Several Japanese medical experts want to bank blood stem cells from workers at the ailing Fukushima Daiichi nuclear plant. The cells would be used as a treatment in case a high radiation exposure makes a worker sick. But the proposal is raising eyebrows among U.S. experts, who say it probably wouldn't save many lives.

In a letter today in The Lancet, Tetsuya Tanimoto of the Japanese Foundation for Cancer Research and four others note that bringing the radiation-leaking nuclear plant under control could take months or years, and some workers could accidentally be exposed to high levels of radiation. While high radiation doses can eventually cause cancer, the immediate health effect is to destroy dividing cells—including blood cells—which wipes out the immune system. The authors point out that some workers after the 1986 Chernobyl disaster received donated bone marrow transplants, and two Japanese nuclear workers got donated stem cell transplants after a 1999 accident.

Stem cell transplant experts in Japan and Europe have endorsed banking the Fukushima workers' stem cells, and medical workers in Japan and in Europe are standing by to help. (The cells would be obtained by giving the workers a drug that nudges blood stem cells from the bone marrow into the bloodstream, then hooking them to a machine that filters out the stem cells.)

Others question the rationale. It's not clear whether donated stem cell transplants helped some Chernobyl workers survive; they received several different types of cells, and there was no control group, says bone marrow transplant expert David Weinstock of the Dana-Farber Cancer Institute in Boston. As for the two Japanese nuclear workers, they eventually died of organ failure caused by radiation anyway, notes radiologist Fred Mettler of the University of New Mexico.

On the other hand, giving the Fukushima workers their own stem cells should work better than donor cells because the patients' own cells won't be rejected by the immune system. Experience with lymphoma patients, who receive a transplant of their own blood or bone cells after radiation to wipe out their cancer, has shown "there's no doubt it helps," says bone marrow transplant expert Nelson Chao of Duke University in Durham, North Carolina.

But a stem cell transplant would help only a worker who received a certain dose—between roughly 5 grays and 10 grays of radiation, Chao says. (Below that, patients survive with other treatments; above it, they would die anyway from damage to the gut and lungs.) The workers would also have had their entire body exposed to radiation. If the workers are partially shielded, like the three who stepped into radioactive water last month, their unaffected bone marrow will replenish the destroyed cells.

The number of the 800 or so workers at the Fukushima plant likely to receive radiation in that narrow dose range "would be pretty limited," Chao says. One scenario that might make more sense, Chao says, is if stem cells were banked only for a subset of 100 or so workers who were the only ones sent into high radiation areas.

Chao says there a "lot of e-mails going around" in response to The Lancet letter, and he expects that a U.S. group that he and Weinstock are part of, the Radiation Injury Treatment Network (RITN), may submit a response. Japan's Nuclear Safety Commission has also opposed the plan because of expert and public disagreements, including a concern that it could give workers false reassurance and make them less careful about taking risks.