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on the line to the service drop wires.* Since the secondary wire was carrying sufficient current to feed the dozen or so service lines directly supplying the local houses, it was producing the strong magnetic field which seemed to be implicated in the increased rate of childhood leukemia. Having consulted a physicist friend, Ed Leeper, about these unusual findings, it became clear to Wertheimer that there was a factor missing in her original equation about the direct and appar- ently straightforward relationship between the increased rate of leukemia in children and the distance of the transformers from the childhood homes of leukemia victims. The correlation could cer- tainly not be explained in terms of the magnetic field generated by the transformer, nor by the alternating electric field generated by the transformer, nor by the alternating electric field generated by the wires as a result of the 60 hertz alternating current which passed through them on its path to households from the transformers. The reason for this is simply that the magnetic field given off by the transformer should in principle drop off so sharply that it would be negligible even at the house closest to It. Nor could the electric field generated by the alternating current in the lines be responsible for the varying rates of leukemia from one house to another, since the voltage upon which these fields would depend does not change in strength according to the wire distance from the transformers.‘ There would be no difference, in other words, in the force of the electric fields as manifest from one house to the other. The key needed to unlock this final door in the investigation was found when Wertheimer enlisted Leeper's help for the production of a gaussmeter, a device used to measure magnetic field strengths. Testing the device in a neighbourhood whose pole and wire config- uration were typical of the distribution network of the electricity system of the city, she was surprised by what she discovered. Beginning at the base of the transformer pole at an alley entrance, the gaussmeter gave off a loud hum, indicating the presence of a strong magnetic field. As she walked up the alley past the first house, however, the hum of the gaussmeter did not subside and strangely continued until she reached the next pole, located at the far corner of the lot of the second house where hum from the gauss- meter suddenly ceased. Wertheimer noticed that this was the point at which several wires known as ‘service drops' linked up with and reduced the current load coming from the secondary distribution line fed by the transformer two houses away. She noticed also that the point at which the first-span secondary distribution line finished, coincided with the pronounced decrease in the childhood leukemia rate. On the basis of these initial observations Wertheimer postulat- ed that the association she was searching for was not the proximity of the neighbourhood transformer to the homes of childhood leukemia victims, but rather the proximity of the secondary distri- bution line which ran from the transformer past the first two houses ... follow-up studies revealed that the rate of leukemia for children living in dwellings where first-span secondary wires ran past them was disproportionately higher than for children living in homes away from these wires. es Wertheimer followed up her preliminary findings with an exten- sive investigation of the correlation between the field strengths of first-span secondary wires and the birth addresses of childhood leukemia victims. These follow-up studies revealed that the rate of leukemia for children living in dwellings where first-span sec- ondary wires ran past them was disproportionately higher than for children living in homes away from these wires.‘ Encouraged by these findings, Wertheimer decided to expand her research to deter- mine whether the incidence of other forms of childhood cancer could be associated with exposure to high-current wiring of any kind, not just first-span secondary wires. Several categories of high-current exposures were identified and included in the study. Homes situated less than 50 feet from first- span secondaries, those within 65 feet of a group of three to five small-gauge primary wires, and homes located within 130 feet of either three-phase, large-gauge primary wires or of a group of six or more small-gauge primary wires, were all regarded as high-current risk homes,’ The results of her research were startling and alarm- ing. As Brodeur puts it: "During 1976 Wertheimer visited the birth and diagnoses addresses of each of the cancer cases, the birth addresses of each of the controls, and the addresses at which control children had been living at the time their matched cases had been diagnosed with cancer. She then proceeded to draw a diagram describing the location, size, type, and proximity of the electrical wires and transformers she had observed in the vicinity of each of these homes. Once that was done, she analysed the data and found that her predic- tion had held up: children who had lived in homes near high-current electrical wires had died of cancer at twice the rate seen in children living in dwellings near low-cur- rent wiring. The association was strongest among those children who had spent their entire lives in a high-current home. Particularly disturbing was the fact that of six chil- dren in the study population who had lived near high-cur- rent wires coming directly from power substations, all were cancer victims." SINGLE STOREY RAT OBSERVATION Although it had previously been assumed that any harmful effects of electromagnetic fields would ordinarily be cancelled in house- hold wiring, by virtue of the fact that retum current tends to balance the supply current, Wertheimer and Leeper argued that such equi- librium is rarely preserved.” The problem is that some of the cur- rent which should return through the wires tends instead to flow through the ground. Inasmuch as most household electrical systems are grounded through the plumbing, the return current passes through the pipes of the house to produce a new magnetic field within the home itself. This suggestion was especially disturbing, since the duration of continuous exposure to a magnetic field SH Vol 2, No 13 - 1993 42¢NEXUS 42 — ————— ————————