designed to prevent the occurrence of these kinds of errors. The scanners' safety requirements include fail-safe controls and multiple overlapping interlocks. These features, combined with fault analysis, ensure that failure of any subsystem results in non-operation of the x-ray generator to prevent accidental exposures. In the United States, the TSA requires that certification to the ANSI N43.17 safety standard is performed by a third party and not by the manufacturer themselves. The European Commission issued a report stating that backscatter x-ray scanners pose no known health risk, and that "assuming all other conditions equal", that backscatter x-ray scanners, which expose people to ionizing radiation, should not be used when millimeter-wave scanners that "have less effects on the human body" are available. However, the European Commission report provides no data substantiating its claim that "all other conditions are equal". One area where backscatter X-ray scanners can provide better performance than MM wave scanners, for example, is in the inspection of the shoes, groin and armpit regions of the body. In a study published in the Archives of Internal Medicine on March 28, 2011 researchers at the University of California "calculated that fully implementing backscatter scanners would not significantly increase the lifetime risk of cancer for travelers." The researchers calculated that for every 100 million passengers who flew seven one-way flights, there would be one additional cancer. Efficacy In March 2012, scientist and blogger Jonathan Corbett demonstrated the ineffectiveness of the technology by publishing a viral video showing how he was able to get a metal box through backscatter x-ray and millimeter wave scanners (including the currently-used "Automated Target Recognition" scanners) in two US airports. In April 2012, Corbett released a second video interviewing a TSA screener, who described firearms and simulated explosives passing through the scanners during internal testing and training. Backscatter scanners installed by the TSA until 2013 were unable to screen adequately for security threats inside hats and head coverings, casts, prosthetics and loose clothing. This technology limitation of current scanners often requires these persons to undergo additional screening by hand or other methods and can cause additional delay or feelings of harassment. The next generation of backscatter scanners are able to screen these types of clothing, according to manufacturers; however, these machines are not currently in use in public airports. In Germany, field tests on more than 800,000 passengers over a 10-month trial period concluded that scanners were