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Long et al. (2012): Potential Indoor Air Exposures and Health Risks from Mercury Off-Gassing of Coal Combustion Products Used in Building Materials Long et al. (2012) measured the rate at which concrete made with and without fly ash emit mercury vapor, and used these measurements to calculate resulting indoor air concentrations in a school. The report then compared these concentrations to health-based benchmarks. The evaluation concluded that potential indoor air concentrations were below levels of concern. Because Long et al. (2012) specifically addressed releases from fly ash concrete, the results are directly applicable to the current 1-3 evaluation. However, a review of the documented methodology found that it did not address the use of fly ash concrete in residential settings, potentially resulting in an underestimation of high-end exposures. Furthermore, the relatively small number of fly ashes evaluated in the study introduces uncertainty as to whether the measured mercury emanation rates adequately characterize the range of potential emanation rates from fly ash concrete. Therefore, the current evaluation retained mercury as a COPC for emanation to air.
Ingersoll (1983): A Survey of Radionuclide Contents and Radon Emanation Rates in Building Materials Used in the United States
United States Geological Survey (USGS) (1997): Radioactive Elements in Coal and Fly Ash:
Abundance, Forms, and Environmental Significance Zielinski et al. (1998): Uranium in Coal and Fly Ash: Abundance, Forms, and Environmental Significance United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (1982, 1988, 1993; 2000; 2008): Ionizing Radiation: Sources and Effects United Kingdom National Radiological Protection Board (UKNRPB) (2001): Radiological Impact on the UK Population of Industries Which Use or Produce Materials Containing Enhanced Levels of Naturally Occurring Radionuclides: Part 1 - Coal-fired Electricity Generation International Atomic Energy Agency (IAEA) (2003): Extent of Environmental Contamination by Naturally Occurring Radioactive Materials (NORM) and Technical Option for Mitigation United Kingdom Health Protection Agency (UKHPA) (2004): Radiological Study of Pulverized Fuel Ash (PFA) from UK Coal-fired Power Stations Kolver et al. (2005a): Radon Exhalation Of Cementitious Materials Made with Coal Fly Ash: Part 1 Scientific Background and Testing of the Cement and Fly Ash Emanation Kolver et al. (2005b): Radon Exhalation Of Cementitious Materials Made with Coal Fly Ash: Part 2 Testing Hardened Cement Fly Ash Pastes National Commission for Radiological Protection and Measurements (NCRP) (2009): Ionizing Radiation Exposure of the Population of the United States Report 160 Kosson et al. (2013): pH-dependent Leaching of Constituents of Potential Concern from Concrete Materials Containing Coal Combustion Fly Ash A broad range of domestic and international evaluations were identified that address radiation from coal, fly ash, or fly ash concrete. Although some of these evaluations do not directly address fly ash concrete, the results are applicable to the current evaluation because the beneficial use of fly ash in concrete will dilute radionuclide concentrations present in the fly ash through mixing with other raw materials. These evaluations include peer-reviewed publications, guidance documents, and voluntary standards that have been developed and reviewed by experts in the field of radiation and health physics. This body of work extends back nearly forty years and has already been well summarized through the literature reviews contained in more recent existing evaluations. Therefore, only these key recent evaluations, which form the basis for the conclusions in this beneficial use evaluation, are summarized in the following text.
International organizations have grouped radiation exposures into three different categories: (1) planned introduction and operation of sources, (2) unexpected emergencies that may arise during a planned situation or from a malicious act, and (3) situations that already exist when a decision on 1-4 control has to be taken. 4 The historical use of fly ash in concrete would fall under group (3), while the continued use would fall under group (1). 5 A number of national and international organizations develop and maintain guidance on managing public exposures to everyday sources of radiation.
Evaluations of radiation exposures often incorporate the recommendations of these guidances, and several of the existing evaluations identified were conducted by one of these organizations to everyday sources of radiation. In the United States, the Nuclear Regulatory Commission (NRC) regulates source and byproduct materials, and can exempt certain products, devices, or equipment that contain radioactive materials from requiring a license (NRC, 2001). EPA has promulgated maximum contaminant limits (MCLs) for radiation levels in public drinking water, and has developed recommendations for mitigating radon levels in indoor air. The American National Standards Institute (ANSI), together with the Health Physics Society (HPS), developed Standard N13.53 for technologically enhanced sources of naturally occurring radiation, based on a review of existing radiation protection standards and guidance from relevant US and European organizations (ANSI/HPS, 2009). International organizations have also developed guidance that has been adopted by many countries. The European Commission (EC) developed Basic Safety Standards Directive 96/29, which recommends exposure limits for various sources of radioactivity and authorizes the exemption of specific practices from regulatory controls (EC, 1999; 2001). The International Commission on Radiological Protection (ICRP) developed the International System of Radiological Protection, used world-wide as the basis for radiological protection standards, legislation, guidelines, programs, and practice (ICRP, 2007). The IAEA develops safety standards and, based on these standards, issues guidance and technical documents on radiation protection. While these organizations set varying exposure limits for different scenarios (e.g., clean-up sites, medical procedures, consumer products), virtually all guidance developed incorporates the principle of “as low as reasonably achievable” to minimize public exposures while taking into account health, economic, and societal factors.
- Ingersoll (1983) measured the concentrations of uranium, thorium, and potassium present in, as well as the rate at which radon emanates from portland cement concrete and other common building materials made with virgin materials collected from ten major metropolitan areas across the United States. The study concluded that each of these building materials contribute only a small fraction of the total radon levels typically measured in US homes. The study also noted that radon measurements previously collected for fly ash concretes fell within the range measured for the portland cement concretes.
- UNSCEAR (1982, 1988, 1993, 2000, 2008) each summarized the available literature on sources of radiation exposure. These reports compiled a great deal of information on the radionuclide activities in coal, fly ash, concrete, and other building materials collected from across the globe.
The data compiled in these reports show the average radionuclide activity of fly ash generated in the United States falls around the upper bound of the range measured in soils, but is generally lower than fly ashes generated in other parts of the globe. The 1988 report also summarized As discussed in International Commission on Radiological Protection Report 103 (ICRP, 2007).
Fly ash has been a commonly used raw material in concrete for at least the past 80 years. The Hoover Dam is one of the first recorded projects in 1929 (http://www.lmcc.com/concrete_news/0607/five_minute_classroom_fly_ash.asp).
1-5 available literature on radon emanation from fly ash concrete. Based on a number of studies that showed either reduced or unchanged radon emanation rates from concrete amended with fly ash, this 1988 report concluded that the use of fly ash in building materials should not result in any additional radiation exposure beyond that from standard portland cement concrete.
- USGS (1997) reviewed data in the US Coal Quality Database on the uranium concentrations in coals mined from the Western United States and the Illinois Basin. This study used the data to estimate the uranium content of fly ash by assuming that concentrations were magnified by a factor of ten during combustion, based on values previously reported in the literature. This study compared the estimated uranium concentrations for fly ash to those previously reported in the literature for common rocks, such as granite and shale. Based on this comparison, USGS concluded that the radionuclide concentrations in fly ash are similar to those found in common rocks. IAEA (2003) reviewed the data presented in USGS (1997) and drew similar conclusions.
USGS (1997) also summarized data later available in Zielinski et al. (1998) on leaching of uranium and radium from fly ash. 6 Zielinski et al. (1998) analyzed the physical and chemical structure of fly ash and concluded that the long-term leaching of uranium will be inhibited by the glassy structure of the ash, while long-term leaching of radium will be inhibited by the formation of insoluble sulfate complexes. Available uranium leachate samples corroborated these predictions. Fly ash samples were collected at one facility from various points in the exhaust stream and at different times. These fly ash samples ranged in pH from about 3 to 12, and had uranium concentrations toward the upper bound predicted by the US Coal Quality Database.
Samples were subjected to column and batch leach tests, which showed concentrations of uranium to be below the corresponding MCL over the pH range relevant to concrete. Based on the available evidence, the study concluded that radionuclides leached from fly ash are generally below levels of concern. It is important to note that all of these data represent pure fly ash. Based on the findings of Kosson et al. (2013), incorporation of fly ash into concrete will further limit leaching. In addition, none of the measured concentrations account for dilution and attenuation that will occur in the environment.
- UKNPRB (2001) calculated potential exposures to gamma radiation and radon resulting from the use of fly ash generated within the United Kingdom in concrete. The report considered exposures to a member of the public that spends majority of their time in a small room with four walls, ceiling, and floor made of fly ash concrete. The report found that potential exposures to gamma radiation and radon from fly ash concrete do not exceed benchmarks established in EC guidance.
Both UKHPA (2004) and NCRP (2009) reviewed the data presented in UKNPRB (2001) and drew similar conclusions.
- Kolver et al. (2005a) reviewed and summarized the literature on radon emanation from concrete.
This study identified several additional studies published since the 1988 UNSCEAR report that found the addition of fly ash either reduced or had little effect on radon emanation. Kolver et al.
(2005b) measured the rate of radon emanation from mortars made with and without fly ash, with variable fly ash replacement rates. Measurements were collected at 7, 28, and 90 days after curing.
USGS (1997) used barium as a chemical analog for radium.
1-6 This study showed that the radon emanation rate from all fly ash amended mortars was less than from those made with only portland cement. The study concluded that the increased densification caused by the inclusion of fly ash was responsible for these lower emanation rates.
All of the existing evaluations identified concluded that radiation exposures from fly ash concrete are not a major source of concern. Several of these existing evaluations compared fly ash concrete to analogous products and found that the potential exposures do not represent an appreciable addition to the background radiation that the general public is subjected to on an annual basis. Naturally occurring radionuclides are present throughout the environment in food, air, water, soil, consumer products, and even the human body. All natural resources used in building construction (e.g., cement blocks, bricks, granite, soil, rocks) contain some trace level of naturally occurring radionuclides. For example, the USGS concluded that “the radioactivity of typical fly ash is not significantly different from that of more conventional concrete additives or other building materials such as granite and red brick.” The NCRP concluded that exposures from living in concrete buildings containing fly ash are “similar to calculations made for individuals living in a brick and masonry home. Consequently, it is assumed that the use of [coal ash] in building materials has not substantially increased the average dose to an individual in the population residing in a building constructed with brick or masonry materials.” Several of these existing evaluations also evaluated the magnitude of potential exposures that may result from fly ash concrete and found them to be in line with existing guidance. For example, the UKHPA concluded that exposures to “…members of the public from the use of [fly ash] in building materials is negligible.” The cumulative body of evidence provided by these evaluations is considered sufficient to demonstrate that radiation from fly ash concrete is either comparable to that from analogous products made without CCRs, or is at or below relevant benchmarks established by national and international standard-setting and regulatory bodies.
Therefore, the current evaluation eliminated radionuclides from further consideration.
1.1.2 Data Collection for Fly Ash Concrete The review of existing evaluations discussed in Section 1.1.1 above identified potential releases and associated COPCs that the literature had not sufficiently addressed. Therefore, the current evaluation assembled data on these remaining releases and associated COPCs from the existing evaluations and other available literature. These data form the basis for the evaluation of COPC releases from fly ash concrete conducted in subsequent steps of this evaluation. The remainder of this section enumerates the major sources from which these data were drawn. Appendix A provides further discussion of each data source, along with a presentation of the corresponding raw data.