Dirty bomb dust proves deadly

By Geoff Brumfiel, Nature News Service, 5 May 2004

Mortality estimates have ignored results of inhaling fallout

A bomb spiked with radioactive material could be more lethal than previously thought, according to physicists who have analysed the consequences of a 1987 accident in Goibna, Brazil.

Estimates made by government officials and scientists could be off by an order of magnitude, Peter Zimmerman of King's College London told attendees of the American Physical Society's annual meeting in Denver, Colorado, on 3 May.

Some officials and nuclear experts say that although radiation from a dirty bomb could cause vast psychological and economic damage, it would result in few, if any, deaths. They argue that the radioactive material contained in the bomb would be too diluted after the blast to expose any one person to a deadly dose.

But Zimmerman says that while those previous estimates consider the effects of exposure to the expected levels of radiation at a blast site, they have failed to take fully into account the possibility that victims might breathe in or ingest radioactive dust.

Zimmerman and a colleague, Cheryl Loeb at the National Defense University in Washington, DC, conducted a new analysis of an incident in Goibna, Brazil, where scrap-metal merchants took a canister containing 1,400 curies of radioactive caesium-137 from an abandoned cancer clinic. Not knowing what the glowing dust was, they dispersed about a tenth of it at a party, during which over 150 people inhaled or swallowed the material.

Six people in the area died as a result of the incident, says Zimmerman, three of whom were not at the party and had had no direct contact with the material.

Using those numbers, Zimmerman estimates that if a bomb dispersed a similar amount of material over a wider area, as many as 150 people could die and 1400 could become ill.

That estimate “seems reasonable”, says Benn Tannenbaum, a physicist at the Federation of American Scientists, an arms control group in Washington, DC. Tannenbaum says that the Goibna incident is particularly disturbing because it is unclear how some of the victims became contaminated, which suggests that even indirect contact with the material was enough to kill them.

However Michael Levi, who is a physicist at the Brookings Institution, a Washington-based think-tank, points out that the Goibna victims did not receive treatment until several days after their exposure. He hopes that the death toll from a dirty bomb might be lowered considerably if victims who ingested or inhaled material were treated immediately following the blast.