Officials at the US Transportation Security Administration (TSA) were mistaken if they thought using ionizing radiation to screen upwards of a billion travelers a year wouldn’t raise potential health concerns. Indeed, the use of airport “backscatter” X-ray scanners, which employ full-body imaging to detect banned and dangerous items, has vocal advocates on both sides of the debate.
Used in nearly 40 US airports, the units work by scattering X-rays on the body’s surface. Different materials (such as skin, plastic and metal) reflect back the X-ray differently; measurements taken from these reflections create an image of the traveler.
The absence of independent safety studies is one reason the scanners are controversial. Further complicating the issue is that security concerns preclude the release of information on how these work and details on the radiation they emit.
There is also a void in the medical literature on the effects of low-dose ionizing radiation. Almost everything we know about exposure to ionizing radiation is in the context of high-dose exposure. The limited number of studies on the effects of long-term, low-dose radiation is an insufficient basis for policy or to establish any safe threshold of exposure. Consequently, current policies and safety thresholds are founded on a series of assumptions and extrapolations.
The case for the scanners’ safety is:
• The dose of radiation for an individual undergoing a scan is so small that it’s unlikely to pose a health risk.
Concerns about potential health effects include:
• The lack of data about the effects of low-dose radiation
• The need for data on how specific subpopulations (like pregnant women, young children, the elderly and the immune-compromised) may be at increased risk.
• Ionizing radiation penetrates skin, red and white blood cells in the skin, reproductive organs, eyes and internal organs. Their effect on any of these is unknown.
• Cumulative exposure (for flight crews, TSA personnel and frequent flyers) is unstudied.
• There is no independent confirmation on the precise dose of radiation (many experts believe it may be up to 50 times higher than reported by the TSA).
The European Union has banned the use of these backscatter X-ray scanners, citing health concerns and the need for further studies. The risk to any one person going through a scanner may be small, but given the volume of people scanned, a small number of additional cancer cases may result each year.
Until adequate studies are completed, questions linger. Similar security scanners employ microwaves (non-ionizing radiation) and are equally effective. So many experts are asking: Why not use this alternative instead?
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