26 May

The legal profession will not be the same. Currently, for instance, actions are taken against polluters when clusters of disease are linked to the release of disease-causing compounds. Consider the case of Keil Chemical in Lake County, Indiana. In 1991 records indicated that Keil Chemical released about nine hundred tons of a potentially carcinogenic solvent called ethylene dichloride; its city permit allowed the company to release 0.02 ton. From 1987 to 1998, the cancer incidence in Lake County was about 20 percent above the incidence that would have been expected based on national averages.The conventional perspective is that cancer is generally caused by genetic alterations by physical agents. According to this perspective, the evidence looks incriminating, even though experts warn against jumping to conclusions. In the Lake County case, an epidemiologist from the National Cancer Institute warned that “we don’t understand what causes ninety to ninety-five percent of childhood cancer.” But these warnings seem like overly cautious science-speak to people who want justice rather than statistics. When scientific proof of causation is not available, the affected people and the legal professionals base their actions on whatever evidence is available. Disease does not wait for science. If there is an excess of cancer deaths and an excess of a potentially carcinogenic chemical, cause and effect will be inferred unless some viable alternative is presented. If a person hears a shot from a room, walks into the room and sees one person dead on the floor from a bullet wound and another person holding a smoking gun, that too is just an association. Unless the person holding the gun has a good alternative explanation handy, the legal profession will tend to assume that the association reflects causation.In the absence of knowledge about the spectrum of disease causation, experts may unwittingly fan the flames. In the Lake County case, physicians apparently told the parents of two daughters afflicted by rare and different cancers that having both cancers in the same family would be extremely unlikely under normal conditions. Presumably that conclusion was derived by multiplying two small probabilities together to obtain the extremely unlikely joint occurrence within one family. The validity of that conclusion depends on the cancers and what causes them. If the rare cancers were both caused by a common pathogen, then having two in a single family might not be so unusual. Many infectious diseases co-occur frequently within families because family members are more likely to be exposed to the same infectious agents than are two people drawn at random from the population. Medical science has only recently begun to understand infectious causation in the common, well-studied cancers, such as liver, stomach, and cervical cancer. Almost nothing is known about the causes of most rare cancers, certainly not enough to conclude that you can multiply the two small probabilities of having either cancer in a family to obtain the probability of having both in the same family.The new understanding of infectious causation dramatically changes this kind of analysis by drawing attention to feasible alternative explanations for the clustering of cancers and other chronic diseases. Cases of infectious diseases typically cluster either because the potential for transmission varies from place to place or because infectious outbreaks spread from somewhere. Clusters of cancer would therefore be expected for cancers that are caused by infection. If such a cluster happened to occur near the release of a carcinogenic chemical, then the chemical pollutant might be falsely accepted as the cause of the cancer. But infectious causation makes the morass even more ambiguous. If no clustering is associated with the release, the oncogenic chemical could be falsely exonerated. To see this point, imagine that the release did cause some of the cancer. Imagine further that the cancer rates in the vicinity would otherwise have been relatively low because an infectious cause of cancer happened to be rare in the area. An observer might not see any increased incidence of cancer in the area because the lower background rate might mask the effect of the chemical carcinogen. Joint causation further complicates the situation. Noninfectious causes of cancer may exacerbate infectious causes.Before we throw the book at alleged perpetrators, we have to look broadly to see the right targets. Historically, the EPA and CDC have been set up to focus on different targets: the EPA has focused on noninfectious causes of disease, and the CDC on infectious causes. This distinction may become increasingly anachronistic and unproductive as we find more disease that is attributable to both causes.*47\225\2*

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