Scientists debate level of tolerance to radiation

["Michael C. Baker" <mcbaker@lanl.gov>]

>http://www.ireland.com/newspaper/ireland/1999/0721/hom13.htm
>
>==================================================
>July 21, 1999
>
>Scientists debate level of tolerance to radiation
>
>By Dick Ahlstrom
>
>The argument that there is no safe level of exposure for nuclear radiation is
>wrong and is not supported by scientific studies, according to a US
>researcher who said that cells were very efficient at repairing radiation
>damage.
>
>"A single fallacy is often more acceptable than a complicated truth," said Dr
>Otto Raabe of the University of California, Davis. He was addressing a
>radiation conference in Dublin yesterday organised by the Dublin Institute of
>Technology during a session on the "linear no-threshold" debate.
>
>The linear no-threshold (LNT) theory assumes that any exposure to radiation
>carries a risk of developing cancer. It is widely applied by radiological
>protection agencies and endorsed by the International Commission on
>Radiological Protection (ICRP).
>
>"The evidence for the threshold has been known for a long time," Dr Raabe
>said. A new Russian study pointed towards a threshold for radiation, a level
>that the body could tolerate without subsequent cancers. Breaks in the
>genetic code inside the cell were commonplace and quickly repaired. On
>average there are up to 150,000 breaks per cell daily. "We already have a
>background of DNA breaks," he said, and any contribution to this total by
>radiation was minor.
>
>"There are still uncertainties that we can't work out because of statistical
>difficulties," he acknowledged, but there was no connection between threshold
>and risk. Dr Jack Valentin, scientific secretary of the ICRP, defended the
>LNT theory. "There is no better hypothesis," he said.
>
>There was no dispute that radiation could cause DNA damage and that such
>damage was an initiating event in cancer development. Single-strand breaks
>were easily repaired, but studies had shown it was not so with double-strand
>breaks. He referred to a 1996 study which suggested that very low radiation
>doses could induce cancers in utero and a UN study soon to be published
>indicated that cancers could be caused at very low radiation doses. Both
>sides were hampered by a lack of statistical power to determine what happened
>with low-dose exposures.

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html