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March 11, 2007
WHY IS THYROID CANCER RATE UP?
March 11, 2007
Why is thyroid cancer rate up?
One research group thinks it knows the answer: fallout from nuclear power plants.
By Ann Wlazelek Of The Morning Call this year, which is about 2 percent of all cancer diagnoses. It's rarely fatal but in 2005 claimed the life of Supreme Court Justice William H. Rehnquist. The latest snapshot of n
A private research group that gained national attention three years ago for finding evidence of nuclear fallout in baby teeth is now linking power plant emissions to Pennsylvania's relatively high rate of thyroid cancer.
The Norristown group, the Radiation and Public Health Project Inc., plotted nuclear reactors on a map with counties reporting the highest rates of thyroid cancer and found a ''remarkable pattern.''
Three of the four nuclear plants are in or near 13 of 14 counties with the highest cancer rates.
''This finding raises the theory that thyroid cancer risk has been raised by exposure to radioactive iodine, which is routinely released as airborne particles from each plant,'' said Joe Mangano, the group's executive director.
Mangano, who holds a master's degree in public health and has had previous reports published in medical journals, brought his findings to The Morning Call because Lehigh County's average rate of thyroid cancer for 1997 through 2003 exceeded the state's. Pennsylvania's rate at 9.89 per 100,000 population is the highest in the country, he said, and Lehigh County's rate is 16.4 per 100,000.
His theory deserves further study, Mangano said, because radiation is the cancer's primary risk factor and the state has a lot of reactors.
Cancer experts puzzled
Cancer experts don't know why the rates vary geographically, why Pennsylvania's rate of thyroid cancer, for example, is twice that of North Carolina's, which has the lowest rate in the country. But they are reluctant to blame emissions.
''There are excruciatingly low levels of radiation coming from power plants,'' said Gene Weinberg, an epidemiologist with the Pennsylvania Department of Health's cancer control program. He said the average person is exposed to about 150 to 300 millirems a year, but only about one ten-thousandth of that comes from nuclear plants. People are exposed to radiation every day from the soil, sun and electrical devices such as TVs and computers.
PPL, the principal owner of the Susquehanna nuclear power plant in Luzerne County, was unaware of Mangano's report but said an independent study conducted by the American Academy of Natural Sciences found ''no known environmental or human health impact'' from the reactor's radioactive releases. The study was conducted over 25 years and was published in a health physics publication last year, said plant spokesman Lou Ramos.
''We know of no studies that show increased cancer around nuclear plants,'' he said.
Mangano said his theory that emissions contribute to thyroid cancer is plausible because the reactors have been operating for years and radiation exposure is cumulative. He would like the help of physicians in continuing the research for publication.
Low-level exposures have not been proven to heighten the risk of thyroid cancer, according to the American Cancer Society. However, several studies have linked radioactive fallout from nuclear weapons and power plant accidents, such as Chernobyl, to a higher risk.
Radiation exposure is chief risk
''There are not that many well-known risk factors,'' said Dr. Elaine Ron, a thyroid expert at the National Cancer Institute. ''The main one is [a history of] radiation exposure in childhood.''
Ron referred to a risk in the 1950s, when doctors sometimes used radiation to treat a child's acne, scalp fungus infections, enlarged thymus gland or to shrink tonsils and adenoids.
Those treatments are no longer performed, and researchers believe the increase in thyroid cancer from such exposures passed by the late 1980s.
But the number of new thyroid cancers diagnosed continue to rise nationwide and at an accelerated pace.
''We've been seeing a steady ratcheting-up,'' said Brenda Edwards, a statistician with the National Cancer Institute. The annual rate increase doubled from 2 percent in the 1980s to 4.6 percent in the 1990s and about 9 percent today, she said.
''Is there something there we are all being exposed to or is the increase amplified because of surveillance?'' Edwards asked.
Conventional wisdom, she said, points to more Americans being probed, screened and scanned, leading to more diagnoses.
Better testing
Dr. Rena Sellin, a professor and thyroid cancer expert at the M.D. Anderson Cancer Center in Texas, said Americans are benefitting from more sensitive and sophisticated diagnostic equipment than in previous decades. By undergoing MRIs, CT scans, PET scans and ultrasound screenings, she said, many patients are discovering thyroid conditions.
Most are accidental or incidental findings, Sellin said, as in church members getting a free screening of their carotid (neck) arteries and being told they have a nodule on their thyroid gland.
AMA findings
A May 10 article in the journal of the American Medical Association came to the same conclusion: that the increasing incidence of thyroid cancer is ''predominantly due to the increased detection of small–cancers.''
The fact that the cancers are being found at a small or early stage, researchers say, lends itself to the theory that the caseload may not be increasing as much as are doctors diagnosing the disease.
Mangano contends the geographic variances suggest more than good detection.
''Are doctors in Pennsylvania twice as good at detecting than in North Carolina?'' he asked.
Maybe, said the state cancer program's Weinberg. Pennsylvania has more medical schools than most other states, he said.
But, he continued, ''It's an interesting cancer. When you see changes in such a short period it's generally an indication that something out there has changed as well. It lends one to think it's something more universal, not just a power plant here or a power plant there.''
An uncommon cancer
Although the fastest-rising cancer in the country, thyroid cancer continues to be a largely uncommon and slow-growing cancer. The American Cancer Society estimates it will strike 33,550 Americans – mostly women – A noticeable change
Logical explanation?
Mangano believes radioactive particles carried downwind of the nuclear plants is a logical explanation for the increase. People inhale or ingest the fallout by drinking water from water supplies or milk from cows in the vicinity, he said.
Although emitted at low levels, radiation can have a cumulative effect.
Pennsylvania experienced the Three Mile Island nuclear accident in 1979 and has five plants with nine out of 12 reactors still functioning, he said.Besides Three Mile Island in Dauphin County and Susquehanna in Luzerne, those plants include Limerick in Montgomery, Peach Bottom in York and Beaver Valley in Beaver counties.
Mangano said his group is not anti-nuclear but is composed of physicists, nurses and researchers interested in radiation's impact on health. The staff has published other studies on thyroid cancer and Chernobyl but is probably best known for a 10-year study completed recently in which some 5,000 baby teeth were tested for a chemical produced by nuclear power plants. The study found the highest amounts in the teeth of children who lived closest to the reactors. It received widespread media attention, with articles in The New York Times, USA Today and on network news channels, but little attention from the scientific establishment.
Mangano said the fact that others in public health are not interested or critical of his work hits him like ''cold water splashed in my face.''
''We're looking for answers,'' he said. ''There's a terrible cancer epidemic in this country.''
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