PHILADELPHIA -- Cancer rates went up among residents living closest to the Three Mile Island nuclear power plant several years after the 1979 accident, but a new study says stress, not radiation, may have caused the increase.
The June issue of the American Journal of Public Health reports that stress resulting from the near-meltdown of the Unit 2 reactor may have triggered "a small wave of excess cancers" in 1982 among people living within about 3 1/2 miles of the south-central Pennsylvania plant.
"We observed a modest post-accident increase in cancer near TMI that is unlikely to be explained by radiation emissions," concluded researchers from Columbia University and the National Audubon Society. "Such a pattern might reflect the impact of accident stress on cancer progression."
A study last year by the same research team found no convincing evidence to link an increase in some forms of cancer among area residents to low-level radiation emissions from the plant during the accident.
Although the theory that stress could somehow trigger the growth of cancer has never been proved, the researchers reported in the journal that they decided to explore the possibility because of "growing interest in the effects of stress on cancer promotion and progression."
Past studies had shown that mental distress was a major consequence of the TMI accident, the worst in the history of commercial nuclear power in the United States. Women and children living within 5 miles of the plant at Middletown, Pa., 10 miles southeast of Harrisburg, were told to evacuate after the accident. Thousands of others left the area on their own in fear of being exposed to radiation.
By searching medical records of hospitals within 30 miles of TMI from 1975 to 1985, researchers identified about 5,500 cancer cases involving people who lived within 10 miles of the plant. They found that cancer rates in those living nearest TMI rose in 1982, remained elevated for a year and then declined.
The researchers found that people living closest to the reactor were 40 percent more likely to have been diagnosed with cancer after the accident than those living farther away.
Even before the accident, the risk for cancer was 20 percent higher for those living near the plant than for those farther away. The study did not address that earlier difference.
Jan Beyea, senior scientist at the Audubon Society, said the higher rates of cancer among people living nearest to TMI could not be attributed to radiation exposure. "This increase has occurred both in areas where there was radiation exposure and where there was not," he said.
The researchers found elevated rates among residents nearest the plant for cancers overall, as well as for specific cancers, including leukemias and lymphoma.
The researchers said those closest to the plant tended to suffer the greatest stress from the accident. They said the stress could have promoted the growth of pre-existing cancers in people, thus bringing them to the point of being diagnosed.
"We can't say it's definitely stress, but it's suggestive of stress," Mervyn Susser, a Columbia University epidemiologist who was the principal investigator for the study, said.
A representative of GPU Nuclear Corp., which operates TMI, said Friday that the company would not comment because company officials had not had a chance to review the report.
The study was paid for by the Three Mile Island Public Health Fund, which was set up under court order to address public health concerns arising from the accident.
GPU Nuclear ended the cleanup of the damaged Unit 2 reactor last year and is now seeking the federal government's permission to put the unit into long-term storage.