Have you been through one of those airport security machines that takes a naked picture of you through your clothes? You might want to consider opting out next time.
A group of UCSF researchers released a letter earlier this year, warning of potential health risks of the machines. Although the backscatter devices are being installed at airports around the country, the researchers are unconvinced that they are safe.
There are a number of problems with the machines. For one thing, the energy that they release tends to remain concentrated in the skin, rather than more safely dissipated throughout the body. Because the concentration is so much higher, there is an increased risk of causing skin cancer.
Or maybe there isn't. The data simply doesn't exist. There haven't been any thorough studies into the concentration of energy in the skin. There are also unanswered questions regarding the effect on eyes and the thymus.
Who's most at risk? Older travelers. Anyone with HIV. Women are at risk due to breast cancer, and men are at risk due to sperm mutagenesis.
And that's not all. Because the machines are capable of photographing travelers' genitals, even when they're fully clothed, there's an added risk that screeners will be tempted to linger on the crotch, heightening the exposure.
Passengers have the option of refusing the backscatter x-ray, at which point they'll receive an intrusive pat-down. So, it's up to you to decide which is worse: getting felt up or getting irradiated.