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One of the most potent weapons in the arsenal of plaintiffs-side asbestos attorneys is the argument that if their client has contracted mesothelioma — a fatal cancer that attacks the lining of the lung — that the cause of the cancer must be asbestos. In one swoop, the plaintiff proves injury and a significant part of causation. Since under the substantial factor test, arguably even a minor exposure to asbestos can contribute to the risk of contracting mesothelioma, and these types of cases typically involve significant damages, the impetus for defendants to settle is overwhelming. In a recent Simian Virus 40 (SV40) case in U.S. District Court for the Central District of California, Horwin v. American Home Products, 00-04523, the asbestos defense bar was presented with a strong new argument that can be used to break the “mesothelioma equals asbestos” equation and provide defendants with a medical defense to causation in at least low-exposure mesothelioma cases. In the right type of case, the defense will at a minimum be able to provide another culpable party to share fault under Proposition 51 and may be able to provide a complete defense. It should be noted that a Prop 51 defense requires the defense to produce evidence about who is responsible for the SV40 that caused the plaintiff’s tumor, while in an alternate causation case, the defense would not. Since the early 1960s, SV40 has been known to be a carcinogen and is now recognized to be one of the most potent carcinogens known to man. It is indigenous to rhesus monkeys and has infiltrated the human population. The cause of the spread from monkeys to humans is hotly debated, but even the government acknowledges that possibly as many as 20 million people were vaccinated with polio vaccine contaminated with SV40 in the early 1960s. Although the pharmaceutical companies argue that SV40 does not cause disease, studies have shown that upward of 50 percent of mesotheliomas are positive for the presence of SV40. A big advantage for the “SV40 defense” is that the presence of SV40 can be objectively detected in the tumor, and the cancer-causing properties can be confirmed by tests. SV40 causes cancer when the virus binds with human cells and then excretes a T-antigen. This T-antigen inactivates the proteins in the cells whose function is to control the division of the cells. These cancer-controlling proteins or tumor suppressors are called P53 and Rb, and when they come into contact with the SV40 T-antigen, they are unable to control the growth and division of the cells. It is the uncontrolled division of cells that is a major promoter of cancer. The presence of SV40 in tumor cells, as well as the expression of the T-antigen, can be objectively confirmed. Thus, the jury is presented with very compelling evidence that the virus is alive, growing and inactivating the cells that are designed to stop cancer. In Horwin, U.S. District Judge William Rea ruled, after a three-week Daubert hearing, that there was a sufficient scientific basis to allow plaintiffs’ expert to testify that SV40 causes cancer generally and that SV40 caused the specific brain cancer in the decedent. While the case dealt with brain cancer, much of the evidence related to SV40′s ability to cause mesothelioma. The main study that the court relied on was written by three of the leading SV40 researchers in the field. The article — “SV40 and human tumours: myth, association or causality?” — was published in Nature Reviews in December 2002. Judge Rea, in an extensive opinion, outlined the arguments for and against the conclusion that SV40 causes cancer. The strongest argument against SV40 being a cancer-causing agent is that at the present time there is no convincing epidemiological evidence to support causation. He recognized that scientific bodies, like the Institute of Medicine, have found that it is difficult, if not impossible, to establish the rate of SV40 in the general population. Without this knowledge, there is no ability to establish a control group, a condition precedent to making any epidemiological assessment. However, relying on cases such as Kennedy v. Collagen Corp., 161 F. 3d 1226 (9th Cir. 1998), Judge Rea concluded that the presence of accepted epidemiological studies demonstrating causation was not a sine qua non for demonstrating that SV40 was a human carcinogen. The court instead looked to animal, human and cellular studies to conclude that SV40 was a human carcinogen in general. As to whether SV40 caused the specific tumor at issue, Judge Rea found the test results that showed the presence of SV40 alive in the tumor as well as the presence of SV40′s T-antigen sufficiently persuasive to allow the issue to go to the jury. Judge Rea’s ruling is significant to asbestos litigants since it can be used as a causation defense in the appropriate type of mesothelioma case. An issue that has remained elusive to the defense bar is how to counter a plaintiff’s argument that only asbestos causes mesothelioma. The experienced asbestos trial lawyer is even confronted with judges who state: “I thought only asbestos causes mesothelioma.” Defendants have tried the idiopathic defense and the radiation defense, among others, all with very little success. This is somewhat surprising, at least with the idiopathic defense, because the state of scientific knowledge is that some mesotheliomas arise spontaneously or are idiopathic in a certain statistically relevant number of cases. Regardless, juries have not been swayed that anything other than asbestos has caused plaintiff’s mesothelioma. Apparently, jurors need something tangible to blame, and asbestos versus nothing or idiopathic presents a fairly easy choice — asbestos is the culprit. SV40 is different because it is alive and growing in the tumor. More importantly, as far as juries are concerned, if SV40 is found in the tumor, technology allows the photographing of the virus and the jury can be shown what was actually causing the cancer. This is powerful evidence and is a major advantage over a claimed idiopathic cause. In fact, it allows the defense to trump the plaintiff’s causation argument with the question: Is the asbestos in the tumor or in the lung? In a very low-exposure case in which the plaintiff can barely stretch to find any exposure, no asbestos is found on the autopsy or in the tissue samples and SV40 is found in the tumor, then a powerful argument can be made that SV40 is the cause. Even if plaintiffs argue that they are co-causes, then they present the defense with at the very minimum more Proposition 51 defendants to share the allocation of fault. Even the plaintiff’s regular pathologists will not testify that SV40 is not causative. As far back as 1997, when asked about SV40′s role in causing mesothelioma, Dr. Sam Hammar testified in deposition that it was not proved, but was worthy of more study. One plaintiffs’ asbestos attorney has taken the step to amend a number of his cases in San Francisco to include a cause of action against the pharmaceuticals who manufactured the SV40-tainted polio vaccine. The irony is that a plaintiff’s theory of liability in one type of toxic tort case could provide a complete defense in another. It is no wonder that the plaintiffs bar, dominated by asbestos attorneys, has not embraced SV40 litigation. They, like Dr. Hammar, have kept their options open and have adopted a wait and see attitude. The wait and see attitude may end up haunting the plaintiffs asbestos bar. Plaintiffs lost in Horwin because Judge Rea found that the plaintiff did not have sufficient evidence to go forward on the issue of whether the source of the SV40 in the decedent’s tumor came from the tainted polio vaccine. Thus, SV40 as independent litigation was dealt a blow, but SV40 as a defense in a low-dose mesothelioma case was given a big push forward because of his positive medical findings. In the right type of asbestos-only case, it could be a very powerful defense. In a take-home case or a case where the exposure is difficult to identify, the fact that the tumor is SV40 positive and the virus is alive and expressing the T-antigen could have a profound effect on jurors looking for something tangible on which to base their decision. Although the SV40 defense is viable, it is not a silver bullet or panacea that should be asserted in every case. In only the right type of case should defendants even consider testing for SV40. In a low- or no-dose case, such as a take-home floor-tile exposure case, if a tumor tests positive, then, given the problematic release of fibers from floor tile, a complete defense could be provided. At a minimum, a very viable Prop 51 defense with a high percentage defendant is provided. Marte J. Bassi and Fred M. Blum are partners at Bassi, Martini & Blum in San Francisco. They can be reached at [email protected] and [email protected] If you are interested in submitting an article to law.com, please click here for our submission guidelines.

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