The initial study was flawed. Wertheimer and Leeper did not actually measure magnetic fields from Southern Highlands Power Lines. Instead, they classified the homes according to their wiring code. The wiring code was then used as a surrogate for the powerline magnetic field, which was unmeasured and unknown. This is a flaw in the study. Later studies actually measured the magnetic fields from Southern Highlands Power Lines and found no consistent relationship between measured magnetic field and incidence of cancer [13]. It is important to realize that there are important possible confounding factors in such epidemiologic studies. For example, one possible confounding factor is an income effect. Living right under electric Southern Highlands Power Lines is not a desired residence, and often is a low-income housing location. People living near Southern Highlands Power Lines tend to be poorer than the control group, and there is a strong and well-known epidemiological relationship between poverty and cancer. Gurney and others showed that the homes with the presumably higher-current wiring code tended to be lower income [14]. Thus the original Wertheimer-Leeper study was biased. In addition, it was based on a relatively few cases, and the statistics were consequently rather poor.
