On 20 February of this year, the Associated Press of Bangkok, Thailand reported:

"Five people have been hospitalized for exposure to radiation that leaked from scrap metal sold to a recycling yard on the outskirts of Bangkok. Two workers who handled the metal cylinder were in a coma, and the man who sold it suffered radiation burns to his hands. The owner of the scrap yard in Samut Prakan province and another worker were also hospitalized.

The Thai Health Ministry reported Saturday that three scrap yard workers had fallen critically ill with blisters, burns and hair loss. They were vulnerable to infections because of a drop in their white blood cell count, the ministry said. Ten more neighbors and relatives of the victims who took blood tests were discharged from the hospital because they showed only very slight exposure to radiation.

Staff from Thailand's small atomic energy research center, who had Geiger counters but no protective clothing, sifted through piles of scrap at the yard Saturday searching for the source of the leak. After 11 hours they found a metal cylinder containing cobalt 60, a radioactive isotope used in the production of gamma rays, mainly used in sterilization by the food industry, or in hospitals for cancer treatment.

This incident was the first ever radioactive leak in Thailand."

(Adopted with permission from the Associated Press)

Based on the description of clinical symptoms, it appears that some of these exposed individuals have received a radiation dose exceeding 10 Gy and are suffering from the Acute Radiation Syndrome. Since the LD50/30 (dose for 50% probability of survival within 30 days) for whole body irradiation is about 3.5 Gy, some of these workers will very likely die because of this exposure.

It is sad that this tragedy occurred, but this is by no means an isolated case. In a similar incident in Brasil in 1987, many individuals were exposed to a cesium-137 source. Four of the casualties eventually died and 28 people developed local radiation injuries. In Taiwan in 1983, cobalt-60-contaminated steel rods were used in construction of a building in the business district of Taipei, exposing the residents for 10 years to more than 1000 times the legal limit for public exposure. The International Atomic Energy Agency has published detailed reports on a number of other similar incidents.

The physical, property and psychological costs resulting from these incidents are tremendous. The Thailand incident struck fear in the population about the use of radiation. This is indeed unfortunate, because this incident, like many others reported, is preventable. Properly managed, the use of radiation in agriculture, medicine and other industries can offer many unique benefits.

How can these incidents be prevented? A very important aspect of safe management of radioactive materials is the "chain-of-custody". The process of the use of any radioactive materials involves many steps: manufacturing, purchasing, receiving, storage, transfer, utilization, and disposal. During each of these steps, someone must be in charge of, and accountable for, the safe handling of the radioactive materials. Behind this accountability is an assumption that the responsible individuals in each step of this process are properly informed and trained. In the Thailand case, the original owner of this cobalt-60 source should never have dumped it to the scrap yard, whose workers do not have proper information and training to handle radioactive materials.

Here at HKUST, our radiation safety program is designed to manage each of the aforementioned steps with a "cradle to grave" approach, i.e., from their arrival on campus to their final disposal. Safety procedures for these steps are established and clearly stated in the Safety and Environmental Protection Manual. Following these procedures will ensure that a proper chain-of-custody is maintained:

1. All radiation-related work must be reviewed and approved for the adequacy of safety procedures through a Radiation Use Authorization (RUA).
2. All radiation users must register with HSEO to receive training on the safe use of radiation.
3. For any purchase and receiving of radioactive materials, HSEO must be notified.
4. Users are responsible for the safekeeping of radioactive materials and are required to maintain a current and accurate inventory of each stock of each purchase order.
5. During usage of radioactive materials, users must follow established safety procedures.
6. HSEO staff will work with radiation users, through inspections of work areas and monitoring of personnel exposure, to ensure that there is no breakdown in safety controls.
7. Finally, when the stock is finished and ready for disposal, they must notify HSEO so the radioactive waste can be collected and properly managed.

By maintaining a proper chain-of-custody, the exposure to our personnel, the public and the environment will be kept as low as reasonably achievable.

This chain-of-custody system requires our radiation users to do a little extra work to ensure that radioactive materials in their custody are properly handled and stored. They also need to keep proper records. Only a good chain-of-custody system can prevent accidental loss or theft, which could cause great embarrassment even when no one is injured as a result.

As an example of what we do not want to see happen, some radioactive phosphorus used in DNA research was discovered to be missing after it was delivered to the Department of Biochemistry at Cambridge University in 1998. It was never found. Cambridge has pleaded guilty to five charges and was heavily fined.

It should be emphasized that each radiation user must make sure that radioactive materials are always accountable, used properly, and disposed in accordance to established safety procedures. Following the requirements of these procedures is not only good practice of radiation safety, it is also required by the law.