Airport security lines could be more chaotic than usual on 24 November as grassroots groups urge passengers to choose “enhanced” pat-downs in protest of full-body scanners.

Airport security lines could be more chaotic than usual on 24 November, perhaps the busiest travel day of the year. Several grassroots groups are declaring the day before Thanksgiving National Opt-Out Day, urging passengers to choose “enhanced” pat-downs in protest of full-body scanners.

The debate
Consumer advocacy groups, bloggers, passengers and even pilots have come out against full-body scanners - with unions representing 14,800 American pilots advising members to avoid them, citing privacy and health concerns. Jeffrey Goldberg, a national correspondent for the Atlantic, made the argument that both full-body scans and their alternative - enhanced pat-downs - could make Americans feel more, not less, terrorized.

Advocates for the new machines say these methods could stop would-be terrorists like last winter's underwear bomber. And a CBS poll released last week finds that 81% of Americans support the scanners, despite privacy and health issues. These numbers could change, though, as more people experience them first-hand, points out statistics expert Nate Silver at The New York Times.

The facts
There are two types of full-body scanners. The backscatter X-ray scanner produces images by bouncing X-rays off the body and detecting the radiation reflected back. The purpose is to perform strip searches without anyone actually having to strip. Therefore, the resulting images look a lot like naked bodies. The other, a millimeter wavelength scanner, uses radio waves rather than X-rays and produces lower resolution and less "revealing" body images.

However, while privacy concerns currently dominate the online discussion, the murkier issue is how safe these machines are.

The backscatter scanner emits about .02 units of radiation. The Transportation Security Administration says that an individual would have to go through the scanner 5,000 times for the radiation level to equal that of one chest X-ray. But scientists say that no amount of radiation is entirely without risk.

While the majority of people probably have nothing to worry about, says David Brenner, head of Columbia University's Center for Radiological Research, groups that are sensitive to radiation make up about 5% of the population. Brenner expressed concerns to Congress, explaining that the prospect of X-raying such a large number of people is unprecedented.

Because radiation from the machines becomes more concentrated in the skin, the biggest threat is a common, curable skin cancer called basal cell carcinoma.

Children are more sensitive to radiation in general. Since, as of last week, the TSA stopped requiring enhanced pat-downs for children, having your kids opt out of X-ray scans may be a wise option.

There are no known radiation risks associated with millimeter wavelength machines and the TSA says that these scanners are just as effective as backscatter X-ray scanners. Both technologies are also comparable in price. So why not stick to the less dangerous machine?

"Our technology strategy," TSA official Maurine Fanguy told NPR, "is to have more than one vendor... to get more competitive pricing [and to make] sure that we don't cut off one avenue of technology that would potentially not allow us to take advantage of innovation later."

That explanation may be little consolation, though, for passengers whose primary concern is personal health.

The day itself
It remains to be seen whether National Opt-Out Day will win one for consumer rights or just add to the stress of air travel on 24 November - or both.

To avoid delays that could potentially arise due to National Opt-Out Day, find out if your airport of departure has begun using these scanners. Here is a list of airports that currently have them. If so, plan ahead. Purchase your ticket in advance online and get to the aeroport extra early. Also, read through the TSA's tips on how to get through security faster. Passengers planning to "opt out" of full-body scans can find details at the official website; travellers departing from other countries should check their local rules before joining the protest.

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