For information only - not an official document
17 August 2010
Re-issued as received
Radiation in Medicine Major Source of Human Exposure to Ionizing Radiation Other than from Nature
VIENNA, 17 August (UN Information Service) - The use of radiation in medicine is the major source of human exposure to ionizing radiation other than from nature, say the findings of a United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report.
The report was published in print on Monday and electronically last month. It was to be discussed at a press conference to be held today during the Committee's 57th session, 16-20 August in the Vienna International Centre.
"Medical exposures account for 98 per cent of the contribution from all artificial sources and are now the second largest contributor to the population dose worldwide, representing approximately 20 per cent of the total," a summary of the report to the UN General Assembly says.
The findings from 1997 - 2007, reported that about 3.6 billion x-ray examinations were performed each year, an increase of more than 40 per cent, or 1.1 billion, from the previous decade. Most of the population dose from the procedures occurred in countries with high levels of health care where average exposure from medical uses is now equal to about 80 per cent of that from natural sources.
In the United States medical exposure, from 1980 - 2006, grew to be comparable with natural background exposure, the report says.
Computed tomography (CT) scans were the major contributor, with other contributions from diagnostic X-rays, interventional procedures, nuclear medicine and others, the report said.
One of the most striking changes over the past decade or so has been the sharp increase in medical exposures owing, for example, to the rapid expansion in the use of CT scanning, the report said. "In several countries this has meant that medical exposure has displaced exposure due to natural sources of radiation as the largest overall component," it said.
The report defines four levels of health care. In the highest, level one, based on the number of physicians per capita in the population, medical X-ray examinations are 65 times more frequent than in level three and four countries with the lowest ratio of physicians per capita.
Nevertheless, as techniques develop and their use widens, said the report, medical uses of radiation continue to increase irrespective of the level of health care being delivered.
The report said that exposure to natural sources of radiation include:
- inhalation of the naturally occurring radioactive radon gas, which accounts for about half the average exposure to natural sources of radiation;
- cosmic radiation,
- ingestion of naturally-occurring radioactive elements in food and water, and
- external irradiation from naturally-occurring radioactive elements in the soil.
Other than medical uses, the artificial sources of exposure (which make up about two per cent of the total exposure to artificial sources) include:
- atmospheric testing of nuclear weapons, whose levels continues to fall;
- occupational exposure - highest population exposures are among mine workers exposed to radon, while exposures at nuclear power plants have been falling steadily;
- declining effects of the Chernobyl accident in 1986; and
- the nuclear fuel cycle, including mining, power generation and disposal of waste (doses to the public vary widely but are generally very small).
The findings are contained in the first of the two volumes of supporting evidence underpinning the UNSCEAR report for 2008 covering medical radiation exposures; the second covers exposures of the public and workers from various sources of radiation.
Publication of the detailed evidence was delayed by funding and staffing problems that have since been addressed. A second volume with three more annexes to the 2008 report is scheduled to be published in the second half of the year. In total the five annexes to the report amount to more than one thousand pages in length.
In future the UN secretariat envisages publishing the detailed supporting evidence for the Committee's findings in electronic format, and on a more frequent basis. Data collection is expected to draw on national reporting by UN Member States, and conducted in coordination with other organizations such as the World Health Organization (WHO) and the International Atomic Energy Agency (IAEA).
Such reporting arrangements ought to allow identification of new trends, particularly in medicine where technological changes occur rapidly, on a more frequent basis.
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