Answer to Question #1723 Submitted to "Ask the Experts"

Q

Please provide information on methods used by the United States Postal Service in irradiating mail. What sources are used? What facilities are using irradiation to sterilize mail? What are the doses or general range of doses administered? What controls are needed to protect workers?

A

The United State Postal Service (USPS) is irradiating targeted mail destined for specific government offices in zip codes beginning with 202, 203, 204, and 205 at two contracted irradiation facilities in Lima, Ohio, and Bridgewater, New Jersey. These electron beam facilities are not capable of handling all the mail for these zip codes, so only those letters or parcels that fit specific criteria are irradiated. The USPS issued contracts in October 2001 to purchase additional irradiation equipment from Titan Corporation. Titan will operate and maintain the systems and the equipment will only be used for targeted mail. The electron beam irradiators deliver doses between 25-40 kilogray (kGy) to the mail, which is sufficient to render harmless any biological agent, including anthrax spores. Irradiation facilities produce very high dose rates so extraordinary safety systems are necessary to prevent anyone from entering the exposure room or chamber when radiation is produced. To ensure that employees and visitors are not exposed to even low levels of radiation produced at the facilities, very thick concrete or lead-lined walls shield the exposure rooms. The radiation levels are closely monitored at the facilities to ensure the complete safety of the workers. Here are some Web sites that provide additional information on mail irradiation:

 

• USPS - Dec 4, 2001 - U.S. Postal Service position on irradiating the mail
• USPS - Latest Facts Update Jan. 29, 2002
• USPS - Latest Facts Update Jan. 31, 2002
• USPS - Dec. 4, 2001 - USPS reiterates its position on irradiating mail
• Mail Irradiation

Ken Kerns, CHP
Iowa State University