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Risk Assessment
Risk Assessment and Federal Guidance Programs:  


Risk Assessment

This page offers risk assessment publications, developed by the Radiation Protection Program. You can downloaded them to your computer or view them on-line.

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Federal Guidance Reports and Related Documents

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(HEAST) Radionuclides Table -- Radionuclide Slope Factors

Health Effects Assessment Summary Tables (HEAST) Radionuclides Table
These tables contain radionuclide slope factors for estimating cancer risks at sites managed under the Comprehensive Environmental Response, Compensation, and Liability Act. EPA has developed these cancer slope factors for ingestion, inhalation and external exposure to radionuclides in units of picocuries (pCi).

Ingestion and inhalation slope factors are central estimates in a linear model of the age-averaged, lifetime attributable radiation cancer incidence (fatal and nonfatal cancer) per unit of activity inhaled or ingested, expressed as risk/pCi.

External exposure slope factors are central estimates of lifetime attributable radiation cancer incidence for each year of exposure to external radiation from photon-emitting radionuclides distributed uniformly in a thick layer of soil, and are expressed as risk/year per pCi/gram soil. When combined with site-specific media concentration data and appropriate exposure assumptions, slope factors can be used to estimate lifetime cancer risks to members of the general population due to radionuclide exposures.

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EPA Assessment of Risks from Radon in Homes

EPA updates its assessment of health risks from indoor radon, which the National Academy of Sciences (NAS) has determined to be the second leading cause of lung cancer after cigarette smoking.

EPA Assessment of Risks from Radon in Homes [EPA 402-R-03-003] June 2003
This risk assessment is based primarily on results from a recent study of radon health effects (BEIR VI) by the NAS, with some technical adjustments and extensions.

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Comparative Dosimetry of BEIR VI Revisited

In support of EPA’s Assessment of Risks from Radon in Homes, the Agency sponsored a study designed to aid in the extrapolation of risk estimates based on data from underground miner cohorts to the case of residential exposures.

Comparative Dosimetry of BEIR VI Revisited Exit EPA Disclaimer, Radiation Protection Dosimetry 108:3-26; 2004) [A.C. James, A. Birchall and G. Akabani]
estimates the radiation doses delivered to target cells in the lung from radon progeny under indoor and mine exposure conditions.

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Blue Book - EPA Risk Models Based on BEIR VII

Blue Book – EPA Radiogenic Cancer Risk Models and Projections for the US Population [EPA 402-R-11-001] April 2011
The EPA Radiogenic Cancer Risk Models and Projections for the U.S. Population, also known as the Blue Book, is a revision to EPA's methodology for estimating cancer risks from radiation exposure. These updates are based on the National Research Council's latest report on the Biological Effects of Ionizing Radiation (BEIR VII) as well as other updated science.

The Blue Book uses the best science available to calculate separate cancer risk estimates by age at exposure, what age a person might get cancer, sex, and potentially affected organ. More specifically, the Blue Book presents new EPA cancer incidence and mortality risk coefficients for the U.S. population from exposure to low doses of ionizing radiation. The document also presents the scientific basis for the estimates.

The Blue Book is an important intermediate step towards updating Federal Guidance Report No. 13 - Cancer Risk Coefficients for Environmental Exposure to Radionuclides (FGR-13), which allows for straightforward calculations of risks from ingestion and inhalation of radioactive substances.

Historical Documents

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Relative Biological Effectiveness of Low-Energy Electrons and Photons

Relative Biological Effectiveness of Low-Energy Electrons and Photons (PDF) (25 pp, 689 K About PDF)
Different types of radiation deposit energy in biological tissues in different ways, which affects the amount of cellular damage. RBE (relative biological effectiveness) is a relative measure of the damage done by a given type of radiation per unit of energy deposited in biological tissues. Compared with higher energy photons such as cobalt-60 gamma rays, lower energy electrons and photons produce more dense clusters of ionizations, leading to more complex damage to the cell's DNA, and thus a higher RBE.

In this work, relative biological effectiveness values were derived for electrons and photons as a function of energy. There is growing evidence to support a relative biological effectiveness greater than one for low-energy electrons and photons. For example, a number of experimental studies suggest RBE values between two and three for tritium, meaning that the low-energy electrons emitted by tritium do two to three times the damage to cells per unit of energy deposited when compared to higher energy radiation. Other radiation sources with similar energy emissions may also exhibit an elevated RBE. Consideration of the potentially greater effectiveness of these radiations is important to improve the quality of risk assessments.

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Perspective on LNT

Perspective on the use of the LNT for Radiation Protection and Risk Assessment by the U. S. Environmental Protection Agency (8 pp, 78 K About PDF)
This paper discusses EPA’s views on the controversy surrounding the use of the linear, no-threshold (LNT) model in radiation risk assessment, guidelines, and regulations.

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Ground-Water Modeling

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