Panel Affirms Radiation Link to Cancer

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Panel Affirms Radiation Link to Cancer

 

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http://news./s/ap/20050629/ap_on_he_me/radiation_risks

 

By H. JOSEF HEBERT, Associated Press Writer 8 minutes

ago

 

WASHINGTON - Even very low doses of radiation pose a

risk of cancer over a person's lifetime, a

National Academy of Sciences panel concluded

Wednesday. It rejected some scientists' arguments that

tiny doses are harmless or may in fact be beneficial.

 

The findings could influence the maximum radiation

levels that are allowed at abandoned reactors and

other nuclear sites. The conclusions also raise

warnings about excessive exposure to radiation for

medical purposes such as repeated whole-body CT scans.

 

" It is unlikely that there is a threshold (of

radiation exposure) below which cancers are not

induced, " scientists said in the report.

 

While at low doses " the number of radiation-induced

cancers will be small ... as the overall lifetime

exposure increases, so does the risk, " the experts

said.

 

Scientists for years have debated how extremely low

doses of radiation affect human health.

 

Pro-nuclear advocates, as well as some independent

scientists, have maintained that the current risk

models for low-level radiation has produced more

stringent requirements than is necessary to protect

public health.

 

It is an issue in determining decontamination

requirements at abandoned reactors and at federal

weapons sites.

 

The academy's panel stood by the " linear, no

threshold " model that generally is the acceptable

approach to radiation risk assessment. This approach

assumes that the health risks from radiation exposure

decline as the dose levels drop, but that each unit of

radiation — no matter how small — is assumed to cause

cancer.

 

" The scientific research base shows that there is no

threshold of exposure below which low levels of

ionized radiation can be demonstrated to be harmless

or beneficial, " said Richard R. Monson, the panel's

chairman. He is a professor of epidemiology at

Harvard's School of Public Health.

 

The panel said new and more extensive data developed

over the past 15 years only strengthen the conclusions

of the panel's last report, in 1990, on low-level

radiation risks.

 

The scientists estimated that one out of 100 people

exposed to 100 millisievert of radiation over a

lifetime probably would develop solid cancer or

leukemia, and that half of those cases would be fatal.

 

It also said that 42 additional cancers can be

expected in the same group from other than low-level

radiation sources.

 

A millisievert is a measurement of radiation energy

deposited in a living tissue. People absorb about 3

millisievent of radiation annually from natural

sources and 0.1 millisivert every time they get a

chest X-ray.

 

The report noted that exposure from a whole body CT

scan is about 10 millisievert, much higher than a

normal X-ray. That raised concerns about the frequency

of such medical diagnostics.

 

The report should not scare people away from nuclear

medicine, said Dr. Henry Royal, a professor of

radiology at Washington University in St. Louis. He

said most often the benefits of such tests and

treatments outweigh the risks.

 

But Royal also said that procedures such as CT scans

should be used to deal with a specific medical

problems and not part of annual medical screenings.

" You should not be exposed to radiation for

superficial reasons, " Royal said in a telephone

interview.

 

Some anti-nuclear advocates said the study reaffirms

that stringent regulations are needed when cleaning up

abandoned nuclear sites or considering health risks

near nuclear power plants.

 

" The NAS panel puts to rest once and for all claims

that low doses of radiation aren't dangerous ...

nuclear advocates have been making this claim for

years " said Daniel Hirsch, president of Committee to

Bridge the Gap, a Los Angeles-based nuclear watchdog

group.

 

Mitchell Singer, a spokesman for the Nuclear Energy

Institute, the industry's lobbying arm, said the

report " is a positive finding. It shows there is very

little risk of exposure from low levels of radiation. "

 

The academy is a private organization chartered by

Congress to advise the government of scientific

matters.

 

___ On the Net:

 

National Academy of Science: www.nationalacademies.org

 

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