The following post is by Geoffrey Kabat, a cancer epidemiologist at the Albert Einstein College of Medicine. Kabat has conducted studies of environmental factors, including EMF, in relation to breast cancer risk, and is the author of Hyping Health Risks: Environmental Hazards in Daily Life and the Science of Epidemiology.
In an earlier post from February 20th I commented on the alarm caused by the report of a “cluster” of eight breast cancer cases diagnosed between 2000 and 2008 in one building on the campus at the University of California at San Diego. I have now examined the report commissioned by the UCSD administration, which was drafted by a UCSD epidemiologist. While providing only limited information about the characteristics of the eight breast cancer cases, the report focuses attention on exposure to electromagnetic fields from the building’s elevator, concluding that such exposure could have made a “modest” contribution to the cluster.
I believe that this initial response to the UCSD cluster is unfortunate and provides an example of how the response to a health scare can have negative consequences, causing needless anxiety and confusion, when what is needed is a systematic and critical approach reflecting the best that epidemiology as a discipline has to offer.
The report by Professor Cedric Garland addresses potential exposures in the Literature Building, where the eight women diagnosed with breast cancer worked as faculty or staff. Professor Garland considers potential hazards from molds, chemical, and radiological exposures, finding no support for these as playing any role in the breast cancer cluster. The final issue, which receives the most attention, is the possibility that exposure to electromagnetic fields (EMF) from the elevator and electrical equipment may have contributed to the cluster.
Professor Garland concludes that “some possibility exists” that exposure to electromagnetic fields on the first floor of the building in very close proximity to the electrical and elevator equipment rooms could have “contributed modestly” to increased risk, although he states that “this exposure is unlikely to be a principal cause of breast cancer that has been diagnosed in people who have worked in this small area” (pp. 20-21).
The Garland report is clearly being taken seriously by the university administration, which has hired a UCLA epidemiologist specializing in EMF to conduct a two-month investigation of the cluster. In addition, the author’s identification of EMF as a possible hazard has caused anxiety and anger, and has prompted calls for the administration to take action to remediate the hazard (see story in Inside Higher Ed). For these reasons, it is important to take a critical look at the case Professor Garland makes for a role of EMF.
Professor Garland implies that weak EMF (as low as 2 milliGauss) can play a role in causing cancer, a belief that is contradicted by a massive amount of scientific evidence. His references to the relevant literature are limited and selected. Furthermore, he shows an uncritical acceptance of the few studies he does cite, even though these have clear deficiencies and are at variance with the preponderance of the evidence. Tellingly, he fails to cite some of the major epidemiologic studies on the topic of EMF and breast cancer or to acknowledge the large body of experimental evidence that has failed to find reproducible evidence of biological effects.
According to the National Research Council (1), ambient levels of 60 Hz magnetic fields “in residences and most workplaces” are typically 0.1-3.0 milliGauss. The NRC concludes that “no conclusive and consistent evidence shows that exposures to residential electric and magnetic fields produce cancer, adverse neurobehavioral effects, or reproductive and developmental effects” (NRC, p. 2).
A critical reading of the Garland report raises a number of specific issues, questions, and ideas for further study, which are spelled out below.
1. Time period defining the cluster
Garland defines the time period during which 8 cases of breast cancer were diagnosed in the Literature Building as 2000-2008. However, he notes that an additional case of breast cancer was diagnosed in 1991 (p. 6). If there were no other cases diagnosed between 1991 and 1999, then the occurrence of breast cancer over the period 1991-2008 is half that in the later period. This information is relevant to assessing the existence of a cluster, as well as a possible cause, especially since, presumably, the elevator on which Garland focuses attention was in operation during the earlier period.
2. Age and duration of employment
Professor Garland gives the ages at diagnosis of the 8 affected women and rightly concludes that the relatively young age (mean age at diagnosis was 53 years) is due to the fact that this is a working population.
However, a crucial piece of information for assessing the role of any environmental exposure in the building is the length of time each woman worked in the Literature Building—when she started working in the building and if she stopped, when. This information is not provided, although it should be readily available.
3. Location in the building
Another basic piece of information necessary to draw any inferences about possible exposures is the office location(s) of each of the eight women over their period of employment. Furthermore, it would be helpful to have a map, or floor plan, of the building, floor by floor, showing the location of the offices where each case worked and the location(s) of the elevator and equipment room as well as the electrical riser.
4. Clinical characteristics of cases
It would also have been valuable to obtain clinical information to determine whether there was any unusual pattern among the cases or whether they were similar to breast cancer cases (of comparable age) in terms of tumor size, stage, grade, histology, hormone receptor status, HER-2/neu status, family history, etc. The presence or absence of an unusual pattern in the distribution of clinical parameters could shed light on the etiology of these cases. For example, if an unusually high proportion of the cases had a family history of breast cancer in a first degree relative, this would help account for the cluster.
5. References to the Scientific Literature
In what purports to be a scientific report attempting to elucidate possible causes of a cluster, one would expect that the relevant literature on EMF and breast cancer would be cited. Three large case-control studies of residential EMF exposure and breast cancer have been published (2-4). These were conducted in Seattle, Washington; on Long Island, New York; and in Los Angeles. None of the 3 studies showed any evidence of an association. (Only one of these studies is cited by Garland). In addition, a larger number of studies have examined the association of electric blanket use and breast cancer (5, 6). Electric blanket use, especially use of older blankets, entailed some of the highest EMF exposures encountered in everyday life. Nevertheless, these studies also show no evidence of an association. (No reference is made to these studies in the report).
Thus, Garland’s statement that “Some epidemiological and laboratory studies have linked exposure to residential levels of electromagnetic fields from high electrical current configurations … to breast and other cancers, although the literature on this association is mixed (p. 12)” is misleading. In fact, consideration of the totality of the epidemiologic and experimental literature on EMF and breast cancer and cancer generally indicates that weak fields of the kind encountered in everyday life do not increase the risk of cancer. Numerous comprehensive reports and reviews support this position (1, and 7). In addition, the possibility that weak EMF can affect biology has been called into question on theoretical grounds (9, 10).
Another basic fact that one might have expected Professor Garland to mention is that the strength of magnetic fields falls off rapidly with increasing distance from the source.
6. Conclusion and future study
The conclusion of the Garland report that EMF from the elevator in the Literature Building may have contributed to the cluster of 8 breast cancer cases is based on a selective and biased interpretation of the extensive epidemiological and experimental literature on EMF exposure and the risk of breast cancer. Rather than collecting all of the information relevant to describing the cluster, due to Professor Garland’s preconceived ideas about EMF, his investigation focused attention on EMF, thereby causing unnecessary alarm, distrust, and confusion in members of the UCSD community.
In order to further evaluate the significance of the cluster, it would be extremely valuable to conduct an historical cohort study of all female UCSD employees who worked in the Literature Building as of 1/1/1990. Such a study would measure the actual population-based breast cancer incidence rate in this cohort and would provide a more systematic assessment of the cluster and of possible explanations.
1. National Research Council. Possible Health Effects of Exposure to Residential Electric and Magnetic Fields. Washington, D.C.: National Academy Press, 1997.
2. Davis S, Mirick DK, Stevens RG. Residential magnetic fields and the risk of breast cancer. Am J Epidemiol 2002; 155: 446-454.
3. Schoenfeld ER, et al. Electromagnetic fields and breast cancer on Long Island: a case-control study. Am J Epidemiol 2003;158:47-58.
4. London SJ, et al. Residential magnetic field exposure and breast cancer risk: a nested case-control study from a multi-ethnic cohort in Los Angeles County, California. Am J Epidemiol 2003;158:969-980.
5. Sandler DP. On blankets and breast cancer (editorial). Epidemiology 2003;14:509.
6. Kabat GC, et al. Electric blanket use and breast cancer on Long Island. Epidemiology 2003;14:514-520.
7. National Institute of Environmental Health Sciences. NIEHS Report on Health Effects from Exposure to Power-Line Frequency Electric and Magnetic Fields. NIH Publication no. 99-4493, Washington, D.C., 1999.
8. Lacy-Hulbert A, Metcalfe JC, Hesketh R. Biological responses to electromagnetic fields. FASEB J 1998;12:395-420.
9. Adair RK. Constraints on biological effects of weak extremely-low-frequency electromagnetic fields. Physical Rev A 1991;43:1039-1048.
10. Bennett WR, Jr. Cancer and power lines. Physics Today (April, 1994):23-29.