In what is probably the largest study ever conducted on EMF exposure, researchers in Sweden announced in 1992, they had determined a dose-response relationship between exposure to EMFs from power-distribution lines and childhood leukemia.

The Feychting/Ahlbom study included data for 500,000 people over a 25 year period. It carefully excluded other factors like socio-economic status, air pollution, and toxic chemicals as causes. They found an increase in childhood leukemia, lymphoma, and brain tumors. In the case of childhood leukemia a clear dose-response relationship was observed. A 1 milligauss EMF resulted in twice the risk of developing leukemia as the controls, a 2 milligauss exposure resulted in three times the risk, and 3 milligauss exposure resulted in four times the risk. While these are rare cancers, these are statistically significant figures.