There were no systematic reviews on the effect of airport-style full body scanners on pregnant women.
One good quality study1 (Evidence level IIb) did investigate the exposure to radiation of models simulating months 1–9 of pregnancy passing through walk through metal detectors. This study found that recommended levels were not exceeded in months 1-5 but that the 6-9 month models were over-exposed.
However, the Health Protection Agency has published an assessment of the radiation doses associated with backscatter body scanners most frequently used at UK airports2 (Evidence level IV). For the general population, the advice is:
“HPA recommends a dose constraint of 300 micro Sv/year to a member of the public from practices involving the deliberate use of ionising radiation sources. A passenger would need to be examined 5000 times before exceeding this constraint value (based on three scans per examination). It is concluded that the potential doses received from the use of a correctly installed and used x-ray backscatter body scanner are likely to be very low. Even in the case of frequent fliers the doses are unlikely to exceed 20 micro Sv/year.”
The advice goes on to consider more vulnerable travellers, including pregnant women:
“Whilst there are stages of pregnancy where a fetus is considered to be more susceptible to harm from radiation, the backscatter technology ensures that negligible doses are absorbed into the body (where the fetus is) and the fetal dose is thus much lower than the dose to a pregnant woman.”
The US Transportation Security Administration (www.tsa.gov), has also published guidance on the technology used in airport full body scanners and the associated health considerations3 (Evidence level IV). This guidance describes backscatter and millimetre wave scanners and compares the emissions to other, every-day activities:
Backscatter machines: Produce low level x-rays and give 2d images. The radiation levels of such machines is equivalent to 2 minutes of air travel.
Millimetre wave units: Produce radio waves and give 3d images. Emission levels are 10,000 lower than a mobile phone.
1. Wu D, Qiang R, Chen J, Seidman S, Witters D, Kainz W. Possible overexposure of pregnant women to emissions from a walk through metal detector. Physics in Medicine & Biology. 52(19):5735-48, 2007.
2. Health Protection Agency, Centre for Radiation, Chemical and Environmental Hazards. MacDonald A, Tattersall P, O’Hagan J, Meara J, Paynter R, Shaw P. Assessment of comparative ionising radiation doses from the use of rapiscan secure 1000 x-ray backscatter body scanner. Health Protection Agency, January 2010. Accessed on 23 February 2010.
3. Imaging technology. Transportation Security Administration. Accessed on 5 February 2010.
5 February 2010; updated 23 February 2010
Classification of evidence levels
- Ia: Evidence obtained from meta-analysis of randomised controlled trials.
- Ib: Evidence obtained from at least one randomised controlled trial.
- IIa: Evidence obtained from at least one well-designed controlled study without randomisation.
- IIb: Evidence obtained from at least one other type of well-designed quasi-experimental study.
- III: Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies.
- IV: Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities.
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