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Health Outcome Data

ATSDR staff look for relevant, site-specific health outcome data (measures of disease occurrence,such as tumor registries and birth defects registries) to see whether diseases are elevated in apopulation exposed to contamination from the site. This presupposes that we have determined thatthe population was exposed or may have been exposed, to environmental contamination at levelsthat could cause adverse health effects.

Exposure information drives all of our health investigations. Without exposures to contamination,there is usually very little we can do with health data. We define exposure as coming in physicalcontact with hazardous materials. Hazardous materials cannot harm anyone unless people eat them,drink them, breathe them, or, in some cases, get them on their skin or come in close proximity tothem; these actions constitute exposures. Often, even when hazardous substances are taken into thebody, they do not cause harm unless they are in sufficient quantities to do so. Therefore, we alwaysconsider whether exposures to hazardous substances are at levels of health concern in theenvironment. Unless they are at levels of health concern, they will not pose a hazard to anyone.

We evaluate whether the numbers of disease cases are elevated in the exposed population bycomparing the disease incidence (new cases in a specified time interval) to the incidence of the samedisease in another population. An elevated incidence rate of a disease in an exposed population mayindicate that environmental contamination caused the disease cases, but it does not prove it. Wecannot fully eliminate the possibility that an increased incidence of a disease in a population may bethe result of other causes.

We do not know of any completed exposure pathways to persistent contamination from the Mound Plant at levels that can cause adverse health effects. However, if we imagine that there were such exposures, we would expect that the highest levels of exposure to releases from the Mound Plant are to people living near the site. Boston University (BU) School of Public Health staff identified and reviewed cancer incidence and cancer mortality data for Montgomery County residents from several sources and cancer mortality data for nine hospitals in the Dayton and Miamisburg area. None of these health outcome data are useful to us for evaluating exposures to environmental contamination near the Mound Plant. This is because we do not have evidence that the entire county population is or was exposed to environmental releases of contamination from the Mound Plant at levels of health concern. The health outcome data that we have come either from the much larger county population or from the population the hospitals serve. In both cases, these are not populations that might have been exposed to contamination originating entirely and exclusively from the Mound Plant. Furthermore, we cannot sort out the data pertaining to the potentially exposed population near the Mound Plant--however we might define the "exposed" population--from the county data because we do not know who was exposed and because the data do not contain sufficient information to allow us to do so.

We are presenting in this appendix a description of each of the health outcome databases that BUstaff identified because members of the community have expressed interest in knowing more aboutthem. The list includes three Mound worker studies that BU staff identified.

Community Health Outcome Data

  1. The 1990 National Cancer Institute (NCI) report Cancer in Populations Living Near Nuclear Facilities [1], compares cancer rates--calculated as standardized mortality ratios, SMRs--for counties near Mound (Butler, Montgomery, and Warren counties) with similar rates for other "control" counties (i.e., Clermont, Clark, Mahoning, Miami, Stark, and Summit counties in Ohio, and Clark and Wayne counties in Indiana). There were few significant differences for the age groups and cancers examined; some of the excesses noted were in the study counties, some in the control counties. There were no apparent differences in childhood leukemias in counties near Mound. In the young adult age range (20-39), there was elevated liver cancer mortality. In the 40-year-old-plus age groups, there was an excess of lung cancer. Because this study is a descriptive study, it is not possible to determine from it whether cancers observed in the three-county area resulted from exposures to contamination from the Mound facility.

  2. We reviewed a report that the Ohio Department of Health (ODH) presented during a DOEpublic meeting in Miamisburg, Ohio, on August 24, 1995 [2]. This report summarized thefirst year (1992) of cancer incidence data from the new Ohio Cancer Incidence SurveillanceSystem (OCISS) for Butler, Montgomery, and Warren counties. There were a number offindings of elevated and decreased rates of different cancers. An excess incidence of lungcancer in Butler and Montgomery counties compared to the numbers expected for Ohio andthe U.S. was notable. The numbers of other cancers were small, and the county-level scaleof the study population makes interpretation of the data difficult. These cancer incidencedata are more helpful than mortality statistics, however, additional years of data and smallergeographic units (zip codes and census tracts) will make these data more informative in thefuture. (Note: The finding that lung cancer is elevated in Montgomery County was alsoreported in the Dayton Daily News on September 12, 1996 [3].)

  3. The Ohio Department of Health (ODH) published cancer mortality rates for 1986-1988 [4]and raw cancer mortality data for 1987-1992 [5]. BU staff calculated mortality rate ratiosfor cancers of interest for Butler and Montgomery counties as compared with rates for Ohiofor both sets of data. They evaluated four primary organ sites: lung, bone, brain, and blood. They did not compare Ohio county rates with rates for the total U.S. population. Only lungcancer mortality rates for Montgomery and Butler Counties exceeded the Ohio rates. Thesefindings are consistent with the initial OCISS results for 1992. These data, however, sufferfrom the usual problems of county-level analyses already noted. Moreover, the datarepresent a very short time interval. These data, therefore, have very limited value in assessing the impact of possible exposure from the Mound Plant on surrounding populations.

  4. The U.S. Centers for Disease Control and Prevention (CDC) maintains cancer mortality data. States--usually state health departments--collect and report the data to the CDC National Center for Health Statistics, using information from death certificates. BU scientists accessed data for Montgomery County through the CDC WONDER (Wideranging ONline Data for Epidemiologic Research) software program. They queried the data for specific types of leukemias most likely related to ionizing radiation exposures, all types except chronic lymphocytic leukemia (CLL) [6]. The age-specific mortality rates from leukemias for every 5-year age group from 0-4 up to 85+ for Montgomery County during the years 1973-1989 are below the corresponding Ohio and U.S. rates [6]. BU scientists also calculated age-adjusted mortality rates (all races, both sexes) for these same types of leukemias in Montgomery County and all of Ohio using the 1970 U.S. Standard Million as the standard population. The age-adjusted mortality rate for Montgomery County was 2.65 per 100,000; for Ohio, it was 6.94 per 100,000. This means that the age-adjusted mortality rate for Montgomery County was 38% of the Ohio rate during the same time period. In comparison with rates for the rest of Ohio or for the U.S. for the years 1973-1989, the Montgomery County leukemia mortality rates are uniformly low.

  5. From 1985 to 1992, the Dayton Area Cancer Association, Inc. collected data on tumorincidence in the Dayton area. Results were presented in separate reports covering 1985, [7],1986-87 [8], 1988-89 [9], and 1990 [10]. All four reports showed similar trends in tumorincidence for the short time intervals examined. The reports were compilations of datapertaining to benign and malignant tumor incidence for 9 of approximately 16 availablehospitals and medical centers in the Dayton, Ohio, area. The authors acknowledged that allarea hospitals did not report to the registry and listed those that did. The data represent 52primary organ sites for tumors by male and female cases. Graphical presentations describethe distribution of malignant cases by county, age/sex, race, tumor stage distribution, andprimary organ site. As expected, the most common cancers constituted the largest number ofcases (lung, breast, colon/rectum, prostate and urinary tract). No rates are given. Becausethe size of the underlying population that gave rise to the cases is unknown, it is impossibleto use these data to make comparisons with rates for other areas in Ohio or with rates for the U.S. population.

  6. BU staff also examined raw data on cancer incidence from one of the hospitals participatingin the Dayton Central Tumor Registry, the Good Samaritan Hospital and Health Center[11]. BU staff received hospital cancer incidence data for residents of Miamisburg andDayton, Ohio, from 1984-1990. They requested these data to identify any cases of the lesscommon radiogenic cancers, not discernible from the Dayton Area Cancer Associationreports. The data did not identify any cancers of interest (bone, leukemia, or brain) for residents living in Miamisburg zip codes.

Mound Worker Studies

One of the great advantages of worker studies is that they provide a population that is easilyidentified and for which the possibility of exposures is more apparent than for the generalpopulation. Such exposures are usually higher than for the general population, making effects easierto see. Also, worker populations are more residentially stable than the general population, making iteasier to follow them for long periods.

On the other hand, workers are, on average, somewhat different than the general population. Thehealthy worker effect refers to the tendency of worker populations to start out healthier than acomparison population of the same age and sex in the general population. This is because those lessfit or less well, on average, do not stay in the stably employed population as readily as more healthypeople. Hence, the general comparison group looks less healthy, at least over the short term, and acomparison of the two groups may result in erroneous conclusions. Similarly, especially sensitivepopulations are not present in worker studies (e.g., few highly sensitive individuals, fewer pregnantwomen, no children or elderly), thus making comparisons with the general population lessinformative than comparisons between populations with more similarities.

There are also problems connected with determining exposures in worker groups. Whenemployment records are used as a proxy for radiation exposure (which was done for the third of thethree studies presented below) and where workers change jobs over time, there is potential formisclassification to occur and to produce a masking of any true effect from exposures.

Another problem with interpreting worker studies involves the necessary time it takes for a diseasesuch as cancer to develop after exposure occurs. Latency periods are typically on the order ofdecades. Observing the worker population "too early" will result in the appearance of no risk when,in fact, there has been insufficient time for the effects of the exposure to appear.

One additional limitation of these studies is that they all utilize mortality data. Mortality data do notaccurately measure the risk of contracting a disease from environmental exposures, because the riskof death from a particular cause is composed of both the risk that a person contracted the disease (thedisease incidence, which we are interested in) and the risk that the person died from that disease andnot from another cause. Because we cannot easily separate these two components of the death rate,using death as a surrogate for contracting a disease may not accurately reflect the health impact fromexposures. Therefore, death rates are not as informative as incidence rates.

BU identified three worker studies, all of them retrospective cohort studies published in 1991. Thestudies classify workers according to exposure categories and compare their death rates from specificmedical conditions with death rates among "unexposed" workers or the state population. Althoughsome of the exposures measured in these studies predate the operations at the present plant site inMiamisburg, we considered the data before 1949 in these studies because the early polonium-210research did occur in the area [12].

Cohort study results are often presented as standardized mortality ratios (SMRs). An SMR is a ratioof actual deaths among the workers to the number "expected" if the death rate among the workerswere the same as that among the reference or control population. ("Standardized" refers to aprocedure to control for one or more confounding factors.) Ratios above 1 mean that more deathsoccurred than were expected, while ratios below 1 mean fewer deaths occurred than were expected. It is customary to multiply the ratio by 100 to avoid decimal points, so an SMR of 100 means thatthe observed deaths were equal to what was expected; values above 100 and below 100 mean observed deaths were more and less than expected, respectively.

  1. A Wiggs et al. study that examined dose-response relationships stated "mortality (for 'allcauses' and 'all cancers') for workers with cumulative radiation doses of at least 10millisieverts (10 mSv, or 1 rem) was not significantly increased when compared with co-workers with cumulative doses of less than 10 mSv" [13]. The authors did note a positivedose-response relationship between deaths from all leukemias and external radiation dose[13]. The one case of CLL was then removed from the analysis (CLL is not considered aradiogenic disease), and a somewhat reduced positive relationship was still suggested [13]. This result was not statistically significant, however, and was based on a single remainingcase of leukemia in the highest exposure group. In summary, specific diseases were elevated in some Mound workers, but these elevations could not be differentiated from chance variation.

  2. The polonium-210 study by Wiggs et al. [14] was a cohort study of white males designed totest the association between mortality and exposure to polonium-210. The SMR wassignificantly elevated for lung cancer in workers employed during 1944 and 1945 [14]. Otherwise, the SMR for deaths due to all causes was significantly less than 100 (SMR=93) suggesting that there was a strong healthy worker effect [14].

  3. The report by Reyes et al.[15] was a cohort study testing the association between mortalityand employment at the Mound Laboratory. The researchers computed SMRs based on U.S.mortality rates. They observed SMRs of 96 for "all causes" and "all cancers" over the entirestudy period (1943-1979), 4% fewer than the numbers they expected [15]. Results variedsomewhat for shorter time periods examined separately. A significantly elevated SMR forlung cancer was observed for workers employed during 1943-1945 (during World War II)[15]. This result is consistent with that found by Wiggs et al. [14]. "All cancersinclusively," "cancers of the rectum," "nonmalignant respiratory diseases," "all causes ofdeath," and "all injuries" were also significantly elevated during World War II [15]. SMRsfor these causes of death were not elevated during the remainder of the polonium-210 era,1946-1959 [15]. The researchers found no elevated SMRs from 1960-1980 [15]. However, there was a very strong healthy worker effect observed during this period [15].

In summary, worker studies at the Mound Plant have revealed some differences in mortality whencompared with rates for the general population, but difficulties typical of such studies makeinterpretation, of both revealed differences and lack of differences, hard to interpret. We thereforedo not feel that theses studies are informative concerning any risks encountered by communitiessurrounding the Mound Plant.

Future Studies

For several years, some members of the community around the Mound Plant (primarily members ofMiamisburg Environmental Safety and Health (M.E.S.H.) expressed great interest in havingATSDR staff conduct a neighborhood health survey. ATSDR scientists have not conducted a healthsurvey, and we do not plan to. However, because of the community members' interest in a healthsurvey, ATSDR staff provided educational support to those people who have expressed this interest. Staff from BU met with members of M.E.S.H. in December 1995 to discuss issues to consider whendesigning and executing a neighborhood survey [16]. Community members are now planning tocollect health information in the neighborhood around the Mound Plant. Members of M.E.S.H.continue to report their progress to the general Department of Energy (DOE) Mound ActionCommittee meetings.

Neighborhood health data can reveal where and how often diseases in the population occur; they canalso be compared with health data for other populations. This information may be of generalinterest to the community and to the county and state health departments. However, we do notbelieve health survey data help us to assess the effects of contamination from the Mound Plant. Thisis because of the reasons previously explained-difficulties with identifying an exposed populationand problems with controlling for other exposures.

Some workers at the Mound Plant also expressed a strong interest in seeing a worker health studyconducted so that the health effects to Mound workers who have been exposed to high levels ofradiation could be documented in the medical literature. This suggestion has scientific merit,particularly for those workers exposed to tritium or polonium-210, because there is limited healthinformation regarding exposures to these radionuclides in humans. Presently, ATSDR staff do nothave recommendations to conduct Mound worker studies because worker exposures have not been afocus of our work. However, scientists from the CDC National Institute of Occupational Safety andHealth are considering further studies of Mound workers exposed to polonium-210 to better assessthe overall risks to internal alpha emitters. The Mound polonium workers are a good population to study because their exposures are well-documented.


  1. Jablon S, Hrubec Z, Boice JD, Stone BJ. Cancer in populations living near nuclear facilities. National Institutes of Health, National Cancer Institute, Division of Cancer Etiology, Epidemiology and Biostatistics Program. NIH 90-874:1990 Jul.

  2. Indian RW. Brief remarks regarding cancer incidence among residents of Butler,Montgomery, and Warren Counties, 1992. Ohio Department of Health, Chronic andEnvironmental Disease Surveillance Section. 1995 Aug 24.

  3. Bennish S. Cancer haunts county. Dayton Daily News. 1996 Sep12.

  4. Ohio Department of Health. Cancer mortality rates in Ohio, 1986 - 88. 1988.

  5. Ohio Department of Health. Cancer mortality rates in Ohio counties, 1987 - 1992 (raw tabular data). 1992.

  6. Centers for Disease Control and Prevention, National Center for Health Statistics. Multiple cause of mortality data set, accessed by the Wide-ranging ONline Data for Epidemiologic Research (CDC WONDER) software program.

  7. Dayton Area Cancer Association. Central registry report, year 1985.

  8. Dayton Area Cancer Association. A report of the Dayton Area Central Tumor Registry: cancer in the Miami Valley, 1986 - 1987.

  9. Dayton Area Cancer Association. Cancer data for the Miami Valley - report: 1988 - 1989.

  10. Dayton Area Cancer Association. A report of the Dayton Area Central Tumor Registry: cancer in the Miami Valley, 1990.

  11. Good Samaritan Hospital and Health Center, oncology data report for Miamisburg andDayton, Ohio for 1994, raw data report.

  12. Shook H, Williams JM. The bomb: it wasn't always fun and games at the Playhouse. The Magazine, Dayton Daily News. 1983 Sep 18. Also; the Dayton Herald. 1945 Aug 7.

  13. Wiggs LD, Cox-DeVore CA, Wilkinson GS, Reyes M. Mortality among workers exposed toexternal ionizing radiation at a nuclear facility in Ohio. J Occup Med 1991;33 (5):632-7.

  14. Wiggs LD, Cox-DeVore CA, Voelz GL. Mortality among a cohort of workers monitored for Po-210 exposure: 1944-1972. Health Phys 1991 Jul;61(1):71-6. Also cited in: U.S. DOE, Comprehensive epidemiological data resource guidance manual (CEDR). 1995. DOE/EH-0339, Revision 1.

  15. Reyes, M., G. S. Wilkinson, G. L. Tietjen, L. D. Wiggs, and W. A. Galke. Mortality among workers at the Mound Facility: a preliminary report. Los Alamos Report LA-11997-MS; 1991 Apr. Also cited in: US DOE, Comprehensive epidemiological data resource guidance manual (CEDR), DOE/EH-0339, Revision 1, 1995.

  16. Meeting, Miamisburg Environmental Safety and Health (M.E.S.H.) members and Boston University staff, Miamisburg, Ohio. 1995 Dec 8.


Absorbed Dose:
Absorbed dose is the amount of energy deposited in any material by ionizing radiation. The unit of absorbed dose, the rad, is a measure of energy absorbed per gram of material. The unit used in countries other than the U.S. is the gray (abbreviated, Gy). One gray equals 100 rad.

The process of taking in, as when a sponge takes up water. Chemicals can be absorbed through the skin into the bloodstream and then transported to other organs. Chemicals can also be absorbed into the bloodstream after breathing or swallowing.

Occurring over a short time, usually a few minutes or hours. An acute exposure can result in short-term or long-term health effects. An acute effect happens a short time (up to 1 year) after exposure.

The guiding principle behind radiation protection is that radiation exposures should be kept "As Low As Reasonably Achievable" (ALARA), economic and social factors being taken into account. This common sense approach means that radiation doses for both workers and the public are typically kept lower than their regulatory limits.

Alpha Particle:
Alpha particles are composed of two protons and two neutrons. Alpha particles do not travel very far from their radioactive source. They cannot pass through a piece of paper, clothes or even the layer of dead cells which normally protects the skin. Because alpha particles cannot penetrate human skin they are not considered an "external exposure hazard" (this means that if the alpha particles stay outside the human body they cannot harm it). However, alpha particle sources located within the body may pose an "internal" health hazard if they are present in great enough quantities. The risk from indoor radon is due to inhaled alpha particle sources which irradiate lung tissue.

Surrounding. For example, ambient air is usually outdoor air (as opposed to indoor air).

A chemical component of a sample to be determined or measured. For example, if the analyte is mercury, the laboratory test will determine the amount of mercury in the sample.

Analytic Epidemiologic Study:
Investigations designed to evaluate the causal nature of associations between exposure to hazardous substances and disease outcome by testing scientific hypotheses.

Applied Research:
An investigative study in which the results are used in actual practice.

Agency for Toxic Substances and Disease Registry. An agency of the U.S. Department of Health and Human Services.

Background Level:
A typical or average level of a chemical in the environment. Background often refers to naturally occurring or uncontaminated levels.

Background Radiation:
Radiation is a part of our natural world. People have always been exposed to radiation that originates from within the Earth ("terrestrial" sources) and from outer space ("cosmogenic" or "galactic" sources).

A unit of radioactivity equal to one disintegration per second (1 dps); abbreviated, Bq. A becquerel is approximately equal to 27 picocuries (27 pCi).

Beta Particle:
Beta particles are similar to electrons except they come from the atomic nucleus and are not bound to any atom. Beta particles cannot travel very far from their radioactive source. For example, they can travel only about one half an inch in human tissue, and they may travel a few yards in air. They are not capable of penetrating something as thin as a book or a pad of paper.

Biological Indicators of Exposure Study:
A study designed to use biomedical testing or the measurement of a chemical (analyte), its metabolite, or another marker of exposure in human body fluids or tissues to validate human exposure to a hazardous substance.

Biological Monitoring:
Measuring chemicals in biological materials (blood, urine, breath, etc.) to determine whether chemical exposure in humans, animals, or plants has occurred.

Biological Uptake :
The transfer of hazardous substances from the environment to plants, animals, and humans. This may be evaluated through environmental measurements, such as measurement of the amount of the substance in an organ known to be susceptible to that substance. More commonly, biological dose measurements are used to determine whether exposure has occurred. The presence of a contaminant, or its metabolite, in human biologic specimens, such as blood, hair, or urine, is used to confirm exposure and can be an independent variable in evaluating the relationship between the exposure and any observed adverse health effects.

Biomedical Testing:
Biological testing of persons to evaluate a qualitative or quantitative change in a physiologic function that may be predictive of a health impairment resulting from exposure to hazardous substance(s).

Body Burden:
The total amount of a chemical in the body. Some chemicals build up in the body because they are stored in fat or bone or are eliminated very slowly.

Any substance that may produce cancer.

Case Study:
The medical or epidemiologic evaluation of a single person or a small number of individuals to determine descriptive information about their health status or potential for exposure through interview or biomedical testing.

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, also known as Superfund. This is the legislation that created ATSDR.

Comprehensive Environmental Response, Compensation, and Liability Information System. The EPA database that tracks Superfund sites.

Occurring over a long period of time (more than 1 year).

Cluster Investigation:
A review of an unusual number, real or perceived, of health events (for example, reports of cancer) grouped together in time and location. Cluster investigations are designed to confirm case reports; determine whether they represent an unusual disease occurrence; and, if possible, explore possible causes and environmental factors.

Community Assistance Panel (CAP):
Community assistance panels are established to (1) facilitate constructive communication between ATSDR and the affected community; (2) provide an ongoing series of community-based meetings to ensure community involvement throughout the range of ATSDR public health activities at a site; and (3) provide information to ATSDR on the community's health concerns for inclusion in the public health assessment.

Comparison Values:
Estimated contaminant concentrations in specific media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. The comparison values are calculated from the scientific literature available on exposure and health effects.

The amount of one substance dissolved or contained in a given amount of another. For example, sea water contains a higher concentration of salt than fresh water.

Any substance or material that enters a system (the environment, human body, food, etc.) where it is not normally found.

A unit of radioactivity; abbreviated, Ci. A curie is equal to 3.7 x 1010 becquerels. A picocurie (pCi) is equal to 1 x 10-12 curie.

Referring to the skin. Dermal absorption means absorption through the skin.

Descriptive Epidemiology:
Study of the amount and distribution of disease within a population by person, place, and time.

Disease- and Symptom-Prevalence Study:
A study designed to measure the occurrence of self-reported disease that may, in some instances, be validated through medical records or physical examination. This study design can only be considered hypothesis generating. Adverse health conditions that are considered to have been reported at an excess rate may require further investigation.

Disease Registry:
A system for collecting and maintaining in a structured record, information on persons having a common illness or adverse health condition.

The U.S. Department of Energy.

The amount of substance to which a person is exposed. Dose often takes body weight into account (e.g., milligrams per kilogram body weight, mg/kg).
Radiation dose is simply the quantity of radiation energy deposited in a material. The effect that radiation has on any material is determined by the "dose" of radiation that the material receives. See also Absorbed Dose.

Dose Reconstruction:
An approach that uses computational models and other approximation techniques to estimate cumulative amounts of hazardous substances internalized by people.

Wastewater--treated or untreated--that flows out of a treatment plant, sewer, or industrial outfall. Effluent generally refers to wastes discharged into surface waters.

Environmental contamination:
The presence of hazardous substances in the environment. From the public health perspective, environmental contamination is addressed when it potentially affects the health and quality of life of people living and working near the contamination.

The U.S. Environmental Protection Agency.

Epidemiologic Surveillance:
The ongoing, systematic collection, analysis, and interpretation of health data and the timely dissemination of these data to those who need to know. The final link in the surveillance chain is the application of these data to prevention and control.

The study of the occurrence and causes of health effects in human populations. An epidemiological study often compares two groups of people who are alike except for one factor, such as exposure to a chemical or the presence of a health effect. The investigators try to determine if any factor is associated with the health effect.

Equivalent Dose:
The equivalent dose is a measure of the effect which radiation has on humans. The concept of equivalent dose involves the impact that different types of radiation have on humans. Not all types of radiation produce the same effect in humans. The equivalent dose takes into account the type of radiation and the absorbed dose. For example when considering beta, x-ray, and gamma ray radiation, the equivalent dose (expressed in sieverts or rems) is equal to the absorbed dose (expressed in grays or rads). For alpha radiation, the equivalent dose is assumed to be twenty times the absorbed dose.

Contact with a chemical by swallowing, breathing, or by direct contact (such as through the skin or eyes). Exposure may be short term (acute) or long term (chronic).
Radiation exposure is a measure of the amount of ionization produced by x-rays or gamma rays as they travel through air. The unit of radiation exposure is the roentgen (R), named for Wilhelm Roentgen, the German scientist who in 1895 discovered x-rays.

Exposure Investigation:
The collection and analysis of site-specific information to determine if human populations have been exposed to hazardous substances. The site-specific information may include environmental sampling, exposure-dose reconstruction, biologic or biomedical testing, and evaluation of medical information. The information from an exposure investigation is included in public health assessments, health consultations, and public health advisories.

Exposure Registry:
A system for collecting and maintaining in a structured record, information on persons with documented environmental exposure(s). The exposure registry evolved from the need for fundamental information concerning the potential impact on human health of long-term exposure to low and moderate levels of hazardous substances.

Gamma Rays:
Gamma rays are an example of electromagnetic radiation, as is visible light. Gamma rays originate from the nucleus of an atom. They are capable of traveling long distances through air and most other materials. Gamma rays require more "shielding" material, such as lead or steel, to reduce their numbers than is required for alpha and beta particles.

Geographic Information System (GIS):
A computer hardware and software system designed to collect, manipulate, analyze, and map referenced data for solving complex resource, environmental, and social problems.

See Absorbed Dose.

The time required for a population of atoms of a given radionuclide to decrease, by radioactive decay, to exactly one-half of its original number is called the radionuclide's half-life. No operation, either chemical or physical, can change the decay rate of a radioactive substance. Half-lives range from much less than a microsecond to more than a billion years. The longer the half-life the more stable the nuclide. After one half-life, half the original atoms will remain; after two half-lives, one fourth (or 1/2 of 1/2) will remain; after three half-lives one eighth of the original number (1/2 of 1/2 of 1/2) will remain; and so on.

A source of risk that does not necessarily imply potential for occurrence. A hazard produces risk only if an exposure pathway exists, and if exposures create the possibility of adverse consequences.

Hazardous Substances and Health Effects Database (HazDat):
The scientific database developed by ATSDR to manage data collection, retrieval, analysis, and utilization through the sophisticated technologies provided by computerization. HazDat allows ATSDR to locate information on the release of hazardous substances into the environment, and to ascertain the effects of hazardous substances on health with improved uniformity, efficiency, and precision.

Health Consultation:
A response to a specific question or request for information pertaining to a hazardous substance or facility (which includes waste sites). It may contain a time-critical element that necessitates a rapid response; therefore, it is a more limited response than an assessment.

Health Education:
A program of activities to promote health and provide information and training about hazardous substances in the environment that will result in the reduction of exposure, illness, or disease. This program--both national and site-specific in focus--includes diagnosis and treatment information for health care providers and activities in communities to enable them to prevent or mitigate the health effects from exposure to hazardous substances at hazardous waste sites.

Health Investigation:
Any investigation of a defined population, using epidemiologic methods, which would assist in determining exposures or possible public health impact by defining health problems requiring further investigation through epidemiologic studies, environmental monitoring or sampling, and surveillance.

Health Outcome Data:
A major source of data for public health assessments. The identification, review, and evaluation of health outcome parameters are interactive processes involving the health assessors, data source generators, and the local community. Health outcome data are community specific and may be derived from databases at the local, state, and national levels, as well as from data collected by private health care organizations and professional institutions and associations. Databases to be considered include morbidity and mortality data, birth statistics, medical records, tumor and disease registries, surveillance data, and previously conducted health studies.

Health Outcomes Study:
An investigation of exposed persons designed to assist in identifying health effects in specific populations. Health studies also define the health problems that require further inquiry by means of, for example, a health surveillance or epidemiologic study.

Health Professional Education:
Any activity or activities directed toward public health professionals and the local medical community. The purpose of this activity is to improve the knowledge, skill, and behavior of health professionals concerning medical surveillance, screening, and methods of diagnosing, treating, and preventing injury or disease related to exposure to hazardous substances. These activities may include immediately disseminating written materials or making database information available, presenting workshops and short courses, or, where appropriate, long-term follow-up activities.

Health Statistics Review:
Evaluation of information and relevant health outcome data for an involved population, including reports of injury, disease, or death in the community. Databases may be local, state, or national; information from private health care providers and organizations may also be used. Databases may include morbidity and mortality data, tumor and disease registries, birth statistics, and surveillance data.

Health Surveillance:
The periodic medical screening of a defined population for a specific disease or for biological markers of disease for which the population is, or is thought to be, at significantly increased risk. The program should include a mechanism to refer for treatment those persons who test positive for disease (also called Medical Monitoring).

The International Commission on Radiological Protection.

Ions are atoms with unequal numbers of electrons and protons, and which, therefore, have an electric charge. If an atom has more electrons than protons, it has a negative charge, and is called a negative ion. Atoms which have fewer electrons than protons are positively charged, and are called positive ions.

Ionizing Radiation:
Ionizing radiation is radiation which has enough energy to cause atoms to lose electrons and become ions. Alpha and beta particles, as well as gamma and x-rays, are all examples of ionizing radiation. Infrared and visible light are examples of nonionizing radiation.

Swallowing (such as eating or drinking). Chemicals can get in or on food, drink, utensils, cigarettes, or hands where they can be ingested. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.

Breathing. Exposure may occur from inhaling contaminants because they can be deposited in the lungs, taken into the blood, or both.

Maximum Contaminant Level. The EPA maximum permissible level of a contaminant in water delivered to any user of a public water system.

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

Medical Monitoring:
The periodic medical testing to screen people at significant increased threat of disease.

All the chemical reactions that enable the body to work. For example, food is metabolized (chemically changed) to supply the body with energy. Chemicals can be metabolized and made either more or less harmful by the body.

Any product of metabolism.

Minimal Risk Level (MRL):
An MRL is defined as an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (noncancer) over a specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration via a given route of exposure. MRLs are based on noncancer health effects only. MRLs can be derived for acute, intermediate, and chronic duration exposures by the inhalation and oral routes.

Illness or disease. Morbidity rate is the number of illnesses or cases of disease in a population in a given period of time (usually one year).

National Exposure Registry:
A listing of persons exposed to hazardous substances. This listing is composed of chemical-specific subregistries. The primary purpose of the registry program is to create a large database of similarly exposed persons. This database is to be used to facilitate epidemiology research in ascertaining adverse health effects of persons exposed to low levels of chemicals over a long period.

National Priorities List (NPL):
The Environmental Protection Agency's (EPA) listing of sites that have undergone preliminary assessment and site inspection to determine which locations pose immediate threat to persons living or working near the release. These sites are most in need of cleanup.

National Toxicology Program (NTP):
NTP conducts toxicological testing on those substances most frequently found at sites on the National Priorities List of the EPA, and which also have the greatest potential for human exposure.

The National Council on Radiation Protection and Measurements.

No Apparent Public Health Hazard:
Sites where human exposure to contaminated media is occurring or has occurred in the past, but the exposure is below a level of health hazard.

No Public Health Hazard:
Sites for which data indicate no current or past exposure or no potential for exposure and therefore no health hazard.

Petitioned Public Health Assessment:
A public health assessment conducted at the request of a member of the public. When a petition is received, a team of environmental and health scientists is assigned to gather information to ascertain, using standard public health criteria, whether there is a reasonable basis for conducting a public health assessment. Once ATSDR confirms that a public health assessment is needed, the petitioned health assessment process is essentially the same as the public health assessment process.

Pilot Health Study:
Any investigation of exposed individuals, using epidemiologic methods, which would assist in determining exposures or possible public health impacts by defining health problems requiring further investigation through epidemiologic studies, environmental monitoring or sampling, surveillance, or registries.

An area of chemicals in a particular medium, such as air or groundwater, moving away from its source in a long band or column. A plume can be a column of smoke from a chimney or chemicals moving with groundwater.

Potential/Indeterminate Public Health Hazard:
Sites for which no conclusions about public health hazard can be made because data are lacking.

Potentially Exposed:
The condition where valid information, usually analytical environmental data, indicates the presence of contaminant(s) of a public health concern in one or more environmental media contacting humans (i.e., air, drinking water, soil, food chain, surface water), and there is evidence that some of those persons have an identified route(s) of exposure (i.e., drinking contaminated water, breathing contaminated air, having contact with contaminated soil, or eating contaminated food).

Public Availability Session:
An informal, drop-by meeting at which community members can meet one-on-one with ATSDR staff members to discuss health and site-related concerns.

Public Comment:
An opportunity for the general public to comment on Agency findings or proposed activities. The public health assessment process, for example, includes the opportunity for public comment as the last step in the draft phase. The purposes of this activity are to 1) provide the public, particularly the community associated with a site, the opportunity to comment on the public health findings contained in the public health assessment, 2) evaluate whether the community health concerns have been adequately addressed, and 3) provide ATSDR with additional information.

Public Health Action:
Designed to prevent exposures and/or to mitigate or prevent adverse health effects in populations living near hazardous waste sites or releases. Public health actions can be identified from information developed in public health advisories, public health assessments, and health consultations. These actions include recommending the separation of individuals from exposures (for example, by providing an alternative water supply), conducting biologic indicators of exposure studies to assess exposure, and providing health education for health care providers and community members.

Public Health Advisory:
A statement by ATSDR containing a finding that a release of hazardous substances poses a significant risk to human health and recommending measures to be taken to reduce exposure and eliminate or substantially mitigate the significant risk to human health.

Public Health Assessment:
The evaluation of data and information on the release of hazardous substances into the environment in order to assess any current or future impact on public health, develop health advisories or other recommendations, and identify studies or actions needed to evaluate and mitigate or prevent human health effects; also, the document resulting from that evaluation.

Public Health Hazard:
Sites that pose a public health hazard as the result of long-term exposures to hazardous substances.

Public Health Statement:
The first chapter of an ATSDR toxicological profile. It is intended to be a health effects summary written in lay language for the general public, especially people living in the vicinity of a hazardous waste site or chemical release.

See Absorbed Dose.

Radiation is energy in the form of waves or particles. Radiation comes from sources such as radioactive material or from equipment such as X-ray machines, or accelerators.
X-rays and gamma rays are electromagnetic waves of radiation, as is visible light. Particulate radiation includes alpha and beta particles. The energy associated with any radiation can be transferred to matter. This transfer of energy can remove electrons from the orbit of atoms leading to the formation of ions. The types of radiation capable of producing ions in matter are collectively referred to as "ionizing radiation".

Radioactive Decay:
Radioactive decay describes the process where an energetically unstable atom transforms itself to a more energetically favorable, or stable, state. The unstable atom can emit ionizing radiation in order to become more stable. This atom is said to be "radioactive", and the process of change is called "radioactive decay".

A system for collecting and maintaining, in a structured record, information on specific persons from a defined population.

A radiation unit for equivalent dose. One rem is equal to 1 x 10-2 sievert. One millirem (mrem) is equal to one one-thousandth (10-3) of a rem.

The process of cleaning up a contaminated site.

In many health fields, risk means the probability of incurring injury, disease, or death. In risk assessment, risk is the probability that something will cause injury, combined with the potential severity of that injury. Risk can be expressed as a value that ranges from zero (no injury or harm will occur) to one (harm or injury will definitely occur).

Risk Communication:
Activities to ensure that messages and strategies designed to prevent exposure, adverse human health effects, and diminished quality of life are effectively communicated to the public. As part of a broader prevention strategy, risk communication supports education efforts by promoting public awareness, increasing knowledge, and motivating individuals to take action to reduce their exposure to hazardous substances or situations.

Route of Exposure:
The way in which a person may contact a chemical substance. For example, drinking (ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.

Significant Health Risk:
Circumstances where people are being or could be exposed to hazardous substances at levels that pose an urgent public health hazard or a public health hazard. ATSDR generally issues public health advisories when urgent public health hazards have been identified.

Site-Specific Surveillance:
Epidemiologic surveillance activity designed to assess the specific occurrence of one or more defined health conditions among a specific population potentially exposed to hazardous substances in the environment.

Substance-Specific Applied Research:
A program of research designed to fill data needs. Activities may include laboratory and other studies to determine short-term, intermediate, and long-term health effects from human exposure to a given substance; laboratory and other studies to determine organ-, site-, and system-specific acute and chronic toxicity; laboratory and other studies to determine the manner in which a substance is metabolized or to develop an understanding of the biokinetics of the substance; and, where there is the possibility of obtaining human exposure data, collecting that information.

Another name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), which created ATSDR.

Superfund Amendments and Reauthorization Act (SARA):
The 1986 legislation that broadened ATSDR's responsibilities in the areas of public health assessments, establishment and maintenance of toxicologic databases, information dissemination, and medical education.

Surveillance Activities:
Those activities that evaluate exposure or trends in adverse health effects over a specified period of time. Surveillance activities address the ongoing systematic collection, analysis, and interpretation of health data in the process of describing and monitoring a health event. Data obtained through surveillance are very important for appropriate decisions regarding the planning, evaluation, or implementation of public health interventions.

Technical Assistance:
A technical assist is a written or an oral response to requests for technical information and public health recommendations. This information is frequently incorporated into a health consultation.

Toxicological Profile:
A document about a specific substance in which ATSDR scientists interpret all known information on the substance and specify the levels at which people may be harmed if exposed. The toxicological profile also identifies significant gaps in knowledge on the substance, and serves to initiate further research, where needed.

Urgent Public Health Hazard:
Sites that pose a serious risk to the public health as the result of short-term exposures to hazardous substances.

Volatile organic compounds (VOCs):
Substances containing carbon and different proportions of other elements such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen; these substances easily become vapors or gases. A significant number of the VOCs are commonly used as solvents (paint thinners, lacquer thinner, degreasers, and dry cleaning fluids).

Voluntary Residents Tracking System:
A collection of persons who are contacted periodically, for a limited time, for the purpose of disseminating information or of coordinating other health-related services.

X-rays are an example of electromagnetic radiation which arises as electrons are deflected from their original paths or inner orbital electrons change their orbital levels around the atomic nucleus. X-rays and gamma rays are capable of traveling long distances through air and most other materials. Like gamma rays, X-rays require more shielding to reduce their intensity than do beta or alpha particles. X- and gamma rays differ primarily in their origin: x-rays originate in the electronic shell, gamma rays originate in the nucleus.

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