Despite the Transportation Safety Administration (TSA) assertion that airport full-body and x-ray scanners aren't hazardous to human health, several studies insist otherwise. In addition to privacy concerns, a controversial study by ProPublica explained that "backscatters" scanners — imaging device that x-rays the human body as it passes through it — were dangerous to our health because they used ionizing radiation.
TSA publically responded to the accusations, and to the ProPublica report, claiming that the radiation each of these machines emitted was "negligible", pointing to some studies. However, TSA consequently decided to remove most of the backscatters and replace them with newer millimeter wave scanners, which pose less radiation as they said.
Ex-Senator Susan Collins who wrote a bill in 2012 to require further investigation regarding TSA backscatters technology said on that occasion that "while TSA has told the public that the amount of radiation emitted from these machines is small, passengers and some scientific experts have raised questions about the impact of repeated exposure to this radiation".