Genomics and Environmental Regulation: Science, Ethics, and Law

6 Genetic Data and Toxic Torts: Intimations of Statistical Reductionism

C H A P T E R 6 Genetic Data and Toxic Torts Intimations of Statistical Reductionism ANDREW ASKLAND AND GARY E. MARCHANT Rapid advances in our knowledge about genomics are affecting many areas of legal policy and practice. This knowledge encompasses the structure and function of genes and their products and also the impacts of genes on conditions and behavior. The condition component includes both etiological accounts for how conditions arise and predictions about avoiding harmful outcomes and promoting beneficial outcomes. The etiological studies are important for tort law because they affect its ability to causally link conduct that may be tortious to detrimental effects on individuals who were exposed to apparently dangerous substances . The matters considered controversial include what level of exposure occurred, what level of exposure can cause harm generally or caused harm to a particular plaintiff, and also what role genetic susceptibility plays in assessing arguably wrongful conduct and apparently harmful consequences. In short, can we prove that this substance causes harm in general, that it caused harm to this plaintiff, and that the harm it caused is better explained by the defendant’s actions than by the plaintiff ’s special genetic vulnerabilities? The focus is the interaction of substances that the defendant controls with the genes of the plaintiff, which may demonstrate the level of her exposure, the impact of that exposure on her health, and her special susceptibilities to the substance to which she was exposed. As to the susceptibility question, many substances are dangerous for all who are exposed if the level of exposure is sufficiently high but are dangerous to only a smaller number of genetically vulnerable people at lower exposures. We are concerned with the combination of a polymorphism (or particular genetic variation) and an occupational or environmental exposure that together increase the risk of illness. These combinations are the focus of much current toxicological research, both with regard to the expression of genes in response to exposure to a toxic substance (toxicogenomics) and the identification of genetic variations affecting susceptibility to these toxic substances (toxicogenetics). Potential Uses of Genomic Data One major application of genomic data for toxic torts is gene expression data and other types of biomarkers, including proteomics and metabolomics. DNA microarrays increasingly will be used to monitor the expression of genes in response to toxic agents. Gene expression patterns may provide signature profiles of specific toxicants or mechanisms of effects. Another major application concerns susceptibility genes. Genetic polymorphisms affect susceptibility to exposure to toxic substances via variations in processes such as xenobiotic metabolism and detoxification, DNA repair, and receptors. This chapter considers various uses of these two types of data in toxic tort cases in which one or more individuals (the plaintiffs) seek compensation for injuries allegedly resulting from toxic exposures created by a business or governmental entity (the defendant). Gene expression data are relevant to issues in general causation, specific causation, quantifying exposure, demonstrating absence of exposure, medical monitoring, and duty to test. Susceptibility gene data are relevant to issues of specific causation , duty to warn, idiosyncratic defenses, assumption of risk, alternative causation, multiple causation, damages, and class certification. We shall consider these issues seriatim. 82 L E G A L P E R S P E C T I V E S Gene Expression Data and Toxic Torts A recurring problem for plaintiffs in toxic tort suits is proving causation , that is, that the substance to which the plaintiff has been exposed does in fact cause harm (general causation) and did in fact cause that harm in this particular plaintiff (specific causation). Many plaintiffs struggle to demonstrate that a particular quantity of exposure has occurred and then, even if they have demonstrated a sufficient level of exposure, that it could have caused their illness. In other words, plaintiffs fail to demonstrate that the toxic agent has the potential to cause the health condition that is the foundation of their complaint. To meet their burden of proving this general causation, plaintiffs must introduce reliable scienti fic evidence that the specific toxic agent they were exposed to causes the specific ailment for which they seek compensation. Gene expression data may provide a tool that can assist plaintiffs in showing this. The specificity of gene expression data will enable reasonable extrapolations from known toxicological impacts to the toxic agents and gene expression evidence in the plaintiff’s case. For example , a plaintiff...