Examining the Reasons for Ending the Cancer Risk Study
Posted by on October 6, 2015
Scott Burnell
Public Affairs Officer
One way NRC regulations protect communities around U.S. nuclear power plants is by requiring the plants to regularly sample air, water, and vegetation around their sites. Samples are sent to state agencies (and in some cases to the NRC) to prove only very tiny amounts of radioactive material are released during normal operations.
Even with this scrutiny — and a 1990 study showing no difference in cancer mortality rates between those living near U.S. reactors and those living elsewhere — questions persist about cancer risk from nearby reactors. The NRC had worked with the National Academy of Sciences (NAS) since 2010 on a study into the potential cancer risk of living near a U.S. nuclear power plant. But we ended this work earlier this month after a hard look at the low likelihood of getting usable results in a reasonable time frame.
How did we reach that decision?
First and foremost, the staff considered existing conditions around U.S. reactors, as shown by the ongoing environmental sampling and analysis we mentioned earlier. That evidence supports the conclusion that the average U.S. citizen’s annual radiation dose from natural sources, such as radon and cosmic rays, is about a hundred times greater than the largest potential dose from a normally operating reactor.
Other
NRC research has examined potential long-term doses from a nuclear
accident. These long-term doses were about 20 percent greater than the
annual U.S. dose from natural sources. The research concluded the risk
of a fatal cancer from the accident-related doses was less than one in
100 million.
This information shows how complicated it would be to single out an operating reactor’s potential contribution to cancer risk. Researchers looking for small effects need a very large study population to be confident in their results. The NAS discussed this issue in its report on Phase 1 of the cancer risk study. The NAS said that the effort “may not have adequate statistical power to detect the presumed small increases in cancer risks arising from… monitored and reported releases.”
The NRC staff considered other issues, such as potential differences between individual states’ cancer registries. Large differences in registry quality or accessibility would hurt the study’s chances of generating useful results.
The NRC staff examined the NAS Phase 2 report plans to validate the methods recommended in Phase 1. The Academy was very clear that the pilot study at seven U.S. sites was unlikely to answer the basic risk question. The NAS proposal said: “any data collected during the pilot study will have limited use for estimating cancer risks in populations near each of the nuclear facilities or for the seven nuclear facilities combined because of the imprecision inherent in estimates from small samples.”
The NAS concluded they would need more than three years and $8 million to complete the pilot study. If the pilot succeeded, expanding the research to all U.S. operating reactors would require additional years and tens of millions of dollars. The NRC decided the time and money would not be well spent for the possible lack of useful results.
The NRC agrees with the NAS that the study’s overall approach is scientifically sound. Interested individuals or groups can examine the NAS Phase 1 and 2 reports for a more detailed discussion of the methods and resources needed to conduct the proposed study. The NRC staff will examine international and national studies on cancer risk to see if we should conduct any future work in this area.http://public-blog.nrc-gateway.gov/2015/10/06/examining-the-reasons-for-ending-the-cancer-risk-study/?source=govdelivery&utm_medium=email&utm_source=govdelivery
Public Affairs Officer
One way NRC regulations protect communities around U.S. nuclear power plants is by requiring the plants to regularly sample air, water, and vegetation around their sites. Samples are sent to state agencies (and in some cases to the NRC) to prove only very tiny amounts of radioactive material are released during normal operations.
Even with this scrutiny — and a 1990 study showing no difference in cancer mortality rates between those living near U.S. reactors and those living elsewhere — questions persist about cancer risk from nearby reactors. The NRC had worked with the National Academy of Sciences (NAS) since 2010 on a study into the potential cancer risk of living near a U.S. nuclear power plant. But we ended this work earlier this month after a hard look at the low likelihood of getting usable results in a reasonable time frame.
How did we reach that decision?
First and foremost, the staff considered existing conditions around U.S. reactors, as shown by the ongoing environmental sampling and analysis we mentioned earlier. That evidence supports the conclusion that the average U.S. citizen’s annual radiation dose from natural sources, such as radon and cosmic rays, is about a hundred times greater than the largest potential dose from a normally operating reactor.
Other
NRC research has examined potential long-term doses from a nuclear
accident. These long-term doses were about 20 percent greater than the
annual U.S. dose from natural sources. The research concluded the risk
of a fatal cancer from the accident-related doses was less than one in
100 million.This information shows how complicated it would be to single out an operating reactor’s potential contribution to cancer risk. Researchers looking for small effects need a very large study population to be confident in their results. The NAS discussed this issue in its report on Phase 1 of the cancer risk study. The NAS said that the effort “may not have adequate statistical power to detect the presumed small increases in cancer risks arising from… monitored and reported releases.”
The NRC staff considered other issues, such as potential differences between individual states’ cancer registries. Large differences in registry quality or accessibility would hurt the study’s chances of generating useful results.
The NRC staff examined the NAS Phase 2 report plans to validate the methods recommended in Phase 1. The Academy was very clear that the pilot study at seven U.S. sites was unlikely to answer the basic risk question. The NAS proposal said: “any data collected during the pilot study will have limited use for estimating cancer risks in populations near each of the nuclear facilities or for the seven nuclear facilities combined because of the imprecision inherent in estimates from small samples.”
The NAS concluded they would need more than three years and $8 million to complete the pilot study. If the pilot succeeded, expanding the research to all U.S. operating reactors would require additional years and tens of millions of dollars. The NRC decided the time and money would not be well spent for the possible lack of useful results.
The NRC agrees with the NAS that the study’s overall approach is scientifically sound. Interested individuals or groups can examine the NAS Phase 1 and 2 reports for a more detailed discussion of the methods and resources needed to conduct the proposed study. The NRC staff will examine international and national studies on cancer risk to see if we should conduct any future work in this area.http://public-blog.nrc-gateway.gov/2015/10/06/examining-the-reasons-for-ending-the-cancer-risk-study/?source=govdelivery&utm_medium=email&utm_source=govdelivery
No comments:
Post a Comment