LONDON (AP) - A review of recent studies on electromagnetic fields failed to determine whether they cause childhood leukemia, researchers said Tuesday, but they believe overhead power lines would not be the main culprit.

The studies show a statistical link between strong electromagnetic fields in the home and childhood leukemia, though that might simply be due to flawed research, said Sir Richard Doll, the man who first confirmed the link between smoking and lung cancer.

"I'm not convinced there is an association, but that's a matter of judgment," said Doll, a professor of epidemiology at Oxford University who led the review panel.

The study, commissioned for the National Radiological Protection Board, a government agency, is the most detailed examination to date of the cancer risk from electromagnetic fields, according to the Imperial Cancer Research Fund.

Other recent reviews have suggested a link, but have not proven it.

The latest findings are based on nine major studies conducted since 1994. The researchers of each of the studies converted their data into a form where they could be pooled so that Doll's group could draw more meaningful conclusions.

"The results of the nine show an increased risk of childhood leukemia, but really only with very high doses," Doll said.

The threshold for a possible link was 0.4 microTesla. Magnetic field exposure is 1/10th of that in the majority of British homes, Doll said, and exposures are similar in continental Europe.

A typical American home has a magnetic field level that ranges from 0.05 microTesla to 0.4 microTesla. with an average value of 0.09.

North America has higher levels, experts say, because electricity is supplied at 110 volts, which produces a stronger magnetic field than the European 220 volt system.

The analysis also revealed that magnetic fields from overhead power lines are unlikely to be the main culprit, the experts said.

"It was quite a surprise to us that the vast majority of homes with high levels of magnetic fields - 80 percent of them - were away from power lines," Doll said. "Is it in the home's wiring? We don't know."

Appliances such as toasters, televisions and microwave ovens only make up between 10 percent and 30 percent of the total magnetic field exposure in the home, said Stuart Allen, head of the radiological protection board's electromagnetic fields group.

One reason why scientists have not been able to reach a definitive conclusion after decades of research is that any link would involve a tiny increased risk of a rare disease in a small number of people, experts said.

Dr. Chris Portier, director of environmental toxicology at the U.S. National Institute of Environmental Health Sciences said scientists need to better understand how childhood leukemia develops before the magnetic field question can be answered.

Because the causes have not been identified, studies cannot be designed to correlate causes with electromagnetic fields, he said.

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