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Regulatory Alert - RA 05-04 - NRC AND EPA RELEASE FINAL DOCUMENTS ON RADIOACTIVE MATERIALS IN BIOSOLIDS

Member Pipeline - Regulatory - Alert (RA 05-04)

To: Members & Affiliates, Biosolids Management Committee
From: National Office
Date: April 28, 2005
Subject: NRC AND EPA RELEASE FINAL DOCUMENTS ON RADIOACTIVE MATERIALS IN BIOSOLIDS
Reference: RA 05-04

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The U.S. Environmental Protection Agency (EPA or Agency) and the Nuclear Regulatory Commission (NRC), through the Interagency Steering Committee on Radiation Standards (ISCORS), recently released final versions of the following two reports concerning radioactivity in sewage sludge (biosolids) and biosolids incinerator ash:

These reports supplement another ISCORS report, released in November 2003, titled:

With the release of these latest reports, the ISCORS effort to assess radioactive materials in sewage sludge (biosolids), which began in 1995, is essentially complete. The Association of Metropolitan Sewerage Agencies[1] (AMSA) played a critical role in the decade-long ISCORS effort and in the development of all three documents. AMSA member representatives Tom Lenhart, Director of Employee Resources at the Northeast Ohio Regional Sewer District, Cleveland, Ohio, and Kevin Aiello, Administrator, Environmental Quality, Middlesex County Utilities Authority, Sayreville, New Jersey, were members of the ISCORS subcommittee tasked with conducting the assessment. All three final documents are available on the ISCORS website library (http://www.iscors.org/library.html).

At the heart of the ISCORS mission was an evaluation of the need for limits on radioactivity in biosolids and biosolids incinerator ash. As a result of their 10 year evaluation effort, ISCORS is not recommending the establishment of regulatory limits on radioactivity in biosolids or biosolids incinerator ash. Instead, their final Recommendations Report provides a screening procedure and some recommended actions for publicly owned treatment works (POTWs) that have concerns about radioactivity in their biosolids or biosolids incinerator ash, and a guideline level for exposures (10 millirems/year) above which POTWs should conduct more extensive investigations. The Recommendations Report clearly states that this guideline exposure level is not a regulatory limit.

The three documents referenced in this Regulatory Alert are the culmination of the ISCORS work. No further efforts are expected from either EPA or the NRC on this issue.

With a combined total of over 600 pages, the three ISCORS documents may present a challenge to many POTWs interested in understanding what this means for wastewater treatment agencies. This Regulatory Alert is intended to provide a brief overview of each document, with important ISCORS recommendations highlighted.

Background
Sanitary sewer disposal of radioactive material began to be scrutinized in the 1980s with the discovery of elevated levels of radioactive materials in biosolids and biosolids incinerator ash at several POTWs. Although the NRC has not seen any further problems since its regulations (which limit the amount of man-made radionuclides that can be discharged annually to the sanitary sewer system) were revised in 1991, the NRC and EPA have been working together since 1995, when ISCORS formed a Sewage Sludge Subcommittee to gain a better understanding of radioactivity-related issues associated with biosolids and biosolids incinerator ash. A 1994 General Accounting Office (now known as the Government Accountability Office) report, Nuclear Regulation: Action Needed to Control Radioactive Contamination at Sewage Treatment Plants, which found that of the more that 22,000 regulated users of radioactive materials, about 9,000 users have the potential to release radioactive materials to sanitary sewer systems, made three recommendations that have been the focus of the ISCORS activities in this area over the past decade:

Summary of Documents
The Recommendations Report that is discussed in more detail below is by far the most critical document with which POTWs should become familiar. However, it is also important to understand how the other two documents relate to the Recommendations Report and when those documents may need to be referenced.

1. ISCORS Assessment of Radioactivity in Sewage Sludge: Survey Results and Analysis
This document presents the results of a voluntary survey of radioactive materials in biosolids/biosolids incinerator ash conducted by the ISCORS Sewage Sludge Subcommittee from 1998 to 2000. The objectives of the survey were to 1) obtain national estimates of high probability occurrences of elevated levels or radioactive materials in biosolids/biosolids incinerator ash; 2) estimate the extent to which these materials come from discharges from NRC/Agreement State licensees or are the result of naturally occurring radioactivity; and 3) support rulemaking decisions by NRC and EPA.

Sludge and/or ash samples were collected from 313 POTWs for analysis as a part of the ISCORS survey. The POTWs were chosen because they had greater potential to receive radionuclides from NRC Licensees or from naturally occurring sources. Thus, the results should be considered conservative and may not represent typical levels occurring at POTWs across the country.

The report summarizes the results in a number of different ways (e.g., by physiographic region (subdivisions of the lower 48 states based on terrain texture, rock type, and geologic structure and history), POTW size, drinking water source in the community, biosolids use/disposal practice). POTWs may find the document useful when trying to determine if sampling may be warranted at their facilities. Additionally, the document provides information on radionuclide concentrations in soil, fertilizer and common building materials. Facilities may find this information helpful when trying to place biosolids/biosolids ash concentrations in context during internal or external meetings. One finding of note was that the three radionuclides with the highest concentrations (I-131, Tl-201 and Sr-89) were medical isotopes with short half-lives.

2. ISCORS Assessment of Radioactivity in Sewage Sludge: Modeling to Assess Radiation Doses
In an effort to help interpret the results of the survey described above, ISCORS undertook human exposure evaluation and dose modeling efforts. This document provides the results of the dose modeling effort, providing descriptions and justifications of the dose assessment methodology used by ISCORS. Seven generic, but conservative, scenarios were constructed to represent typical situations in which members of the public or POTW workers could be exposed to radioactive materials in biosolids/biosolids incinerator ash. Available models were then used to generate sludge concentration-to-dose conversion factors for various radionuclides. ISCORS notes that the results of the dose assessment tend to be conservative (i.e., estimated doses are probably higher than the actual expected doses) given the choices used for input parameters and assumptions.

The basic conclusions of the ISCORS survey and dose assessment are as follows:

Agencies interested in understanding the detailed assumptions that were used in the exposure evaluation and dose modeling assessment and/or are interested in the results of sensitivity analyses should review this document. This document also discusses uncertainty and variability associated with the modeling. Having a thorough understanding of this document is particularly important for those wastewater treatment agencies that are contemplating conducting site specific exposure and dose modeling evaluations at their POTWs.

3. ISCORS Assessment of Radioactivity in Sewage Sludge: Recommendations on Management of Radioactive Materials in Sewage Sludge and Ash at Publicly Owned Treatment Works (Recommendation Report)
Most agencies will want to place their initial focus on this Recommendations Report. While the report generally concludes that radioactive materials in biosolids pose little risk, it does recommend that each POTW assess its own system to determine whether there are any sources that could contribute to elevated levels of radioactive materials. The Recommendations Report is designed to alert POTWs to the possibility that radioactive materials may be present in their biosolids/biosolids incinerator ash, assist POTWs in assessing the levels of radioactive materials present, and provide guidance on reducing the potential for exposure should elevated levels be present. Of particular importance to POTWs are Chapters 5-7. On page xxvi of the Executive Summary, a flowchart provides a concise outline of the recommended process for assessing the occurrence and level of radioactive materials in biosolids/biosolids incinerator ash. Chapters 5 through 7 provide further detail on this recommended process.

ISCORS notes that three overall conclusions can be drawn from their decade-long effort: 1) Elevated levels of radioactive materials were found in some biosolids and biosolids incinerator ash samples, but did not indicate a wide-spread problem; 2) Estimated doses to potentially exposed individuals are generally well below levels requiring radiation protection actions; and 3) For limited POTW worker and certain residential scenarios, doses above protective standards could occur (primarily due to indoor radon generated as a decay product of naturally occurring radionuclides).

The POTW Recommendations Report is written in a straightforward manner, but is lengthy and contains a significant amount of information. The document Abstract on page vii provides a concise overview of the ISCORS assessment, the results of the survey and dose modeling efforts, and a brief description of each chapter in the document. Below is an overview of the chapters in the Recommendations Report and a more detailed discussion of Chapters 5 through 7.

Recommendations Report Chapter Overview
Chapters 1-4
Chapters 1 through 4 provide important background information for POTWs that may be less familiar with radioactivity issues. Specifically:

Chapter 5 (What Can a POTW Operator Do to Determine if There is Radioactive Contamination? Who Can Help?)
Chapter 5 provides information that POTWs can use to determine:

Sections 5.1 and 5.2 are vital to assessing whether POTWs may want to consider conducting more detailed investigations of their biosolids/biosolids incinerator ash. Section 5.1 outlines some recommended actions for POTWs to determine if their plants may be receiving wastewater that contains radioactive materials or if there are other sources present that could contribute to elevated levels of radioactive materials at their plant or in the biosolids (e.g., the plant may be located in an area with high background levels of radium or uranium in water supplies that could lead to elevated levels in biosolids and releases of elevated levels of radon). Section 5.2 goes on to also provide guidance on when sampling of biosolids/biosolids ash or monitoring for radon may be appropriate. Section 5.3 provides guidance on establishing a sampling/monitoring plan. ISCORS suggests that POTWs might want to consider employing a consultant when evaluating the potential for contamination with radioactive materials.

Chapter 6 (How Can a POTW Operator Interpret Levels of Radioactivity Detected in the Plant?)
Chapter 6 is a critical chapter that provides a method for estimating potential doses from radioactive material in biosolids/biosolids incinerator ash, a screening approach that can be used to determine the significance radionuclides that may be present in biosolids/ash, and guidance on steps that POTWs can take to collect additional information. By using biosolids and ash sampling results and tables presented in Chapter 6, a POTW can calculate the annual dose from all radionuclides detected in its biosolids. ISCORS states that there is no need for further action when the estimated dose is 10 mrem/year or less. ISCORS clearly states that the 10 mrem/year screening level:

Instead of including radon in the calculation of 10 mrem/year, it is recommended that POTWs test for the presence of radon gas, especially in enclosed areas where biosolids/ash is handled, and for action to be taken to reduce radon concentration levels if test results average 4 pCi/liter (picocurie/liter) or greater (a guideline level used for schools and homes).

ISCORS recommends that POTWs contact their state radiation protection agency (a list of these agencies is provided in Appendix E) if the POTW sampling and exposure assessment indicates that annual doses are above the screening level of 10 mrem/year. AMSA understands, however, that some state programs may not be set up to deal with these types of requests and in those instances POTWs may wish to contact the Association for additional guidance. Consultation with a state radiation protection regulatory agency may result in one of several recommendations being made:

If screening calculations suggest that potential doses to workers (within the POTW or those who handle biosolids/ash outside of the POTW) may be above the acceptable radiation dose level (as determined after consultation with the State agency), the POTW operator may want to conduct a more thorough evaluation of the levels detected in the biosolids, biosolids incinerator ash, or indoor air, based on site-specific conditions. This evaluation may involve additional sampling or monitoring, use of modeling scenarios developed for the ISCORS dose modeling project and substitution of actual site-specific input data, creation of more directly applicable modeling scenarios than those used in the ISCORS dose modeling project, or actual physical surveys of potentially affected areas of the POTW or other biosolids management locations. Results of the surveys of biosolids management locations should be reported to the State radiation control program to determine the appropriate standards for comparison.

Chapter 7 (What Can be Done to Reduce Radiation Doses and Radon Levels?)
Chapter 7 provides guidance on what can be done to reduce radiation doses and radon levels, including contacting regulatory agencies for assistance, controlling sources, and reducing exposure to radioactivity from biosolids both at the plant and at land application sites.

AMSA Recommendations for Member Agencies
AMSA recommends that its members review Sections 5.1 and 5.2 to determine whether sampling or additional investigations are warranted. Many AMSA members have already conducted sampling and analysis of their biosolids or biosolids incinerator ash either in conjunction with the ISCORS survey effort or independently. Those agencies should consider using the screening process in Chapter 6 to help determine the significance of their sample results. For those AMSA members who have not already done so, conducting some basic biosolids sampling to establish a baseline level of radionuclides may be valuable not only for assessing potential exposure but also for future comparison purposes.

If you have any questions or require additional information, please do not hesitate to contact Chris Hornback, AMSA’s Director of Regulatory Affairs at 202/833-9106 or chornback@amsa-cleanwater.org or Dave Taylor, Director of Special Projects, Madison Metropolitan Sewerage District, Madison, Wisconsin and Co-Chair of AMSA’s Biosolids Management Committee at 608/222-1201, ext. 276 or davet@madsewer.org.

 

 [1] As of May 2, 2005, AMSA’s name will become the National Association of Clean Water Agencies (NACWA).