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The Psychology of Cancer Clusters

Fire in the MindBy George JohnsonMarch 29, 2013 5:46 AM


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"About Cancer and Cancer Clusters." Delaware Department of Health and Social Services, Division of Public Health My last two posts about the Erin Brockovich case are part of a tangent that began with an article I wrote for Slate about cancer clusters. Before continuing I want to step back and tie this all more firmly into one of the themes of this column: how the human brain, flooded with the information storming our senses, is driven to pick out patterns -- or to impose them if they are not there. This is how I put it in my book, Fire in the Mind: Science, Faith, and the Search for Order:

Psychologists have found that if you put people in a room with a contraption of lightbulbs wired to blink on and off at random, they will quickly discern what they believe are patterns, theories for predicting which bulb will be next to blink. Once a person becomes enmeshed in an ideology or a scientist in a hypothesis, it is difficult not to see confirmation everywhere. Our brains are wired to see order, but we are cursed with never knowing whether we are seeing truths out there in the universe or inventing elaborate architectures.

That is what makes cancer clusters such a vexing phenomenon. In my piece for Slate I concentrated on the case of Toms River, New Jersey. There was no question that the water had been irresponsibly polluted. And there appeared to be more childhood cancer than in the general population -- 56 cases in the entire township over 13 years when 43 would have been normal. In the end a very thorough investigation and statistical analysis failed to find an association between pollution and any of the cancers except one: leukemia.* Even then the epidemiologists could only say, with great uncertainty, that a few of the cases might have been caused by the pollution, but only among the girls and not the boys. This is what I wrote:

As epidemiologists parsed the numbers this way and that — including one age group in their calculations and excluding another, or making different assumptions about when contamination reached the water taps — were they closing in on a deeply hidden truth or picking and choosing among the data? There was no biological explanation for why male and female fetuses would respond differently to the carcinogens. If limiting the analysis to girls hadn’t uncovered an association, would the next step have been to distinguish between those with brown hair and blond?

Were the leukemias caused by the pollution or were they a random fluctuation in the numbers? We will probably never know. For the Brockovich case, which involved the town of Hinkley, California, the evidence was even weaker. The water was indeed polluted, and people were getting cancer, though (as later discovered) in no greater numbers than for the general population. It just seemed that way. As in Toms River the companies responsible for the contamination agreed out of court to pay a large settlement. I think there was justice in that. Their actions had been irresponsible and caused fear and unending agony among people who will always wonder why their children got sick. For those of us far away from Hinkley or Toms River, our brains also demand a satisfying explanation. But we will settle for a good story. A town was polluted. Its citizens got cancer. A villain must be found and made to answer. But you can sympathize with the children and abhor the polluters without believing there was really a connection. *Updated: Dan Fagin, the author of Tom's River, has persuaded me to soften the wording of this sentence: "In the end a very thorough investigation and statistical analysis ruled out pollution as a cause of any of the cancers except one: leukemia." "Failed to find an association" is more precise. Here is the study I'm referring to (a pdf) and a page about the investigation on the State of New Jersey's website. Related posts: Erin BrockovichThe Brockovich Story, Part 2

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