Airport body scanners: how much radiation is involved?

This page is for travelers, including people in cancer care, who wonder whether airport body scanners are a radiation risk. It explains the two kinds of scanner, FDA's dose comparisons, the safety standard, and your right to ask for other screening.

Airport checkpoints have used more than one technology, and the distinction changes the answer completely.

Millimeter wave systems use non-ionizing electromagnetic radiation. That is the same broad family as radio and wireless signals — energy without enough punch to break apart the molecules in your cells. There is a national safety standard for this kind of energy. FDA says that systems which meet it cause no known adverse health effects. They come in active and passive versions.

X-ray systems, sometimes called backscatter, create an image from x-rays that have bounced off the person being screened. These do use ionizing radiation, which is why dose limits and standards apply to them.

Numbers about radiation are hard to feel. FDA translates them into everyday terms, and the translations are striking.

• In 42 minutes of ordinary living, a person receives more radiation from naturally occurring sources than from screening with any general-use x-ray security system.
• General-use systems must deliver less than the dose a person receives during 4 minutes of airline flight. The TSA describes its own limit as less radiation from one scan than from 2 minutes of flying.
• A person would have to be screened more than a thousand times in one year in order to exceed the annual radiation dose limit.

Read together, those three statements say something simple. On FDA's comparison, a few minutes of flying involves more radiation than one scan.

By FDA's own comparison, a general-use x-ray scan adds less than 42 minutes of natural background radiation.

These machines are not judged by opinion. The applicable standard is ANSI/HPS N43.17-2009, which sets a reference effective dose limit of 0.25 microsieverts per screening and 250 microsieverts over a twelve-month period.

The gap between those two figures is where the thousand-scans-a-year statement comes from.

Honesty about limits matters. This page does not carry a statement about cancer risk from screening one way or the other. Its health comment is confined to millimeter wave systems, where it says there are no known adverse health effects.

So we can tell you the dose is very small by the comparisons the agency itself chose. We cannot tell you the agency has published a cancer risk estimate for airport screening, because it has not on this page.

The FDA page does not discuss declining a scan. If you would prefer other screening, ask the TSA officer at the checkpoint what options are offered.

Some travelers have specific situations they want to raise: an implanted device, an ostomy bag, a port, a prosthesis. Those are worth mentioning to the screening officer, not because of radiation, but because they can make the process smoother and less uncomfortable.

If you are in cancer care, you are probably having imaging that matters far more to your total radiation picture than a checkpoint does — CT scans in particular. That is the conversation with more substance in it. Ask:

• What is each scan for?
• What will it change?
• Would an alternative without ionizing radiation answer the same question?

Bring that to your oncology team. It is a better use of your attention than a few seconds in a checkpoint scanner.