New study: Nuclear workers at higher risk for cancer

Comment: Nuclear plants are not clean, green and will make you sick!

By BOB AUDETTE, Reformer Staff
Thursday, July 2

BRATTLEBORO -- Are nuclear power plant workers at higher risk to die of cancer?
A study conducted by a Canadian researcher concluded the risk is substantially higher to them than to the general public.

The document, "Exposure to Radiation and Health Outcomes" was made public last week. It was written by Mark Lemstra, who was formerly a senior research epidemiologist for the Saskatoon, Canada, Health Region.

Lemstra left -- or was relieved of, depending on which source you read -- his job last year after a dispute over a report he authored that documented the health disparities between different socioeconomic categories in Saskatoon.

In the radiation report, in which Lemstra reviewed 1,725 articles related to radiation studies, he concluded that nuclear power plant workers have a "relative excess risk" of getting cancer.

In epidemiology, excess risk is defined as the difference between the proportion of subjects in a population with a particular disease who were exposed to a specific risk factor and the proportion of subjects with that same disease who were not exposed.

In the case of nuclear power plant workers, that risk factor is low-dose radiation.

Radiation protection standards are based mainly on risk estimates from studies of atomic bomb survivors in Japan, according to a report called "The 15-Country Collaborative Study of Cancer Risk Among Radiation Workers in the Nuclear Industry."

There has been some controversy over the validity of basing low-dose standards on the results of high-dose exposure.

Of the 1,725 reports reviewed by Lemstra, 22 were cited as references.

Lemstra concluded that not only do nuclear power workers have a higher risk of dying of cancer, they also have a higher risk of dying of other causes not related to cancer, such as heart problems.

Lemstra also quoted a German report that determined that children who live within 10 miles of a nuclear power plant have a higher rate of leukemia than those who live outside that radius.

What Lemstra failed to note in his report however, is that the German researchers said they could not conclusively state that the rates were higher because of the proximity to the nuclear power plants or because of some other environmental factor.

Lemstra's report was briefly reviewed by Bill Irwin, Radiological Health Chief of the Vermont Department of Health, who withheld most comment on the report until he has had a chance to further review it.

Nonetheless, said Irwin, "This kind of literature review is rarely used for policy making, but some people find it useful."

While Lemstra used "highly reputable references" such as the United Nations Scientific Committee on the Effects of Atomic Radiation, said Irwin, "It may be better for people to read the complete reference rather than rely on just those parts of the references cited in the report. A more complete picture is provided in the original documents, and readers may draw different conclusions than those drawn by Dr. Lemstra in his report."

The Nuclear Regulatory Commission also hesitated to comment on Lemstra's report, stated Neil Sheehan, NRC spokesman, in an e-mail to the Reformer.

"One observation made by a staffer who reviewed it was that the controls apparently were not as rigid as would have been expected," he stated. "We will continue to evaluate new studies to determine if further action on the NRC's part is warranted."

A spokesman for Vermont Yankee nuclear power plant had no comment on the Lemstra report other than plant worker exposure limits are set by the NRC based on recommendations by the National Council on Radiation Protection.

There is no database of cancer deaths for power plant workers at specific plants such as Vermont Yankee because death certificates are filed at the place of death and have no reference to the person's occupation.

In 2004, a study conducted by Columbia University's Mailman School of Public Health was released, which tracked workers from 15 nuclear utilities in the U.S. for periods of up to 18 years between 1979 and 1997.

More than 53,000 U.S. nuclear power workers were included in the study, which concluded "that employees in the commercial nuclear industry are less likely than the general population to die from cancer or non-cancer diseases due, in large measure, to the so-called 'healthy worker effect,'" according to an executive summary of the report.

The healthy worker effect is based on the premise that nuclear industry workers have to be healthy and are usually required to have annual medical check-ups.

"The researchers did report, however, a strong positive and statistically significant association between radiation dose and death from arteriosclerotic heart disease, including coronary heart disease," stated the executive summary.

However, stated the principal investigator of the Columbia/Mailman study, Geoffrey Howe, "While associations with heart disease have been reported by some other occupational studies, the magnitude of the present association is not consistent with them, and, therefore, needs cautious interpretation and merits further attention."

He suggested that further follow-up studies be conducted to clarify the study's findings.

"The most important results of this study were findings with respect to radiation-related leukemia and radiation-related other cancers," stated the executive summary. "Positive, although non-statistically-significant, associations with radiation were seen for mortality from some forms of leukemia and other cancers as a whole."

While Lemstra refers to two studies conducted following the 1979 accident at Three Mile Island in Pennsylvania, which concluded there was no increased rates of cancer deaths in nearby residents, he does not cite other studies such as the Columbia/Mailman study.

However, he does cite the 15-Country Study, which found that of 24,158 deaths, 6,734 were from cancer.

"These results suggest that an excess risk of cancer exists, albeit small, even at the low doses and dose rates typically received by nuclear workers in this study," according to the study.

Some researchers have cautioned that it is easy for systemic errors to creep into large epidemiological studies "that originate from different countries with different recording procedures," according to the Journal of Radiological Protection.

Researchers have also been quick to point out that correlation does not imply causation, which means that correlation between two variables does not automatically imply that one causes the other.

It does mean however, that a correlation discovered in a study should be the subject of further investigation.

Lemstra's report can be found at www.policyalternatives.-ca/reports_studies.

Bob Audette can be reached at raudette@reformer.com, or 802-254-2311, ext. 273.

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