NORA Manufacturing Sector Strategic Goals
927Z6TE - Radiation Risk Assessment
Principal Investigator (PI)
Primary Goals Addressed
Secondary Goal Addressed
Attributed to Manufacturing
The purpose of this project is to improve the understanding of the relationship between adverse health effects - notably cancer - and low linear energy transfer radiation based on epidemiologic studies and to provide OSHA with pertinent information for future rulemaking by supporting NIOSH authoritative recommendations.
It will accomplish this purpose by providing a final report to OSHA summarizing the results of the literature reviews done on adverse health effects and exposure to ionizing radiation, the quantitative risk assessment, the comparison of the risk models with those in the literature and a summary of future research needs.
This report will provide OSHA with information that is essential for future rulemaking and it will be the basis of one or more scientific manuscripts submitted to journals.
The purpose of this project is to provide the quantitative risk assessment information essential for future rulemaking efforts to limit occupational exposure to ionizing radiation.
The National Research Council Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation recently published its seventh report on the Biological Effects of Ionizing Radiation (BEIR VII) (1). The BEIR VII report provides risk estimates for cancer and other health effects from exposure to low-LET ionizing radiation and supports a “linear-nothreshold” (LNT) risk model. The Committee acknowledges that continued research is needed to further increase the understanding of the health risks of low levels of ionizing radiation. The BEIR VII report also identifies top research needs such as reduction of uncertainties, continued medical radiation and occupational radiation studies, and epidemiologic studies of nuclear industry workers.
The National Institute for Occupational Safety and Health (NIOSH) is actively involved in studying the health effects from exposure to ionizing radiation, primarily through epidemiologic and exposure assessment research. Since 1990, intramural and NIOSH-funded extramural research projects have been conducted under a memorandum of understanding between the U.S. Department of Health and Human Services and the U.S Department of Energy (DOE), with worker populations at DOE nuclear weapons facilities, national laboratories, and the U.S. Navy Portsmouth Naval Shipyard (PNS). There are several recently published NIOSH studies that are not included in the BEIR VII report. Examples are three separate studies evaluating the mortality experience of civilian workers at the PNS (2-4), and a cohort mortality study of more than 63,000 current and former workers at the Idaho National Engineering and Environmental Laboratory (5). While some studies observed negative or weakly positive associations between adverse health outcomes and ionizing radiation, others reported increased mortality associated with external radiation exposure (i.e., significant dose response relationship). For example, a nested case-control study at the PNS found an 8% increase in the risk of leukemia death at 10 mSv cumulative exposure (4). These recently completed studies should provide useful information to OSHA in evaluation of potential actions necessary to address worker protection from ionizing radiation exposure.
To improve the understanding of the relationship between adverse health effects and low-LET ionizing radiation exposure and to provide OSHA with pertinent information for future rulemaking, REB, in collaboration with research partners in IWSB, DSHEFS, proposes to conduct the following tasks:
• Comprehensive review of up-to-date scientific literature on adverse health effects and exposure to ionizing radiation. This review includes those studies not used by or not yet published at the time of BEIR VII report, especially the PNS studies and other available NIOSH intramural and extramural studies. Cancers were the main focus in the first phase of this review which was completed in 2007, but is subject to being updated as new information becomes available.
• Evaluation of available literature for use in the risk assessment. This task evaluates main health outcomes of interest, cohort characteristics, exposure measurements, analytic methods and estimated risks used in the literature. This information will be used to develop inclusion criteria for these epidemiologic studies. This was accomplished in 2008.
• Conduct an assessment of adverse health risks among workers exposed to low levels of ionizing radiation. This task includes assessment of available epidemiologic data, selection of adverse health outcomes and radiation exposures that support quantitative risk estimates, and development of appropriate risk models that may include other modifying factors such as sex, age, smoking habits and other chemical exposures.
• This was first accomplished in 2008 and extended in 2010. However, an ongoing effort by NIOSH to update the five US cohorts studied by Schubaver-Berigan et al. (2007) will be completed by 2011 and an update of the quantitative risk assessment is planned for 2012.
• Identify needs for future research.
According to estimates by the National Council on Radiation Protection and Measurements (NCRP), approximately 1.5 million workers are occupationally exposed to ionizing radiation each year in the U.S. and a substantial body of research on its adverse health effects continues to be developed. There are many challenges associated with understanding the relationship between adverse health effects and ionizing radiation exposure, especially among workers chronically exposed to low doses of low linear energy transfer (low-LET) radiation. Differences exist between the recommendations for permissible exposure levels from lead radiation protection agencies as well as quantitative risk assessment of adverse health effects associated with ionizing radiation.
Epidemiologic research continues to be developed that evaluates the health effects from protracted exposure to low levels of ionizing radiation and the results of these studies may provide critical information to the Occupational Safety and Health Administration (OSHA) in examining information related to its promulgated occupational radiation protection standards (e.g., 29 CFR 1910.1096 and 29 CFR 1926.53) and future rule making efforts.
This project will develop the necessary quantitative risk assessment information of adverse health effects associated with occupational exposure to ionizing radiation that incorporates the latest epidemiologic research in support of these efforts. Together with the recent meta-analyses of Jacob et al.(6) and Schubauer-Berigan and Daniels (7).