ACR protests listing of x-rays as human carcinogen

April 1, 2005

It didn't surprise many radiologists when the government formally classified ionizing radiation as a known human carcinogen earlier this year. After all, shielding has been used for decades. But the American College of Radiology doesn't like the label and is working to have it removed.

It didn't surprise many radiologists when the government formally classified ionizing radiation as a known human carcinogen earlier this year. After all, shielding has been used for decades. But the American College of Radiology doesn't like the label and is working to have it removed.

ACR officials cautioned the National Toxicology Program (NTP), which produced the Report on Carcinogens, Eleventh Edition, not to include diagnostic imaging in the same document that warns against, among other things, chemicals used for making dyes, paints, and inks.

"X-rays and gamma rays are not substances the general public has access or exposure to, and they do not belong on a list of substances that pose a risk to people in the course of their normal daily lives," said Dr. James P. Borgstede, chair of the ACR board of chancellors.

The program's rules allow it to consider petitions for changes in the list, and Borgstede promised that the ACR would ask to have x-rays and gamma rays removed.

But Dr. Stephen R. Baker called the ACR's position an intellectually bankrupt one. He sees the government's move as an opportunity for radiology to hold open, honest discussions about radiation exposure and use. Patients should know that repeated x-rays have consequences and that alternatives are available.

"A little bit of questioning may be a good thing because radiology has not acted to control utilization," said Baker, radiology chair at the University of Medicine and Dentistry of New Jersey.

A petition to remove ionizing radiation from the list of known human carcinogens probably won't have much effect, said Christopher Portier, Ph.D., associate director of the NTP.

"The evidence, both human and animal, is strong," he said.

The NTP has published the toxicology report every two years for the last two decades. Its officials had placed low priority on ionizing radiation only because they had many other lesser known carcinogenic agents about which the public needed to be informed. With a strict budget, the agency can review only six to eight agents annually. But the time had come to finally include it, Portier said.

Dr. Donald Frush, division chief of pediatric radiology at Duke University, said there has been a sea change in imaging's approach to radiation dose, particularly in pediatrics. Scanners include dose modification techniques, hospitals and facilities employ body-mass charts to set an appropriate dose, and researchers seek ways to use nonionizing energy for many indications.

Baker, too, has seen progress in minimizing individual dose per exam, but he laments the lack of attention paid to reducing the number of studies an individual undergoes. He often lectures to private practitioners and academicians about overutilization. They agree it's a problem, but that may not translate into action.

"We can't go on like this. I applaud the government's decision because it will raise the issue to public consciousness," Baker said.