The risk is certainly greater for them, said radiation biologist Jackie Williams of the Center for Biophysical Assessment and Risk Management Following Irradiation at the University of Rochester Medical Center. All the immediate casualties at Chernobyl were among workers at the site who were exposed to heavy doses of radiation.
Medical physicist Jerrold Bushberg of UC Davis has received reports that radiation exposure in the site was 1,000 microsieverts per hour. "That's a high level, but not extraordinarily high," he said. "Even if someone had to work in that environment for 48 hours, that is below what radiation workers would be allowed in a year."
How does the possible exposure compare with what happened at Three Mile Island and Chernobyl?
The average radiation dose to evacuees from the most highly contaminated areas involved in the Chernobyl disaster was 33,000 microsieverts, according to the IAEA. Among the 600,000 people most affected, there were an estimated 4,000 additional fatal cancers on top of the 100,000 fatal cancers expected in that population.
The average dose of radiation absorbed by people who lived within 10 miles of Three Mile Island at the time of the 1979 accident was 80 microsieverts, according to the American Nuclear Society. For the sake of comparison, the exposure from a single X-ray is 100 microsieverts.
Has the threat of a meltdown or further explosions passed?
Most experts believe the chances of such a disaster are remote. But some observers said Japanese officials have not provided enough details to allay their fears.
"We're very, very concerned about the lack of information coming out of the government, " said Aileen Mioko Smith with Green Action in Kyoto, Japan. She said there was already vocal opposition in Japan about building new power plants. "I think there will be large public implications from this."
Could radiation make its way to the United States?
A catastrophic meltdown in Japan would probably not threaten the health of Americans living in Hawaii or on the West Coast, experts said.
"There would be no cause for any concern," Bushberg said. Any radiation that escaped from the plant would be diluted by air currents as it traveled over the Pacific Ocean. Should a meltdown occur, the U.S. Departments of Energy and Defense would surely track the movement of any radiation plume, Alvarez said.
What measures were taken after the explosion ?
Officials of Tokyo Electric Power Co., which owns the plants, began pumping seawater into the disabled reactor to keep it cool. The company reported to the IAEA that this action had reduced the release of radiation. Some experts called that an act of desperation that seemed likely to fail.
"I would describe this measure as a Hail Mary pass," said Robert Alvarez, an energy expert at the Institute for Policy Studies. Alvarez spoke at news conference Saturday organized by the environmental group Friends of the Earth.
Others, however, said the reduced levels of radiation at the site indicate the plan is working. "I've been encouraged by what I've been hearing," said Ron Chesser, director of the Center for Environmental Radiation Studies at Texas Tech University.
Why didn't they pump in seawater before?
The salty water is very corrosive and can damage the pipes in the cooling system, so it has never been used for cooling a nuclear core, experts said. But when the explosion destroyed the system for circulating freshwater through the core, company officials thought they had little choice left but to inject cold seawater into the containment vessel as a last-ditch measure to cool it. At this point, damage to the pipes is inconsequential.
Photos: Scenes from the earthquake
Time staff writer Amina Khan contributed to this report.