The cobalt-60 source began its life as a medical instrument at Ramathibodi Hospital in Bangkok, treating cancer patients with precisely directed gamma radiation. The hospital retired the unit in 1994 and sold it to Kamol Sukosol Electric Company, the Thai agent for its Canadian replacement. The problem was that nobody could take the old machine back -- Siemens had stopped servicing the model, and the Canadian supplier Nordion had not manufactured it. KSE stored the unit in a warehouse alongside two other unlicensed devices, but when the lease expired in 1999, the company moved all three to an unused car park in Bangkok's Prawet District, owned by its parent company. The car park was fenced, but the fence had been breached. Neighborhood residents regularly entered to play football in the open spaces. Thailand's Office of Atomic Energy for Peace, the regulatory agency responsible for tracking such sources, was never informed of the transfer. The cobalt-60 had become what nuclear regulators call an orphan source -- radioactive material outside any system of regulatory control.

The four men who pried open the cylinder on that February day immediately began feeling ill -- headaches, nausea, vomiting. They did not connect their symptoms to the metal they had handled. The scrap collectors sold the dismantled pieces at a local scrapyard, where employees continued handling the contaminated material. When the scrapyard workers grew sicker over the following week, the owner blamed the metal itself and told the collectors to take it elsewhere, discarding two smaller pieces. But the damage was already spreading. The scrapyard owner, her husband, her mother, and her maid -- all of whom lived across the street -- began developing symptoms as well. A stray dog that frequented the scrapyard died. By mid-February, those exposed were presenting with burn wounds, swollen hands, diarrhea, fever, and hair loss. One by one, they arrived at hospitals across Samut Prakan and Bangkok. It was not until February 18, when doctors at Samut Prakan Hospital noticed that multiple patients shared the same unusual constellation of symptoms including leukopenia, that someone finally thought to ask about radiation.

The OAEP's emergency response team arrived at the scrapyard on the evening of February 18 and found radiation levels at the entrance measuring one millisievert per hour -- far above normal background levels. The recovery operation that followed was improvised and urgent. An excavator cleared a path into the scrapyard. A lead wall was erected to shield workers. Scrap metal was removed piece by piece using grasping tools, while an electromagnet lashed to a five-meter bamboo rod handled smaller fragments. To pinpoint the source capsule amid the clutter of scrap, the team used a fluorescent screen -- but they had to wait for cloud cover to block the moonlight before they could see the screen's faint glow. The cobalt-60 capsule was finally retrieved shortly after midnight on February 19 and placed in a shielded container. Traced back to the abandoned car park, investigators found one of the three teletherapy units with its drawer assembly missing. The orphan had been identified.

Ten people were ultimately hospitalized with radiation sickness: the four scrap collectors, the two scrapyard employees, the scrapyard owner, her husband, her mother, and her maid. Four of them had received doses exceeding six gray -- a level that causes severe, often fatal damage to the bone marrow and immune system. Three died within two months of exposure: the two scrapyard workers and the owner's husband, all from uncontrolled infection and sepsis as their immune systems collapsed. One of the scrap collectors lost a finger to radiation burns. Beyond these direct casualties, 1,872 people living within 100 meters of the scrapyard had been potentially exposed to varying levels of ionizing radiation. Nearly half sought medical attention. The company responsible, KSE, was fined 15,000 baht -- roughly 450 US dollars. When residents near a Buddhist temple learned that one of the victims was to be cremated nearby, they protested and blocked the ceremony, fearing the body could spread radiation.

The international radiation trefoil -- that familiar three-bladed symbol in black and yellow -- had been printed on the teletherapy head. None of the scrap collectors knew what it meant. There were no written warnings in Thai. The Samut Prakan disaster, along with similar orphan-source incidents worldwide, prompted the International Atomic Energy Agency and the International Organization for Standardization to develop an entirely new warning symbol. Published in 2007 as ISO 21482, the redesigned icon depicts the radiation source, a skull, and a running figure -- intuitive enough to convey danger without requiring any specialized knowledge. It was a global safety reform born from a scrapyard in suburban Bangkok, where the people who handled the deadliest object in the room had no way of knowing what they held.