On a brisk New England evening, state health officials pulled out maps littered with tiny red, yellow and green pins. Each marked the home of someone who had developed cancer in Plymouth or its environs.
About 40 residents listened patiently in the town hall as one official explained how the locations of the cancer victims might help investigators discover why the region has an unusually higher rate of leukemia.
However, discovering the cause of those tumors may be elusive.
Even when all the cancers have been tracked down, health officials say, investigators may never be able to point the finger at the source, even though some residents feel they already know--the Pilgrim nuclear power plant.
Nearly 370 years after European settlers arrived to conquer the New World, the coastline near this historic town is a beachhead for nuclear power opponents, who argue that radiation released by Pilgrim in 1974 and 1975 has been killing residents.
Boston Edison Co., which owns Pilgrim, says the suspicions cannot be true because the plant has not emitted enough radiation to cause any harm, especially in the neighboring communities of Kingston, Marshfield, Scituate and Duxbury, where high leukemia rates have also been seen.
David Tarantino, a Pilgrim spokesman, said the total amount of radioactivity released by the plant "has not been sufficient to cause one case of cancer, never mind cancer in places far removed."
However, nobody disputes that the leukemia rate is elevated. Between 1982 and 1986 there were 55 leukemia deaths in Plymouth and the other four towns along the coast--19 more than statistically expected.
Leukemia is one type of cancer that can appear several years after exposure to radiation and cancer cases are notorious for their ability to pop up in clusters, giving the appearance of a mini-epidemic.
Most of the time, however, investigators conclude that the cluster was just a random clumping of cases.
"Clusters do occur. They come and go and there's no reason for it," said Richard W. Clapp, former director of the state's cancer registry. But the cluster near the plant "was highly statistically significant compared to the rest of the state."
The fact that leukemia appears about nine years after exposure to radiation and the cancer cases popped up about nine years after Pilgrim released radiation into the air is "not proof by any means. But it certainly raises your level of suspicion," he said.
Tarantino said the amount of radiation released was only "slightly elevated" and "none of the detectors outside the plant boundaries have detected radiation beyond normal background" levels.
But that's because Pilgrim's detectors are not sensitive to the dominant type of radiation released by the plant, according to Ellen B. Cargill, a nuclear medicine researcher.
She also said federal documents show that Pilgrim is permitted to release more radiation than other plants and that the nuclear plant has periodically exceeded that unusually high standard.
The suggested link between the plant and the leukemia cases has been buttressed by a theory that sea breezes might be able to trap radiation released by Pilgrim. According to the theory, the breezes were constantly concentrating and exposing residents to radioactive particles.
Tarantino said that the theory, by Dr. Sidney Cobb, a retired Brown University professor, was discredited by a study called the Spengler Report.
But that report concluded: "The sea breeze and gradient winds would advect (carry by wind) emissions over populated areas. . . . Thus a modified 'Cobb hypothesis' is probable."
The Pilgrim plant this month went to 100% power for the first time since April, 1986, when it was shut down after a series of technical problems.
After extensive management changes and equipment repair, the plant was started up again on Dec. 31, 1988, and the Nuclear Regulatory Commission has allowed a gradual increase in power ever since.
The next chapter in the controversy will probably be written when the Health Department finishes placing all of its red, yellow and green pins in its maps.
If all the leukemia cases are concentrated near the plant, while an assortment of other randomly selected cancer cases are spread out all over the rest of the town, it would be strong circumstantial evidence that something in or around the plant has caused the leukemias.
That analysis is going to take some time because the Health Department has been the target of severe budget cutbacks.
However, the people of Plymouth have been waiting for an answer for years, and some are getting impatient.
During the last meeting between department officials and the Board of Selectmen, the board's chairwoman, Alba C. Thompson, felt that she had to resort to profanity to fully describe her frustration over the progress of the study.
"It is damn slow," she said, prompting the audience to break into applause.