By George Johnson | March 21, 2013
This week in a piece for Slate about cancer clusters, like the one made famous by the movie Erin Brockovich, I describe how they almost always turn out to be illusions — examples of what the epidemiologist Seymour Grufferman called “the Texas sharpshooter effect.” Here is how I described it in my article: Stand way back and blast the side of a barn with a shotgun and then find some holes that are crowded together. Draw a circle around them and you have what looks like a bull’s-eye.
The pollution that was blamed for the malignancies may be very real — the Brockovich case involved a metal called hexavalent chromium or chromium 6 that had been discharged during the 1950s and 60s into the drinking water of Hinkley, a small town in the Mojave Desert. The people who lived there were naturally afraid of what the chemical might be doing to their health. But long after the movie was gone from the theaters and the residents and their lawyers had received a $300 million settlement, a 12-year epidemiological study was completed. No elevation of cancer was found…..To Read More…..