The risks of nuclear terrorism are commonly misunderstood. It’s unlikely, given technological difficulties and security measures, that an extremist group could build a large-scale atomic weapon. But a group could easily obtain material for a smaller radiological weapon: a so-called dirty bomb.

Thousands of businesses and medical centers around the world, for example, keep potentially deadly stockpiles of the radioactive isotope cesium-137. Even a small amount of cesium-137, dispersed through a crude conventional bomb, could render a square mile or more of a populated area uninhabitable. While such a blast would kill no more people than a conventional explosion would, millions of people in the fallout area could be exposed to cancer-causing radiation. Cleanup costs could run into the tens of billions of dollars.

Yet supplies of cesium-137 and three other substances — cobalt-60, iridium-192 and americium-241 — are insufficiently regulated and ill-protected from theft. What’s needed is an international effort to secure these radiological materials — just as the International Atomic Energy Agency has helped member countries protect nuclear energy waste.

Cesium-137 is a radioactive isotope with a half-life of 30 years used in hospital irradiators to purify blood for transfusions. About 500 hospitals in the U.S. — 35 in New York City alone — operate such machines. They contain about 3,000 curies of cesium-137 in water-soluble, powdered form, which would be easy for terrorists to spread via an explosion.

The remarkable fact is that these irradiators aren’t even necessary anymore. High-powered X-ray machines can now do the same job. The new machines cost about $250,000 each — but that’s far less than what a hospital would need to pay in liability costs if its cesium were used as a “weapon of mass disruption.” And the federal government has already agreed to pay for the removal and disposal of the cesium.

The three other most worrisome isotopes are not so easily replaced. Cobalt-60, used in so-called Gamma Knife cancer treatment, has a short half-life of five years. Although it’s a solid metal and therefore harder to disperse than a powder, it is still a serious radiation threat. Americium-241 and iridium-192 have industrial applications; the former is used in oil exploration, even in developing nations where security is negligible.

The growing terrorist threat should give industry and government agencies new incentive to ramp up research to find alternative technologies. All 168 member states of the IAEA should sign on to the global joint statement on enhancing radiological security — and make mandatory the agency’s recommendations for increasing security of stockpiles, notifying neighbors of potential thefts and phasing out the use of dangerous isotopes.

Small, deadly and capable of spreading terror: Extremist groups such as Islamic State and deadly isotopes have a lot in common. Keeping the world safe means keeping them apart.

(c) 2016, Bloomberg View · No Author