For Radiation, How Much Is Too Much?

["Bjorn Cedervall" <bcradsafers@HOTMAIL.COM>]

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Bjorn Cedervall    bcradsafers@hotmail.com

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For Radiation, How Much Is Too Much?

November 27, 2001, By GINA KOLATA



In their efforts to protect Americans from the hazards of

radiation, federal agencies have found themselves in a

quandary. People are constantly exposed to radiation from

natural sources - from cosmic rays, radon seeping out of

the earth and radioactive substances in soil, water, food

and even from potassium in the human body itself.



Compared with this radiation, the amounts coming from human

efforts like nuclear plants are, relatively, minuscule. So,

the question is, How closely must this radiation be

regulated?



Up to now, regulators have typically acted as if every bit

of excess exposure is potentially hazardous. But some

scientists question this assumption.



The issue is becoming increasingly pressing as more than

100 nuclear power plants are being relicensed so they can

continue to operate. At the same time, the country faces a

growing predicament of what to do with nuclear waste from

power plants and weapons sites.



"The issue rages because we are regulating doses that are

lower than the natural background of radiation," said Dr.

Arthur Upton. A radiation expert and former director of the

National Cancer Institute, Dr. Upton is a professor of

environmental and community medicine at the University of

Medicine and Dentistry of New Jersey.



In a report last year on radiation standards, the General

Accounting Office, the investigative arm of Congress, said:

"The standards administered by E.P.A. and N.R.C. to protect

the public from low-level radiation exposure do not have a

conclusive scientific basis, despite decades of research."



The situation is further confused, experts say, because

regulatory standards are a hodgepodge.



The Environmental Protection Agency advocates a standard

for all radiation exposure from a single source or site at

15 millirem a year, with no more than 4 coming from ground

water. A standard chest X-ray, in comparison, gives about

10 millirem to the chest, which is equivalent to 1 or 2

millirem to the whole body. The Nuclear Regulatory

Commission sets its acceptable level of radiation exposure

from any one source at 25 millirem a year. In contrast, the

natural level of background radiation in the United States,

on average, is about 350 millirem a year, and in some areas

of the country it is many times higher than that.



In New York, for example, people absorb about 100 millirem

of radiation each year from cosmic rays alone, said Dr.

John Boice Jr., a radiation expert, who is the scientific

director of the International Epidemiology Institute in

Rockville, Md. In Denver, exposure from cosmic rays

averages 200 millirem a year, he said, and natural

variation in radiation exposure is many times the amounts

of radiation that are being disputed by regulatory

agencies.



"We eat, breathe and drink low levels of radiation," Dr.

Boice said.



At the same time, said Dr. Fred Mettler, chairman of the

radiology department at the University of New Mexico

medical school, major medical sources of radiation, like

CAT scanners, have fallen outside the purview of any

regulatory agency.



"A whole lot of places aren't regulated at all," Dr.

Mettler said. "It's a bit of a nightmare."



"When you look at the exposure of the population from

radiation, about two-thirds is due to natural background

and about 15 percent is due to your friendly doctors and

chiropractors," Dr. Mettler said. "Everything else is, to

tell you the truth, very minimal. Less than a couple of

percent is from all the nuclear reactors and all the

research industry."



But, asked Dr. John Evans, a risk analyst at the Harvard

School of Public Health, Why should the level of background

radiation matter to the question of how much additional

risk from human-generated sources is acceptable? "Why isn't

the more relevant question, How much of this risk can be

mitigated at what cost to you?" he asked.



The quandary over how to set radiation levels does not

result from a lack of research or analysis, scientists say.





"Radiation's effects on people have been studied for over a

century," Dr. Mettler said. "There's a vast literature.

There are probably more studies on the harmful effects of

radiation than for any other toxic or noxious agents in the

environment."



And as scientists studied radiation, committees to evaluate

the data proliferated.



"We have national and international standing committees

that periodically review the world's literature on ionizing

radiation," said Dr. Boice, who is a member of many such

groups. "At the International Committee on Radiological

Protection, we just celebrated our 75th anniversary and we

meet two or three times a year."



Then, he said, there is the United Nations Scientific

Committee on the Effects of Atomic Radiation. "That started

in 1955," Dr. Boice said. "We meet every year in Vienna and

we publish volumes."



In the United States, the Environmental Protection Agency,

the Nuclear Regulatory Commission and the National Council

on Radiation Protection and Measurements wrestle with the

radiation standards question, and the National Academy of

Sciences has been called upon periodically since the 1950's

to weigh in with its committee, called the Biological

Effects of Ionizing Radiation committee. The Department of

Energy and the National Institutes of Health conduct

extensive research.



The science has grown rapidly. In 1980, Dr. Boice set up

the radiation epidemiology section at the National Cancer

Institute with just a handful of researchers. Now, he said,

while he moved on to form the International Epidemiology

Institute, which conducts research for industry and the

government, the cancer institute's radiation department is

no longer a section, it is a branch, and one of the largest

branches there, with hundreds of scientists.



"A lot of people say, `Gee, we don't know a lot about the

risks of radiation,' " Dr. Boice said. "I say: `We know a

whole lot. We've studied populations all over the world

since the turn of the last century. We know what happens at

high doses. We know what happens at medical doses. And we

know that at low doses the risks are low. The controversy

is just how low are they. Are they really low or are they

really, really low?' "



As with other toxic substances in the environment, the

stricter the standards, the more it costs to meet them.



The G.A.O. report last year, which had the subtitle

"Scientific Basis Inconclusive, and E.P.A. and N.R.C.

Disagreement Continues," gave some examples of the costs of

complying with standards setting different levels of

radiation. The cost of cleaning soil around reactors and

nuclear weapons facilities could range from thousands of

dollars to more than $100 million, depending on whether the

standard was an exposure of 15 or 25 millirem a year, the

report said.



The report said that for groundwater, the cost of going

from the Nuclear Regulatory Commission's limits of 25

millirem a year to the level that the Environmental

Protection Agency wants could be billions of dollars.



Scientists usually rely on a mathematical model in

estimating radiation risk. The most widely used model is

known as the linear-nonthreshold dose-response model. It

assumes that there is no safe dose of radiation and that

the risk of getting cancer or genetic damage increases

along with radiation exposure.



"For better or worse, that is our model," said Stephen

Page, the director of the environmental agency's office of

radiation and indoor air. And with that model, he said,

"the E.P.A. has tried to be as protective as possible." The

agency, he added, uses that model to make sure the risk

from radiation is within the allowable range from toxic

chemicals, 1 in 10,000 to 1 in a million chance of

developing cancer.



Some say that the linear model is the best way to estimate

radiation risk, but others say that there is, in fact, a

threshold below which radiation poses no hazard to health.

And still others say that low doses of radiation are

actually beneficial.



The linear hypothesis had its origin in 1927, when the

geneticist Dr. H. J. Muller published a paper on his work

eliciting gene mutations in fruit flies by bombarding them

with radiation from X-rays. In a paper published in the

journal Science, Dr. Muller showed that the number of

mutations in fruit flies was proportional to the dose of

X-rays that had struck the insects.



"He said: `Aha! There's a linear relationship,' " said Dr.

Dade W. Moeller, a radiation expert and professor emeritus

at Harvard who runs a consulting company, Dade Moeller &

Associates in New Bern, N.C. Yet, Dr. Moeller points out,

those studies by Dr. Muller used very high doses of

radiation, and he elicited gene mutations, not cancer. But

the idea that radiation's effects were directly

proportional to its dose caught hold and soon was being

used to predict cancer cases. The difficulty was in

demonstrating it.



The risks of getting cancer from exposure to radiation

increase with dose. But since a third of all people get

cancer anyway, at some time in their lives, the problem is

to find evidence that low doses of radiation cause cancers

that would not have otherwise occurred. Even for people

exposed to large radiation doses, like the 80,000 to 90,000

survivors of the atomic bombs exploded over Hiroshima and

Nagasaki, it has been hard to find excess cancers.



"They were exposed in 1945 and nearly half are still

alive," Dr. Moeller said.



Dr. Mettler said the latest data show that 12,000 of these

atomic bomb survivors had died from cancer. He said the

number of excess cancers in the group is about 700.



Those data, Dr. Mettler said, show that there is a small

risk of cancer with an exposure of tens of thousands of

millirem of radiation.



"There's a group that says that if you can't see it, it

doesn't exist," Dr. Mettler said. "Then there's another

group that says, `That's nice, but it doesn't mean it

doesn't happen.' "



Now, some scientists even say low radiation doses may be

beneficial. They theorize that these doses protect against

cancer by activating cells' natural defense mechanisms. As

evidence, they cite studies, like one in Canada of

tuberculosis patients who had multiple chest X-rays and one

of nuclear workers in the United States. The tuberculosis

patients, some analyses said, had fewer cases of breast

cancer than would be expected and the nuclear workers had a

lower mortality rate than would be expected.



Dr. Boice said these studies were flawed by statistical

pitfalls, and when a committee of the National Council on

Radiation Protection and Measurement evaluated this and

other studies on beneficial effects, it was not convinced.

The group, headed by Dr. Upton of New Jersey, wrote that

the data "do not exclude" the hypothesis. But, it added,

"the prevailing evidence has generally been interpreted as

insufficient to support this view."



In the meantime, the regulatory agencies are at a

stalemate, continuing to disagree on radiation standards.

And the committee reports and committee meetings on

radiation standards go on.



A recent report, issued in June by the National Council on

Radiation Protection and Risks, is 287 pages long and

devoted entirely to evaluating the linear-nonthreshold

model. It explains that the council "has sought to leave no

significant aspect of the subject unaddressed."



Its conclusion?



For lack of a better model, it recommends

keeping the linear one.



"There is not conclusive evidence on which to reject" the

model, the report says, adding that "it may never be

possible to prove or disprove the validity of the linear

nonthreshold assumption."



http://www.nytimes.com/2001/11/27/health/policy/27RADA.html?ex=1007862474&ei=1&en=71d61d6cef60a69b







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