Could missing Wal-Mart signs wind up as dirty bomb?
Muriel Kane
Published: Sunday February 15, 2009

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A little over a year ago, a routine audit at Wal-Mart reported a few missing exit signs at the company's stores and warehouses. As the audit continued, more and more signs turned up missing, and a month ago, Wal-Mart revealed that as many as 20% of the 70,000 signs at its 4500 facilities cannot be accounted for, a stunning total of 15,800 signs in all.

This would be of no particular concern -- except that the signs are radioactive. They contain tritium gas, a form of hydrogen which is used for emergency exit signs because of its ability to glow in the dark when the power goes out.

Tritium is not radioactive enough to be considered dangerous on casual contact. But if eaten or inhaled it can become absorbed into the body and may lead to cancer or reproductive abnormalities. Sean-Patrick Stensil of Greenpeace Canada told the Toronto Star, "The problem is that because it's hydrogen it can actually become part of your body. The radiation doesn't emit far, but when it actually becomes part of your cell it's right next to your DNA. So for a pregnant woman, for example, it can be really dangerous."

There are more than 2 million such signs in North America, and their use and disposal is supposed to be monitored by the U.S. Nuclear Regulatory Commission. Despite this, broken signs are often simply thrown away and wind up leaching their tritium into landfills. In February 2006, the Pennsylvania Department of Environmental Protection found that more than half of its water measurements downstream from landfills showed tritium levels that violated EPA guidelines for drinking water.

The NRC, whose records reveal a long series of event notification reports concerning Wal-Mart, has been seriously shaken up by the oversight failure. On January 16, it sent out a request for "61 organizations to check tritium exit signs in their possession against their records and to report any lost or missing signs to the agency."

The list includes such heavy users of the signs as AMC Theaters, Boeing, Brigham Young University, the Department of Veterans Affairs, Hilton Hotels, Home Depot, the Smithsonian Institution, and the U.S. Postal Service.

Although there is no indication that the Wal-Mart case involves anything worse than sloppy disposal methods, the greatest fear is that similar signs could be mixed with explosives and used to create a dirty bomb. "Most experts think the main purpose of a dirty bomb is to cause panic, disruption and expensive cleanup rather than lots of dead bodies," Norm Rubin, the director of nuclear research at a Toronto firm, told the Star. "A bunch of tritium, especially if oxidized in an explosion, would probably do that job fine."

Canada is one of the world's major producers of tritium, which is an abundant by-product of the particular design used in its nuclear reactors, and two Canadian firms are the leading North American suppliers of the signs. Compared to the U.S., Canada has been relatively lax when it comes to standards for tritium devices and does not require licensing or close record-keeping.

In 2007, Greenpeace warned that "releases of radioactive tritium from Canadian nuclear power plants are so elevated that children under 4 and pregnant women shouldn't live within 10 kilometres of an atomic generating station, and those living within five kilometres shouldn't eat food grown in their gardens."

In response, the Canadian Nuclear Safety Commission issued a report (pdf) in January 2008, asserting that there was no threat to health because "current tritium levels in drinking water are orders of magnitude less than the GL of 7,000 Bq/L near nuclear facilities, and similarly well below the European Unionís GL of 100 Bq/L."

Ontario Hydro also stated that it would cost $1 billion to lower tritium emissions to the level recommended by Ontarioís Advisory Committee on Environmental Standards, and in the end, no official action was taken. Now Canadian environmental activists appear to be hoping that the Wal-Mart incident will raise public awareness of the potential risks of tritium.