1) The first thing is that I don't believe that these machines will prevent terrorism. There are too many ways to thwart the machines, they have many vulnerabilities, and they don't address the fact that if a terrorist is about to die, what is to stop him from inserting explosives into his body cavities? What will be next, random body cavity searches? Or maybe they will just turn up the juice on these machines and give everybody a full body chest x-ray.
2) I think they are an invasion of privacy. Being able to see underneath clothing? Call me a prude, but that's just wrong. Everyone is now treated as a criminal before boarding a plane.
3) The most important reason: No amount of X-ray radiation is beneficial and x-rays have an accumulative effect in the body over time. What does the National Academy of Sciences have to say about x-ray exposure?
The committee's thorough review of available biological and biophysical data supports a "linear, no-threshold" (LNT) risk model, which says that the smallest dose of low-level ionizing radiation has the potential to cause an increase in health risks to humans...The scientific research base shows that there is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless or beneficial.The European union banned x-ray scanners pending review "in order not to risk jeopardising citizens' health and safety, [and] only security scanners which do not use X-ray technology are added to the list of authorised methods for passenger screening at EU airports." In September 2012, the machines were scrapped permanently. Research has suggested that, despite the low radiation dosage, that because of the large number of scanners in the U.S., hundreds of passengers a year could get cancer. TSA personnel really have it bad since they are standing next to these machines all day long. It will be interesting to see if in ten or so years time, the TSA agents develop higher than normal levels of cancer. There have already been reports of an increase in cancer cases among the TSA workers. But that is also the problem: It is hard to determine cause and effect when the time between the two is on the matter of decades. The government glossed over cancer concerns and many prominent scientists have raised objections to the safety.
Sure, the TSA claims that the technology is safe. Does that make you feel better that a government contractor has told you what is safe? Never mind the fact that there has yet to be any independent testing of these machines. Scientists have wondered how the stated radiation exposure could be so low and have hypothesized that the actual exposure could be 10 to 20 times the manufacturer’s calculations. And how many times has a government agency claimed something was safe and it was later found out not to be? They don't have the best track record. Agent Orange, perhaps? FDA approved Vioxx, maybe? These types of cases happen all the time. Oops.