ALMOST without exception, scientists and policy makers agree that hybrid vehicles are good for the planet. To a small but insistent group of skeptics, however, there is another, more immediate question: Are hybrids healthy for drivers?

There is a legitimate scientific reason for raising the issue. The flow of electrical current to the motor that moves a hybrid vehicle at low speeds (and assists the gasoline engine on the highway) produces magnetic fields, which some studies have associated with serious health matters, including a possible risk of leukemia among children.

With the batteries and power cables in hybrids often placed close to the driver and passengers, some exposure to electromagnetic fields is unavoidable. Moreover, the exposure will be prolonged  unlike, say, using a hair dryer or electric shaver  for drivers who spend hours each day at the wheel.

Some hybrid owners have actually tested their cars for electromagnetic fields using hand-held meters, and a few say they are alarmed by the results.