts Bar Reservoir have decreased over time, exposures to radiation in utero, in infants, and in children are not expected to cause adverse health effects in the present or in the future.

VIII. CONCLUSIONS

Having thoroughly evaluated past public health activities and available current environmental information, ATSDR has reached the following conclusions.

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 those situations as posing no apparent public health hazard from exposure to radionuclides related to X-10. This classification means that people could be or were exposed, but that their level of exposure would not likely result in any adverse health effects. (Definitions of ATSDR's public health categories are included in the glossary in Appendix A.)

Past Exposure

ATSDR concludes that past exposures to White Oak Creek radionuclide releases from walking on the shoreline, drinking milk and water, or eating meat and fish from the Clinch River are not a health hazard and are not expected to result in adverse health effects or cancer.

• Using the results of the Task 4 report, ATSDR re-evaluated past exposures (1944–1991) to radionuclides released from White Oak Creek into the Clinch River. People who used or lived near the Clinch River could have come in contact with X-10 radionuclides by eating fish and meat, drinking milk and water, and walking on shoreline sediment. Using organ doses from the Task 4 report, ATSDR estimated whole-body doses (annual dose and committed effective dose over 70 years). An individual exposed to the primary radionuclides in Clinch River fish, shoreline sediment, meat, milk, and drinking water was expected to receive a committed effective dose to the whole body of less than 300 mrem over 70 years. This dose is about 18 times less than ATSDR's radiogenic comparison value of 5,000 mrem over 70 years. Doses below the radiogenic comparison value are not expected to result in observable health effects.



• ATSDR's estimated annual whole-body dose from combining the organ doses was 4 mrem/year and well below (25 times less than) ATSDR's MRL of 100 mrem/year and the ICRP, NRC, and NCRP maximum dose recommendation of 100 mrem/year for members of the public. ATSDR's MRL for ionizing radiation is based on noncancer health effects only; it is not based on a consideration of cancer effects. MRLs are estimates of daily human exposures to substances that are unlikely to result in noncancer effects over a specified duration. The maximum dose constraint for members of the public of 100 mrem/year recommended by the ICRP, NRC, and NCRP considers both noncancer and cancer health effects.



• The estimated committed equivalent doses to all the organs from eating fish caught near Jones Island exceeded dose estimates for all other exposure pathways (walking along the shore and ingesting water, milk, and meat) by at least a factor of six. The estimated committed equivalent doses to the organs from past exposures to radionuclides in and along the Clinch River varied by critical organ (bone, lower large intestine, red bone marrow, breast, and skin).



• The highest committed equivalent dose to the organs was 810 mrem to the bone for people who ate fish often (1 to 2.5 fish meals per week) and caught their fish near Jones Island. Doses to the bone were much lower for people who consumed fewer fish and who caught their fish further downstream. The estimated total committed equivalent dose to the bone over a lifetime (70 years) from all exposure pathways was less than 1,600 mrem over 70 years. This estimated total lifetime bone dose is well below (243 times less than) the doses of 390,000 to 620,000 mrem shown to cause bone cancers in radium dial workers.



• ATSDR analyzed radiation doses from drinking water at K-25/Grassy Creek (CRM 17 to 5) and the city of Kingston (CRM 2 to 0), located downstream from the mouth of White Oak Creek. The doses to the bone, lower large intestine, red bone marrow, breast, and skin from drinking Clinch River water were at least 7 times lower than the doses to those same organs from eating Clinch River fish. The highest annual whole-body dose from drinking water of 0.3 mrem was estimated for K-25/Grassy Creek. This annual whole-body dose is more than 1,000 times less than the background dose of 360 mrem that the average U.S. citizen receives each year. Lower doses were associated with drinking water further downstream at the city of Kingston. Organ-specific doses from drinking city of Kingston water were at least 13 times less than the doses estimated for K-25/Grassy Creek drinking water.



• After reviewing information provided by a community member about the former Happy Valley settlement, ATSDR conducted a separate analysis of possible exposures to radionuclides for Happy Valley residents who relied on the K-25 water intake for their drinking water. ATSDR's estimated annual whole-body dose of 14 mrem from drinking water for a former Happy Valley resident is at least 7 times lower than ATSDR's MRL of 100 mrem/year and the ICRP, NRC, and NCRP maximum dose recommendation of 100 mrem/year for members of the public.



• The estimated total committed equivalent dose to the lower large intestine from all pathways was less than 1,200 mrem over 70 years. This estimated dose is 4 times less than ATSDR's radiogenic comparison value of 5,000 mrem over 70 years, which is based on studies of atomic bomb survivors, radiation workers, and radiation workers' children.



• The estimated total committed equivalent dose to the red bone marrow over a lifetime (70 years) from all exposure pathways was less than 1,200 mrem over 70 years. This estimated total lifetime bone dose is well below (i.e., 325 times less than) the doses of 390,000 to 620,000 mrem associated with bone cancers in radium dial workers.



• The estimated total committed equivalent dose to the breast in females over a lifetime (70 years) from all exposure pathways was less than 500 mrem over 70 years, which is well below (20 times less than) the 10,000 mrem dose shown to cause effects in atomic blast survivors.



• The estimated total committed equivalent dose to the skin over a lifetime (70 years) from all exposure pathways was less than 700 mrem over 70 years, which is well below (12 times less than) the 9,000 mrem dose shown to cause effects in patients irradiated for the treatment of ringworm.



• All the estimated organ doses and whole-body doses from past exposure to radionuclides in the Clinch River are lower than ATSDR's comparison values and doses reported in radiological and epidemiological studies on the effects of radiation exposure. Therefore, considering the many conservative assumptions used in calculating the dose estimates, ATSDR believes that the actual likelihood of developing disease for people who were exposed to radionuclides in the Clinch River is small, if it exists at all.

Current Exposure

ATSDR concludes that current exposures to White Oak Creek radionuclide releases to the Clinch River and LWBR are not a health hazard and are not expected to result in adverse health effects or cancer. This conclusion is based on ATSDR's evaluation of current exposure to radionuclides by consumption of surface water, by dermal contact with surface water and sediment, and by consumption of fish from the Clinch River and the Lower Watts Bar Reservoir, as well as by consumption of turtles and geese from the Clinch River.

Lower Watts Bar Reservoir

• Using available environmental data collected from 1988 to 1994, ATSDR evaluated current exposures to radionuclides via ingestion of fish, ingestion of surface water, and external exposure from dermal contact with surface water and shoreline and dredged channel sediment of the Lower Watts Bar Reservoir. Even assuming maximum concentrations of radionuclides and using conservative exposure scenarios, current exposure to radionuclides in the Lower Watts Bar Reservoir would result in radiation doses below levels expected to cause adverse health effects. ATSDR's estimated committed effective dose to the whole body for all pathways combined is less than 1,900 mrem over 70 years—2.5 times below ATSDR's radiogenic CV of 5,000 mrem over 70 years. The estimated annual whole-body dose is less than 30 mrem, and below ATSDR's screening comparison value of 100 mrem/year. Therefore, the estimated exposures for the LWBR are not expected to result in adverse health effects based on an evaluation of radiological, epidemiological, and medical literature.

Clinch River

• Using available environmental data collected from 1989 to 2003, ATSDR evaluated current exposures to radionuclides via ingestion of biota (i.e., fish, geese, and turtles), incidental ingestion of surface water, and external exposure from dermal contact with surface water and shoreline sediment of the Clinch River. ATSDR's estimated committed effective dose to the whole body for all pathways along the Clinch River combined is less than 240 mrem to 70 years of age—more than 20 times below ATSDR's radiogenic CV of 5,000 mrem over 70 years. The estimated annual whole-body dose is less than 3.4 mrem, nearly 30 times below ATSDR's screening comparison value of 100 mrem/year. Therefore, the estimated exposures for the Clinch River are not expected to result in adverse health effects.



• Doses to organs varied by exposure pathway. ATSDR's estimates show that the bone would receive the highest total committed equivalent dose over a lifetime (to 70 years of age) of exposure to the radionuclides detected along the Clinch River. The highest doses to the bone were from ingestion of geese muscle or liver (230 mrem) and fish (114 mrem) by a 15-year-old based on a 55-year exposure, resulting in a committed equivalent dose of 344 mrem over 55 years. The committed equivalent dose to the bone from all pathways combined was based on exposures for adults, considering exposure to 70 years of age. The estimated dose to the bone is less than 218 mrem to 70 years of age—at least 1,788 times lower than the doses of 390,000 to 620,000 mrem associated with bone cancers in radium dial workers.



• The committed equivalent dose to the lower large intestine from all pathways combined, based on a 20-year-old adult exposed to age 70, was less than 270 mrem. This estimated dose is about 18 times lower than ATSDR's radiogenic comparison value of 5,000 mrem over 70 years.



• The committed equivalent dose to the skin over a 50-year exposure for adults is less than 6 mrem—1,500 times less than the value of 9,000 mrem. This is based on a review of the Biological Effects of Ionizing Radiation (BEIR) V report of patients irradiated for the treatment of ringworm.



• ATSDR analyzed drinking water samples collected around the cities of Kingston, Spring City, and Rockwood from 1990 to the present. ATSDR evaluated these samples for radiological content, and determined that all water samples were below EPA's maximum contaminant level (MCL). Therefore, ATSDR considers this water safe for consumption and other potable uses.

Future Exposure

Lower Watts Bar Reservoir and Clinch River

• ATSDR concludes that future exposures to White Oak Creek radionuclides released to the Clinch River and LWBR are not a health hazard and are not expected to result in adverse health effects or cancer. This is based on ATSDR's evaluation of current doses and exposures related to releases from White Oak Creek, data on current contaminant levels in the LWBR and the Clinch River, and consideration of the possibility that radionuclides could be released to White Oak Creek during remedial activities. ATSDR also factored in engineering controls to prevent off-site contaminant releases and institutional controls in place to monitor contaminants in the LWBR and the Clinch River, as well as the assumption that DOE will continue its expected appropriate and comprehensive system of monitoring, maintenance, and institutional and engineering controls. These institutional controls consist of



• prevention of sediment-disturbing activities in the Clinch River and LWBR,
• DOE's annual monitoring of Clinch River and LWBR surface water, sediment, and biota,
• DOE's monitoring of White Oak Creek releases,
• TDEC's monitoring of public drinking water supplies in Tennessee under the Safe Drinking Water Act for EPA-regulated contaminants, and
• TDEC DOE Oversight Division's quarterly radiological monitoring of five public water supplies on the ORR and in its vicinity under the EPA's Environmental Radiation Ambient Monitoring System program.

IX. RECOMMENDATIONS

Having evaluated the past, current, and future public health activities and the available environmental information, ATSDR offers the following:

1. Tennessee Department of Environment and Conservation (TDEC) should continue to monitor public drinking water supplies in Tennessee under the Safe Drinking Water Act for U.S. Environmental Protection Agency (EPA)-regulated contaminants, and TDEC's Department of Energy (DOE) Oversight Division should continue its quarterly radiological monitoring of public water supplies on the Oak Ridge Reservation (ORR) and in its vicinity under the EPA's Environmental Radiation Ambient Monitoring System program.



2. Contaminants are not uniformly distributed in the sediment of the Lower Watts Bar Reservoir (LWBR) and their concentrations vary by sediment composition, location, and depth. Therefore, the contaminated sediment of the LWBR should not be removed, dredged, or otherwise disturbed without careful review by the Watts Bar Interagency Working Group in accordance with the permitting process outlined in the Watts Bar Interagency Agreement. Given the current knowledge of contamination, ATSDR believes that the measures undertaken by the working group, if followed, are protective of public health.



3. DOE should continue to annually monitor the Clinch River and the LWBR for ORR-related radiological contaminants in surface water, biota, and sediment, and also continue its regular monitoring of White Oak Creek radionuclide releases.

X. PUBLIC HEALTH ACTION PLAN

The Public Health Action Plan (PHAP) for White Oak Creek describes actions to be taken by ATSDR and other government agencies at and in the vicinity of the site after the completion of this public health assessment. The purpose of this PHAP is to ensure that this public health assessment not only identifies public health hazards, but that it also provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment. If additional information about White Oak Creek releases to the Clinch River and the Lower Watts Bar Reservoir becomes available, then that information could change a conclusion or the conclusions of this public health assessment; if that occurs, then human exposure pathways should be re-evaluated and these conclusions and recommendations should be amended, as necessary, to protect public health.

• ORR staff will notify ATSDR if environmental monitoring data indicate that statistically significant contaminant levels in the Clinch River or the Lower Watts Bar Reservoir are increasing. Upon such notification, ATSDR will determine appropriate public health actions.



• ATSDR will develop and implement additional environmental health education materials as necessary to help community members understand the findings and implications of this public health assessment.



• ATSDR supports DOE's remedial actions for the Lower Watts Bar Reservoir (LWBR) as being protective of public health. These actions include leaving the contaminated sediment in place with ongoing environmental monitoring and applying institutional controls to prevent disruption of contaminated sediment. Under the Watts Bar Interagency Agreement (established by DOE, EPA, TVA, TDEC, and USACE), the agencies will continue to work together to review permitting and any other activities that could possibly disturb LWBR contaminated sediment.

XI. PREPARERS OF REPORT

Paul A. Charp, Ph.D.
Senior Health Physicist
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry

Jack Hanley, M.P.H.
Environmental Health Scientist
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry

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APPENDIX A: ATSDR GLOSSARY OF ENVIRONMENTAL HEALTH TERMS

The Agency for Toxic Substances and Disease Registry (ATSDR) is a federal public health agency with headquarters in Atlanta, Georgia, and 10 regional offices in the United States. ATSDR's mission is to serve the public by using the best science, taking responsive public health actions, and providing trusted health information to prevent harmful exposures and diseases related to toxic substances. ATSDR is not a regulatory agency, unlike the U.S. Environmental Protection Agency (EPA), which is the federal agency that develops and enforces environmental laws to protect the environment and human health.

This glossary defines words used by ATSDR in communications with the public. It is not a complete dictionary of environmental health terms. If you have questions or comments, call ATSDR's toll-free telephone number, 1-888-42-ATSDR (1-888-422-8737).

Absorption:

The process of taking in. For a person or animal, absorption is the process through which a substance gets into the body through the eyes, skin, stomach, intestines, or lungs.

Activity:

The number of radioactive nuclear transformations occurring in a material per unit time. The term for activity per unit mass is specific activity.

Acute:

Occurring over a short time [compare with chronic].

Acute exposure:

Contact with a substance that occurs once or for only a short time (up to 14 days) [compare with intermediate-duration exposure and chronic exposure].

Adverse health effect:

A change in body function or cell structure that might lead to disease or health problems.

Ambient:

Surrounding (for example, ambient air).

Analytic epidemiologic study:

A study that evaluates the association between exposure to hazardous substances and disease by testing scientific hypotheses.

Background level:

An average or expected amount of a substance or radioactive material in a specific environment, or typical amounts of substances that occur naturally in an environment.

Background radiation:

The amount of radiation to which a member of the general population is exposed from natural sources, such as terrestrial radiation from naturally occurring radionuclides in the soil, cosmic radiation originating from outer space, and naturally occurring radionuclides deposited in the human body.

Becquerel (Bq):

The Systeme International basic unit of radioactivity. The number of curies must be multiplied by 3.7 × 10¹⁰ to obtain an equivalent number of Bq.

Biota:

Plants and animals in an environment. Some of these plants and animals might be sources of food, clothing, or medicines for people.

Body burden:

The total amount of a substance in the body. Some substances build up in the body because they are stored in fat or bone or because they leave the body very slowly.

Cancer:

Any one of a group of diseases that occurs when cells in the body become abnormal and grow or multiply out of control.

Cancer risk:

A theoretical risk of getting cancer if exposed to a substance every day for 70 years (a lifetime exposure). The true risk might be lower.

Carcinogen:

A substance that causes cancer.

Case-control study:

A study that compares exposures of people who have a disease or condition (cases) with people who do not have the disease or condition (controls). Exposures that are more common among the cases may be considered as possible risk factors for the disease.

Central nervous system:

The part of the nervous system that consists of the brain and the spinal cord.

CERCLA:

[See Comprehensive Environmental Response, Compensation, and Liability Act of 1980.]

Chronic:

Occurring over a long time (more than 1 year) [compare with acute].

Chronic exposure:

Contact with a substance that occurs over a long time (more than 1 year) [compare with acute exposure and intermediate-duration exposure].

Committed Effective Dose Equivalent (CEDE):

The sum of the products of the weighting factors applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to the organs or tissues. The committed effective dose equivalent is used in radiation safety because it implicitly includes the relative carcinogenic sensitivity of the various tissues. The unit of dose for the CEDE is the rem (or, in SI units, the sievert—1 sievert equals 100 rem.)

Comparison value (CV):

Calculated concentration of a substance in air, water, food, or soil that is unlikely to cause harmful (adverse) health effects in exposed people. The CV is used as a screening level during the public health assessment process. Substances found in amounts greater than their CVs might be selected for further evaluation in the public health assessment process.

Completed exposure pathway:

[See exposure pathway.]

Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA):

CERCLA, also known as Superfund, is the federal law that concerns the removal or cleanup of hazardous substances in the environment and at hazardous waste sites. ATSDR, which was created by CERCLA, is responsible for assessing health issues and supporting public health activities related to hazardous waste sites or other environmental releases of hazardous substances.

Concentration:

The amount of a substance present in a certain amount of soil, water, air, food, blood, hair, urine, breath, or any other medium.

Contaminant:

A substance that is either present in an environment where it does not belong or is present at levels that might cause harmful (adverse) health effects.

Curie (Ci):

A unit of radioactivity. One curie equals that quantity of radioactive material in which there are 3.7 × 10¹⁰ nuclear transformations per second. The activity of 1 gram of radium is approximately 1 Ci; the activity of 1.46 million grams of natural uranium is approximately 1 Ci.

Decay product/daughter product/progeny:

A new nuclide formed as a result of radioactive decay: from the radioactive transformation of a radionuclide, either directly or as the result of successive transformations in a radioactive series. A decay product can be either radioactive or stable.

Depleted uranium (DU):

Uranium having a percentage of U 235 smaller than the 0.7% found in natural uranium. It is obtained as a byproduct of U 235 enrichment.

Dermal:

Referring to the skin. For example, dermal absorption means passing through the skin.

Dermal contact:

Contact with (touching) the skin [see route of exposure].

Descriptive epidemiology:

The study of the amount and distribution of a disease in a specified population by person, place, and time.

Detection limit:

The lowest concentration of a chemical that can reliably be distinguished from a zero concentration.

Disease registry:

A system of ongoing registration of all cases of a particular disease or health condition in a defined population.

DOE:

The United States Department of Energy.

Dose (for chemicals that are not radioactive) :

The amount of a substance to which a person is exposed over some time period. Dose is a measurement of exposure. Dose is often expressed as milligrams (a measure of quantity) per kilogram (a measure of body weight) per day (a measure of time) when people eat or drink contaminated water, food, or soil. In general, the greater the dose, the greater the likelihood of an effect. An "exposure dose" is how much of a substance is encountered in the environment. An "absorbed dose" is the amount of a substance that actually gets into the body through the eyes, skin, stomach, intestines, or lungs.

Dose (for radioactive chemicals):

The radiation dose is the amount of energy from radiation that is actually absorbed by the body. This is not the same as measurements of the amount of radiation in the environment.

Dose-response relationship:

The relationship between the amount of exposure [dose] to a substance and the resulting changes in body function or health (response).

EMEG:

Environmental Media Evaluation Guide, a media-specific comparison value that is used to select contaminants of concern. Levels below the EMEG are not expected to cause adverse noncarcinogenic health effects.

Enriched uranium:

Uranium in which the abundance of the U 235 isotope is increased above normal.

Environmental media:

Soil, water, air, biota (plants and animals), or any other parts of the environment that can contain contaminants.

Environmental media and transport mechanism:

Environmental media include water, air, soil, and biota (plants and animals). Transport mechanisms move contaminants from the source to points where human exposure can occur. The environmental media and transport mechanism is the second part of an exposure pathway.

EPA:

The United States Environmental Protection Agency.

Epidemiologic surveillance:

The ongoing, systematic collection, analysis, and interpretation of health data. This activity also involves timely dissemination of the data and use for public health programs.

Epidemiology:

The study of the distribution and determinants of disease or health status in a population; the study of the occurrence and causes of health effects in humans.

Equilibrium, radioactive:

In a radioactive series, the state that prevails when the ratios between the activities of two or more successive members of the series remain constant.

Exposure:

Contact with a substance by swallowing, breathing, or touching the skin or eyes. Exposure can be short-term [see acute exposure], of intermediate duration [see intermediate-duration exposure], or long-term [see chronic exposure].

Exposure assessment:

The process of finding out how people come into contact with a hazardous substance, how often and for how long they are in contact with the substance, and how much of the substance they are in contact with.

Exposure-dose reconstruction:

A method of estimating the amount of people’s past exposure to hazardous substances. Computer and approximation methods are used when past information is limited, not available, or missing.

Exposure investigation:

The collection and analysis of site-specific information and biological tests (when appropriate) to determine whether people have been exposed to hazardous substances.

Exposure pathway:

The route a substance takes from its source (where it began) to its end point (where it ends), and how people can come into contact with (or get exposed to) it. An exposure pathway has five parts: a source of contamination (such as an abandoned business); an environmental media and transport mechanism (such as movement through groundwater); a point of exposure (such as a private well); a route of exposure (eating, drinking, breathing, or touching), and a receptor population (people potentially or actually exposed). When all five parts are present, the exposure pathway is termed a completed exposure pathway.

Exposure registry:

A system of ongoing follow up of people who have had documented environmental exposures.

Feasibility study:

A study by EPA to determine the best way to clean up environmental contamination. A number of factors are considered, including health risk, costs, and what methods will work well.

Food chain:

An arrangement of organisms within an ecological community according to the order of predation in which each uses the next usually lower member as a food source.

Grand rounds:

Training sessions for physicians and other health care providers about health topics.

Gray (Gy):

The Systeme International unit for the energy absorbed from ionizing radiation, equal to one joule per kilogram.

Groundwater:

Water beneath the earth's surface in the spaces between soil particles and between rock surfaces [compare with surface water].

Half-life (t_½):

The time it takes for half the original amount of a substance to disappear. In the environment, the half-life is the time it takes for half the original amount of a substance to disappear when it is changed to another chemical by bacteria, fungi, sunlight, or other chemical processes. In the human body, the half-life is the time it takes for half the original amount of the substance to disappear either by being changed to another substance or by leaving the body. In the case of radioactive material, the half-life is the amount of time necessary for one half the initial number of radioactive atoms to change or transform into other atoms (normally not radioactive). After two half-lives, 25% of the original number of radioactive atoms remain.

Hazard:

A source of potential harm from past, current, or future exposures.

Hazardous waste:

Potentially harmful substances that have been released or discarded into the environment.

Health consultation:

A review of available information or collection of new data to respond to a specific health question or request for information about a potential environmental hazard. Health consultations are focused on a specific exposure issue. They are therefore more limited than public health assessments, which review the exposure potential of each pathway and chemical [compare with public health assessment].

Health education:

Programs designed with a community to help it know about health risks and how to reduce these risks.

Health investigation:

The collection and evaluation of information about the health of community residents. This information is used to describe or count the occurrence of a disease, symptom, or clinical measure and to estimate the possible association between the occurrence and exposure to hazardous substances.

Health statistics review:

The analysis of existing health information (i.e., from death certificates, birth defects registries, and cancer registries) to determine if there is excess disease in a specific population, geographic area, and time period. A health statistics review is a descriptive epidemiologic study.

Indeterminate public health hazard:

The category used in ATSDR's public health assessment documents when a professional judgment about the level of health hazard cannot be made because information critical to such a decision is lacking.

Incidence:

The number of new cases of disease in a defined population over a specific time period [contrast with prevalence].

Ingestion:

The act of swallowing something through eating, drinking, or mouthing objects. A hazardous substance can enter the body this way [see route of exposure].

Inhalation:

The act of breathing. A hazardous substance can enter the body this way [see route of exposure].

Intermediate-duration exposure:

Contact with a substance that occurs for more than 14 days and less than a year [compare with acute exposure and chronic exposure].

Ionizing radiation:

Any radiation capable of knocking electrons out of atoms and producing ions. Examples: alpha, beta, gamma and x rays, and neutrons.

Isotopes:

Nuclides having the same number of protons in their nuclei, and hence the same atomic number, but differing in the number of neutrons, and therefore in the mass number. Identical chemical properties exist in isotopes of a particular element. The term should not be used as a synonym for "nuclide," because "isotopes" refers specifically to different nuclei of the same element.

Lowest-observed-adverse-effect level (LOAEL):

The lowest tested dose of a substance that has been reported to cause harmful (adverse) health effects in people or animals.

Metabolism:

The conversion or breakdown of a substance from one form to another by a living organism.

mg/kg:

Milligrams per kilogram.

mg/m³:

Milligrams per cubic meter: a measure of the concentration of a chemical in a known volume (a cubic meter) of air, soil, or water.

Migration:

Moving from one location to another.

Minimal risk level (MRL):

An ATSDR estimate of daily human exposure to a hazardous substance at or below which that substance is unlikely to pose a measurable risk of harmful (adverse), noncancerous effects. MRLs are calculated for a route of exposure (inhalation or oral) over a specified time period (acute, intermediate, or chronic). MRLs should not be used as predictors of harmful (adverse) health effects [see reference dose].

Mortality:

Death. Usually the cause (a specific disease, condition, or injury) is stated.

Mutagen:

A substance that causes mutations (genetic damage).

Mutation:

A change (damage) to the DNA, genes, or chromosomes of living organisms.

National Priorities List for Uncontrolled Hazardous Waste Sites (National Priorities List or NPL):

EPA’s list of the most serious uncontrolled or abandoned hazardous waste sites in the United States. The NPL is updated on a regular basis.

No apparent public health hazard:

A category used in ATSDR's public health assessments for sites where human exposure to contaminated media might be occurring, might have occurred in the past, or might occur in the future, but is not expected to cause any harmful health effects.

Noncancerous effects:

Health effects or health endpoints other than cancer, such as cardiovascular disease or genetic effects, that result from exposure to a particular hazardous substance. ATSDR derives health guidelines for noncancerous effects, called minimal risk levels (MRLs), and compares exposure doses to these MRLs. Doses below MRLs are unlikely to cause noncancerous health effects; those above MRLs are evaluated further.

No-observed-adverse-effect level (NOAEL):

The highest tested dose of a substance that has been reported to have no harmful (adverse) health effects on people or animals.

No public health hazard:

A category used in ATSDR's public health assessment documents for sites where people have never and will never come into contact with harmful amounts of site-related substances.

NPL:

[See National Priorities List for Uncontrolled Hazardous Waste Sites.]

Parent:

A radionuclide which, upon disintegration, yields a new nuclide, either directly or as a later member of a radioactive series.

Plume:

A volume of a substance that moves from its source to places farther away from the source. Plumes can be described by the volume of air or water they occupy and the direction in which they move. For example, a plume can be a column of smoke from a chimney or a substance moving with groundwater.

Point of exposure:

The place where someone can come into contact with a substance present in the environment [see exposure pathway].

Population:

A group or number of people living within a specified area or sharing similar characteristics (such as occupation or age).

ppb:

Parts per billion.

ppm:

Parts per million.

Prevalence:

The number of existing disease cases in a defined population during a specific time period [contrast with incidence].

Prevention:

Actions that reduce exposure or other risks, keep people from getting sick, or keep disease from getting worse.

Public comment period:

An opportunity for the public to comment on agency findings or proposed activities contained in draft reports or documents. The public comment period is a limited time period during which comments will be accepted.

Public health action plan:

A list of steps to protect public health.

Public health advisory:

A statement made by ATSDR to EPA or a state regulatory agency that a release of hazardous substances poses an immediate threat to human health. The advisory includes recommended measures to reduce exposure and reduce the threat to human health.

Public health assessment (PHA):

An ATSDR document that examines hazardous substances, health outcomes, and community concerns at a hazardous waste site to determine whether people could be harmed by coming into contact with those substances. The PHA also lists actions that need to be taken to protect public health [compare with health consultation].

Public health hazard:

A category used in ATSDR's public health assessments for sites that pose a public health hazard because of long-term exposures (greater than 1 year) to sufficiently high levels of hazardous substances or radionuclides that could result in harmful health effects.

Public health hazard categories:

Statements about whether people could be harmed by conditions present at the site in the past, present, or future. One or more hazard categories might be appropriate for each site. The five public health hazard categories are no public health hazard, no apparent public health hazard, indeterminate public health hazard, public health hazard, and urgent public health hazard.

Public health statement:

The first chapter of an ATSDR toxicological profile. The public health statement is a summary written in words that are easy to understand. It explains how people might be exposed to a specific substance and describes the known health effects of that substance.

Public meeting:

A public forum with community members for communication about a site.

Quality factor (radiation weighting factor):

The linear-energy-transfer-dependent factor by which absorbed doses are multiplied to obtain (for radiation protection purposes) a quantity that expresses - on a common scale for all ionizing radiation - the approximate biological effectiveness of the absorbed dose.

Rad:

The unit of absorbed dose equal to 100 ergs per gram, or 0.01 joules per kilogram (0.01 gray) in any medium [see dose].

Radiation:

The emission and propagation of energy through space or through a material medium in the form of waves (e.g., the emission and propagation of electromagnetic waves, or of sound and elastic waves). The term "radiation" (or "radiant energy"), when unqualified, usually refers to electromagnetic radiation. Such radiation commonly is classified according to frequency, as microwaves, infrared, visible (light), ultraviolet, and x and gamma rays and, by extension, corpuscular emission, such as alpha and beta radiation, neutrons, or rays of mixed or unknown type, such as cosmic radiation.

Radioactive decay:

Transformation of the nucleus of an unstable nuclide by spontaneous emission of charged particles and/or photons.

Radioactive material:

Material containing radioactive atoms.

Radioactivity:

Spontaneous nuclear transformations that result in the formation of new elements. These transformations are accomplished by emission of alpha or beta particles from the nucleus or by the capture of an orbital electron. Each of these reactions may or may not be accompanied by a gamma photon.

Radioisotope:

An unstable or radioactive isotope (form) of an element that can change into another element by giving off radiation.

Radionuclide:

Any radioactive isotope (form) of any element.

RBC:

Risk-based Concentration, a contaminant concentration that is not expected to cause adverse health effects over long-term exposure.

RCRA:

[See Resource Conservation and Recovery Act (1976, 1984).]

Receptor population:

People who could come into contact with hazardous substances [see exposure pathway].

Reference dose (RfD):

An EPA estimate, with uncertainty or safety factors built in, of the daily lifetime dose of a substance that is unlikely to cause harm in humans.

Rem:

A unit of dose equivalent that is used in the regulatory, administrative, and engineering design aspects of radiation safety practice. The dose equivalent in rem is numerically equal to the absorbed dose in rad multiplied by the quality factor (1 rem is equal to 0.01 sievert).

Remedial investigation:

The CERCLA process of determining the type and extent of hazardous material contamination at a site.

Resource Conservation and Recovery Act (1976, 1984) (RCRA):

This act regulates management and disposal of hazardous wastes currently generated, treated, stored, disposed of, or distributed.

RfD:

[See reference dose.]

Risk:

The probability that something will cause injury or harm.

Route of exposure:

The way people come into contact with a hazardous substance. Three routes of exposure are breathing [inhalation], eating or drinking [ingestion], and contact with the skin [dermal contact].

Safety factor:

[See uncertainty factor.]

Sample:

A portion or piece of a whole; a selected subset of a population or subset of whatever is being studied. For example, in a study of people the sample is a number of people chosen from a larger population [see population]. An environmental sample (for example, a small amount of soil or water) might be collected to measure contamination in the environment at a specific location.

Screening index:

A calculated probability of developing cancer.

Sievert (Sv):

The SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose, in gray, multiplied by the quality factor (1 sievert equals 100 rem).

Solvent:

A liquid capable of dissolving or dispersing another substance (for example, acetone or mineral spirits).

Source of contamination:

The place where a hazardous substance comes from, such as a landfill, waste pond, incinerator, storage tank, or drum. A source of contamination is the first part of an exposure pathway.

Special populations:

People who might be more sensitive or susceptible to exposure to hazardous substances because of factors such as age, occupation, gender, or behaviors (for example, cigarette smoking). Children, pregnant women, and older people are often considered special populations.

Specific activity:

Radioactivity per unit mass of material containing a radionuclide, expressed, for example, as Ci/gram or Bq/gram.

Stakeholder:

A person, group, or community who has an interest in activities at a hazardous waste site.

Statistics:

A branch of mathematics that deals with collecting, reviewing, summarizing, and interpreting data or information. Statistics are used to determine whether differences between study groups are meaningful.

Substance:

A chemical.

Surface water:

Water on the surface of the earth, such as in lakes, rivers, streams, ponds, and springs [compare with groundwater].

Surveillance:

[see epidemiologic surveillance]

Survey:

A systematic collection of information or data. A survey can be conducted to collect information from a group of people or from the environment. Surveys of a group of people can be conducted by telephone, by mail, or in person. Some surveys are done by interviewing a group of people.

Toxicological profile:

An ATSDR document that examines, summarizes, and interprets information about a hazardous substance to determine harmful levels of exposure and associated health effects. A toxicological profile also identifies significant gaps in knowledge on the substance and describes areas where further research is needed.

Toxicology:

The study of the harmful effects of substances on humans or animals.

Uncertainty factor:

A mathematical adjustment for reasons of safety when knowledge is incomplete—for example, a factor used in the calculation of doses that are not harmful (adverse) to people. These factors are applied to the lowest-observed-adverse-effect-level (LOAEL) or the no-observed-adverse-effect-level (NOAEL) to derive a minimal risk level (MRL). Uncertainty factors are used to account for variations in people's sensitivity, for differences between animals and humans, and for differences between a LOAEL and a NOAEL. Scientists use uncertainty factors when they have some, but not all, the information from animal or human studies to decide whether an exposure will cause harm to people [also sometimes called a safety factor].

Units, radiological:

Units	Equivalents
Becquerel* (Bq)	1 disintegration per second = 2.7 × 10-11 Ci
Curie (Ci)	3.7 × 1010 disintegrations per second = 3.7 × 1010 Bq
Gray* (Gy)	1 J/kg = 100 rad
Rad (rad)	100 erg/g = 0.01 Gy
Rem (rem)	0.01 sievert
Sievert* (Sv)	100 rem

*International Units, designated (Systeme International [SI])

Urgent public health hazard:

A category used in ATSDR's public health assessments for sites where short-term exposures (less than 1 year) to hazardous substances or conditions could result in harmful health effects that require rapid intervention.

Watershed:

A watershed is a region of land that is crisscrossed by smaller waterways that drain into a larger body of water.

Other Glossaries and Dictionaries:

Environmental Protection Agency http://www.epa.gov/OCEPAterms/
National Center for Environmental Health (CDC) http://www.cdc.gov/nceh/
National Library of Medicine http://www.nlm.nih.gov/medlineplus/mplusdictionary.html

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