Earlier this week, the National Academy of Sciences held a public meeting to discuss the Nuclear Regulatory Commission's request for a study of cancer risk in populations living near nuclear power plants. According to the NRC's announcement, the purpose of the study is to update a similar 1990 study by the National Cancer Institute. During the April 26 meeting, the NAS's Nuclear and Radiation Studies Board heard recommendations from representatives of government, industry and public interest groups. (An audio recording of the meeting is available here. A fellow blogger's summary is available here.)
NEI was among the organizations invited to address the NRSB. NEI's Senior Director, Radiation Safety and Environmental Protection, Mr. Ralph Andersen, a Certified Health Physicist, spoke on the challenges facing the NRSB. In his remarks, Mr. Andersen shared the perspective of the Health Physics Society, the association of radiation protection professionals, on epidemiological studies of this nature. The HPS says that:
The key term is "sufficiently powerful". The HPS is referring to the statistical power needed to discern changes in the incidence of cancer.
"Studies of...occupationally and environmentally exposed populations...are useful in addressing allegations of adverse health effects in the population and in demonstrating a concern for the health of the exposed people. However, unless they are sufficiently powerful, they do not add to the scientific knowledge of low dose effects."
According to the National Research Council, on average 42 out of 100 people - nearly half - will be diagnosed with cancer during their lifetime [Note 1]. With so many people contracting cancer throughout the population, the statistician's challenge is to determining when changes in that "natural background" occurrence of cancer are meaningful. As the focus of the study shrinks to smaller and smaller groups, the statistical challenge of distinguishing random variations from meaningful differences grows more difficult. When the focus is on the population around one or a handful of power plants, it becomes extremely difficult to discern meaningful differences. A very accessible description of the problem is provided at RadiationAnswers.org.
We welcome the NRC's request for this study and applaud the NRSB for taking this on. In shaping the scope and methods of its study, we hope and trust that the NRSB will heed the advice of the Health Physics Society. As we learn more about the NRSB study, we will do our part to help the public and policymakers understand the complexities of gauging the impacts of nuclear power plants on their environs.
Note 1: See Figure PS-4, page 7, in the National Research Council's 2006 report, "Health Risks from Exposure to Low Levels of Ionizing Radiation, BEIR VII Phase 2".