The causes of ALL are unknown. Like any source of electrical current, power lines produce an electromagnetic field. Even the 60Hz electric lines in American homes produce a weak electromagnetic field. Electromagnetic fields are invisible and can penetrate living tissue. High energy electromagnetic fields are utilized in medicine in the form of ionizing radiation, which is a common treatment of cancer.
Ionizing radiation is hypothesized to kill cancer cells by breaking DNA bonds.
In contrast, low frequency electromagnetic fields such as those generated from power lines cannot break molecular bonds and has no known effect whatsoever on living tissue. The association of power lines and cancer, particularly ALL, has been of great debate in the medical and lay community for over 18 years. The debate began with a report in 1979 which concluded that living near high voltage power lines caused leukemia. This report was based a small cluster of leukemia cases in Denver and relied on wire configurations not actual electromagnetic field measurements. However, it prompted widespread fear and resulted in dozens of further investigations.