How the medical experts reached their conclusions
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Penn epidemiologists Brian L. Strom and James D. Lewis conducted a study for The Inquirer of cancers among emergency workers exposed to the Wade dump fire.
Strom, a professor of medicine, biostatistics and epidemiology, has been director of Penn's Center for Clinical Epidemiology and Biostatistics since 1993. Lewis, an assistant professor of medicine, is a senior scholar at the center.
The Inquirer, which tracked down 207 people who had been to the blaze, provided the researchers with detailed data on 199, including age, race, date of diagnosis and, if available, smoking history. Information also was assembled on the amount of time each person spent at the scene, his proximity to the fire, and skin contact with chemicals. The epidemiologists eliminated 18 individuals for whom some information was lacking.
The analysis found elevated rates of both lung cancer and melanoma.
There were four cases of melanoma among the 181 people studied. The number expected in the general population was 0.65. The incidence of the disease among the Wade group, therefore, was roughly six times higher.
"The elevated risk of melanoma is striking," the epidemiologists wrote. "The occurrence of two of the four melanomas on the feet is somewhat unusual."
Most studies have found that firefighters are no more likely to get lung cancer than the general public. In this group, however, there were 10 cases, nearly five times the expected number of 2.09.
The epidemiologists said there was less than a 5 percent chance that the elevated cancer rates occurred by coincidence.
"However," they added, "these data do not prove causality between the exposure [at the Wade dump] and the subsequent cancer risk."