That means that over the course of a month, roughly 1.8 million people receive a pat-down. That’s more than four times the population of Atlanta.
That doesn’t sound like “very, very, very” few people to us.
According to the agency and many radiation experts, the dose is so low, even for children or cancer patients, that someone would have to pass through the machines more than a thousand times before approaching the annual limit set by radiation safety organizations.
But the letter to the White House science adviser, signed by five professors at University of California, San Francisco, and one at Arizona State University, points out several flaws in the tests. Studies published in scientific journals in the last few months have also cast doubt on the radiation dose and the machines’ ability to find explosives.
A number of scientists, including some who believe the radiation is trivial, say more testing should be done given the government’s plans to put millions of passengers through the machines. And they have been disturbed by the TSA’s reluctance to do so.
After her article was published, Smith-Bindman was contacted by a TSA public affairs officer. During the conversation, she suggested that she or other outside scientists be allowed to test the machine. The official was shocked by the suggestion and said such access could tip off people who want to avoid detection, Smith-Bindman said.
One scenario posed by scientists is that of mechanical failure. The backscatter beam moves quickly, thanks to a high-speed rotating wheel that keeps it from sticking on one point of a body, which could create medical problems. Scientists are concerned that machines in operation 24/7/365 could experience malfunction in the wheel. TSA says that they have fail-safe systems and emergency stop buttons to keep passengers safe, but that’s not what Johns Hopkins researchers found:
When Johns Hopkins researchers visited the Rapiscan facility, the automatic termination appeared to work. But the full results of the shutoff tests are redacted.
What’s more, the test system didn’t have an emergency stop button.