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APRIL 26, 17:40 EDT Radiation May Cause DNA Changes By PAUL RECER WASHINGTON (AP) — Cells may be more
sensitive to genetic damage caused by radiation from radon gas than
previously believed, according to research that found high energy particles
do not need to hit the nucleus of a cell to cause DNA changes. In a laboratory study to be published
Tuesday, researchers aimed alpha particles — a decay product from radon gas —
at the fluid surrounding nuclei in cells taken from a hamster, and they found
that radiation could cause genetic changes. ``The prevailing view has been that in
order to cause genetic damage you have to irradiate the DNA directly in the
cell nucleus,'' said Gerhard Randers-Pehrson of Columbia University, a
co-author of the study in the Proceedings of the National Academy of
Sciences. ``What we find is that you can irradiate outside of the nucleus and
still cause that type of damage.'' Randers-Pehrson said scientists who
calculate the health effects of radiation exposure will have to take this new
finding into account, but that it is not yet clear how the research will
affect the risk estimates. ``It may turn out there is more damage
to the DNA at low doses than previously assumed, but that is something that
scientists who make these extrapolations will have to determine,'' said
Randers-Pehrson. ``It is unclear as yet whether the results imply greater or
lesser risk.'' Exposure to radon gas, a natural
byproduct from the decay of uranium and radium in soil and rocks, is thought
to cause about 21,000 American lung cancer deaths annually, second only to
smoking. Radon gas can leak from the earth and
collect in basements. When inhaled, the gas can leave in the lungs alpha
particles that emit low levels of radiation over long periods of time. Just how much radon poses a health risk
has been controversial, but the Environmental Protectection Agency recommends
that the concentration of radon gas in homes be kept below 4 picocuries (a
measure of radiation) per liter of air. A National Academy of Sciences study
last year estimated that since 1980, Americans have spent about $400 million
on radon gas tests and on renovations to vent buildings where the gas can
collect. The study estimated that about 6 percent of American homes have
radon concentrations that would merit corrective action. Radon cancer risk estimates have been
based, in part, on the belief that mutations that can lead to cancer occur
only if radiation particles directly hit the cell nucleus that contains the
DNA. In the new study, Randers-Pehrson and
his colleagues used a machine to zap cytoplasm, the part of the cell outside
of the nucleus, with precise numbers of alpha particles. The number of
particles is representative of the intensity of radiation exposure. They found that cytoplasm hits of three
to eight particles could trigger a genetic change in a cell. Randers-Pehrson
said they also found that when the cytoplasm was hit, the cells tended to
survive and were more likely to pass mutations into new generations of cells,
a critical step in the formation of cancer. Alpha particles striking the DNA
directly tends to cause such extensive damage that the cell is generally
killed and does not make new cells, he said. Andrew J. Grosovsky, a radiation
biologist at the University of California, Riverside, said the Columbia
University study may ``prompt a reassessment'' of the risks of radon gas. But
he noted that ``it is way too early to tell what the consequences of this new
understanding will be'' in recommendations about radon gas exposure. |
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Copyright 1999 Associated Press. All rights reserved. |
