The Facts about Low frequency EM fields 1. Is there something to worry about? In 1979 Wertheimer and Leeper reported an association between childhood leukaemia and certain features of the wiring connecting their homes to the electrical distribution lines. Abstract An excess of electrical wiring configurations suggestive of high current-flow was noted in Colorado in 1976--1977 near the homes of children who developed cancer, as compared to the homes of control children. The finding was strongest for children who had spent their entire lives at the same address, and it appeared to be dose-related. It did not seem to be an artifact of neighborhood, street congestion, social class, or family structure. The reason for the correlation is uncertain; possible effects of current in the water pipes or of AC magnetic fields are suggested. There have been many studies since, but no cause-and-effect link between ELF field exposure and cancer has been confirmed. 2. Perry Review article 2.1 The question Are cancers or other health problems linked to exposure to LF EM fields?After nearly a hundred studies anomalous results make no clear conclusion possible. Little as yet is known about possible mechanisms. The question remains, is it necessary to reduce exposure to LF EM fields or is the commotion just the birth of another fad? 2.2 EM Frequency Spectrum See figure right. 2.3 Health effects of EM radiation ELF fields interact with living tissues only by inducing electric fields and currents in them. The magnitude of these induced currents from exposure to ELF fields at levels normally found in our environment, is less than the currents occurring naturally in the body. There is no convincing evidence that exposure to ELF fields causes direct damage to biological molecules, including DNA. It is thus unlikely that they could initiate the process of carcinogenesis. 3. Power lines Electric and magnetic fields underneath overhead transmission lines may be as high as 12 kV/m and 30 µT respectively. Around generating stations and substations, electric fields up to 16 kV/m and magnetic fields up to 270 µT may be found. 3.1 Electric Field Studies Available evidence suggests that, apart from stimulation arising from electric charge induced on the surface of the body, the effects of exposures of up to 20 kV/m are few and innocuous. Electric fields have not been shown to have any effect on reproduction or development in animals at strengths over 100 kV/m. 3.2 Magnetic fields Distance at which magnetic fields are reduced to background levels Field Earth's magnetic field intensity, at its surface Domestic electrical appliances Source television desktop light transmission line 3.3 At 30 cm 1.299 3.281 30.0 µT 50 0.02 to 7 Microtesla (µT) At 1.0 m 0.111 0.121 1.1 Magnetic Field Studies There is little confirmed experimental evidence that ELF magnetic fields can affect human physiology and behaviour at field strengths found in the home or environment. 1 Exposure of volunteers for several hours to ELF fields up to 5 millitesla had little effect on a number of clinical and physiological tests, including blood changes, ECG, heart rate, blood pressure, and body temperature. 4. Ethical questions 1. What is the ethical thing to do when designing in a situation where some doubt about safety exists? 2. If there are potential, but not well understood, hazards in building a product, what are the future consequences of doing nothing? 3. Does the same thing apply to security issues in the design of software? e.g. protection from virus attack, data encryption 4. When it is a matter of public safety, how much expert evidence is enough? 5. Are warnings to the consumer enough to get the designer off the hook? 6. Must a product be engineered to be totally safe at all costs, even if the user is at fault? 7. In designing equipment for consumers where does the balance between cost, efficiency and safety lie? 8. In light of research findings indicating that there is no hazard associated with low-frequency magnetic fields, how much time effort and money should be expended when designing products that will emit this type of radiation? 9. How does this relate to practice in IT? References Wertheimer N, Leeper E, ‘Electrical wiring configurations and childhood cancer’, Am J Epidemiol, 1979 Mar;109(3):273-84. Perry, T.S., Spectrum, IEEE, Dec. 1994, Volume: 31, Issue: 12 Electromagnetic fields from Power lines, Wiring & Appliances, http://www.greenfacts.org/en/power-lines/l2/power-lines-1.htm 1 5 mT = 5,000 µT