Readers Respond to “Do CT Scans Cause Cancer?”

Letters to the editor from the November 2013 issue of Scientific American.
July 2013 cover

Scientific American


In “How Much Do CT Scans Increase the Risk of Cancer?” Carina Storrs accurately discusses the reasons diagnostic imaging with computed tomography scans has increased and the limited scientific knowledge of the effects of this increased radiation exposure on inducing cancer in patients. As a radiologist, I find that Storrs neglects to include one cause for the increase in CT scans: the current structure for how these exams are ordered in the U.S. health care system.

In the U.S., practicing physicians order diagnostic studies that they believe are appropriate. Radiologists, who are the experts in the advantages and disadvantages of different imaging modalities and are the ones that interpret the studies, have no ability to either reject or change the requested study without permission from the ordering physician. Consequently, a certain amount of nonoptimal and unneeded exams will be ordered.

This generally occurs because of lack of communication with the ordering physician to optimize the diagnostic test (the American College of Radiology has developed appropriateness criteria for diagnostic studies to address this issue). Sadly, it also occurs because in the current U.S. reimbursement structure, there is no financial incentive to cancel a nonindicated or nonoptimized study.

Benjamin L. Viglianti
Department of Radiology
University of Michigan


In “Oil Sands May Irrevocably Tar the Climate,” David Biello reports on efforts to halt the Keystone XL pipeline. By allowing for increased heavy oil production in the Alberta tar sands, the pipeline would accelerate the buildup to the cumulative carbon-emissions threshold of one trillion metric tons, at which we will reach the feared “tipping point” of more than two degrees Celsius of warming. The article points out that emissions must drop by 2.5 percent a year, starting now, for us not to exceed that threshold by 2041. Such an annual reduction would mean cutting energy use from carbon in half in about 30 years. One possible way to get there is by cutting world economic output in half. No one will willingly do that. At least not until economic collapse occurs following runaway atmospheric heating.

Incredible innovation and cooperation among nations are required. That will happen only when the majority of the powerful people of the wealthy nations realize they breathe the same air as the weak and the poor. The history of human behavior makes that outcome seem most unlikely.

Tom Faulkner
via e-mail

For 40 years I have watched environmentalists block hydroelectric power, nuclear power, offshore oil drilling, continental gas drilling and wind power projects. This focus on “purity of purpose” rather than “consequences of actions” resulted in utilities building dozens of heavily polluting coal plants and oil companies investing billions of dollars in Canadian tar sands.

The recent breakthroughs in fracking have reduced carbon emissions as utilities have begun to switch from coal to now dramatically cheaper natural gas. The potential use of natural gas in vehicles will reduce emissions even more. Unfortunately, since fracking doesn't meet the zealots' agenda, these significant environmental benefits are being strongly opposed.

Robert Gallant
Midland, Mich.

There is one major omission with regard to alternatives if Keystone fails: the energy-transport company Enbridge. While all attention has been on Keystone, Enbridge has been quietly building its own tar sands network to the Gulf and East coasts.

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