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  • Print publication year: 2016
  • Online publication date: May 2016

4 - Evidence of Toxicity


The law provides the institutional rules within which science will be utilized in toxic tort cases. Science in turn provides important factual content needed to assist in the resolution of legal disputes. However, scientific evidence is arcane, complex, and subtle. In order to better understand the law-science interaction, then, one should understand some of basic toxicity studies that are needed in the law. This chapter reviews these subjects. Chapter 5 discusses how scientists reason about studies to draw conclusions about human harm.

Early in this chapter, I provide some basic information about some of the main kinds of studies on which experts rely to make inferences about the potential of toxicants to cause adverse effects in persons. This summary seeks to acquaint readers, who might not be fully familiar with the science, with some of the types of studies and their features. I also review other kinds of evidence with which courts have had greater difficulties and that are less well understood. However, they are or potentially can be quite important in tort cases.

However, a deeper and broader understanding of the science and its context for the tort law is needed as well. There are implicit, explicit, and subtle barriers to providing the scientific evidence needed in toxic tort suits that may not be understood by courts or the wider public. Consequently, Chapter 6 explores some subtler but important pragmatic barriers to providing the needed science.


Chemical substances have some special features that in general make the identification and assessment of their causal properties difficult. In the tort law, these features pose particular problems, stressing and straining the institution in various ways. Although many substances could serve as examples, consider one: polychlorinated biphenyls (PCBs) and some of the risks they pose. PCBs were the main substances at issue in Joiner, but that is not the reason for presenting them here. This is a class of substances that is clearly toxic, but whose properties have not been quickly or easily understood.

PCBs are thermally stable, are resistant to oxidation, acids, bases, and a number of other chemical substances, have excellent dielectric and insulation properties, and make good commercial products. Until 1972 they were used as transformer cooling liquids, hydraulic fluids, lubricants, plasticizers, surface coatings, sealants, pesticide extenders, and copy paper.