TSA and X-Ray Scanners

I was trying to answer a biological physics question from a family member about TSA's use of X-ray scanners, when I came across a very interesting article from Scientific American:

One after another, the experts convened by the Food and Drug Administration raised questions about the machine because it violated a longstanding principle in radiation safety — that humans shouldn’t be X-rayed unless there is a medical benefit. 

... Today, the United States has begun marching millions of airline passengers through the X-ray body scanners, parting ways with countries in Europe and elsewhere that have concluded that such widespread use of even low-level radiation poses an unacceptable health risk. The government is rolling out the X-ray scanners despite having a safer alternative that the Transportation Security Administration says is also highly effective. 

That safer alternative is the millimeter-wave scanner, which uses low-frequency radio waves which do not have enough energy to damage DNA.  Radiation of X-ray frequency can damage DNA and thus, in high enough doses, cause cancer.

I told my concerned family member that as an individual person, the risk that you will get cancer from an X-ray scanner is apparently negligible:  about 1 incidence of cancer per 10 million scans, by one estimate.  The drive to the airport and the flight itself are probably more dangerous, and if you really want to minimize the risk of cancer you can forget about sunbathing on the beach once you arrive at your destination.  But from a public health standpoint, when you have a population of millions of people it becomes likely that a few of them will get cancer each year from X-ray scanners.  Why risk the health of even one traveler unless absolutely necessary?