[ RadSafe ] Airport Body Scanners

[Hansen, Richard]

There is an ANSI/HPS standard for security screening systems that use x-rays and are designed to be used on people. This standard states maximum dose per scan, the maximum dose to the operators, and the minimum information to be provided to the persons being scanned.

ANSI/HPS N43.17-2002
American National Standard Radiation Safety For Personnel Security Screening Systems Using X-rays

Under maximum operating parameters, the effective dose shall not exceed 0.10 microsievert (10 microrem) per scan of the subject's front.

The facility shall be operated to ensure that no individual scanned receives from the facility an effective dose in excess of 0.25 millisievert (25 millirem) in any twelve-month period.

The system should be positioned and operated such that personnel at any work station do not exceed a dose of 1 millisievert (100 millirem) per year.

At a minimum, the institution operating the system shall inform each person being scanned of the following:
a) The system emits radiation;
b) The dose from one scan shall not exceed 0.1 μSv (10 μrem);
c) An example shall be provided to compare the dose to a commonly known source of radiation, such as "The radiation from one scan is equivalent to approximately 20 minutes of exposure to naturally occurring background radiation";
d) The system conforms with the ANSI/HPS consensus standard N43.17; if requested, information on how to acquire this standard shall be provided.

What is interesting is to compare the dose a passenger would get from a security scan (0.10 microsievert, 10 microrem) to the length of time it would take for that passenger to receive the same dose on the airline flight. Using the FAA Civil Aeromedical Institute Federal Aviation Administration CARI program (http://jag.cami.jccbi.gov./cariprofile.asp), I made a rough estimate for a flight from Los Angeles to New York City. Each passenger would receive a dose of about 18.60 microsieverts (1860 microrem), with a dose rate of about 3.8 microsievert per hour (380 microrem/h) at a cruising altitude of 30,000 feet. This means the dose from the x-ray scanner is equivalent to the dose a passenger would receive in less than 2 minutes at cruising altitude. Or another way to look at it is that getting the x-ray scan increases the passenger's dose for the airline trip by less than 0.6% (not counting the dose from natural background during the 2+ hours the passenger was on the ground at the airport before boarding and after exiting the aircraft).

Best regards,
Rick Hansen
Senior Scientist
Counter Terrorism Operations Support Program
National Security Technologies, LLC, for the U.S. Dept of Energy
hansenrg at nv.doe.gov
www.ctosnnsa.org