Health and safety authorities in many countries have turned to radiation technology to sanitize medical supplies, foodstuffs, and other commodities moving in national and global trade. Now US officials are beginning to apply the technology for scanning postal mail to protect workers and citizens from health threats posed by anthrax-tainted letters and parcels.
More than 50 countries have approved the use of irradiation to guard against food-borne diseases, processing a range of food products and ingredients to eliminate targeted bacteria and pathogens. Other applications include sterilizing pharmaceuticals and pre-packaged hospital and medical supplies, from gloves to syringes, to meet stringent health-care standards. National and international health authorities back the safety and effectiveness of these irradiation processes, which do not induce radioactivity in processed materials.
In the United States, the Postal Service has announced new safety measures that include processing mail with electron beam technology, which uses machines called electron accelerators powered by electricity to eliminate potentially dangerous bacteria. It also is exploring the use of gamma irradiators, which use radionuclides as the energy source.
Why Irradiation is an Effective Option. One of the most important uses of ionizing radiation is based on the lethal effect it can have on microorganisms like bacteria, parasites and pathogens. The effect is attributed primarily to the energy deposition in the bacteria's critical cell components, such as DNA carrying the genetic code.
On a commercial scale, irradiation is known to be an effective control measure for eliminating pathogenic bacteria and parasites, especially in solid foods. Bacteria like Salmonella, Campylobacter, Yersinia, Listeria, Shigella, and Vibrio E coli 0157:H7 are eliminated from processed products.
The technology has been applied in some countries against different species of Bacillus, including the anthrax pathogen, Bacillus anthracis. Irradiation was successfully used in Australia in the 1960s, for example, to destroy anthrax spores in imported goat hair used in making carpets. To destroy anthrax pathogens in mail, experts estimate that a dose of 45 kGy would be required to sanitize letters with a load of one billion spores per gram.
The IAEA has been a key organization in the research and application of ionizing radiation for health and safety applications in medical, food, and industrial fields.
How the Process Works. Two types of radiation are used at commercial scale in a wide range of sterilization applications:
- electromagnetic (X and gamma) radiation, which is in the form of waves or vibrations of electric and magnetic fields
- particulate (electron or beta) radiation, which is in the form of rapidly moving subatomic particles
The radiation field can be produced by radioactive material, by X-ray machines or by electron accelerators. Typical sources of gamma radiation are cobalt-60 and, to a lesser extent, caesium-137.
Industrial or commercial radiation facilities must be licensed, regulated, and inspected by national radiological safety and health authorities, many of whom base their rules upon standards and codes of practice jointly established by the IAEA, World Health Organization, and Food and Agriculture Organization. Common features of commercial facilities are an irradiation room or chamber and a system to transport the processed material, such as conveyors or rail systems. Processed materials are exposed to controlled doses of radiation, and they can be handled safely immediately after treatment.