A MELANOMA OUTBREAK
Rising incidence rates can get pretty scary. Among the classic examples occurred during the 1970s and ‘80s at Lawrence Livermore National Laboratory, across the bay from San Francisco. This lab is part of the U.S. United states doe and is engaged in nuclear weapons research in addition to experimenting with various forms of energy. This is big-time physics and chemistry, so you may imagine, there are potential exposures to a variety of radiation and toxic substances.
In the mid-1970s numerous Livermore employees were diagnosed with melanoma. Although no known occupational exposures were associated with melanoma, California health officials and presumably laboratory employees were worried. They found that the incidence among Livermore employees was three times that of the surrounding community. Investigators tried to nail down what was happening.
They compared the 19 employees who had been diagnosed with melanoma with those who had not. Employees with melanoma were no more likely to be scientists; they were no more likely to have heard of any kind of radiation; they were no more likely to have worked in the lab a long time in fact, their average tenure at Livermore was slightly less compared to workers who did not have melanoma. Adding to the mystery, there was no excess incidence of melanoma at the sister facility, Los Alamos National Laboratory in New Mexico, which hosted virtually identical research activities.
The story made it to the New York Times and the Washington Post. The incidence rate among laboratory employees continued to be more than twice that of neighboring counties through the early 1980s. But then investigators noticed something interesting: all the increase in incidence was in melanomas less than 1. millimeters thick so-called thin melanoma.
This is just the kind of small abnormality in which pseudodisease will be common and about which pathologists will likely disagree whether cancer is present. Investigators found no increase in the incidence of thick melanomas, however, and, more important, no increase in melanoma mortality among lab workers. And they noticed something else: laboratory employees were more likely to see dermatologists and more likely to have skin biopsies than others living in the same community.
The difference was most dramatic after the initial reports of excess incidence, when employees were biopsied at nearly five times the rate of other people in the area. What happened at Livermore? My guess is that the process was started by a chance event. All it would take is one staff member developing a very aggressive melanoma, due simply to bad luck, which quickly spreads and leads to death. Given preexisting concerns about a variety of exposures in the laboratory, coworkers become uneasy. Their response is understandable: they see a doctor and get checked for questionable moles.
Questionable moles are of course found, and more skin biopsies are performed. Another case of melanoma is diagnosed. Concern spreads throughout the laboratory, and administrators feel pressed to respond. One tactic was in fact an "educational and awareness campaign," conducted by the laboratory's health services.
I also suspect that the involvement of the health department (and the press) began to influence the concept of local doctors, who examined Livermore employees more carefully and were more likely to biopsy. The patients looked harder, the doctors looked harder, there were more biopsies, and more early-stage melanoma was found.
The sad thing would be that the worry seems to persist, affecting another generation. Just not too long ago, the Los Angeles Times reported on the high incidence of melanoma among children born in the area around the lab.
Over 30 years there had been eight cases, six more than statistically expected. But there had been no increase in the childhood cancers we know are related to radiation: leukemia and lymphoma.
The natural response to concerns about a "cancer epidemic" is to look hard for cancer. Unfortunately, looking hard for cancer can trigger a cancer epidemic.
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