U.S. Customs reviews impact of X-rays on truck drivers

X-ray equipment at border crossings has emerged as a crucial weapon in the fight against terrorism but does it carry a hidden health cost?

Based on concern expressed by drivers who are scanned by U.S. Customs’ "x-ray" machines, U.S. Customs at Pacific Highway requested a review of the machine and the risk to humans by the Radiation Protection Division of the Washington State Department of Health.

Some truck drivers have stated that they pass through the scanning system 3-4 times per day and have said that they were told to "stop when the cab is directly in line with the beam." However, Customs officers are instructed to tell drivers to pull ahead to a specific location and stop. At this point the tractor portion of the truck-trailer rig is beyond the beam. When the scanning procedure is set to begin, the shutter is opened and the driver is instructed to proceed forward at walking speed while the trailer portion is scanned. This takes approximately 20 to 30 seconds. The highest reading in the cabs of several trucks during the scanning was measured at 150 microrem (urem) per hour at the beginning of the scan. The reading gradually decreased as the trailer passed through the beam.

Based on passing through the machine four times per day, five days per week and 52 weeks per year (i.e., 1,040 trips per year), the exposure is 1,300 urem or 1.3 millirem (mrem) annual accumulative exposure. This is 1.3 percent of the maximum allowable yearly exposure of 100 mrem for the general public. (The maximum allowable yearly exposure for "radiation" workers is 5,000 mrem).

Therefore, for a truck driver to reach 100 mrem, he/she would have to pass through the border scanner 80,000 times in a year or 219 times per day. The Radiation Protection Division concluded that "there should be no health and safety concerns with the truck scanning process as observed during on site investigations for truck drivers or customs inspectors."

This finding is in keeping with the conclusion of the Canadian Nuclear Safety Commission, which also reviewed similar Canadian equipment and training of Canadian Customs officers.