Lay a chessboard on a table. Then grab a handful of rice and let the grains fall and scatter where they may. They won’t spread out uniformly with the same number occupying each square. Instead there will be clusters. Now suppose that the chessboard is a map of the United States and the grains are cases of cancer.
Each year about 1.6 million cases of cancer are diagnosed in the United States, and epidemiologists regularly hear from people worried that their town has been plagued with an unusually large visitation. Time after time, the clusters have turned out to be statistical illusions—artifacts of chance.
The Erin Brockovich incident, one of the most famous, is among the many that have been debunked. Hexavalent chromium in the water supply of a small California town was blamed for causing cancer, resulting in a $333 million legal settlement and a movie starring Julia Roberts. But an epidemiological study ultimately showed that the cancer rate was no greater than that of the general population. The rate was actually slightly less.
Of the handful of residential clusters that have not been dismissed as flukes, only two in the United States have been associated, with a great deal of uncertainty, with environmental contaminants. Both involved childhood cancer. One was found in the 1980s in Woburn, Mass. The other was found about a decade later in Toms River, N.J., and is the subject of an absorbing new book by Dan Fagin, a former reporter for Newsday and the director of the science, health, and environmental reporting program at New York University. I first read it in manuscript about a year ago, and I’ve been puzzling over it ever since.
We’re not talking about thousands of cancer cases unleashed in a town by industrial poisons. Or hundreds. Cancer clusters occur on a far smaller scale. An early study of Toms River in 1995, as suspicions were beginning to grow, found a total of 56 childhood cancers in the township (population 76,000) over a period of 13 years. Based on figures for the whole state, 43 of those cases might have occurred anyway. They were part of the normal background rate, cancers that may happen for no apparent reason.
In the central part of Toms River, there were 14 childhood cancers during those years when between nine and 10 would have been expected. But however closely you analyzed the cases, it was extremely difficult—and maybe impossible—to distinguish the blips in the data from what could have occurred by chance. For the children and their parents these were not blips but tragedies. They naturally wanted an explanation. Something or someone to blame.
Fagin was just finishing Toms River: A Story of Science and Salvation when I met up with him at a journalism conference last spring. At a reception one evening, we came to realize that we both were writing books about cancer that would be published this year. (My book, The Cancer Chronicles, is scheduled for August.) Later, as we read and commented on each other’s drafts, we were struck by how we saw the issue of cancer and the environment in very different ways.
Toms River is a story of determined parents forcing reluctant government officials to persist until they found a plausible source for their children’s illnesses. But as I read and reread the book, I couldn’t shake the feeling that the bigger story was how human grief can drive the brain to see cause and effect whether or not it’s really there. After five years and an investigation that cost more than $10 million, it is not certain that anyone in Toms River got cancer from toxic waste discharged by local companies into the atmosphere. The frustrating thing about the science of cancer is that we will probably never know.