NAS X-ray study looks at risk
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Posted June 30, 2005 |
By Craig Palmer Washington — Low doses of radiation such as those from medical and dental X-rays, natural and other manmade sources pose some risk for cancer though the risk is small, a National Academy of Sciences panel said in a comprehensive update of the scientific literature. More information is needed to assess other possible low-dose health effects, the panel said.
American Dental Association guidelines posted on ADA.org and communicated in ADA publications recommend that dentists consider exposure risk in evaluating and diagnosing oral diseases and conditions. "The dentist must weigh the benefits of taking dental radiographs against the risk of exposing a patient to X-rays, the effects of which accumulate from multiple sources over time," says the ADA, Food and Drug Administration Guide to Patient Selection for Dental Radiographs.
"The dentist, knowing the patient's health history and vulnerability to oral disease, is in the best position to make this judgment in the interest of each patient," the ADA, FDA guidelines say.
When a radiograph is indicated, the ADA recommends that dentists:
- follow the "As Low As Reasonably Achievable" (ALARA) principle and order X-rays only when necessary for diagnosis;
- use protective thyroid collars whenever possible and aprons on all patients during X-rays;
- encourage patients to visit the dental office regularly to maintain good oral health.
An oral health topics page on ADA.org offers public information on frequently asked questions: How do dental X-rays work, how often should X-rays be taken, what are the benefits of a dental X-ray examination and how do dental X-rays compare to other sources of radiation.
The National Academies' National Research Council report says a preponderance of scientific evidence shows that even low doses of ionizing radiation, such as gamma and X-rays, are likely to pose some risk of adverse health effects.
New data have "strengthened confidence" in earlier estimates of some cancer risk from even low doses of X-radiation, the panel of scientists said. "It is unlikely that there is a threshold below which cancers are not induced, but at low doses the number of radiation-induced cancers will be small."
The panel called for continued medical radiation and occupational radiation studies, noting in summary, "Studies of medical and dental occupational exposures do not currently provide quantitative estimates of radiation related risks, due to the absence of radiation dose estimates."
Approximately 400 million medical diagnostic examinations and 150 million dental X-ray examinations are performed annually in the United States, according to the report.
A draft of the report from the NAS-NRC committee to assess the health risks from exposure to low levels of ionizing radiation is available online at the NAS Web site. The final report is in publication and not yet available.
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