Radiation Exposure Negligible From Airport Security Scans

Pam Harrison

March 08, 2013

Exposure to ionizing radiation from airport security scanners is negligible unless people travel frequently or work for the aviation industry, investigators report.

Not all security scanners rely on x-rays, John Damilakis, PhD, from the University of Crete in Iraklion, Crete, Greece, pointed out to Medscape Medical News.

Backscatter scanners, however, employ the same ionizing radiation used in medicine. In airport security, they are designed to detect the presence of suspicious or concealed items hidden under clothes.

During a single backscatter scan, a traveller will be exposed to between 0.05 to 0.1 microsievert of radiation.

According to US standards, the maximal permissible dose per screening is a dose of 0.25 microsievert.

By way of comparison, radiation received during a standard chest x-ray is almost 100 times higher than from a single backscatter scan.

"On the other hand, flight attendants and pilots in the US receive between 240 and 380 scans per year," said Dr. Damilakis.

Frequency of exposure clearly increases the total amount of ionizing radiation received, he added, so flight attendants and pilots could receive as much as a 300 millisievert (or 300,000 microsievert) of ionizing radiation from airport security scans each year.

Frequent flyers who average more than 200 flights a year may also be exposed to as much as 200 microsievert of radiation.

Dr. Damilakis discussed the safety of airport security scans here at the European Congress of Radiology (ECR) 2013.

Improve Security

Backscatter scanners improve security by detecting the presence of plastic explosives and other concealed weapons, but are not necessarily effective at detecting plastic explosives that have been ingested or hidden in body cavities.

"Security scanners screen for plastic explosives that escape detection from metal detectors so they do provide additional security against risk," Dr. Damilakis said. "But under certain conditions, plastic explosives can be missed and we need better performance indices to better assess how well these scanners detect threats compared with false alarms."

Mike Kemp, PhD, from Iconal Technology in Cambridge, United Kingdom, told Medscape Medical News that from his assessment of all the studies performed to date, the radiation dose from a backscatter scan seems to be within acceptable limits on individual scans.

"Yes, if you fly a lot and have many scans, the dose gets higher but it's still very much smaller than the dose you get flying as a pilot or a flight attendant who are flying several hundred hours a year," Dr. Kemp said.

"It's for these people that the radiation dose received could be very significant."

The possible public health effects from low-level exposure to ionizing radiation are still unknown.

However, "risks from low levels of exposure are small for all cancers," affirmed Peter Volk, MD, from Bern University Hospital in Switzerland - even though whatever adverse events that do accrue from exposure to ionizing radiation are real, even in radiology, he added.

Physical Pat Down

Groups working on radiation protection have adopted the "as low as reasonably achievable" (ALAR) principle designed to keep radiation to a minimum.

For this reason, speakers here at the meeting agreed that nonionizing technology should be considered before x-ray scanners become a primary screening tool in aviation security.

After 3 years of experimentation, the European Union banned backscatter x-ray scanners and now use nonionizing microwaves.

Similarly, major US airports have recently decided to switch from backscatter x-ray scanners to microwave systems.

Travellers can also opt for a physical pat down instead of submitting to a backscatter security scan.

It's estimated that in the US alone, approximately 1 billion scans are performed each year.

The investigators and Dr. Volk have disclosed no relevant financial relationships. Dr. Kemp founded Iconal Technology and works as an advisor on detection of explosives programs.

European Congress of Radiology (ECR) 2013. Abstracts A51, A52, and A53. Presented March 7, 2013.