Considered for Carcinogen List
by Steve Waldrop
January 13, 2003
The federal government
has begun evaluating whether medical X-rays should be declared a carcinogen,
a move that experts say could reduce unnecessary exposures to radiation
and force doctors to pay closer attention to the risks involved.
The evaluation, which will be conducted over the next year, was prompted
by a request from the National Institute of Environmental Health Sciences.
The listing is being considered for the National Toxicology Program's
11th Report on Carcinogens due in 2004.
Cancer risks from radiation exposure are well documented in studies of
atomic bomb survivors, but risks from medical sources are controversial
and often down- played by physicians.
"There is a lot of data showing that radiation is a carcinogen at
very high levels," said G. Donald Frey of the American Association
of Physicists in Medicine. "What is scientifically unsettled is whether
it causes cancer at low levels. We don't really absolutely know."
According to the National Cancer Institute, major organizations "agree
there probably is no low-dose radiation "threshold" for inducing
cancer, i.e., no amount of radiation should be considered absolutely safe."
The NIEHS is concerned
that use of Computed Tomography (CT) scans, fluoroscopy, mammography in
younger women and medical X-rays are exposing the public to increasingly
higher levels of radiations, says its director, Christopher Portier.
Fred Mettler, a spokesman for the American College of Radiology and professor
of radiology at the University of New Mexico, says radiologists are supposed
to "optimize" radiation doses by exposing patients only to enough
radiation to get a clear image. The risk of exposure is balanced against
the medical benefit.
A CT scan is equal to 100 chest X-rays. For every 1 million children scanned
with CT, an estimated 1,500 will develop cancer two decades later. Up
to 3 million children receive CT scans each year. Children are typically
given adult doses during CT scans.
Last October, The NCI issued an alert to radiologists asking them to lower
CT doses to children.