Radiation dose reconstruction refers to the process of estimating radiation doses that were received by individuals or populations in the past as a result of particular exposure situations of concern. [1] The basic principle of radiation dose reconstruction is to characterize the radiation environment to which individuals have been exposed using available information. In cases where radiation exposures can not be fully characterized based on available data, default values based on reasonable scientific assumptions can be used as substitutes. The extent to which the default values are used depends on the purpose of the reconstruction(s) being undertaken.
The methods and techniques used in dose reconstructions have been growing and evolving rapidly. It wasn’t until the late 1970s that dose reconstruction emerged as a scientific discipline [2] and it has been used in practice in the United States for the last two decades. [3] The scientific methods and practices used to complete dose reconstructions are often based on the standards published by international consensus organizations such as the International Commission on Radiological Protection. [2]
When conducted properly, dose reconstruction is a scientifically valid process for estimating radiation dose received by an individual or group of individuals. It is commonly used in occupational epidemiological studies to determine the amount of radiation workers may have received as part of their employment. For these types of studies, dose reconstruction is similar to the process of estimating how much radiation current workers receive, for example at a nuclear facility, except dose reconstructions evaluate past exposures. The terms historical and retrospective often are used to describe a dose reconstruction. [3] Dose estimation is the term sometimes used to describe the process used to determine radiation exposures to current populations or individuals.
Dose reconstruction methods have also commonly been applied in environmental settings to assess radionuclide releases into the environment from nuclear sites. One such environmentally focused study was published in 1983 by the U.S. Nuclear Regulatory Commission entitled Radiological Risk Assessment: A Textbook on Environmental Dose Analysis. This book was updated with major revisions in 2008 and it details the steps of radiological assessments, which uses similar methods and techniques as a dose reconstruction. [4]
Dose reconstruction methods are not limited to just measuring exposures to radiation. Dose reconstruction principles can be used to reconstruct exposures to other hazardous materials and to determine the health effects of those toxins to populations or individuals.
The dose reconstruction process has several basic elements, which have been identified as follows:
Basic element | Summary description |
---|---|
Definition of exposure scenarios | Activities of individuals in areas where radiation exposure could occur and characteristics of radiation environment in those areas |
Identification of exposure pathways | Relevant pathways of external and internal exposure |
Development and implementation of methods of estimating dose | Data, assumptions, and methods of calculation used to estimate dose from relevant exposure pathways in assumed scenarios |
Evaluation of uncertainties in estimates of dose | Evaluation of effects on estimated dose of uncertainties in assumed exposure scenarios and uncertainties in models and data used to estimate dose in assumed scenarios, to obtain expression of confidence in estimated dose |
Presentation and interpretation of results | Documentation of assumptions and methods of estimating dose and discussion of results in context of purpose of dose reconstruction |
Quality assurance and quality control | Systematic and auditable documentation of dose reconstruction process and results |
Summary of Basic Elements of Dose Reconstruction Process as found in A Review of the Dose Reconstruction Program of the Defense Threat Reduction Agency [1]
Radiation dose reconstruction methods are used to a large extent in occupational, environmental, and medical epidemiological research studies. The Centers for Disease Control and Prevention (CDC) has been involved in several dose reconstruction projects.
Several CDC agencies are involved in dose reconstruction projects: the Agency for Toxic Substances and Disease Registry (ATSDR), the National Center for Environmental Health (NCEH), and the National Institute for Occupational Safety and Health (NIOSH).
The Agency for Toxic Substances and Disease Registry (ATSDR) conducts dose reconstructions in relation to work done at Superfund sites. ATSDR defines exposure-dose reconstruction as an approach that uses computational models and other approximation techniques to estimate cumulative amounts of hazardous substances internalized by individuals presumed to be or who are actually at risk from contact with substances associated with hazardous waste sites.
In March 1993, ATSDR established the Exposure-Dose Reconstruction Program (EDRP). EDRP represents a coordinated, comprehensive effort to develop sensitive, integrated, science-based methods for improving health scientists’ and assessors’ access to current and historical exposure-dose characterization. EDRP was created to confront the challenge that faced health scientists and assessors who have not always had access to information-especially historical information regarding an individual’s direct measure of exposure to and dose of chemicals associated with hazardous waste sites. [5]
The National Center for Environmental Health (NCEH) coordinates program and conducts environmental epidemiological health studies using dose reconstruction principles. NCEH has undertaken a series of studies to assess the possible health consequences of off-site emissions of radioactive materials from DOE-managed nuclear facilities in the United States. [6] Dose reconstruction as used by NCEH is defined as the process of estimating doses to the public from past releases to the environment of radionuclides or chemicals. These doses form the basis for estimating health risks. Past exposures are the focus of the NCEH studies. [6]
The National Institute for Occupational Safety and Health (NIOSH) completes dose reconstructions as a component of ongoing worker health studies. The NIOSH Occupational Energy Research Program’s mission is to conduct relevant, unbiased research to identify and quantify health effects among workers exposed to ionizing radiation and other agents; to develop and refine exposure assessment methods; to effectively communicate study results to workers, scientists, and the public; to contribute scientific information for the prevention of occupational injury and illness; and to adhere to the highest standards of professional ethics and concern for workers’ health, safety and privacy. [7]
One of the largest mass applications of individual dose reconstruction principles is also being undertaken by NIOSH. NIOSH is the designated agency responsible for completing radiation dose reconstructions for individuals under the Energy Employees Occupational Illness Compensation Program of 2000 (the Act). Under the Act, individuals, and in some cases their survivors, are eligible for compensation for specified illnesses they received from occupational exposures to beryllium, asbestos, toxic materials, and radiation if they worked at a covered Department of Energy (DOE) facility or a facility that contracted with DOE to produce nuclear weapons or components, known as Atomic Weapons Employers (AWE). The program is administered by the Department of Labor. NIOSH’s responsibility under the Act is to determine the probability that an individual’s cancer was a result of their occupational radiation exposure at a DOE or AWE facility. This probability is determined by DOL and is based on the radiation dose reconstruction completed by NIOSH. The dose reconstructions are completed by individuals trained in the field of health physics.
The science behind the NIOSH dose reconstruction process has been published in the peer-reviewed professional journal Health Physics: The Radiation Safety Journal in July 2008. This edition of the Journal was dedicated entirely to the NIOSH Radiation Dose Reconstruction Program.
The Department of Veterans Affairs uses dose reconstructions to process claims under the Nuclear Test Personnel Review (NTPR) program. The NTPR is a Department of Defense program that works to confirm veteran participation in U.S. atmospheric nuclear tests from 1945 to 1962, and the occupation forces of Hiroshima and Nagasaki, Japan. If the veteran is a confirmed participant of these events, NTPR may provide either an actual or estimated radiation dose received by the veteran. The Defense Threat Reduction Agency completes the dose reconstructions for the NTPR program.
The sievert is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing radiation, which is defined as the probability of causing radiation-induced cancer and genetic damage. The sievert is important in dosimetry and radiation protection. It is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dose measurement and research into the biological effects of radiation.
Berylliosis, or chronic beryllium disease, is a chronic allergic-type lung response and chronic lung disease caused by exposure to beryllium and its compounds, a form of beryllium poisoning. It is distinct from acute beryllium poisoning, which became rare following occupational exposure limits established around 1950. Berylliosis is an occupational lung disease.
Chlordane, or chlordan, is an organochlorine compound that was used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was banned 10 years earlier for food crops like corn and citrus, and on lawns and domestic gardens.
The Agency for Toxic Substances and Disease Registry (ATSDR) is a federal public health agency within the United States Department of Health and Human Services. The agency focuses on minimizing human health risks associated with exposure to hazardous substances. It works closely with other federal, state, and local agencies; tribal governments; local communities; and healthcare providers. Its mission is to "Serve the public through responsive public health actions to promote healthy and safe environments and prevent harmful exposures." ATSDR was created as an advisory, nonregulatory agency by the Superfund legislation and was formally organized in 1985.
Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.
Radioactive contamination, also called radiological pollution, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases, where their presence is unintended or undesirable.
Occupational hygiene is the anticipation, recognition, evaluation, control, and confirmation (ARECC) of protection from risks associated with exposures to hazards in, or arising from, the workplace that may result in injury, illness, impairment, or affect the well-being of workers and members of the community. These hazards or stressors are typically divided into the categories biological, chemical, physical, ergonomic and psychosocial. The risk of a health effect from a given stressor is a function of the hazard multiplied by the exposure to the individual or group. For chemicals, the hazard can be understood by the dose response profile most often based on toxicological studies or models. Occupational hygienists work closely with toxicologists for understanding chemical hazards, physicists for physical hazards, and physicians and microbiologists for biological hazards. Environmental and occupational hygienists are considered experts in exposure science and exposure risk management. Depending on an individual's type of job, a hygienist will apply their exposure science expertise for the protection of workers, consumers and/or communities.
The linear no-threshold model (LNT) is a dose-response model used in radiation protection to estimate stochastic health effects such as radiation-induced cancer, genetic mutations and teratogenic effects on the human body due to exposure to ionizing radiation. The model statistically extrapolates effects of radiation from very high doses into very low doses, where no biological effects may be observed. The LNT model lies at a foundation of a postulate that all exposure to ionizing radiation is harmful, regardless of how low the dose is, and that the effect is cumulative over lifetime.
Pentachlorophenol (PCP) is an organochlorine compound used as a pesticide and a disinfectant. First produced in the 1930s, it is marketed under many trade names. It can be found as pure PCP, or as the sodium salt of PCP, the latter of which dissolves easily in water. It can be biodegraded by some bacteria, including Sphingobium chlorophenolicum.
Iodine-131 is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nuclear energy, medical diagnostic and treatment procedures, and natural gas production. It also plays a major role as a radioactive isotope present in nuclear fission products, and was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a large fraction of the contamination hazard in the first weeks in the Fukushima nuclear crisis. This is because 131I is a major fission product of uranium and plutonium, comprising nearly 3% of the total products of fission. See fission product yield for a comparison with other radioactive fission products. 131I is also a major fission product of uranium-233, produced from thorium.
An environmental hazard is a substance, state or event which has the potential to threaten the surrounding natural environment or adversely affect people's health, including pollution and natural disasters such as storms and earthquakes. It can include any single or combination of toxic chemical, biological, or physical agents in the environment, resulting from human activities or natural processes, that may impact the health of exposed subjects, including pollutants such as heavy metals, pesticides, biological contaminants, toxic waste, industrial and home chemicals.
The Armed Forces Radiobiology Research Institute (AFRRI) is an American triservice research laboratory in Bethesda, Maryland chartered by Congress in 1960 and formally established in 1961. It conducts research in the field of radiobiology and related matters which are essential to the operational and medical support of the U.S. Department of Defense (DoD) and the U.S. military services. AFRRI provides services and performs cooperative research with other federal and civilian agencies and institutions.
Exposure assessment is a branch of environmental science and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. These are the final steps in the path to release an environmental contaminant, through transport to its effect in a biological system. It tries to measure how much of a contaminant can be absorbed by an exposed target organism, in what form, at what rate and how much of the absorbed amount is actually available to produce a biological effect. Although the same general concepts apply to other organisms, the overwhelming majority of applications of exposure assessment are concerned with human health, making it an important tool in public health.
An occupational exposure limit is an upper limit on the acceptable concentration of a hazardous substance in workplace air for a particular material or class of materials. It is typically set by competent national authorities and enforced by legislation to protect occupational safety and health. It is an important tool in risk assessment and in the management of activities involving handling of dangerous substances. There are many dangerous substances for which there are no formal occupational exposure limits. In these cases, hazard banding or control banding strategies can be used to ensure safe handling.
The Energy Employees Occupational Illness Compensation Program Act (EEOICPA) was passed by Congress in 2000 and is designed to compensate individuals who worked in nuclear weapons production and as a result of occupational exposures contracted certain illnesses. EEOICPA was signed into law by President Bill Clinton on October 30, 2000.
Occupational safety and health (OSH) or occupational health and safety (OHS), also known simply as occupational health or occupational safety, is a multidisciplinary field concerned with the safety, health, and welfare of people at work. These terms also refer to the goals of this field, so their use in the sense of this article was originally an abbreviation of occupational safety and health program/department etc. OSH is related to the fields of occupational medicine and occupational hygiene.
Exposure to ionizing radiation is known to increase the future incidence of cancer, particularly leukemia. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial. The most widely accepted model posits that the incidence of cancers due to ionizing radiation increases linearly with effective radiation dose at a rate of 5.5% per sievert; if correct, natural background radiation is the most hazardous source of radiation to general public health, followed by medical imaging as a close second. Additionally, the vast majority of non-invasive cancers are non-melanoma skin cancers caused by ultraviolet radiation. Non-ionizing radio frequency radiation from mobile phones, electric power transmission, and other similar sources have been investigated as a possible carcinogen by the WHO's International Agency for Research on Cancer, but to date, no evidence of this has been observed.
Nuclear labor issues exist within the international nuclear power industry and the nuclear weapons production sector worldwide, impacting upon the lives and health of laborers, itinerant workers and their families.
Atomic Energy Project was started at the University of Rochester as a graduate teaching program. Also known as the University of Rochester Atomic Energy Project or URAEP.
Occupational toxicology is the application of toxicology to chemical hazards in the workplace. It focuses on substances and conditions that people may be exposed to in workplaces, including inhalation and dermal exposures, which are most prevalent when discussing occupational toxicology. These environmental and individual exposures can impact health, and there is a focus on identifying early adverse affects that are more subtle than those presented in clinical medicine.