On Sept. 29, the National Academy of Sciences issued a report on using backscatter X-ray machines to screen airport passengers. Sheldon H. Jacobson, a U. of I. computer science professor and expert on aviation security, was a member of the panel that assembled the report. In an interview with News Bureau physical sciences editor Liz Ahlberg, Jacobson talked about the committee’s findings on the safety of backscatter X-ray and his thoughts on security screening.
What is backscatter X-ray? What was the purpose of the report?
Backscatter X-ray is an imaging technology that looks for hidden weapons or explosives that airport passengers may be carrying. Backscatter X-ray machines use ionized radiation, which is reflected to create the image that the machine detects.
The Transportation Security Administration commissioned the National Academy of Sciences to review whether backscatter X-ray machines meet the standards for safety to humans when used as an advanced imaging technology for passenger screening at airports in the United States. Although not within the rubric of the study, one can infer that it is also reasonable to establish safety looking ahead to possible next-generation technologies of this type.
What did the committee find about the safety of backscatter X-ray machines for screening humans?
Following a rigorous evaluation of data available on backscatter X-ray machines, as well as collecting our own data on the operation of such machines, we determined that the radiation emitted by these machines is compliant with existing health and safety standards.
Did you evaluate the appropriateness of the health and safety standards themselves?
This was outside the purview of the charge of the committee. We used existing standards, and evaluated the machine based on such standards.
As an aviation security expert, do you foresee changes at airports in light of this report?
Backscatter X-ray machines were used at one time, but due to a requirement imposed by Congress to have automatic target recognition capabilities, backscatter X-ray machines were removed from airports in the spring of 2013. If the TSA wishes to use backscatter X-ray machines once again, they have two options. One possible, though unlikely, direction is to redeploy the machines that were removed back in 2013, with appropriate automatic target recognition capabilities added. The more likely direction is that a next-generation backscatter X-ray machine will be developed and deployed at airports in the future.
How do you think the results of the report may alter the effectiveness of screening?
The TSA is committed to a risk-based security paradigm, which targets screening technologies and procedures based on risk. TSA PreCheck is the biggest success story for the TSA since its inception, and exemplifies the risk-based security paradigm, which uses targeted layers of information, technologies and procedures to secure the air system.
Based on my experience in aviation security, if next-generation backscatter X-ray machines are added to the arsenal of technologies available and used appropriately, they can strengthen these layers and further enhance the effectiveness of risk-based security operations at airports across the United States.