The Wertheimer-Leeper scheme comprises 5 categories: buried, very low current configuration (VLCC), ordinary low current configuration (OLCC), ordinary high current configuration (OHCC), and very high current configuration (VHCC). These categories were dichtomized as low (buried, very low, and ordinary low) and high (ordinary high and very high) wire codes. The modified wire codes analyzed in the present study were derived based on their relations with measured fields. The three categories of the modified wire code are high wire code (HWC, homes within 20 m of a transmission or three-phase primary line), medium wire code (MWC, homes that are not HWC but have a transmission line or three-phase primary line within 46 m or an open secondary line within 26 m), and low wire code (LWC).
|Reference group 1||Wertheimer-Leeper scheme, wire code: buried wire|
|Group 2||Wertheimer-Leeper scheme, wire code: very low current|
|Group 3||Wertheimer-Leeper scheme, wire code: ordinary low current|
|Group 4||Wertheimer-Leeper scheme, wire code: ordinary high current|
|Group 5||Wertheimer-Leeper scheme, wire code: very high current|
|Reference group 6||wire code: low|
|Group 7||wire code: high|
|Reference group 8||modified wire code: low (LWC)|
|Group 9||modified wire code: medium (MWC)|
|Group 10||modified wire code: high (HWC)|
The modified wire code generated risk estimates that were precise elevated for the high wire code compared to low wire code classifications. The odds ratios for childhood cancer, leukemia, and brain cancer were significantly elevated. Potential confounding was examined and generally found to be absent.
The reanalysis of the data on childhood cancer and wire configuration codes showed a stronger relationship for the modified wire codes as to the original Wertheimer-Leeper scheme.
Selection bias due to different participation of controls in the study cannot be ruled out.