WASHINGTON -- Hand-held metal detectors, used for security checks at airports and a growing number of other sites, do not harm pregnant women or their fetuses, Food and Drug Administration scientists reported yesterday.

"So far as we know, this is the first study of actual radiation exposure levels from hand-held metal detectors," Dr. Wolfgang Kainz said. He is with the FDA's Center for Devices and Radiological Health, which regulates radiation-emitting electronic products.

Kainz and three associates tested nine models of hand-held metal detectors, the kinds most widely used by security personnel.

Use of the devices has increased substantially since the Sept. 11, 2001, terrorist attacks, and pregnant women often are concerned about how they might affect their unborn children.

Hand-held detectors -- like walk-through security screening stations and anti-theft systems near the exits in stores and libraries -- do not release the damaging form of radiation found in X-rays or nuclear devices. They employ electromagnetic radiation similar to that passing through people from radio and television broadcasts, mobile telephones, electric power lines or alarm systems.

Airport baggage screening machines do use X-rays, but are heavily shielded and do not expose workers or passengers to dangerous radiation.

Kainz's group calculated the radiation that would reach the fetus in a woman in her eighth month of pregnancy during a typical concealed weapons sweep. They compared it to standards posted by international radiation-safety organizations to protect people against the heating effects of radiation and against nerve stimulation.

Scanning with a metal detector would expose a fetus to 60,000 times less than the limit for tissue heating.

Kainz said he plans similar tests on walk-through metal detectors anti-theft systems to verify their safety. Experts widely regard the devices as safe for pregnant women, including those in early stages of pregnancy when the fetus is most vulnerable.