By Aditya Mattoo, MD
Faculty Peer Reviewed
Prompted by personal experience, I thought I would explore the alleged causative role of power lines in hematologic malignancies for the next installment of Myths and Realities. In recent years, two close family friends living at separate locations but in homes adjacent to lots with electrical transformers were diagnosed with Multiple Myeloma and Non-Hodgkin’s Lymphoma. Naturally, the coincidence was not unnoticed, so I decided to put power lines on trial and look through the literature to see if a correlation exists or if it is all just media-hyped paranoia.
Coincidently, this past month is the 30th anniversary of the beginning of this saga. In March of 1979, Wertheimer et al published an article that suggested a higher incidence of hematologic malignancies in children who lived near high current power lines in the Denver area.(1) This initial study implied a possible carcinogenic role of the electromagnetic fields (EMFs) generated by power lines although the authors clearly state in the article that there is “no independent evidence or theoretical understanding which seems to support this possibility.”
That didn’t stop the mainstream media frenzy that ensued. The general public was put on alert to this potential silent killer, largely as a result of the works of Paul Brodeur. As a writer for The New Yorker magazine, he brought national attention to this debate in a series of articles and books (one sensationally titled “Currents of Death”) published in the late 1980s and early 1990s. His “exposes” also alleged a government and industrial conspiracy to cover up the relationship between EMFs and cancer.
A quick physics refresher might be in order at this point. Harkening back to our premedical days, recall that the movement of a charged particle (i.e. a current) generates an electric and magnetic field. The electric field is the difference of the electrical potential between two points a circuit (i.e. voltage). The flow of the current generates a magnetic field. These two fields together are referred to as EMFs. The EM spectrum can be classified into non-ionizing waves (low frequency waves, radio wave, microwave, infrared, visible light, near ultraviolet waves) and ionizing waves (medium/far ultraviolet, x-ray and gamma ray) according to the ability of the EMF to break molecular bonds. Ionizing radiation has mutagenic potential as it can break the bonds of DNA. However, when discussing the EMFs generated by the typical 60-Hz residential electric current, we fall in the extremely low frequency (non-ionizing) area of the EM spectrum. These EMFs are on the order of 0.01 to 0.05 µTesla and have weaker EMFs than radio waves. To put this in perspective, an editorial published in the New England Journal of Medicine on this debate noted that the earth’s static magnetic field is on the order of 50 µT and the EMF generated by using an electrical razor is approximately 60 µT, both of which are 1000 times greater than the EMF generated by the current delivered to your home.(2)
Although the Wertheimer study spurred the scientific community to publish hundreds of subsequent studies attempting to draw a correlation between EMFs and a variety of cancer types in differing age groups, the majority of studies have focused on hematologic malignancies in children. I am pleased to report that the literature has failed to demonstrate any consistent and statistically significant evidence to suggest a relationship. Most studies have been plagued by limitations in design including small sample size, unblinded investigators and the use of wiring codes as surrogates for EMFs. Detractors of the original study criticize Wertheimer’s incorrect assumption that the wiring code of a home could be used as a surrogate for EMF exposure and that EMFs levels were not directly measured.(3)
I will briefly take a moment to mention two of the better designed studies. One of the largest studies to date, conducted by the Children’s Cancer Group, failed to demonstrate any statistically significant relationship of either directly measured EMFs or wiring codes in the homes of 638 children with acute lymphoblastic leukemia as compared to controls.(4) The second study was a meta-analysis that pooled the data of nine separate studies. It showed that of the 3203 children with leukemia exposed to less than 0.4 µT of directly measured EMFs, there was no significant relationship when compared to controls.(5) The one caveat of this meta-analysis is that less than one percent of the pooled study participants (44 children) were exposed to EMF levels greater than 0.4 µT and had a relative risk of 2 in the development of leukemia. Again, the small sample size has critics questioning the validity of this positive finding.
Overall, there is little evidence demonstrating that living near power lines increases the risk of cancer, particularly childhood leukemias. Media supported paranoia can be a powerful force as people to this date still believe an association may exist (myself included prior to researching this post). Also it is important to note that even though we are increasingly exposed to EMFs as technology infiltrates every aspect of our lives, the overall incidence of leukemia has been slowly declining for several decades. Therefore, as judge and jury I find the defendant, Power Lines, not guilty. Court is adjourned until our next installment of Myths and Realities.
Dr. Matoo is a third year resident in internal medicine at NYU Medical Center.
Peer Reviewed by Theresa Ryan MD, Assistant Professor of Medicine, NYU Division of Medical Oncology
1. Wertheimer N et al. Electrical wiring configurations and childhood cancer. American Journal of Epidemiology 109:273-284, 1979.
2. Campion EW. Power lines, cancer, and fear. New England Journal of Medicine 337:44-46, 1997.
3. Farley JW, 2003. Power lines and cancer. Nothing to Fear [online]. Quackwatch. Available from http://www.quackwatch.org/01QuackeryRelatedTopics/emf.html
4. Linet MS, et al. Residential exposure to magnetic fields and acute lymphoblastic leukemia in children. The New England Journal of Medicine 1997; 337(1): 1-7.
5. Ahlbom A, Day N, Feychting M, et al. A pooled analysis of magnetic fields and childhood leukaemia. British Journal of Cancer 2000; 83(5): 692-698.