Ask the Chair

At the conclusion of the Phase 1 study, the chair of the Phase 1 committee answered questions about the report that were submitted by members of the public.

Question: What are the cancer risks for living near a nuclear facility?

This Phase 1 study did not evaluate cancer risks associated with living near a nuclear facility.  Rather, it evaluated the methodologies available to assess cancer risks in terms of scientific merit, feasibility, and utility for addressing public concerns. The assessment of cancer risks would be provided in a Phase 2 study, should the USNRC decide to proceed with an epidemiology study of cancer risks.

Question:  What have studies to date shown about cancer risks from living near nuclear facilities?

Concerns about the potential health effects from living near nuclear facilities are not new or unique to the United States. A number of epidemiologic studies of cancer risks in populations near nuclear facilities have been carried out in at least eleven countries (Canada, Finland, France, Germany, Great Britain, Israel, Japan, Spain, Sweden, Switzerland, and the United States). The majority of these studies investigated rates of cancer deaths or cancer incidence in populations living in various-size geographic units including counties and municipalities. These studies have come to different conclusions, with some suggesting a positive association between living in proximity to a nuclear facility and cancer risk. However, studies have been unable to attribute positive associations to radioactive releases from the facilities.

A widely publicized study with a positive finding is the German Kinderkrebs in der Umgebung von Kernkraftwerken (KiKK) study, which was carried out by researchers from the German Childhood Cancer Registry (GCCR) in Mainz on behalf of the Federal Office of Radiation Protection. Study results published in 2008 (Kaatsch et al., 2008) indicated that for a child of age 0-5 years, the risk of developing leukemia doubles if that child lives in the vicinity of a nuclear plant. However, the methodology, presentation, and interpretation of results from the study have been strongly criticized.

Results from two other epidemiology studies were published during this Phase 1 study; neither provided significant evidence of a positive association between the plants and cancer risk: The 14th report of the Committee on Medical Aspects of Radiation in the Environment (COMARE), which provided further consideration of the incidence of childhood leukemia around nuclear plants in Great Britain (COMARE 2011), and a study on the risk of childhood leukemia and all childhood cancers in the vicinity of Swiss nuclear plants (Spycher et al., 2011).

A third report from France showed that children living within 5 km of nuclear plants are twice as likely to develop leukemia compared to those living 20 km or further away from the plants. However, analysis of the same population of children using a dose-based geographic zoning approach, instead of distance, did not support the findings. The authors suggest that the absence of any association with the dose-based geographic zoning approach may indicate that the observed association of distance and cancer risk may be due to some unidentified factors other than the releases from the nuclear power plants (Sermage-Faure et al., 2012).

COMARE [Committee on Medical Aspects of Radiation in the Environment] (2011). Fourtheenth report: Further consideration of the incidence of childhood leukemia around nuclear power plants in Great Britain.

Kaatsch, P., C. Spix, et al. (2008). “Leukaemia in young children living in the vicinity of German nuclear power plants.” Int J Cancer 122(4): 721-726.

Sermage-Faure C., Laurier D., Goujon-Bellec S., Chartier M., Guyot-Goubin A., Rudant J., Hémon D., Clavel J., Childhood leukemia around French nuclear power plants – the Geocap study, 2002-2007, International Journal of Cancer, accepted preprint

Spycher, B. D., M. Feller, et al. (2011). “Childhood cancer and nuclear power plants in Switzerland: a census-based cohort study.” Int J Epidemiol.

Question: Is it possible to assess the radiation “dose” received by individuals living near nuclear facilities?

In spite of the challenges of carrying out studies of health effects in populations, the data on radioactive releases from nuclear power plants, direct exposure, and weather data collected by nuclear facility licensees are likely to be sufficiently accurate to develop annual dose estimates that adequately reflect variations as a function of distance and direction.

Environmental monitoring data have limited usefulness for estimating doses from effluent releases around nuclear plants and fuel cycle facilities. Almost all environmental measurements reported by facilities are either below the minimum detection limits or are not sensitive enough to allow for the development of adequate dose estimates.

Computer models have been developed to estimate absorbed doses in individuals exposed to radiation from airborne and waterborne radioactive effluent releases. These models combine information on effluent release timing and magnitude, transport of the released effluents through the environment, and the exposure of individuals to radiation from these releases to estimate absorbed doses. Such models could be used to estimate doses to individuals near nuclear facilities to support an epidemiology study.

Absorbed doses to individuals near nuclear facilities are anticipated to be very low, in most cases well below variations in levels of natural background radiation in the vicinity of individual facilities. Absorbed doses to these individuals are also anticipated to be below levels of radiation received by some members of the public from medical procedures and air travel. Consequently, dose estimates used in an epidemiologic study need to account for these other sources of radiation exposures and possibly for other potential confounding factors such as exposure to hazardous (and potentially carcinogenic) materials released from industrial facilities located near nuclear facilities.

Question: Since there are many more coal power plants, are there comparisons in carcinogenic emissions and effects on nearby populations?  I ask this to maintain a perspective that seems lost to the general population.

The report does not discuss comparative assessment of risks from living near a nuclear power plant versus living near a coal power plant.

Question: I have reviewed the report, and I wonder why the committee is not recommending to start out with a disease surveillance method, such as cluster analysis, to identify “hot spots” in which cancer rates are high, followed by traditional epidemiology methods. The modern approaches to disease surveillance are not like what used to be available to researchers 20 years ago, and the references cited for not using a cluster analysis in the report go back to the early 1990′s. A software like SaTScan allows you to integrate information from a Poisson Regression to adjust for multiple covariates, and it allows you to conduct a multivariate analysis for multiple cancer types, as the NAS board has recommended for Phase I.  

The committee discussed surveillance approaches as a possible way to detect areas of higher incidence.  In reviewing the options, the committee noted that the statement of task focuses on comparing cancer incidence in populations near nuclear facilities with populations not near such facilities.  That is, the populations of interest are defined and the goal is to propose a design (and accompanying methodology) to best address this comparison.  While the committee discussed methods such as SaTScan as appropriate for deciding the radius of interest, the committee did not judge that the methods directly addressed the primary questions of interest as directly as the proposed designs.

Question: Your response to “Is it possible to assess the does?” indicates that it isn’t since the does is below detectable levels.  Yet you estimate doses using exposure models based on reported effluent radioactivity concentrations.  The validity of this approach, “you can’t measure it but you can calculate it”, seems very weak if not unacceptable. 

I also find the response on comparative analysis of health effects resulting from exposure to coal fired or gas-fired power plant effluents is unacceptable. How do we know which type of plant has be the lowest health effect??  It could be the nuclear power plants are preferable for exposure to public health effects. 

This study does nothing to resolve the ‘fear factor” associated with nuclear plants and probably because it cites discredited studies; e.g., the German study does nothing but increase the “fear” arising from uncertainty.

The U.S. Nuclear Regulatory Commission (USNRC) requires that nuclear power plant operators measure radioactivity in the environment surrounding the plants. The purpose of the environmental monitoring program is to demonstrate that the nuclear power plant releases do not exceed the regulatory limits; it is not to measure doses to the populations surrounding the plants which could be used in an epidemiology study. For this reason, data from the environmental monitoring programs cannot be used alone to estimate doses to individuals, as they are either below the detection limits or are not sensitive enough for use in dose estimation. To estimate doses to individuals, data from effluent releases could be used.

To reiterate, the USNRC asked the National Academies to develop a design for a cancer epidemiology study to assess potential cancer risks associated with living near the nuclear facilities it regulates. A comparative analysis was not part of the study request.

The committee presents in its report an extensive literature review on studies of cancer risks near nuclear facilities (see Appendix A). The German study is one of the many studies described in the review and its strengths and limitations are discussed.

Question: In order to analyze cancer risks near nuclear facilities, data on radioactive releases – in the air, water, and soil – from nuclear facilities are of paramount importance.  However, the available data on radioactive releases have serious shortcomings, and the Nuclear Regulatory Commission (NRC) has not fixed these shortcomings over time.

The shortcomings of data on radioactive releases from nuclear power plants include:

1. The data are obtained by the individual power plants (owned by private companies) and provided to the NRC.  How accurate/reliable are these data?  Have these data been audited every so many years by an independent agency for accuracy and reliability?

2. Are these data consistently obtained by all nuclear power plants?  That is:

a. Are they obtained on the same day/week of specific months during the year;

b. Are they obtained from a same direction/site downwind (northeast) from the nuclear power plants? 

c. Are they obtained from the same distance from the nuclear power plants? 

d. Are they obtained under similar weather/wind conditions?  If the reading is done 50 yards from the power plants and there are strong winds, they can take the radioactive releases in the air and blow them well beyond 50 yards; therefore, these radioactive releases will not be recorded by the censors.

The readings on radioactive releases – in the air, water, and soil – need to be consistently measured for all nuclear facilities, with respect to the variables noted above, and they need to be made available to the public (on the internet, for one) in a format that is easy to understand.  Otherwise, they are of very dubious value.

3. These data have not been made easily available to the public by the NRC, on their website.  Why not?  The NAS staff had to make special requests of the NRC for these data. 

4. It is not clear that the data on radioactive releases made through the NUREG publications include both “routine” releases and “accidental” releases.  Do they?  If not, why not?

5. Radioactive releases from nuclear plants include those that occur as a result of accidents and incidents.  However, the NRC has not collected data on nuclear incidents (Cutter, 2001), that can also be made available to the public.  Why not, given the importance of radiation to public health?   

1. The committee did not examine the reliability/accuracy of the reported data on radioactive releases.

2. As the geography and meteorological conditions (weather/wind conditions) around a nuclear facility vary depending on its location, universal specifications in radioactivity reporting in terms of direction, distance, weather conditions may not be meaningful. The specifications of the environmental monitoring programs of the nuclear facilities need to be “customized” so that each facility’s program serves its purpose: demonstrate that the releases from the nuclear facility do not exceed the regulatory limits.

3. As far as the committee has determined, reports from the environmental monitoring programs and effluent releases programs for the recent years are publicly available on the USNRC’s Agencywide Documents Access Management System (ADAMS). Reports from earlier years (prior to 1975) may be available in microfiche in the USNRC library. The committee was able to retrieve some but not all reports it requested from the library for earlier years.

4. The nuclear facility operators are required to report to the USNRC both routine and accidental releases.

5. See response above.

Question: Advances in genetic analyses and correlations with the potential development of cancer and other diseases are giving new insight into the liklihood of an individual to develop specific cancers.  For example, the average U.S. male has about a 1 in 6 chance of deveoping prostate cancer.  My genetic profile indicates about a 1 in 3 chance of developing prostate cancer and I did  experience the disease. 

Women with some specific genetic mutations are at greater risk of breast cancer than is the average U. S. female.  These mutations may be transmitted to female children and may be expressed as breast cancer in female progeny if a long-term prospective study is performed.  A retrospective study might detect a breast cancer “cluster” caused by a genetic mutation within a single family.

How will the the new “Analysis of Cancer Risks in Populations near Nuclear Facilities” study handle the genetic aspects of detected cancers within the populations surrounding nuclear facilities?

The recommended studies would not handle the issue of genetic susceptibility of cancer within the populations living near nuclear facilities. However, this limitation of the studies would only be of concern if—for some unidentified reason—people that live closer to the nuclear facilities are genetically different from those that live further away and their cancer development is independent of exposure to radiation. There is no reason to believe that such a differential distribution of genetic profiles would exist, although one can argue that such differential distribution of adverse genetic profiles could happen by chance.

The mutations the commenter refers to that predispose women to developing breast cancer, most notably the rare mutations in the BRCA1 and BRCA2 DNA repair genes, also make women carriers more susceptible to the carcinogenic effects of ionizing radiation. A study of cancer risks in populations living near nuclear facilities that would concentrate on genetically susceptible subgroups would have increased statistical power to detect a potential effect. To date, however, either the genetic variants are too rare to be studied separately or to have much impact in general-population studies, or the susceptibility variants show only small elevations in risk and frequently are not replicable. For these reasons, the committee did not recommend that a proposed study concentrate on genetically susceptible subpopulations.

Question: Figure 2.1 on page 2.44 shows “Noble gas releases from (A) BWRs and (B) PWRs in 2008.”

Activity amounts are indicated by lengthe of bar graph on a logarithmic scale.  A problem of interpretation arises in that the bars may include more than one isotope quantity, and the lengths represented by segments in a given bar are multiplicative rather than additive.

Would it not be better to represent the releases from individual plants in clusters of three independent graphs, or else simply represent the single bar as a sum representative of one or more of the three isotopes shown on the legend?

The commenter raises a good point. However, the committee wanted to make two simple points with these graphs: a) there is variation in the noble gas releases between BWRs and PWRs and b) there is variation in the noble gas releases across nuclear plants within these two categories.