In our frightening new world, x-rays and CTs have become as important for airports as for hospitals. Hand luggage is put through x-ray scanners; because one pass exposes your items to only a tiny fraction of the energy used in a chest x-ray, these scanners are safe for photographic film — and for the security personnel who use them all day long. But checked baggage is passed through CT scanners that are far more powerful; they will damage your film but not your medications.
The new full-body scanners have raised concerns about privacy and safety. The privacy issue is personal, but the safety issue is a scientific matter — and scientists agree that scanners are safe. Two types are in use. Millimeter wave scanners use radio waves to generate images, and they don’t expose travelers to any ionizing radiation. Backscatter scanners do use low-intensity x-rays, but they bounce off the skin without penetrating the body. They deliver only a tiny amount of radiation, about the same amount as you get in three to nine minutes of daily living, or about 1/1000 as much as an ordinary chest x-ray. A person would need to have 2,500 to 5,000 backscatter scans a year to reach the established annual safety limit.
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