Rethinking the "Cancer-Cluster Myth"
In February 2011, I reported a story for High Country News about the Environmental Protection Agency’s efforts to solve environmental health problems through funding epidemiological research. The Agency had announced it would focus on “cumulative impacts,” or the compounding effects of toxic exposure and other stressors on public health. Those I interviewed from communities around the Houston, Texas Ship Channel, where some of the research was based, were pleased with the Agency, which, until then, had mostly investigated the health effects of isolated chemicals. But they knew from experience that these studies would take a long time — and may not reveal conclusive answers. They doubted, even, that any significant findings would be put to use. “The studies are done. They’re scientifically proven, ” Juan Parras, director of the Houston environmental advocacy group TEJAS, told me. “Then they sit in the library, and nobody addresses the solution.”
Epidemiology is a notoriously difficult science, particularly when it comes to linking cancer cases to a common cause. By the 1980s, the Centers for Disease Control and Prevention had largely given up investigating cancer clusters; of 108 such investigations in the ‘60s and ‘70s, none pointed to a culprit. A popular theory dismissed clusters as a matter of happenstance, or, as Atul Gawande wrote for The New Yorker in 1999, in “The Cancer-Cluster Myth,” “the result of almost irresistible errors in perception” — of the human instinct to see coincidence as cause for alarm.
In any circumstance, clusters have become casualties of statistics. Scientific significance — and a low margin of error — requires a large sample size. Often, communities with clusters are so small that studies result in false negatives, demonstrating no conclusive link between a toxin and the cluster, when, really, a link could exist. “It’s a huge source of frustration for everyone, scientists and communities alike,” Rachel Morello-Frosch, a professor of public health at the University of California, Berkeley, told me. “By the time you see a relationship between environmental exposure and a health concern, you’re basically doing a dead body count.”
With the support of a 2013 National Health Journalism Fellowship, I’ll examine why epidemiology and other scientific inquiries into environmental health problems rarely secure regulatory change or care for those impacted. My story is based in a small town in central Nevada, site of the most significant childhood cancer cluster on national record. Given the town’s small size, there is a one in 232 millionth chance that the cluster was merely coincidental. Statistically, it seems, the cases had to have a common cause.
There wasn’t a lack of suspects; the problem may have been that there were too many. The CDC launched a lengthy investigation and several federal agencies followed, but none of the studies turned up answers. Four children died, and as the cluster appeared to taper off, public attention waned.
But the recent diagnosis of three more children and a lawsuit against a possible culprit have caused town residents to wonder, again: What caused the cluster, and could the cause have lingered? My investigation is, in part, an unearthing of an old mystery. It’s also a critical look at the way communities, scientists, companies, and government agencies solve — and often fail to solve — environmental health problems. I’ll examine 12 years of scientific findings that were buried under the inevitable insignificance of small numbers, and I’ll meet the researchers who are still looking for answers. I’ll meet parents who put their faith in science to come to their defense and were confused and angry when it did not. I’ll reflect, too, on the general uncertainty of science and question the standard approach to environmental health problems. In this case, as in many, the onus was on victims to prove that an injustice was committed against them, rather than on industry to ensure its practices were safe.
Image by Pam and Phil via Flickr