The use of radiation in medicine accounts for most human exposure to ionizing radiation, according to a report issued today by the United Nations scientific committee on the effects of atomic radiation.
“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,” the UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) said in a summary of the report to the UN General Assembly.
Radiation produces toxic free radicals when absorbed by the body. Exposure to high levels can cause substantial damage to human body tissues, and may lead to death. Prolonged exposure to lower levels is also associated with an increased risk of ill-health.
The UNSCEAR report was discussed at a press conference today on the sidelines of the Committee’s four-day 57th session, which got under way yesterday at the Vienna International Centre.
The findings of the report, based on data collected from 1997 to 2007, showed 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 medical procedure radiation doses to the population 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.
Between 1980 and 2006 in the United States, medical exposure grew to levels comparable with natural background exposure, the report said. Computed tomography (CT) scans were the major contributor, with others being diagnostic X-rays, interventional procedures and nuclear medicine.
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,” the report pointed out.
It defined 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.
The reported noted that as techniques developed and their use widened, medical uses of radiation continued to increase irrespective of the level of health care being delivered.
According to the report, 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 2 per cent of the total exposure to artificial sources – are: the atmospheric testing of nuclear weapons, whose levels continues to fall; occupational exposure – the highest population exposures are among mine workers exposed to radon, while exposures at nuclear power plants have been falling steadily; the declining effects of the Chernobyl nuclear plant accident in 1986; and the nuclear fuel cycle, including mining, power generation and disposal of waste.
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.
In future the UN Secretariat envisages publishing the detailed supporting evidence of 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 UN International Atomic Energy Agency (IAEA).